Comet Updates, Meteor Showers & the Secrets of Uranus' Moon Ariel

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Andrew Dunkley: Hello again. Thanks for joining us on another

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episode of Space Nuts. Where we talk

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astronomy and space science. My name is

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Andrew Dunkley, your host, and it's good to

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have your company. Coming up on this

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episode, we will be doing an update on

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3i Atlas. Yes, I did pronounce it correctly.

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This week we'll also take, uh, a look at a

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few other comets. That are skimming around

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our, uh, region at the moment. Um,

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from comets to meteor showers that are making

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the news. And including the Draconids media

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shower. And the, uh, the

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moon of Uranus called Ariel, or

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Ariel is making the news. This is a really

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interesting story. And we'll be talking about

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asteroids being thrown at us by Venus

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in the next few thousand years. That's all

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coming up on this episode of space

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nuts.

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Jonti Horner: 15 seconds. Guidance is internal.

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10, 9. Ignition

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sequence start. Space nuts. 5, 4,

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3, 2, 1, 2, 3.

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Space nuts.

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Andrew Dunkley: Astronauts report at Neil's. Good.

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And as you would be aware, Professor Fred

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Watson is on the road or on a plane or

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on a bus or something. Uh, but he'll be away

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for several weeks. And in his

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stead is Professor Jonti Horner. Professor of

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astrophysics at the University of Southern

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Queensland, joining us again. Hello, Jonti.

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Jonti Horner: Good morning. How are you getting on?

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Andrew Dunkley: I'm getting on quite well. What about you?

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Jonti Horner: Um, oh, not too bad. I've never been a great

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fan of mornings, but I'm. I'm powering

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through and mainlining coffee and doing all

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those kind of healthy things to try and be

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coherent today.

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Andrew Dunkley: Mainlining m Coffee. I love that I should try

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it. But, uh, yeah, it's good to have you

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back. We've had a few people asking, you

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know, is he. Is he coming back? When.

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Jonti Horner: When will we.

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Andrew Dunkley: When will we see him again? Well, today. So

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great to have you back, Jonti. And, uh, and.

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And we're going to get straight into it

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because we got a lot to talk about.

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Jonti Horner: And.

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Andrew Dunkley: And we'll start off with a, um, an update on

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the comet. Uh, the Exo

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Comet, I suppose you'd call it. I don't know,

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3I Atlas. What's happening there?

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Jonti Horner: Well, it keeps getting lots and lots of

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media. And unfortunately, it keeps getting

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lots and lots of bad media as well. Thanks to

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a certain, uh, astronomer in the US who

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should probably remain nameless. And I wish

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he would remain nameless. It is the

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object, of course, that was found a few

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months ago. Speeding through the solar

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system. Much, much faster than a speeding

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bullet. Everybody uses a speeding bullet

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analogy. And in kind of solar system terms,

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bullets are really slow. So pretty much

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everything's faster than speeding bullet. But

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anyway, this thing's tearing through our

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solar system at such a speed that even when

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it gets so far away from the sun that it

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doesn't notice the sun anymore, it will still

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be going at more than 58 kilometers a second.

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Wow. Which is pretty remarkable all

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told. And it's been coming through the solar

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system on this slightly curved path

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because the sun will deflect it, it's going

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to change its direction coming through. And

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um, we've been getting a good view of it and

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it's the third ever interstellar object that

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we've got to see after Ummao MAU and Borisov.

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And it's a relatively small, fairly run of

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the mill comet, except for the fact that it's

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a comet that formed around a star that isn't

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the sun.

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Andrew Dunkley: Yeah.

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Jonti Horner: And that is pretty awesome and really

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fantastic. And because we found it so early,

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people have had a lot of time to study it.

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Get some really good data now, unfortunately

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from the Earth, it's now ducked out of view.

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It's passing closest to the sun on the 29th

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of this month. It's just come very close to

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Mars, which I'll come to in a minute, but

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it's swinging in towards its closest approach

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to the sun, getting more active, all looking

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good, but it's passing through on the far

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side of the sun. So it's now from the Earth's

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point of view, effectively lost to view for a

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couple of months. It's ducked out of sight

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and we can't really see it.

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Fortunately we're still going to get

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something of a view of it though, because as

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I just mentioned, it's just passed close to

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Mars. Came within about 30 million

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kilometers of Mars, very roughly speaking.

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Mhm. Which means if you were on Mars

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and you weren't worried about getting home,

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you still wouldn't be able to see it with the

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naked eye. It's genuinely quite a dim,

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faint comet from that point of view. So from

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Mars at the minute will probably be about

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factor of 100 times 2. Fancy with the naked

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eye, but we have all these spacecraft both

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orbiting Mars and on Mars surface that can

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look up and hopefully gather some data. So

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I saw actually a Reddit thread this morning

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claiming to show the first images from the

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Perseverance rover of the comet. Now

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I'm a little bit skeptical about this because

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I saw it on a Reddit thread that someone had

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posted a random image rather than on the NASA

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website. But at this close approach,

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there's been a concerted effort for both the

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European Space Agency's missions and the

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NASA spacecraft around and, uh, on Mars

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to actually try and get some data and try and

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get some images of this object. Now, we've

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not got any of that back yet, notwithstanding

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the claimed first image from perseverance.

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But this is going to be really, really useful

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because it allows us to peer at this object

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as it's getting closest to the sun, when it

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should technically be most active and

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therefore there'd be the most to learn about

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it. It's giving off the most gas, so there's

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the most to observe while it's hidden out of

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view. From our point of view, that's going to

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be really, really interesting. It's

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unfortunate that the shutdown in the US is

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happening at the minute. I mean, it's

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unfortunate for many, many reasons, but one

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of them is that a lot of staff working with

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NASA are currently furloughed and not able to

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work. And that will probably delay the

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results coming out. But it doesn't stop the

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spacecraft working. They just get on with it.

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So we will get to see the results at some

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point, but sadly not quite yet.

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And however we're going to get them. It's

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not the end of the story in terms of

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spacecraft looking at this thing though,

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because there's a couple of other spacecraft

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that will probably be able to snag some good

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photos as it moves further through the solar

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system. We've got the wonderful name Juice,

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which is a Jupiter Icy Moons explorer, which

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is currently winging its way out towards

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Jupiter. That will get a really good view of

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Three Eye Atlas over the next month or so

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as it goes one way and ATLAS goes the other

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way. Effectively not as close as Mars is to

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it. But the advantage is Juice will be

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inside, closer to the sun than the comet. So

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it will be looking away from the sun, get a

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decent view now, but it'll get an even better

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view in about a month's time when it's a bit

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further from the sun and can therefore

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observe for longer without overheating the

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spacecraft effectively. Yeah, so we're going

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to get that data, uh, and it's going to be

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really interesting to see what comes of this.

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I think it's going to be one of these cases

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where the data we get

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now from Mars, from Juice and all the data we

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gather from Earth will be yielding results

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that have been discussed for years to come.

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You know, we'll talk a little bit later about

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results about Jupiter's moon, about, sorry,

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about Uranus's. Moon aerial, which are, uh,

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based in part on observations that were taken

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40 years ago. So these things have a really

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long lifetime and it takes a long time for

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everybody to pick through them to get all of

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the wonderful juicy bits of gossip out,

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essentially all the wonderful information we

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can learn. So I think all this data is going

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to give us stuff that will be yielding

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awesome scientific results, new stories,

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new discussions on space nuts for 5, 10 years

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to come at least.

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Andrew Dunkley: Yeah, we're starting to see a lot of, um,

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that happen these days with new technology

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that you'd be able to reanalyze old data and

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come up with new concepts and sometimes new

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answers. Uh, another factor that you just

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mentioned was, uh, the photo on Reddit. Uh,

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we are now reaching a point where

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it's difficult to trust

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what's happening because of AI. And that's a

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discussion for another day. But I suppose the

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way around that is to go to reputable

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sources, which you mentioned NASA. So that's,

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yeah, it's, it's, it's getting, uh, like I

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spend a lot of time on social media and

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sometimes I look at an image and, or a video

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and go, hang on a minute. That,

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that's not. Yeah, but it looks so convincing.

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And that's, that's the problem. Uh, so that's

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three I atlas and we'll have more to talk

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about, uh, in the not too distant future. Few

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other comments that we might, uh, skim over.

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Jonti Horner: Boom, boom.

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Andrew Dunkley: Uh, with, um, within our,

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um, perimeters, I suppose, or our, um, uh,

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close to Earth.

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And the first One is, uh, C 2025

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R2.

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Jonti Horner: Swan. Yes.

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Andrew Dunkley: Uh, what's happening with that one?

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Jonti Horner: Quickly, this one was a big

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surprise. You know, people like me who are

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dead keen on going out and looking at comets,

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it's um, they're not really my kind of main

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professional focus. But there's something

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I've always loved since I was a little kid as

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an amateur astronomer. So I get really

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excited and hyped up when we get a good

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comet. So I've always got this kind of

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background awareness of what bright comets

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are coming up. I check a couple of really

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good websites I keep an eye on and I go to

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those every couple of weeks and just see if

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anything new's cropped up. And I'm also in a

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Facebook comic group, um, purely as an

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observer, I've got to say I don't really post

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in there because I'm not an expert and I see

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people posting in there when new discoveries

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are made. And normally when we get A comet

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that gets bright enough to be visible with

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the naked eye, we get at least a few months

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notice. We're getting better and better at

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finding these things further and further out.

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And that of course is going to get even more

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the case in the years to come with the

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incredible Vera Rubin Observatory. But if you

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go back to uh, kind of our, ah, parents or

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grandparents, generations, there was this

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real possibility for bright comet to just

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suddenly pop up out of nowhere and

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totally unexpected. A really good example of

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this is back in 1910 when everybody was

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hyped up, looking forward to an apparition of

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Comet Hallie, which appeared in May that

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year. And, um, was really good that time. It

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00:09:32.020 --> 00:09:34.540
wasn't like 1986 when it was, to be honest,

255
00:09:34.540 --> 00:09:36.500
pretty ropey. It was pretty awful.

256
00:09:36.500 --> 00:09:37.420
Andrew Dunkley: I remember that.

257
00:09:37.580 --> 00:09:39.500
Jonti Horner: Yeah, that was the worst apparition of Comet

258
00:09:39.500 --> 00:09:42.140
Hallie for 2000 years. It will be better next

259
00:09:42.140 --> 00:09:43.780
time around. And just to make you and I feel

260
00:09:43.780 --> 00:09:45.740
old, it's now closer to the next apparition

261
00:09:45.740 --> 00:09:47.780
of Comet Hallie than the last. So it is

262
00:09:47.780 --> 00:09:50.740
nearer to 2061 than 1986. But

263
00:09:50.740 --> 00:09:53.460
back in 1910 everybody was hyped up and

264
00:09:53.460 --> 00:09:55.100
looking forward to Comet Hallie, which was

265
00:09:55.100 --> 00:09:57.910
going to put on a really good show. And then

266
00:09:57.910 --> 00:10:00.630
in January 1910, suddenly this comet was

267
00:10:00.630 --> 00:10:02.910
discovered by miners in the Transvaal when

268
00:10:02.910 --> 00:10:04.350
they were leaving the mine first thing in the

269
00:10:04.350 --> 00:10:06.830
morning in South Africa. Visible with a

270
00:10:06.830 --> 00:10:09.710
naked eye as bright as the brightest stars

271
00:10:09.870 --> 00:10:12.830
in the dawn sky before sunrise. Um, that

272
00:10:12.830 --> 00:10:15.710
was the Great Comet of 1910 and it was

273
00:10:15.710 --> 00:10:18.270
first visible when it was at perihelion

274
00:10:18.830 --> 00:10:20.630
because it sneaked up on us from the far side

275
00:10:20.630 --> 00:10:23.550
of the sun, effectively. Um, and now that was

276
00:10:23.790 --> 00:10:25.590
really quite close to the sun. It was visible

277
00:10:25.590 --> 00:10:28.150
in broad daylight for four days continuously.

278
00:10:28.150 --> 00:10:30.610
That's how it was one of the brightest comets

279
00:10:30.610 --> 00:10:31.850
of the 20th century.

280
00:10:32.250 --> 00:10:35.150
Which brings us to this one, 2025 R

281
00:10:35.150 --> 00:10:38.050
AH2 Swan. It is not as bright as

282
00:10:38.050 --> 00:10:40.170
a Great Comet of 1910. If it was, everybody

283
00:10:40.170 --> 00:10:42.570
would know about it. Yes, but back

284
00:10:42.890 --> 00:10:44.810
bizarrely about three weeks ago now,

285
00:10:45.610 --> 00:10:48.010
it went from being unknown to being the

286
00:10:48.010 --> 00:10:50.690
brightest comet in the night sky at the time

287
00:10:50.690 --> 00:10:53.570
it was discovered, which is unheard of. And

288
00:10:53.570 --> 00:10:55.610
it was almost naked eye visibility when it

289
00:10:55.610 --> 00:10:57.950
was discovered. Um, it was about magnitude 7

290
00:10:57.950 --> 00:11:00.070
and a half, so a factor of two to three times

291
00:11:00.070 --> 00:11:02.990
too faint to see with the naked eye. If

292
00:11:02.990 --> 00:11:04.710
you've got good eyesight and a really dark

293
00:11:04.710 --> 00:11:07.710
sky, it is still on the cusp

294
00:11:07.710 --> 00:11:09.270
of naked eye visibility. Some of the

295
00:11:09.270 --> 00:11:11.030
observations people are sending in of it

296
00:11:11.110 --> 00:11:12.910
report it being just Bright enough to see

297
00:11:12.910 --> 00:11:15.310
with the naked eye, others just a little bit

298
00:11:15.310 --> 00:11:17.670
too faint. This one is still

299
00:11:17.990 --> 00:11:19.550
better seen for people in the Southern

300
00:11:19.550 --> 00:11:21.070
hemisphere than the Northern hemisphere,

301
00:11:21.070 --> 00:11:23.520
which, it's seems to be a recurring theme for

302
00:11:23.520 --> 00:11:26.240
comets, but it's not always the case. And um,

303
00:11:26.360 --> 00:11:28.840
there's been some absolutely glorious photos

304
00:11:28.840 --> 00:11:30.960
coming of it, particularly in the first few

305
00:11:30.960 --> 00:11:32.400
days after it was discovered actually because

306
00:11:32.400 --> 00:11:34.560
it was discovered very near to the bright

307
00:11:34.560 --> 00:11:36.920
star Spiker in the constellation Virgo,

308
00:11:37.400 --> 00:11:40.360
near Mars, which was close to Spiker at

309
00:11:40.360 --> 00:11:42.240
the time. So you've got these glorious photos

310
00:11:42.240 --> 00:11:44.680
taken by some of the world's best comet

311
00:11:44.680 --> 00:11:47.440
photographers that show this beautiful comet

312
00:11:47.440 --> 00:11:49.700
with a lovely long iron tail next to the

313
00:11:49.700 --> 00:11:52.340
bright red star Mars, the bright blue, bright

314
00:11:52.340 --> 00:11:54.300
red planet Mars, sorry, bright blue star

315
00:11:54.540 --> 00:11:56.980
Spiker in Virgo. And uh, just putting on an

316
00:11:56.980 --> 00:11:59.860
incredible shot. And it stayed. It's not

317
00:11:59.860 --> 00:12:01.820
brightened much more because we discovered it

318
00:12:01.820 --> 00:12:03.580
when it was about as bright as it was going

319
00:12:03.580 --> 00:12:05.340
to get. But it's hovering on the edge of

320
00:12:05.340 --> 00:12:07.740
naked eye. Visibility will remain so for

321
00:12:07.740 --> 00:12:10.500
another few weeks because it's been moving

322
00:12:10.500 --> 00:12:12.380
away from the sun but towards the uh, Earth.

323
00:12:12.380 --> 00:12:14.300
And that's been balancing out effectively.

324
00:12:14.460 --> 00:12:16.300
Yeah, so that's been putting on a fabulous

325
00:12:16.300 --> 00:12:19.130
show particularly for astrophotographers down

326
00:12:19.130 --> 00:12:21.170
here in the Southern hemisphere. Seems that

327
00:12:21.170 --> 00:12:22.730
it's a comet that comes around about every

328
00:12:22.730 --> 00:12:24.450
thousand years or so. There were even

329
00:12:24.450 --> 00:12:26.370
suggestions that uh, the Earth could get a

330
00:12:26.370 --> 00:12:28.890
minor meteor shower from this comet

331
00:12:29.130 --> 00:12:31.730
around today or yesterday as we cross where

332
00:12:31.730 --> 00:12:34.090
the comet is going to be in a few weeks time.

333
00:12:34.330 --> 00:12:36.770
We cross its orbit today. That seems

334
00:12:36.770 --> 00:12:39.290
unlikely. Although, um, totally in passing, I

335
00:12:39.290 --> 00:12:41.250
have seen notifications that uh, there has

336
00:12:41.250 --> 00:12:43.290
been a brand new meteor shower observed for

337
00:12:43.290 --> 00:12:45.130
the very first time just over the last couple

338
00:12:45.130 --> 00:12:48.040
of weeks deep in our southern sky by

339
00:12:48.040 --> 00:12:50.200
these old sky camera networks. Now, probably

340
00:12:50.200 --> 00:12:53.000
not related at all, but it's interesting how

341
00:12:53.000 --> 00:12:54.720
all these things happen at once. So that's

342
00:12:54.720 --> 00:12:56.600
been a really interesting comment and it's a

343
00:12:56.600 --> 00:12:59.120
real reminder that we might not

344
00:12:59.120 --> 00:13:01.839
necessarily get really good warning the next

345
00:13:01.839 --> 00:13:03.360
time we get a really good comment. We

346
00:13:03.360 --> 00:13:05.360
probably will, especially with Vera Rubin.

347
00:13:05.520 --> 00:13:07.480
But there's always a possibility that

348
00:13:07.480 --> 00:13:09.120
something like this will come along where

349
00:13:09.600 --> 00:13:12.490
effectively due to the quirks of

350
00:13:12.490 --> 00:13:15.370
celestial mechanics, it approaches the sun

351
00:13:16.250 --> 00:13:19.010
swinging in on a curved orbit whilst

352
00:13:19.010 --> 00:13:21.610
hiding behind the sun from our point of view,

353
00:13:21.610 --> 00:13:24.130
staying within about 30 or 40 degrees of the

354
00:13:24.130 --> 00:13:25.890
sun in the sky, which means it's lost in the

355
00:13:25.890 --> 00:13:28.530
twilight glare and it only pops up, it swings

356
00:13:28.530 --> 00:13:31.210
around the sun to our side of the Sun. That's

357
00:13:31.210 --> 00:13:32.530
what's happened here that's what happened

358
00:13:32.530 --> 00:13:35.410
with the Great Comet in 1910 as well. It just

359
00:13:35.410 --> 00:13:37.490
happened to come in. In such a direction that

360
00:13:37.490 --> 00:13:40.220
as it moved, it stayed hidden. You know,

361
00:13:40.300 --> 00:13:42.140
bit like a small child playing peekaboo, I

362
00:13:42.140 --> 00:13:43.660
guess, kind of trying to stay hidden behind

363
00:13:43.660 --> 00:13:44.700
the thing as you move around.

364
00:13:44.940 --> 00:13:47.740
Andrew Dunkley: Yep. Okay, so that's Swan,

365
00:13:47.740 --> 00:13:50.020
and, uh, it's a. It's around for a little

366
00:13:50.020 --> 00:13:52.420
while longer. Uh, the other two that are in

367
00:13:52.420 --> 00:13:54.860
the news at the moment are a six lemon and

368
00:13:54.860 --> 00:13:57.660
R3 pan stars. What's happening there?

369
00:13:58.460 --> 00:14:00.900
Jonti Horner: A three lemon is one that was discovered back

370
00:14:00.900 --> 00:14:03.180
in January. So with these comet names,

371
00:14:03.260 --> 00:14:04.980
they're a little bit like a calendar that can

372
00:14:04.980 --> 00:14:06.780
tell you exactly when comets are found. So if

373
00:14:06.780 --> 00:14:08.610
you hear a Comet described as

374
00:14:08.610 --> 00:14:11.570
C2025A6, which is what

375
00:14:11.570 --> 00:14:14.330
we've got with Comet Lemon, the C tells you

376
00:14:14.330 --> 00:14:17.170
that it's a comet that is not a short period

377
00:14:17.170 --> 00:14:18.890
comet. It's not been seen at multiple

378
00:14:18.890 --> 00:14:21.330
apparitions. In this case, it's a comet with

379
00:14:21.330 --> 00:14:22.970
a period of more than a thousand years, but

380
00:14:22.970 --> 00:14:25.250
less than 10,000 years, probably about 1400.

381
00:14:25.580 --> 00:14:25.930
Andrew Dunkley: Mhm.

382
00:14:26.450 --> 00:14:28.890
Jonti Horner: The 2025 tells you it was discovered in the

383
00:14:28.890 --> 00:14:31.450
year 2025. And, um, the letter tells you

384
00:14:31.450 --> 00:14:33.250
which fortnight of the year it was discovered

385
00:14:33.250 --> 00:14:35.170
in. So the letter A here tells you the first

386
00:14:35.170 --> 00:14:37.470
two weeks of January. Right. So this comet

387
00:14:37.470 --> 00:14:39.350
was found right at the start of this year.

388
00:14:39.830 --> 00:14:41.550
And, um, it looked like it was going to be

389
00:14:41.550 --> 00:14:44.350
promising, but it wasn't heralded as

390
00:14:44.350 --> 00:14:46.430
being the equivalent of kind of Comet Atlas

391
00:14:46.430 --> 00:14:47.750
we had at the start of the year, or Comet

392
00:14:47.750 --> 00:14:49.510
Church in Shan Atlas last year, which were

393
00:14:49.750 --> 00:14:51.950
great comets. I'd classify them as they were

394
00:14:51.950 --> 00:14:54.470
really bright, easily visible from even

395
00:14:54.470 --> 00:14:56.590
brightly light polluted areas. They were

396
00:14:56.590 --> 00:14:59.510
really spectacular. This comet is currently

397
00:14:59.670 --> 00:15:01.670
best visible from the northern hemisphere. We

398
00:15:01.670 --> 00:15:03.350
don't really get to see it down south just

399
00:15:03.350 --> 00:15:05.950
yet, but it's swinging into perihelion. It's

400
00:15:05.950 --> 00:15:08.470
currently about the same brightness as the

401
00:15:08.470 --> 00:15:10.950
comet I just discussed, Comet R2, Swan.

402
00:15:11.190 --> 00:15:13.390
But this one is still brightening, and at its

403
00:15:13.390 --> 00:15:15.830
brightest it will, unless it does something

404
00:15:15.830 --> 00:15:18.430
unexpected. You know, comets famous saying

405
00:15:18.430 --> 00:15:20.230
says comets are like cats. They have tails

406
00:15:20.230 --> 00:15:22.190
and they do whatever they want. There's

407
00:15:22.190 --> 00:15:24.510
always a chance that this thing could undergo

408
00:15:24.510 --> 00:15:26.630
a fragmentation event and brighten by a

409
00:15:26.630 --> 00:15:28.390
factor of 100. That kind of thing does

410
00:15:28.390 --> 00:15:31.200
happen. Not necessarily all that likely,

411
00:15:31.920 --> 00:15:33.680
but if it continues brightening as it

412
00:15:33.680 --> 00:15:35.320
currently is, and it's behaving really well

413
00:15:35.320 --> 00:15:37.240
at the minute, it will probably at its

414
00:15:37.240 --> 00:15:39.240
brightest, be comparably bright to the

415
00:15:39.240 --> 00:15:41.880
Andromeda Galaxy. So Visible, uh, with the

416
00:15:41.880 --> 00:15:44.240
naked eye from dark sky sites, if you know

417
00:15:44.240 --> 00:15:46.800
where to look, but not visible from the

418
00:15:46.800 --> 00:15:49.040
middle of like polluted Sydney or Brisbane or

419
00:15:49.120 --> 00:15:51.320
somewhere like that, unless you've got

420
00:15:51.320 --> 00:15:53.560
binoculars. But it's going to be the

421
00:15:53.560 --> 00:15:56.360
brightest comet in our sky since Comet Atlas

422
00:15:56.360 --> 00:15:58.240
back in January. It's going to be a fairly

423
00:15:58.240 --> 00:16:00.320
good site. Again, there are some absolutely

424
00:16:00.320 --> 00:16:02.240
astonishingly good photographs coming in from

425
00:16:02.240 --> 00:16:03.760
the northern hemisphere of this. It's really

426
00:16:03.760 --> 00:16:06.360
photogenic and it's going to be above the

427
00:16:06.360 --> 00:16:08.520
threshold for naked eye visibility for about

428
00:16:08.520 --> 00:16:11.160
two months, building up to that peak and then

429
00:16:11.160 --> 00:16:13.520
fading away again. So it's going to be a

430
00:16:13.520 --> 00:16:15.600
really good site. Currently, it is best

431
00:16:15.600 --> 00:16:18.360
visible from the Northern hemisphere, I

432
00:16:18.360 --> 00:16:20.600
believe it's currently quite high in the

433
00:16:20.600 --> 00:16:23.120
northern sky, edging towards the,

434
00:16:23.500 --> 00:16:25.300
the southern outskirts of Ursa Major, that

435
00:16:25.300 --> 00:16:27.700
kind of part of the sky. But it's then going

436
00:16:27.700 --> 00:16:30.580
to start ducking southwards and by the

437
00:16:30.580 --> 00:16:32.460
time it's at its brightest, which is going to

438
00:16:32.460 --> 00:16:34.940
be the start of November, it will be visible

439
00:16:34.940 --> 00:16:37.580
from both hemispheres, albeit I think,

440
00:16:37.660 --> 00:16:39.699
easier to see from the Northern hemisphere

441
00:16:39.699 --> 00:16:41.860
still. But this is going to be a naked eye

442
00:16:41.860 --> 00:16:44.220
comet. Naked eye caveat,

443
00:16:44.620 --> 00:16:46.740
not that spectacular, but visible if you know

444
00:16:46.740 --> 00:16:49.620
where to look. Um, for those who go out and

445
00:16:49.620 --> 00:16:51.380
look at comets and that therefore it's

446
00:16:51.380 --> 00:16:53.580
probably a little bit brighter than Pons

447
00:16:53.580 --> 00:16:56.380
Brooks was last year. Pons Brooks was, you

448
00:16:56.380 --> 00:16:58.940
know, captors of Devil's Comet and all those

449
00:16:58.940 --> 00:17:00.740
kind of weird names that these things seem to

450
00:17:00.740 --> 00:17:02.940
get in the media. If you saw that one with

451
00:17:02.940 --> 00:17:05.380
the naked eye, this comet should be a bit

452
00:17:05.380 --> 00:17:07.380
brighter than that and a bit easier to spot.

453
00:17:07.380 --> 00:17:08.940
But it's probably a really good opportunity

454
00:17:08.940 --> 00:17:11.740
for people to dust off their camera gear, do

455
00:17:11.740 --> 00:17:13.300
a little bit of planning and go take some

456
00:17:13.300 --> 00:17:16.020
photos. So it's going to be pretty good. And

457
00:17:16.100 --> 00:17:18.010
nobody complains about a naked eye comet.

458
00:17:18.160 --> 00:17:18.800
Andrew Dunkley: No, they don't.

459
00:17:18.800 --> 00:17:21.120
And R3 pan starrs, I'm guessing from its

460
00:17:21.120 --> 00:17:23.120
name, is a very recent discovery.

461
00:17:23.360 --> 00:17:25.640
Jonti Horner: It is. This was discovered very, very

462
00:17:25.640 --> 00:17:27.880
recently and we still know surprisingly

463
00:17:27.880 --> 00:17:30.120
little about it, actually. I mean, if I go to

464
00:17:30.120 --> 00:17:32.520
the place I normally look at the light curves

465
00:17:32.520 --> 00:17:34.520
for these comets from where it aggregates all

466
00:17:34.520 --> 00:17:36.480
the observations and tries to predict forward

467
00:17:36.560 --> 00:17:38.840
how bright it's going to be. That has a

468
00:17:38.840 --> 00:17:41.640
really nice light curve for this object, but

469
00:17:41.640 --> 00:17:44.280
it has no observations on the light curve at

470
00:17:44.280 --> 00:17:46.670
the minute. So this is very new. It is still

471
00:17:46.670 --> 00:17:48.270
very faint. I mean, with this one we're

472
00:17:48.270 --> 00:17:50.310
talking about something that's probably a

473
00:17:50.310 --> 00:17:53.310
factor of 50,000 times too fancy with the

474
00:17:53.310 --> 00:17:56.110
naked eye at uh, the minute, very recent

475
00:17:56.110 --> 00:17:58.750
discovery by that wonderful automated

476
00:17:58.750 --> 00:18:00.790
search facility on the top of Hawaii Pan

477
00:18:00.790 --> 00:18:03.310
starts. The reason this has got my attention

478
00:18:03.310 --> 00:18:05.710
is that it is going to pass

479
00:18:05.710 --> 00:18:08.470
incredibly close to the line between the sun

480
00:18:08.470 --> 00:18:11.110
and the Earth, uh, which we've seen with

481
00:18:11.110 --> 00:18:13.070
those two great comets we had in the last 12

482
00:18:13.070 --> 00:18:15.540
months. And when you get an object that

483
00:18:15.540 --> 00:18:17.300
passes directly between the sun and the

484
00:18:17.300 --> 00:18:19.300
Earth, if it happens to be a particularly

485
00:18:19.300 --> 00:18:21.100
dusty comet and shedding a lot of dust,

486
00:18:21.660 --> 00:18:23.100
there's a phenomenon called forward

487
00:18:23.100 --> 00:18:25.780
scattering which we in Australia are fairly

488
00:18:25.780 --> 00:18:27.580
familiar with on, um, dusty days because near

489
00:18:27.580 --> 00:18:29.820
sunset the sky is unbearably bright and it's

490
00:18:29.820 --> 00:18:32.300
awful driving west at sunset, which is

491
00:18:32.300 --> 00:18:33.780
something people in Toowoomba, um, are very

492
00:18:33.780 --> 00:18:35.260
familiar with because our roads are kind of

493
00:18:35.260 --> 00:18:37.940
east, west, north, south. And so around the

494
00:18:37.940 --> 00:18:40.540
equinoxes you drive towards the sunset and

495
00:18:40.540 --> 00:18:43.290
get snow blind effects. Skiers are familiar

496
00:18:43.290 --> 00:18:45.290
with it for the same reason. You know, on a

497
00:18:45.290 --> 00:18:47.130
kind of day where there's a lot of small ice

498
00:18:47.130 --> 00:18:49.290
crystals in the air, the sky can be very

499
00:18:49.290 --> 00:18:52.050
bright in the direction of the Sun. This

500
00:18:52.050 --> 00:18:54.490
phenomenon of forward scattering can make

501
00:18:54.490 --> 00:18:57.410
comets brighten by more than a

502
00:18:57.410 --> 00:18:59.810
factor of 100, depending on the orientation

503
00:19:00.370 --> 00:19:03.310
when they're close to the sun in the sky, um,

504
00:19:03.310 --> 00:19:04.770
or when they're close to that line between

505
00:19:04.770 --> 00:19:07.530
the Earth and Sun. Now this object Pan stars,

506
00:19:07.530 --> 00:19:09.450
it looks like it's a fairly small comet, but

507
00:19:09.450 --> 00:19:11.490
we've not got much information about it yet.

508
00:19:11.930 --> 00:19:14.530
But its orbit's fairly well constrained and

509
00:19:14.530 --> 00:19:16.490
it is going to come very close to the sun in

510
00:19:16.490 --> 00:19:18.010
the sky from our point of view. For a time,

511
00:19:18.010 --> 00:19:19.890
people were even suggesting it could transit

512
00:19:19.890 --> 00:19:21.490
the disk of the sun, um, even though we

513
00:19:21.490 --> 00:19:22.970
wouldn't see anything because it'd be too

514
00:19:22.970 --> 00:19:25.170
small to be visible, it could pass so

515
00:19:25.170 --> 00:19:26.930
perfectly between us, it will cross across

516
00:19:26.930 --> 00:19:28.650
the disc of the sun from our point of view.

517
00:19:29.690 --> 00:19:32.410
What that all means is that if this

518
00:19:32.410 --> 00:19:34.810
comet becomes fairly active,

519
00:19:35.210 --> 00:19:37.210
there's a chance that it could become quite

520
00:19:37.210 --> 00:19:40.130
bright in April next year. Now,

521
00:19:40.130 --> 00:19:43.090
how bright is utterly unknown at the

522
00:19:43.090 --> 00:19:44.410
minute, but it's worth flagging up because

523
00:19:44.410 --> 00:19:46.770
it's an interesting one. The light curve I'm

524
00:19:46.770 --> 00:19:49.770
looking at as I talk about this is, in

525
00:19:49.770 --> 00:19:51.370
all honesty, with the lack of observations,

526
00:19:51.370 --> 00:19:53.010
we've got something of a fiction. It could

527
00:19:53.010 --> 00:19:54.970
get a lot brighter than this or fainter than

528
00:19:54.970 --> 00:19:57.170
this. But it suggests that without this

529
00:19:57.170 --> 00:19:59.290
forward scattering process, this comet will

530
00:19:59.290 --> 00:20:01.410
be too small to be visible with a naked eye.

531
00:20:01.570 --> 00:20:03.650
But with forward scattering, it could get as

532
00:20:03.650 --> 00:20:06.300
bright or brighter than Comet Lemon. So it

533
00:20:06.300 --> 00:20:08.100
could get brighter than the andromeda Galaxy,

534
00:20:08.100 --> 00:20:09.820
albeit when it's quite close to the sun in

535
00:20:09.820 --> 00:20:12.020
the sky and therefore it could be visible to

536
00:20:12.020 --> 00:20:14.500
the naked eye for a week or two. Now if it

537
00:20:14.500 --> 00:20:16.540
turns out to be a larger, more substantial

538
00:20:16.540 --> 00:20:19.020
comet than those first observations suggests,

539
00:20:19.260 --> 00:20:21.499
that all ramps up and it could be even

540
00:20:21.499 --> 00:20:24.180
better. There's a small chance I'd say that

541
00:20:24.180 --> 00:20:25.740
this thing could be visible with the naked

542
00:20:25.740 --> 00:20:28.380
eye in April, but it's just again one, once

543
00:20:28.380 --> 00:20:31.370
again a reminder of as we get better at uh,

544
00:20:31.430 --> 00:20:33.910
these kind of all sky surveys, we're going to

545
00:20:33.910 --> 00:20:36.550
find interesting comets earlier. We're

546
00:20:36.550 --> 00:20:38.150
eventually going to get to the point where an

547
00:20:38.150 --> 00:20:40.350
object like Comet R2 Swan that we've got at

548
00:20:40.350 --> 00:20:43.030
the minute can't surprise us because we'll

549
00:20:43.030 --> 00:20:44.550
get our telescopes good enough that we'd find

550
00:20:44.550 --> 00:20:46.790
it a really long way away before it hides

551
00:20:46.790 --> 00:20:49.290
behind the sun. And so uh,

552
00:20:49.590 --> 00:20:51.470
you know, it wouldn't surprise me if the next

553
00:20:51.470 --> 00:20:53.670
great comet was found months ahead of time

554
00:20:53.670 --> 00:20:55.390
rather than weeks ahead of time. And we get

555
00:20:55.390 --> 00:20:58.280
prior artists, um, and because it's

556
00:20:58.280 --> 00:21:01.000
observed that early, we might have this level

557
00:21:01.000 --> 00:21:03.400
of uncertainty in an object that's a bit

558
00:21:03.400 --> 00:21:06.200
brighter than this and people will either

559
00:21:06.200 --> 00:21:09.000
be calm and cautious or hyperbolic

560
00:21:09.000 --> 00:21:11.880
and excited. And then we get to see that's

561
00:21:11.880 --> 00:21:12.720
part of the fun of it.

562
00:21:13.020 --> 00:21:14.240
Andrew Dunkley: M. Yeah, indeed.

563
00:21:14.240 --> 00:21:16.960
Okay, so plenty, uh, or potentially plenty

564
00:21:16.960 --> 00:21:19.600
for skywatchers to look forward to and a lot

565
00:21:19.600 --> 00:21:21.040
going on at the moment. And while you've been

566
00:21:21.040 --> 00:21:22.200
talking about those comments, I've been

567
00:21:22.200 --> 00:21:24.170
looking up some of the media pictures and

568
00:21:24.250 --> 00:21:26.970
it's interesting to see that um, the quality

569
00:21:26.970 --> 00:21:29.770
of the outlet dictates the

570
00:21:30.090 --> 00:21:32.290
genuineness uh, of the photo. Let me just say

571
00:21:32.290 --> 00:21:35.010
that this, this is Space

572
00:21:35.010 --> 00:21:37.610
Nuts with Andrew Dunkley and John de Horner.

573
00:21:38.170 --> 00:21:40.410
Jonti Horner: 3, 2, 1.

574
00:21:40.970 --> 00:21:43.490
Andrew Dunkley: Space nuts from comets to

575
00:21:43.490 --> 00:21:46.410
meteor showers. And there's uh, there's a

576
00:21:46.410 --> 00:21:47.770
few making the news at the moment.

577
00:21:47.770 --> 00:21:50.580
Jonti Horner: Jonti, there are. It's a good time of the

578
00:21:50.580 --> 00:21:53.300
year for meteor observers, um, particularly

579
00:21:53.300 --> 00:21:55.820
in the Northern hemisphere. Whilst comets

580
00:21:55.820 --> 00:21:57.500
seem to get a slightly better deal in the

581
00:21:57.500 --> 00:21:59.380
Southern hemisphere over long periods of

582
00:21:59.380 --> 00:22:01.060
time. The Northern hemisphere gets the better

583
00:22:01.060 --> 00:22:03.460
of the meteor showers. We're getting a fair

584
00:22:03.460 --> 00:22:05.780
bit of coverage already about the Orionid

585
00:22:05.780 --> 00:22:08.740
meteor shower which is already

586
00:22:08.740 --> 00:22:10.940
active but is building to a peak around the

587
00:22:10.940 --> 00:22:13.820
20th, 21st of October. Now the

588
00:22:13.820 --> 00:22:16.060
Orionids are uh, a meteor shower that's

589
00:22:16.060 --> 00:22:18.400
caused by Comet Hallie which has been

590
00:22:18.400 --> 00:22:19.880
whizzing around the sun on its current

591
00:22:20.040 --> 00:22:22.720
roughly 76 year orbit for thousands, if not

592
00:22:22.720 --> 00:22:25.120
tens of thousands of years. It's a very big

593
00:22:25.120 --> 00:22:27.400
cometary nucleus Laying down lots of dust.

594
00:22:27.960 --> 00:22:30.000
And that dust has spread out to such an

595
00:22:30.000 --> 00:22:32.240
extent that every year the Earth, uh, crosses

596
00:22:32.240 --> 00:22:34.360
through that tube of dust left behind by the

597
00:22:34.360 --> 00:22:36.880
comet on two separate occasions. Yeah, we get

598
00:22:36.880 --> 00:22:39.840
the Etraquarian meteor shower in May, which

599
00:22:39.840 --> 00:22:42.240
is one of the year's best meteor showers. But

600
00:22:42.240 --> 00:22:44.510
it's really hard to see. Um, you need to be

601
00:22:44.510 --> 00:22:46.310
up in a couple of hours before dawn to see

602
00:22:46.310 --> 00:22:47.990
anything. And that favors Southern Hemisphere

603
00:22:47.990 --> 00:22:49.910
observers. So it's not as well known, not as

604
00:22:49.910 --> 00:22:52.830
well observed. Then you have the Orionids

605
00:22:52.830 --> 00:22:55.630
in October. And, um, the Orionids are not as

606
00:22:55.630 --> 00:22:58.270
good as the Aquarids. They're probably in the

607
00:22:58.270 --> 00:23:00.350
second kind of tier of meteor showers. So

608
00:23:00.350 --> 00:23:02.710
you've got the big three in the form of the

609
00:23:02.710 --> 00:23:05.030
Quadrantids in January, the Perseids in

610
00:23:05.030 --> 00:23:07.310
August, and, um, the Geminids, which are the

611
00:23:07.310 --> 00:23:09.030
best meteor shower in a typical year in

612
00:23:09.030 --> 00:23:11.820
December. And they're reliable every

613
00:23:11.820 --> 00:23:13.620
year, uh, really good rates. And they're the

614
00:23:13.620 --> 00:23:15.660
ones that, uh, you tell your friends who are

615
00:23:15.660 --> 00:23:17.300
not into astronomy to go out and look at

616
00:23:17.300 --> 00:23:18.700
because they're good enough that someone

617
00:23:18.700 --> 00:23:20.660
who's not that excited already will still see

618
00:23:20.660 --> 00:23:23.460
a good show. The Orion into the, like, the

619
00:23:23.460 --> 00:23:25.859
next tier down, they are. If you're someone

620
00:23:25.859 --> 00:23:27.420
who's really keen on astronomy and you're

621
00:23:27.420 --> 00:23:29.180
happy to spend an hour or two sitting out in

622
00:23:29.180 --> 00:23:31.060
the middle of the night, you'll see a

623
00:23:31.060 --> 00:23:33.180
reasonable number and they're lovely to see,

624
00:23:33.660 --> 00:23:35.660
but they're probably not active enough that

625
00:23:35.660 --> 00:23:37.540
someone who's not that keen on astronomy will

626
00:23:37.540 --> 00:23:40.000
get a real buzz out of it, if that makes

627
00:23:40.000 --> 00:23:42.960
sense. So if you're somewhere in

628
00:23:42.960 --> 00:23:44.680
Northern Europe and North America, where

629
00:23:44.680 --> 00:23:47.560
you've got long dark nights at the minute and

630
00:23:47.560 --> 00:23:49.760
you were out all night, you might see 15 or

631
00:23:49.760 --> 00:23:52.040
20 of these per hour in the early morning

632
00:23:52.040 --> 00:23:54.920
hours in late October, you know,

633
00:23:54.920 --> 00:23:57.360
the kind of 19th, 20th, 21st, 22nd

634
00:23:58.480 --> 00:24:00.560
from Australia, the rates are a bit lower

635
00:24:00.560 --> 00:24:02.440
because a point in the sky these meters come

636
00:24:02.440 --> 00:24:04.360
from the radiant is lower in the sky at its

637
00:24:04.360 --> 00:24:07.320
highest. And geometry means, therefore, the

638
00:24:07.320 --> 00:24:09.000
same number of meteors are spread over a

639
00:24:09.000 --> 00:24:11.440
larger volume of atmosphere. So you'll see a

640
00:24:11.440 --> 00:24:13.200
smaller number of them from wherever you're

641
00:24:13.200 --> 00:24:15.880
sat. But you can still see if you're in kind

642
00:24:15.880 --> 00:24:18.160
of the top end of Australia, I'd say 10 or 15

643
00:24:18.160 --> 00:24:19.920
per hour. If you're down at the southern end,

644
00:24:20.000 --> 00:24:21.680
a little bit less than that. The further

645
00:24:21.680 --> 00:24:23.960
south you go, the worse it'll get. This year,

646
00:24:23.960 --> 00:24:25.680
though, is particularly good because it's New

647
00:24:25.680 --> 00:24:28.200
Moon. And so what that means is you've Got

648
00:24:28.200 --> 00:24:30.800
ideal viewing conditions. You don't have

649
00:24:31.290 --> 00:24:34.250
the glowing orb of doom scattering light in

650
00:24:34.250 --> 00:24:36.050
the sky and basically blocking the view of

651
00:24:36.050 --> 00:24:38.210
all the interesting stuff. I've always been,

652
00:24:38.210 --> 00:24:40.130
as an amateur astronomer that side of my

653
00:24:40.130 --> 00:24:42.450
life. Frustrated by the Moon because it stops

654
00:24:42.450 --> 00:24:44.890
us seeing all the good stuff. But, um, that's

655
00:24:44.890 --> 00:24:47.650
particularly true of meteor showers. That's

656
00:24:47.650 --> 00:24:49.090
iron. It's. They're getting a lot of

657
00:24:49.090 --> 00:24:51.930
coverage. Um, what I would say with it is

658
00:24:51.930 --> 00:24:54.170
unless you're a really avid meteor observer

659
00:24:54.170 --> 00:24:56.650
or unless you're going out anyway, don't buy

660
00:24:56.650 --> 00:24:59.070
into the hype. There'll be a lot of overblown

661
00:24:59.070 --> 00:25:00.630
articles. And I'm seeing them already from

662
00:25:00.630 --> 00:25:02.470
some of the less reputable media outlets

663
00:25:02.470 --> 00:25:05.030
online. Talking about the skies falling. And

664
00:25:05.030 --> 00:25:06.790
this will be the best thing you'll ever see.

665
00:25:06.790 --> 00:25:08.630
And that just sets people up for

666
00:25:08.630 --> 00:25:10.470
disappointment. So it was a little bit sad.

667
00:25:10.470 --> 00:25:12.550
But if you do want to go out and see the

668
00:25:12.550 --> 00:25:15.230
Orionids. Around the 20th of October

669
00:25:15.630 --> 00:25:18.270
is the best time. Unlike

670
00:25:18.830 --> 00:25:21.470
most meteor showers, the Orionids and the

671
00:25:21.550 --> 00:25:23.590
Aquarids in May, both these Comet Hallie

672
00:25:23.590 --> 00:25:26.530
meteor showers have quite a broad maximum. So

673
00:25:26.530 --> 00:25:28.290
if it's cloudy on the night of the peak.

674
00:25:28.610 --> 00:25:30.450
You'll still get a decent show for two or

675
00:25:30.450 --> 00:25:32.290
three nights either side. It's a much flatter

676
00:25:32.370 --> 00:25:34.810
plateau, effectively. And they do sometimes

677
00:25:34.810 --> 00:25:37.170
throw a bit of a surprise our way. They are

678
00:25:37.170 --> 00:25:39.770
fast meteors, um, have a tendency to produce

679
00:25:39.770 --> 00:25:41.930
quite a few bright ones as well. And you see

680
00:25:41.930 --> 00:25:43.770
them best if you're out in the early hours of

681
00:25:43.770 --> 00:25:45.490
the morning, after midnight. That's kind of

682
00:25:45.490 --> 00:25:46.970
the best time. With the best rates being just

683
00:25:46.970 --> 00:25:49.370
before dawn. But they are visible from about

684
00:25:49.370 --> 00:25:50.450
10:30 at night.

685
00:25:51.120 --> 00:25:51.600
Andrew Dunkley: Okay.

686
00:25:51.760 --> 00:25:54.680
Now, um, the other meteor shower

687
00:25:54.680 --> 00:25:56.440
that you wanted to talk about, uh, that could

688
00:25:56.440 --> 00:25:58.480
be worth a look is the Draconids. I don't

689
00:25:58.480 --> 00:25:59.520
know much about this one.

690
00:26:00.240 --> 00:26:02.800
Jonti Horner: This is a really fun little shower. Because

691
00:26:02.800 --> 00:26:05.680
it's illustrative of how meteor showers are

692
00:26:05.680 --> 00:26:08.560
really changeable over time. The

693
00:26:08.560 --> 00:26:11.120
way a meteor shower forms is you've got a

694
00:26:11.120 --> 00:26:13.400
comet going around the sun. And a comet is a

695
00:26:13.400 --> 00:26:15.360
dirty snowball, a snowy dirt ball. So when

696
00:26:15.360 --> 00:26:17.490
it's far from the sun, it just looks like an

697
00:26:17.490 --> 00:26:19.250
asteroid. Nothing's happening. It's a tiny

698
00:26:19.250 --> 00:26:21.610
speck of light, few kilometers across.

699
00:26:22.330 --> 00:26:24.210
When it gets close to the sun, the surface

700
00:26:24.210 --> 00:26:26.490
gets hot. And all the ices on the surface

701
00:26:26.730 --> 00:26:29.290
sublime. They turn to gas, erupt from the

702
00:26:29.290 --> 00:26:32.130
surface in jets. Because they only sublime if

703
00:26:32.130 --> 00:26:34.370
they're exposed to enough heat to get off.

704
00:26:34.370 --> 00:26:36.050
And a lot of the surface is caked up and

705
00:26:36.050 --> 00:26:38.130
blocked up. So you get these little active

706
00:26:38.130 --> 00:26:40.730
areas casting jets of material into space

707
00:26:41.210 --> 00:26:43.130
and carrying with them a lot of dust.

708
00:26:44.580 --> 00:26:46.380
So comets, when they're closer to the sun,

709
00:26:46.380 --> 00:26:47.980
shed gas and dust. And that's why they get

710
00:26:47.980 --> 00:26:49.700
the coma and the tails that make them

711
00:26:49.700 --> 00:26:51.220
brighter and easier to see and so

712
00:26:51.220 --> 00:26:54.180
spectacular. The dust that they shed

713
00:26:54.180 --> 00:26:56.820
is ejected from them at, uh, speeds of

714
00:26:56.820 --> 00:26:59.460
meters or tens of meters or maybe hundreds of

715
00:26:59.460 --> 00:27:02.340
meters per second. But typically 1 or

716
00:27:02.340 --> 00:27:04.820
10 meters a second while the comet's going

717
00:27:04.820 --> 00:27:06.620
around the sun at a speed measured in tens of

718
00:27:06.620 --> 00:27:09.020
kilometers per second. So that means that the

719
00:27:09.020 --> 00:27:10.900
dust will end up moving on essentially the

720
00:27:10.900 --> 00:27:13.360
same orbit as the comet. It won't move on to

721
00:27:13.360 --> 00:27:16.120
a drastically different orbit. The

722
00:27:16.120 --> 00:27:18.120
smallest grains of dust are blown away by the

723
00:27:18.120 --> 00:27:20.120
sun and the solar wind and radiation

724
00:27:20.120 --> 00:27:22.600
pressure. But the bigger bits of dust kind of

725
00:27:22.600 --> 00:27:24.440
stay moving around the sun on an orbit

726
00:27:24.440 --> 00:27:26.800
similar to that of the comet. But because of

727
00:27:26.800 --> 00:27:29.160
that ejection speed, some of the dust grains

728
00:27:29.160 --> 00:27:31.000
move on orbits that have a shorter period

729
00:27:31.080 --> 00:27:33.520
than the comet. Some move on periods slightly

730
00:27:33.520 --> 00:27:35.600
longer than the comet. So over time, they

731
00:27:35.600 --> 00:27:37.600
spread out ahead and behind the comet in its

732
00:27:37.600 --> 00:27:40.060
orbit until eventually the orbit is clogged

733
00:27:40.060 --> 00:27:42.700
with dust all the way around. So if you go

734
00:27:42.700 --> 00:27:44.260
across the orbit when the comet isn't there,

735
00:27:44.260 --> 00:27:45.780
you'll still run into dust because there'll

736
00:27:45.780 --> 00:27:48.740
always be something there. Then when you

737
00:27:48.740 --> 00:27:50.180
get the Earth, uh, running across one of

738
00:27:50.180 --> 00:27:52.020
these orbits, if they intersect in space

739
00:27:52.500 --> 00:27:54.139
every year, we'll go through that dust and

740
00:27:54.139 --> 00:27:56.980
we'll get a meteor shower. Now, comets,

741
00:27:56.980 --> 00:27:59.500
orbits are constantly changing. And that's

742
00:27:59.500 --> 00:28:01.540
particularly true of a family of comets we

743
00:28:01.540 --> 00:28:03.140
call the Jupiter family comets, or the short

744
00:28:03.140 --> 00:28:05.050
period comets. These are comets captured by

745
00:28:05.050 --> 00:28:06.890
Jupiter, flung into the inner solar system,

746
00:28:07.370 --> 00:28:09.410
moving on orbits that are kind of five, six,

747
00:28:09.410 --> 00:28:12.370
seven years long. So you'll get a comet

748
00:28:12.370 --> 00:28:14.770
will be nudged, dropped onto a new orbit, and

749
00:28:14.770 --> 00:28:17.130
it will start laying down dust on that orbit.

750
00:28:17.210 --> 00:28:18.730
But it might not be there particularly long

751
00:28:18.730 --> 00:28:20.410
until it's flung onto a different orbit. The

752
00:28:20.410 --> 00:28:22.490
orbit's constantly being tweaked and changed.

753
00:28:23.450 --> 00:28:25.890
That means that you get these dust trails

754
00:28:25.890 --> 00:28:27.330
that build up over time, but you can even

755
00:28:27.330 --> 00:28:29.050
orphan them. You can take the comet away and

756
00:28:29.050 --> 00:28:30.850
the dust trail remains, which is the case of

757
00:28:30.850 --> 00:28:33.740
some of our meteor showers. It also means,

758
00:28:33.800 --> 00:28:36.300
uh, that when a comet is relatively newly

759
00:28:36.300 --> 00:28:39.260
placed onto a given orbit, that

760
00:28:39.260 --> 00:28:41.300
orbit won't have fully clogged up with dust

761
00:28:41.300 --> 00:28:43.660
yet. So most years when we cross where that

762
00:28:43.660 --> 00:28:45.740
orbit will be, we'll get very few meteors

763
00:28:45.980 --> 00:28:47.820
because the dust just hasn't had time to

764
00:28:47.820 --> 00:28:50.220
spread out yet. But if you catch it on a year

765
00:28:50.220 --> 00:28:52.860
when the comet is relatively nearby, you

766
00:28:52.860 --> 00:28:55.860
might run into dust. The final little

767
00:28:55.860 --> 00:28:57.500
piece of all this puzzle that I'm talking

768
00:28:57.500 --> 00:28:59.300
through is that dust, uh, that was emitted,

769
00:28:59.300 --> 00:29:01.920
uh, at the last few apparitions of the comet

770
00:29:02.320 --> 00:29:04.360
will not have had time to spread out a huge

771
00:29:04.360 --> 00:29:06.760
amount laterally. So you get these almost

772
00:29:06.760 --> 00:29:09.560
like javelins. Very thin, very long

773
00:29:09.560 --> 00:29:12.240
filaments of dust that are much

774
00:29:12.240 --> 00:29:15.040
denser. And if the Earth goes through one of

775
00:29:15.040 --> 00:29:16.479
those, suddenly, you can get a really big

776
00:29:16.479 --> 00:29:18.480
meteor outburst. And, um, instead of getting

777
00:29:18.480 --> 00:29:20.240
one or two meters an hour, you might get

778
00:29:20.240 --> 00:29:23.000
hundreds or thousands. Wow. So that's a

779
00:29:23.000 --> 00:29:24.960
lengthy bit of background exposition to kind

780
00:29:24.960 --> 00:29:26.880
of explain what's happening in the background

781
00:29:26.880 --> 00:29:29.860
here. The Draconig meteor shower is one that

782
00:29:29.860 --> 00:29:32.420
kind of shot to fame in the year, uh, 1933,

783
00:29:32.900 --> 00:29:34.670
when there was an incredible meteor storm,

784
00:29:34.670 --> 00:29:37.380
um, where people saw literally

785
00:29:37.380 --> 00:29:40.220
thousands of meteors per hour. That's more

786
00:29:40.220 --> 00:29:42.740
than one a second raining down,

787
00:29:42.980 --> 00:29:45.140
Absolutely incredibly spectacular.

788
00:29:45.860 --> 00:29:47.620
All radiating out from this point in the

789
00:29:47.620 --> 00:29:48.980
night sky. Near the Northern hemisphere

790
00:29:48.980 --> 00:29:51.780
constellation of Draco. There was a slightly

791
00:29:51.780 --> 00:29:53.660
less spectacular but still very intense

792
00:29:53.660 --> 00:29:55.520
meteor storm from this shower in

793
00:29:55.520 --> 00:29:58.240
1946. And since then,

794
00:29:58.560 --> 00:30:01.240
most years you get two or three meters an

795
00:30:01.240 --> 00:30:02.760
hour from this meteor shower. They're very

796
00:30:02.760 --> 00:30:05.040
slow meteors. They're typically fairly faint

797
00:30:05.040 --> 00:30:07.920
as well. But there's always a little bit

798
00:30:07.920 --> 00:30:10.800
going on. But every six years or so,

799
00:30:11.440 --> 00:30:13.280
the comet comes back to perihelion, and

800
00:30:13.280 --> 00:30:15.080
there's a chance of us getting an outburst.

801
00:30:15.080 --> 00:30:17.400
Now, whether we get one or not depends on the

802
00:30:17.400 --> 00:30:19.200
gravity of all the other planets pulling the

803
00:30:19.200 --> 00:30:20.800
comet's orbit. And these debris streams

804
00:30:20.800 --> 00:30:23.120
around, Sometimes they'll miss us underneath

805
00:30:23.120 --> 00:30:24.720
or they'll miss us above. And we don't run

806
00:30:24.720 --> 00:30:27.680
through them. But it's become an active thing

807
00:30:27.680 --> 00:30:29.240
of trying to figure out what's going to

808
00:30:29.240 --> 00:30:32.040
happen next. Could we ever get another

809
00:30:32.040 --> 00:30:34.960
meteor storm from this shower? Now, we've

810
00:30:34.960 --> 00:30:37.000
had a few outbursts that are not storms, but

811
00:30:37.000 --> 00:30:38.680
are good. A few years ago, there was an

812
00:30:38.680 --> 00:30:40.360
outburst where there were a hundred meters an

813
00:30:40.360 --> 00:30:41.960
hour visible for a couple of hours, which is

814
00:30:41.960 --> 00:30:44.840
a pretty good meteor shower. Yeah. That's

815
00:30:44.840 --> 00:30:47.120
led to, uh, people using this meteor shower

816
00:30:47.120 --> 00:30:49.640
as a really good test bed for how we model

817
00:30:49.640 --> 00:30:52.280
how these things work. Trying to improve our

818
00:30:52.280 --> 00:30:54.440
computer models of how all the dust moves,

819
00:30:54.440 --> 00:30:56.680
where it's all going to be so that we can

820
00:30:56.680 --> 00:30:58.360
predict forward and say what's going to

821
00:30:58.360 --> 00:31:00.720
happen at the next operation. And a paper

822
00:31:00.720 --> 00:31:03.720
came out literally just a couple of days ago

823
00:31:04.600 --> 00:31:07.200
that explored this in some depth it's from

824
00:31:07.200 --> 00:31:09.440
some of the leading meteor astronomers in the

825
00:31:09.440 --> 00:31:12.040
world. Doing modeling of the Draconids. And

826
00:31:12.040 --> 00:31:13.880
what it suggested is that this week,

827
00:31:14.810 --> 00:31:16.650
literally the week that we're recording this.

828
00:31:17.450 --> 00:31:19.490
There is a potential for the Draconis to have

829
00:31:19.490 --> 00:31:22.250
a fairly good outburst. On Wednesday

830
00:31:22.330 --> 00:31:24.730
night. Into Thursday morning Australian time.

831
00:31:24.730 --> 00:31:27.330
So that's around the 8th of November, the

832
00:31:27.330 --> 00:31:29.242
evening of the 8th of November, universal

833
00:31:29.338 --> 00:31:32.090
time, early hours of the morning. 9th, sorry,

834
00:31:32.090 --> 00:31:35.050
October 8th of October, universal time,

835
00:31:35.290 --> 00:31:37.010
early hours of the morning of the 9th of

836
00:31:37.010 --> 00:31:38.250
October, for us here in Australia.

837
00:31:39.940 --> 00:31:41.780
That there'll be a bit of an outburst. Now,

838
00:31:41.780 --> 00:31:44.540
this is probably not going to be an outburst.

839
00:31:44.540 --> 00:31:46.500
That's particularly spectacular visually.

840
00:31:47.140 --> 00:31:49.420
Reason for that is its full Moon. So it

841
00:31:49.420 --> 00:31:51.020
brings us back to the Moon. Getting in our

842
00:31:51.020 --> 00:31:53.620
way and spoiling all of our fun. If the full

843
00:31:53.620 --> 00:31:56.460
Moon wasn't the full Moon. It's likely that

844
00:31:56.460 --> 00:31:58.420
this outburst. Could be somewhere between 30

845
00:31:58.420 --> 00:32:01.180
meters per hour and 100, maybe even 200 per

846
00:32:01.180 --> 00:32:03.500
hour. But the Draconids tend to come in

847
00:32:03.500 --> 00:32:05.220
fairly slow. And they tend to be small, faint

848
00:32:05.220 --> 00:32:07.810
meteors. So almost all of them will be lost

849
00:32:07.810 --> 00:32:10.290
to the naked eye in the moonlight.

850
00:32:10.530 --> 00:32:12.290
Unless they're not, because this is just a

851
00:32:12.290 --> 00:32:14.610
prediction. So something could happen that is

852
00:32:14.610 --> 00:32:17.250
better than we expect. What's most likely to

853
00:32:17.250 --> 00:32:18.810
happen, though, is that, uh, people will see

854
00:32:18.810 --> 00:32:21.410
a few meteors through the moonlight. And that

855
00:32:21.410 --> 00:32:23.090
will tell you there's a lot more going on

856
00:32:23.330 --> 00:32:25.850
than you can see. But the

857
00:32:25.850 --> 00:32:28.530
astronomers doing observations with radar

858
00:32:29.650 --> 00:32:32.410
will see an outburst. And it will probably be

859
00:32:32.410 --> 00:32:34.730
the strongest radar meteor shower of the

860
00:32:34.730 --> 00:32:37.530
year. So these are people almost doing

861
00:32:37.530 --> 00:32:40.170
kind of, uh. Beyond the horizon. Radio

862
00:32:40.170 --> 00:32:41.930
listening. One of the most common ways you

863
00:32:41.930 --> 00:32:44.330
can listen to meteors in radio

864
00:32:44.330 --> 00:32:45.170
wavelengths.

865
00:32:45.330 --> 00:32:48.090
Is to look at an angle low to the

866
00:32:48.090 --> 00:32:50.130
horizon. When you're in a country where there

867
00:32:50.130 --> 00:32:52.570
are, uh, other countries far enough away.

868
00:32:52.570 --> 00:32:55.210
That their radio broadcasts can bounce off

869
00:32:55.210 --> 00:32:57.330
the ionized trails left behind by the meteors

870
00:32:57.330 --> 00:32:59.090
80 kilometers up. And bounce back down to

871
00:32:59.090 --> 00:33:01.650
you. So, obviously, for a lot of places, this

872
00:33:01.650 --> 00:33:03.050
just doesn't work. Because you're looking out

873
00:33:03.050 --> 00:33:05.730
over the ocean. But people in Europe or

874
00:33:05.730 --> 00:33:08.170
people in North America. Quite often there's

875
00:33:08.170 --> 00:33:10.130
a city at about the right distance. It's

876
00:33:10.130 --> 00:33:12.370
quite a big bit of wiggle room. That if

877
00:33:12.370 --> 00:33:14.210
you're pointing your detector roughly in that

878
00:33:14.210 --> 00:33:16.170
direction. Every time there's a meteor.

879
00:33:16.250 --> 00:33:18.850
You'll suddenly get this reflective ionized

880
00:33:18.850 --> 00:33:21.810
trail 80 km up. Radio waves that would

881
00:33:21.810 --> 00:33:23.410
have normally escaped the atmosphere. And

882
00:33:23.410 --> 00:33:25.010
gone on into space. Will bounce off that and

883
00:33:25.010 --> 00:33:26.770
bounce down to you. And you'll get a little

884
00:33:26.770 --> 00:33:29.530
burst of radio noise. And so that means

885
00:33:29.530 --> 00:33:31.930
people can count meteors. And it's likely

886
00:33:31.930 --> 00:33:33.650
that this draconian outburst will be

887
00:33:33.650 --> 00:33:35.210
confirmed not by people looking with the

888
00:33:35.210 --> 00:33:38.070
naked ey, but by people listening with radio

889
00:33:38.070 --> 00:33:40.270
antennas. And they're saying in terms of

890
00:33:40.270 --> 00:33:42.190
radio signals, you could get more than a

891
00:33:42.190 --> 00:33:44.750
thousand per hour. So it could be a fairly

892
00:33:44.750 --> 00:33:47.270
intense outburst, just not one that is really

893
00:33:47.270 --> 00:33:50.070
visible with a naked eye. It's worth flagging

894
00:33:50.070 --> 00:33:52.990
up though, is it's a good insight into how we

895
00:33:52.990 --> 00:33:54.510
do the science of this, that kind of

896
00:33:54.510 --> 00:33:56.950
beautiful interplay of theory and experiment

897
00:33:56.950 --> 00:33:59.110
and observation where we predict something,

898
00:33:59.110 --> 00:34:00.830
we test that prediction, and that allows us

899
00:34:00.830 --> 00:34:02.230
to improve our models to make the next

900
00:34:02.230 --> 00:34:04.350
prediction, prediction even better. But it's

901
00:34:04.350 --> 00:34:06.750
also worth flagging up because the one

902
00:34:06.750 --> 00:34:08.150
prediction you can make is that all

903
00:34:08.150 --> 00:34:10.470
predictions will be wrong. And so while we're

904
00:34:10.470 --> 00:34:12.550
saying that it'll probably be only 40 or 50

905
00:34:12.550 --> 00:34:15.190
per hour or 20 per hour with the naked eye,

906
00:34:15.190 --> 00:34:17.350
and the Moon will hide most of them, you

907
00:34:17.350 --> 00:34:18.990
can't rule out that it'll be better than

908
00:34:18.990 --> 00:34:20.990
that. So if you're up in the early hours of

909
00:34:20.990 --> 00:34:23.670
the morning on Wednesday night into

910
00:34:23.670 --> 00:34:25.550
Thursday morning, it's worth having a bit of

911
00:34:25.550 --> 00:34:27.590
a look. The forecast peak is forecast to be

912
00:34:27.590 --> 00:34:30.510
at 3pm Universal Time, between 3 and 4pm

913
00:34:30.510 --> 00:34:33.170
Universal Time, which is Greenwich Mean Time.

914
00:34:33.250 --> 00:34:35.250
So you can work out from that what time it'll

915
00:34:35.250 --> 00:34:37.250
be for you. For many people it'll be in the

916
00:34:37.250 --> 00:34:39.250
daytime. So sorry, but this time kind of

917
00:34:39.250 --> 00:34:41.250
favors people in East Asia and Australia,

918
00:34:41.410 --> 00:34:44.130
that kind of area. So we might see something,

919
00:34:44.450 --> 00:34:46.290
we might not. But it's worth a look.

920
00:34:46.290 --> 00:34:48.370
Andrew Dunkley: Okie doke. Yeah. Uh, if you want to read

921
00:34:48.370 --> 00:34:50.850
about that, uh, you can do so at the Harvard

922
00:34:51.010 --> 00:34:53.810
Edu website or go to the Arxiv

923
00:34:54.130 --> 00:34:56.930
website where the paper was published. And

924
00:34:57.970 --> 00:34:59.970
I'd read out, I'd read out the whole thing,

925
00:34:59.970 --> 00:35:02.170
but you'll never remember it.

926
00:35:02.570 --> 00:35:04.290
Jonti Horner: I was going to say one thing I should mention

927
00:35:04.290 --> 00:35:07.090
with that is the draconids are best seen from

928
00:35:07.090 --> 00:35:08.930
the northern hemisphere. So if you're in the

929
00:35:08.930 --> 00:35:10.490
southern hemisphere and you want to see this

930
00:35:10.490 --> 00:35:12.410
nearer to the equator, you are the better.

931
00:35:12.810 --> 00:35:15.690
And in reality, I'd say that people south

932
00:35:15.690 --> 00:35:17.250
of the line about at, uh, Brisbane's

933
00:35:17.250 --> 00:35:19.450
latitude, it's not even worth bothering

934
00:35:19.450 --> 00:35:21.170
because the radiant will be so low in the sky

935
00:35:21.170 --> 00:35:23.570
that you will see nothing at all really is

936
00:35:23.570 --> 00:35:24.970
more of a Northern Hemisphere thing. So I

937
00:35:24.970 --> 00:35:26.720
want, you know, want to make sure that we

938
00:35:26.720 --> 00:35:28.400
don't get somebody down in New Zealand going

939
00:35:28.400 --> 00:35:30.680
out looking for it and saying, I saw nothing.

940
00:35:30.680 --> 00:35:32.840
But, well, you saw nothing because you can't

941
00:35:32.840 --> 00:35:34.520
see anything from there. I'm really sorry.

942
00:35:34.600 --> 00:35:36.640
Andrew Dunkley: Yes, that's the way it goes though. That's

943
00:35:36.640 --> 00:35:37.440
the way it goes. Yeah.

944
00:35:37.440 --> 00:35:37.840
Jonti Horner: Yes.

945
00:35:37.840 --> 00:35:40.240
Andrew Dunkley: All right, uh, this is Space Nuts with Andrew

946
00:35:40.240 --> 00:35:42.200
Dunkley and Professor Jonti Horner.

947
00:35:42.760 --> 00:35:43.800
Jonti Horner: Space Nuts.

948
00:35:44.120 --> 00:35:46.960
Andrew Dunkley: All right, let's move on to Uranus and

949
00:35:46.960 --> 00:35:49.320
the Moon. Ariel. This is a really

950
00:35:49.400 --> 00:35:51.800
fascinating story about, uh, what might have

951
00:35:51.800 --> 00:35:54.410
been, uh, in its past. A

952
00:35:54.410 --> 00:35:56.970
hidden ocean on, on a rather small object.

953
00:35:57.530 --> 00:36:00.370
Jonti Horner: It is, and it's part of this ongoing

954
00:36:00.370 --> 00:36:02.250
journey, discovery that we're getting where

955
00:36:02.970 --> 00:36:05.370
fundamentally the kind of world that I grew

956
00:36:05.370 --> 00:36:08.090
up in as a kid excited by astronomy in the

957
00:36:08.090 --> 00:36:10.650
80s and 90s just isn't the same anymore.

958
00:36:10.890 --> 00:36:13.210
I was growing up and the kind of accepted

959
00:36:13.210 --> 00:36:15.570
wisdom was that water was incredibly rare and

960
00:36:15.570 --> 00:36:18.250
liquid water particularly rare, and therefore

961
00:36:18.250 --> 00:36:20.010
life would be uncommon in the cosmos. And

962
00:36:20.010 --> 00:36:21.730
this was one of the kind of centerpieces of

963
00:36:21.730 --> 00:36:24.380
the rare Earth hypothesis, which basically

964
00:36:24.380 --> 00:36:25.900
said don't even bother looking for life

965
00:36:25.900 --> 00:36:27.900
elsewhere because where all there is. And

966
00:36:27.980 --> 00:36:30.420
I've never particularly put much stock in

967
00:36:30.420 --> 00:36:32.860
that idea. But what we've seen in the last 30

968
00:36:32.860 --> 00:36:35.740
years or so is that, uh, water is actually

969
00:36:35.740 --> 00:36:38.660
incredibly more common than people would

970
00:36:38.660 --> 00:36:40.580
have thought. And that's not a surprise. You

971
00:36:40.580 --> 00:36:43.140
know, if you look at, uh, the universe as a

972
00:36:43.140 --> 00:36:45.340
whole, Hydrogen is by far the most common

973
00:36:45.340 --> 00:36:47.780
atom. Oxygen is the third most common atom.

974
00:36:47.780 --> 00:36:49.180
And if you put them together, you get water.

975
00:36:50.190 --> 00:36:52.430
And we see in the after solar system, we see

976
00:36:52.430 --> 00:36:53.990
in the form of these comets we talked about

977
00:36:53.990 --> 00:36:56.950
earlier on. Water ice is incredibly abundant

978
00:36:56.950 --> 00:36:59.910
and in fact of the solid material in the

979
00:36:59.910 --> 00:37:02.870
solar system, water ice is by far the

980
00:37:02.870 --> 00:37:05.150
largest amount of mass of everything.

981
00:37:05.710 --> 00:37:07.750
Once you're out at Jupiter's orbit and

982
00:37:07.750 --> 00:37:09.470
further out, all the icy moons, all the

983
00:37:09.470 --> 00:37:12.010
comets, all the trans neptunian objects are

984
00:37:12.010 --> 00:37:13.950
uh, basically lots of water ice with a bit of

985
00:37:13.950 --> 00:37:16.520
other stuff going on. So solid water is

986
00:37:16.520 --> 00:37:19.280
really common. Liquid water though, people

987
00:37:19.280 --> 00:37:21.080
said, well, we've got a lot of it on Earth,

988
00:37:21.080 --> 00:37:22.640
but elsewhere it's not that common. And then

989
00:37:22.640 --> 00:37:25.400
we found liquid water in Mars as polar caps.

990
00:37:25.400 --> 00:37:27.160
And we've found all these deeply buried

991
00:37:27.640 --> 00:37:30.200
subsurface oceans, the kind of poster child

992
00:37:30.200 --> 00:37:33.080
of which is Europa. And you know, even in the

993
00:37:33.080 --> 00:37:34.640
kind of wonderful films, you know, all these

994
00:37:34.640 --> 00:37:36.720
worlds are yours except Europa. Attempt no

995
00:37:36.720 --> 00:37:38.920
landing there, that whole kind of thing.

996
00:37:39.640 --> 00:37:41.600
So we found all these subsurface oceans and

997
00:37:41.600 --> 00:37:43.240
the more we look, the more we find them.

998
00:37:43.240 --> 00:37:45.320
There was a story earlier this year that the

999
00:37:45.320 --> 00:37:47.180
dwarf planet series in the Ashram asteroid

1000
00:37:47.180 --> 00:37:49.460
belt had a subsurface ocean in the past.

1001
00:37:49.540 --> 00:37:50.020
Yeah.

1002
00:37:50.180 --> 00:37:53.020
And now we come to Ariel. Ariel is one

1003
00:37:53.020 --> 00:37:55.580
of Uranus's moons. And Uranus's moons we got

1004
00:37:55.580 --> 00:37:58.180
some lovely images of, from the Voyager 2

1005
00:37:58.180 --> 00:38:00.740
spacecraft back when, back when I was a wee

1006
00:38:00.740 --> 00:38:02.922
band back in kind of 1985,

1007
00:38:03.078 --> 00:38:05.540
1986 time. Voyager 2

1008
00:38:05.700 --> 00:38:08.180
flew past Uranus as part of its grand tour of

1009
00:38:08.180 --> 00:38:10.820
the outer solar system. And

1010
00:38:10.900 --> 00:38:13.620
as we always say, it flew past faster than a

1011
00:38:13.620 --> 00:38:15.420
speeding bullet. So it didn't have very long

1012
00:38:15.420 --> 00:38:18.270
to hang around and take images. And because

1013
00:38:18.910 --> 00:38:21.750
Uranus is tipped over on its side and

1014
00:38:21.750 --> 00:38:24.110
its moon's orbit above Uranus's equator,

1015
00:38:24.110 --> 00:38:26.110
they're all tipped over on their side. So you

1016
00:38:26.110 --> 00:38:28.910
had basically mid summer at Uranus there.

1017
00:38:28.990 --> 00:38:30.990
And all of these moons had one hemisphere

1018
00:38:30.990 --> 00:38:33.670
illuminated and one hemisphere dark, which

1019
00:38:33.670 --> 00:38:36.030
meant that as Voyager 2 flew through,

1020
00:38:36.510 --> 00:38:38.470
we got all these beautiful pictures of

1021
00:38:38.470 --> 00:38:40.470
Uranus's moons. But for all those moons, we

1022
00:38:40.470 --> 00:38:42.870
only saw one side of them. We saw the

1023
00:38:42.870 --> 00:38:45.030
southern hemisphere illuminated by daylight,

1024
00:38:45.030 --> 00:38:47.570
but we didn't get to see the other side. Uh,

1025
00:38:47.570 --> 00:38:49.380
and we saw these really unusual objects.

1026
00:38:49.380 --> 00:38:51.300
Miranda is kind of the most famous for this,

1027
00:38:51.300 --> 00:38:53.660
which almost looks like somebody's taken a

1028
00:38:53.660 --> 00:38:55.380
moon and smashed it apart with a hammer and

1029
00:38:55.380 --> 00:38:58.180
then rebuilt it haphazardly. You've got all

1030
00:38:58.180 --> 00:38:59.860
these very different features next to each

1031
00:38:59.860 --> 00:39:02.460
other. It looks really odd. Ariel

1032
00:39:02.860 --> 00:39:05.010
is a bit bigger than Miranda and also, um,

1033
00:39:05.300 --> 00:39:07.100
looks really odd. It's got areas on its

1034
00:39:07.100 --> 00:39:09.100
surface that are clearly very, very old.

1035
00:39:09.900 --> 00:39:12.860
They're fairly relatively low albedo, they're

1036
00:39:12.860 --> 00:39:14.540
not that reflective, and they're incredibly

1037
00:39:14.540 --> 00:39:17.460
heavily cratered. But it also has these

1038
00:39:17.460 --> 00:39:19.980
areas that are much more reflective,

1039
00:39:20.540 --> 00:39:23.100
much smoother. They have far fewer craters.

1040
00:39:23.180 --> 00:39:25.340
And they've also got these incredibly large

1041
00:39:25.420 --> 00:39:28.260
canyons, fishering Valley type features on

1042
00:39:28.260 --> 00:39:31.100
them. And, um, again, it looks a very

1043
00:39:32.140 --> 00:39:34.220
odd world, a bit like Miranda. You've got

1044
00:39:34.220 --> 00:39:36.340
very different surfaces relatively close to

1045
00:39:36.340 --> 00:39:38.260
each other that look very different to one

1046
00:39:38.260 --> 00:39:40.300
another geologically. They look like they've

1047
00:39:40.300 --> 00:39:43.280
got very different histories. That's 40 years

1048
00:39:43.280 --> 00:39:44.840
ago. And this is a really good example of

1049
00:39:44.840 --> 00:39:47.760
what we talked about earlier, where data

1050
00:39:47.760 --> 00:39:50.160
from the past continues to have value as our

1051
00:39:50.160 --> 00:39:52.880
tools improve so we can better understand

1052
00:39:52.960 --> 00:39:55.560
it. Because a new result that's come out in

1053
00:39:55.560 --> 00:39:58.160
the last couple of weeks is a result of

1054
00:39:58.560 --> 00:40:01.480
really impressive computer modeling trying to

1055
00:40:01.480 --> 00:40:03.480
figure out what's going on with Arial. Why

1056
00:40:03.480 --> 00:40:05.440
does it look so unusual?

1057
00:40:06.160 --> 00:40:08.840
Typically, when we see smooth surfaces with

1058
00:40:08.840 --> 00:40:11.630
far fewer craters, we consider

1059
00:40:11.630 --> 00:40:14.430
them to be younger because impact craters are

1060
00:40:14.430 --> 00:40:16.270
happening all the time. And so the longer you

1061
00:40:16.270 --> 00:40:18.470
have to be exposed to space, the more craters

1062
00:40:18.470 --> 00:40:20.830
you'll get. Which leads to this kind of

1063
00:40:21.150 --> 00:40:23.670
science of crater counting, where you can

1064
00:40:23.670 --> 00:40:25.550
estimate the edge of a surface by seeing how

1065
00:40:25.550 --> 00:40:27.750
many craters it's got per square kilometer or

1066
00:40:27.750 --> 00:40:30.710
whatever. Yeah. So the fact that

1067
00:40:30.710 --> 00:40:33.510
aerial surface is in places smoother

1068
00:40:33.510 --> 00:40:35.590
and brighter suggests that that surface is

1069
00:40:35.590 --> 00:40:37.200
younger, um, and that there's been

1070
00:40:37.200 --> 00:40:39.920
significant resurfacing there. And the idea

1071
00:40:39.920 --> 00:40:41.920
is that there was probably cryovolcanism,

1072
00:40:41.920 --> 00:40:44.440
where molten water was erupting over the

1073
00:40:44.440 --> 00:40:46.000
surface and then freezing in just the same

1074
00:40:46.000 --> 00:40:48.240
way that molten rock on Earth erupts and then

1075
00:40:48.240 --> 00:40:50.760
sets in volcanic eruptions.

1076
00:40:51.720 --> 00:40:54.720
But that was a bit speculative. What

1077
00:40:54.720 --> 00:40:56.840
this new modeling has done is it's looked at

1078
00:40:56.840 --> 00:40:59.640
the history of the orbit of Ariel and

1079
00:40:59.640 --> 00:41:01.600
suggested that in the past, Ariel's orbit was

1080
00:41:01.600 --> 00:41:03.520
probably a little bit more eccentric than it

1081
00:41:03.520 --> 00:41:05.880
is now. Probably an eccentricity up to about

1082
00:41:05.880 --> 00:41:08.800
0.04, which is a bit more eccentric

1083
00:41:08.800 --> 00:41:10.040
than the orbit of the Earth, but less

1084
00:41:10.040 --> 00:41:12.960
eccentric than the orbit of Mars. On an

1085
00:41:12.960 --> 00:41:15.000
orbit that is just slightly eccentric like

1086
00:41:15.000 --> 00:41:17.040
that. Ariel, which is sandwiched in between

1087
00:41:17.040 --> 00:41:19.600
all these other moons and, um, is near a

1088
00:41:19.600 --> 00:41:21.640
pretty massive planet in the form of Uranus,

1089
00:41:21.960 --> 00:41:23.800
would have been subject to fairly intense

1090
00:41:23.800 --> 00:41:26.680
tidal forces that would have squashed and

1091
00:41:26.680 --> 00:41:29.200
squeezed it. And that's very much

1092
00:41:29.200 --> 00:41:30.840
equivalent to what's happening in the Jupiter

1093
00:41:30.840 --> 00:41:33.720
system with IO and Europa, these

1094
00:41:33.720 --> 00:41:35.240
moons that are squashed and squeezed by

1095
00:41:35.240 --> 00:41:37.840
Jupiter's gravity in the nearby moons, which

1096
00:41:37.840 --> 00:41:39.800
dumps a lot of heat into the interior of

1097
00:41:39.800 --> 00:41:42.320
these moons, keeping them hot, driving

1098
00:41:42.320 --> 00:41:45.080
volcanism, allowing that deeply buried

1099
00:41:45.080 --> 00:41:47.240
ocean in Europa. Uh, well said, deeply

1100
00:41:47.240 --> 00:41:49.720
buried, probably under about 10km of ice to

1101
00:41:49.720 --> 00:41:51.480
stay liquid because it's an internal heat

1102
00:41:51.480 --> 00:41:54.000
source driven by this tidal heating. Yeah.

1103
00:41:54.000 --> 00:41:56.240
What this work has said is that Ariel, too,

1104
00:41:56.720 --> 00:41:59.200
probably had a lot of internal heat from

1105
00:41:59.200 --> 00:42:01.470
tidal heating. It's a big object that's

1106
00:42:01.470 --> 00:42:03.150
primarily made of water ice. And when you

1107
00:42:03.150 --> 00:42:05.870
heat water ice, what happens is it melts. And

1108
00:42:05.870 --> 00:42:07.670
so the idea is that, uh, for a very long

1109
00:42:07.670 --> 00:42:09.390
period of time, probably hundreds of millions

1110
00:42:09.390 --> 00:42:12.030
of years, if not billions of years, buried

1111
00:42:12.030 --> 00:42:13.870
under the surface of Ariel, and possibly even

1112
00:42:13.870 --> 00:42:16.630
relatively shallow at some times, was this

1113
00:42:16.630 --> 00:42:19.310
ocean of liquid water that, again,

1114
00:42:19.630 --> 00:42:21.630
just like Europa, probably contained more

1115
00:42:21.630 --> 00:42:24.270
liquid water than there is on the entirety of

1116
00:42:24.270 --> 00:42:25.150
the planet Earth.

1117
00:42:25.390 --> 00:42:25.870
Andrew Dunkley: Wow.

1118
00:42:26.230 --> 00:42:28.910
Jonti Horner: That water would have behaved like the mantle

1119
00:42:28.910 --> 00:42:31.510
of the Earth, with volcanic eruptions of

1120
00:42:31.510 --> 00:42:34.390
water breaking through cracks in the surface,

1121
00:42:35.270 --> 00:42:37.790
resurfacing these areas of Ariel, giving us

1122
00:42:37.790 --> 00:42:40.670
the clues that we see now, probably

1123
00:42:40.670 --> 00:42:42.590
more than a billion years after this ocean

1124
00:42:42.590 --> 00:42:44.790
for a solid, Ariel's orbit settled down.

1125
00:42:44.950 --> 00:42:47.390
Tidal forces Lessened on, uh, it. It cooled

1126
00:42:47.390 --> 00:42:50.190
down, Everything froze solid. But we're left

1127
00:42:50.190 --> 00:42:52.980
with these fossilized clues that are

1128
00:42:52.980 --> 00:42:55.660
evidence of this much more interesting past,

1129
00:42:55.660 --> 00:42:57.300
potentially when you have this moon with a

1130
00:42:57.300 --> 00:43:00.020
soft central liquid center. Yeah, and it's,

1131
00:43:00.100 --> 00:43:02.140
it's interesting in itself. It's interesting

1132
00:43:02.140 --> 00:43:04.500
because of this interplay between observation

1133
00:43:04.500 --> 00:43:07.140
and theory and, um, how it shows you that

1134
00:43:07.140 --> 00:43:09.860
observations may not bear fruit for

1135
00:43:09.860 --> 00:43:12.100
decades. It might be that the observations we

1136
00:43:12.100 --> 00:43:15.100
make now are not fully understood for 10, 20,

1137
00:43:15.180 --> 00:43:17.620
30 years as our technology and m. Our

1138
00:43:17.620 --> 00:43:19.840
modeling and our theories develop in that

1139
00:43:19.840 --> 00:43:22.440
time. But it's also interesting from the

1140
00:43:22.440 --> 00:43:24.440
whole question of, are we alone in the

1141
00:43:24.440 --> 00:43:27.040
universe? Is there life elsewhere? Because

1142
00:43:27.040 --> 00:43:29.520
it's reminding us that liquid water is much

1143
00:43:29.520 --> 00:43:31.720
more commonplace in the cosmos than we think

1144
00:43:31.720 --> 00:43:34.560
it is now. Finding life on

1145
00:43:34.560 --> 00:43:37.520
buried oceans is challenging

1146
00:43:37.520 --> 00:43:39.040
in the solar system. It's not really

1147
00:43:39.040 --> 00:43:40.800
something that's feasible going forward,

1148
00:43:41.120 --> 00:43:43.800
looking at planets around other stars. But it

1149
00:43:43.800 --> 00:43:45.160
is a reminder that there might be an

1150
00:43:45.160 --> 00:43:47.440
incredible diversity of potential habitats

1151
00:43:47.920 --> 00:43:50.080
for life to become, develop and thrive

1152
00:43:51.040 --> 00:43:53.560
all, all through the solar system, all out

1153
00:43:53.560 --> 00:43:55.840
there in the cosmos, and certainly in the

1154
00:43:55.840 --> 00:43:57.520
solar system. These are the kind of locations

1155
00:43:57.520 --> 00:43:59.640
that we can visit. There's a really growing

1156
00:43:59.640 --> 00:44:02.240
push among, um, planetary scientists that

1157
00:44:02.240 --> 00:44:04.600
Uranus should be the next place to get a

1158
00:44:04.600 --> 00:44:07.600
probe. We've seen incredible

1159
00:44:07.600 --> 00:44:10.440
science done by orbiters like Galileo and

1160
00:44:10.440 --> 00:44:12.760
Juno that went to Jupiter, like cne that went

1161
00:44:12.760 --> 00:44:15.590
Saturn. But for Uranus, we've only seen one

1162
00:44:15.590 --> 00:44:17.750
face of the planet, one face of all its moons

1163
00:44:18.070 --> 00:44:20.710
as we flew through on a drive by,

1164
00:44:20.790 --> 00:44:23.670
essentially. And the argument is,

1165
00:44:23.670 --> 00:44:25.910
if we could send a spacecraft there, that did

1166
00:44:25.910 --> 00:44:28.550
for Uranus what Cassini did for Saturn, what

1167
00:44:29.109 --> 00:44:32.030
Galileo and Juno did for Jupiter. There is

1168
00:44:32.030 --> 00:44:34.030
so much we'd learn. And Uranus is such an

1169
00:44:34.030 --> 00:44:35.870
oddity among the planets with its satellite

1170
00:44:35.870 --> 00:44:38.390
system, with everything all tipped over. It's

1171
00:44:38.390 --> 00:44:40.510
got a very different history to the other

1172
00:44:40.510 --> 00:44:43.510
planets. There's some violent event in

1173
00:44:43.510 --> 00:44:45.590
the past, quite possibly something more

1174
00:44:45.590 --> 00:44:47.230
massive than the Earth, uh, hitting Uranus,

1175
00:44:47.230 --> 00:44:49.270
knocking it over, disrupting the satellite

1176
00:44:49.270 --> 00:44:52.190
system, giving us the moons we see as a

1177
00:44:52.190 --> 00:44:53.910
secondary satellite system. The original

1178
00:44:53.910 --> 00:44:56.270
moons were destroyed, formed a disk of

1179
00:44:56.270 --> 00:44:58.190
material, and new moons formed from them.

1180
00:44:58.430 --> 00:45:00.990
It's a very wonderful narrative

1181
00:45:01.150 --> 00:45:03.510
that is our best explanation for what we see.

1182
00:45:03.510 --> 00:45:05.390
But it may not be the right one. And, um, the

1183
00:45:05.390 --> 00:45:06.790
only way we'll find out, the only way we'll

1184
00:45:06.790 --> 00:45:09.690
learn more about this is to go there, send

1185
00:45:09.690 --> 00:45:12.130
a spacecraft there. So this is

1186
00:45:12.610 --> 00:45:15.210
so exciting for people that it's actually the

1187
00:45:15.210 --> 00:45:18.170
top priority of the planetary science decadal

1188
00:45:18.170 --> 00:45:21.090
plan. In the US Trying to argue for

1189
00:45:21.090 --> 00:45:23.650
funding to build a mission. Now, if that

1190
00:45:23.650 --> 00:45:26.170
mission was approved, it will probably be

1191
00:45:26.170 --> 00:45:28.330
another 20 years before it gets there, uh, if

1192
00:45:28.330 --> 00:45:30.690
not more. And um, that's one of the

1193
00:45:30.690 --> 00:45:32.570
challenges that people face because you are

1194
00:45:32.570 --> 00:45:34.170
dealing with governments that change on

1195
00:45:34.170 --> 00:45:36.970
timescales of three or four years, who

1196
00:45:37.370 --> 00:45:39.450
often seem to have the policy that whatever

1197
00:45:39.450 --> 00:45:41.250
the previous government decided was wrong. So

1198
00:45:41.250 --> 00:45:43.690
therefore we need to cancel it. And you've

1199
00:45:43.690 --> 00:45:45.730
got to navigate those waters to try and get a

1200
00:45:45.730 --> 00:45:48.050
mission to happen where the development alone

1201
00:45:48.050 --> 00:45:50.370
can be 10 or 20 years. So it's really

1202
00:45:50.370 --> 00:45:51.770
challenging, especially in the current

1203
00:45:51.849 --> 00:45:54.530
climate. But the hopes of planetary

1204
00:45:54.530 --> 00:45:57.290
scientists across the world are that at some

1205
00:45:57.290 --> 00:45:59.250
point a mission like this will get approved

1206
00:45:59.250 --> 00:46:00.850
and we'll get to go back there and find out

1207
00:46:00.850 --> 00:46:01.830
what's actually going on.

1208
00:46:02.060 --> 00:46:04.180
Andrew Dunkley: Yes, indeed. But, um, what I'm finding

1209
00:46:04.180 --> 00:46:06.860
fascinating is that, um, the more we look and

1210
00:46:06.860 --> 00:46:09.340
the more information we gather and

1211
00:46:09.340 --> 00:46:11.980
analyze, uh, these ice

1212
00:46:11.980 --> 00:46:14.940
moons, these subsurface ocean moons in

1213
00:46:14.940 --> 00:46:16.780
the outer solar system are starting to become

1214
00:46:17.580 --> 00:46:18.860
the norm really.

1215
00:46:21.420 --> 00:46:23.900
They're identifying more and more of them, or

1216
00:46:23.900 --> 00:46:25.820
at least they're suspicious that some of them

1217
00:46:25.820 --> 00:46:28.020
are there that we weren't thinking about

1218
00:46:28.020 --> 00:46:30.980
before that are starting to show those kinds

1219
00:46:30.980 --> 00:46:33.740
of tendencies. And his is yet another

1220
00:46:33.740 --> 00:46:36.540
one. So, uh, yeah, there's plenty to, to look

1221
00:46:36.540 --> 00:46:39.060
for out, uh, out around that, uh, that

1222
00:46:39.300 --> 00:46:41.860
where the gas giants are and beyond. Really

1223
00:46:41.860 --> 00:46:42.900
fascinating stuff.

1224
00:46:43.540 --> 00:46:46.320
Uh, now finally, let's uh, do this one. Uh,

1225
00:46:46.320 --> 00:46:48.860
asteroids controlled by Venus and what that

1226
00:46:48.860 --> 00:46:50.980
means for Earth, our sister planet, might

1227
00:46:50.980 --> 00:46:53.340
start throwing stuff at us in a few thousand

1228
00:46:53.340 --> 00:46:54.020
years time.

1229
00:46:54.420 --> 00:46:57.220
Jonti Horner: Oh, absolutely. This is a story that's all

1230
00:46:57.220 --> 00:47:00.030
about few objects that have been discovered

1231
00:47:00.030 --> 00:47:02.110
relatively recently that are very, very hard

1232
00:47:02.110 --> 00:47:05.070
to spot that fall under the broad heading

1233
00:47:05.070 --> 00:47:06.910
of near Earth asteroids. They're things

1234
00:47:07.150 --> 00:47:09.390
moving in the inner solar system on unstable

1235
00:47:09.390 --> 00:47:12.030
orbits. And obviously we've seen deep impact,

1236
00:47:12.030 --> 00:47:14.430
we've seen Armageddon. We know that these

1237
00:47:14.430 --> 00:47:16.550
things can pose as a threat. And there's a

1238
00:47:16.550 --> 00:47:19.110
big growing push to find them and to peer

1239
00:47:19.110 --> 00:47:21.310
through the growing numbers of starlink

1240
00:47:21.310 --> 00:47:23.110
satellites that make it harder and harder for

1241
00:47:23.110 --> 00:47:25.050
us to do that. And it's one of the things

1242
00:47:25.050 --> 00:47:26.770
Vera Rubin is going to be great at. Vera

1243
00:47:26.770 --> 00:47:28.410
Rubin is going to be great at everything, to

1244
00:47:28.410 --> 00:47:30.730
be honest. But it'll be fabulous. NEAR EARTH

1245
00:47:30.730 --> 00:47:33.370
ASTEROID FINDING MACHINE but these ones

1246
00:47:33.530 --> 00:47:35.930
are going to be challenging even for Rubin.

1247
00:47:36.170 --> 00:47:38.450
These are asteroids that spend their entire

1248
00:47:38.450 --> 00:47:41.410
orbits closer to the sun than us. I've seen

1249
00:47:41.410 --> 00:47:44.170
them described as apaheel asteroids as their

1250
00:47:44.170 --> 00:47:46.690
family name. These are things where even when

1251
00:47:46.690 --> 00:47:48.250
they're furthest from the sun, they're still

1252
00:47:48.250 --> 00:47:50.520
closer to the sun than we are. And what that

1253
00:47:50.520 --> 00:47:52.840
means is that they're always to some degree

1254
00:47:52.840 --> 00:47:55.400
lost in the Sun's glare. They're hard to

1255
00:47:55.400 --> 00:47:57.840
spot. Now there's a growing

1256
00:47:58.000 --> 00:48:00.080
population of these that have been found that

1257
00:48:00.080 --> 00:48:01.880
are moving, uh, on orbits with a similar

1258
00:48:01.880 --> 00:48:04.680
orbital period to Venus, maybe even trapped

1259
00:48:04.680 --> 00:48:06.720
in one to one resonance with Venus. So they

1260
00:48:06.720 --> 00:48:08.480
complete one lap of the sun in the time it

1261
00:48:08.480 --> 00:48:11.440
takes Venus to complete one lap. And we found

1262
00:48:11.440 --> 00:48:14.400
a few of these. All of the ones we found are

1263
00:48:14.400 --> 00:48:16.160
on relatively eccentric orbits,

1264
00:48:16.160 --> 00:48:18.880
eccentricities of about 0.38 or greater,

1265
00:48:19.450 --> 00:48:21.090
which means that the point at ah, which

1266
00:48:21.090 --> 00:48:23.450
they're furthest from The sun is 38% bigger

1267
00:48:23.450 --> 00:48:25.090
than their mean distance, their semi major

1268
00:48:25.090 --> 00:48:27.210
axis and the point at which they're closest

1269
00:48:27.210 --> 00:48:29.530
to the sun is 38% smaller,

1270
00:48:30.170 --> 00:48:32.290
basically. So if you know the semi major

1271
00:48:32.290 --> 00:48:35.050
axis, call that letter A, the

1272
00:48:35.050 --> 00:48:37.010
distance between these objects and the sun at

1273
00:48:37.010 --> 00:48:39.770
their aphelion, their furthest point is

1274
00:48:39.770 --> 00:48:42.650
equal to 1 plus the eccentricity

1275
00:48:42.890 --> 00:48:45.170
multiplied by semi major axis. So next entry

1276
00:48:45.170 --> 00:48:47.420
of 0.38 gives you

1277
00:48:47.420 --> 00:48:49.860
1.38 times the semi major axis. That's

1278
00:48:49.860 --> 00:48:52.180
basically the way this works out. So what

1279
00:48:52.180 --> 00:48:54.540
that means is if you're on an orbit that is

1280
00:48:55.100 --> 00:48:57.220
a semi major axis, the same as Venus, which

1281
00:48:57.220 --> 00:48:59.540
is a little bit more than 0.7 astronomical

1282
00:48:59.540 --> 00:49:02.300
units, if you have an eccentricity of about

1283
00:49:02.300 --> 00:49:05.220
0.38 or more, you'll get close to the

1284
00:49:05.220 --> 00:49:06.740
Earth's orbit when you're furthest from the

1285
00:49:06.740 --> 00:49:09.060
sun, uh, and that means that you're further

1286
00:49:09.060 --> 00:49:10.980
from the sun in the sky and you're easier to

1287
00:49:10.980 --> 00:49:13.580
find. So we've got an observation bias.

1288
00:49:14.150 --> 00:49:16.030
If we find a lot of objects then in the one

1289
00:49:16.030 --> 00:49:18.030
to one resonance with Venus that are on

1290
00:49:18.030 --> 00:49:20.910
eccentric orbits, we can suggest that

1291
00:49:20.910 --> 00:49:22.430
there are going to be far more of them that

1292
00:49:22.430 --> 00:49:24.390
are not on eccentric orbits because they're

1293
00:49:24.390 --> 00:49:26.510
harder to find. So we're finding the law

1294
00:49:26.510 --> 00:49:29.230
hanging fruit. So the idea is that there is a

1295
00:49:29.230 --> 00:49:31.190
population of hundreds of these objects,

1296
00:49:31.190 --> 00:49:33.790
possibly even thousands of them, m ranging in

1297
00:49:33.790 --> 00:49:35.910
size up to hundreds of meters, maybe even a

1298
00:49:35.910 --> 00:49:38.910
few kilometers in size, that are uh, near

1299
00:49:38.910 --> 00:49:40.630
Earth asteroids that have evolved quite a

1300
00:49:40.630 --> 00:49:42.190
long time in their orbits, moved into the

1301
00:49:42.190 --> 00:49:44.430
inner solar system and bounce down to Venus

1302
00:49:44.750 --> 00:49:46.630
and they're kind of held in a freezer there.

1303
00:49:46.630 --> 00:49:48.470
They're kind of held out of our way in a

1304
00:49:48.470 --> 00:49:51.350
reservoir. Not to be worried about. The

1305
00:49:51.350 --> 00:49:53.550
new work is that people have done some

1306
00:49:53.550 --> 00:49:55.750
orbital simulations of the kind that I do in

1307
00:49:55.750 --> 00:49:58.590
my day. To day life. And um, they've looked

1308
00:49:58.590 --> 00:50:00.190
at what will happen to these things over

1309
00:50:00.190 --> 00:50:01.990
time. Because moving on orbits in the inner

1310
00:50:01.990 --> 00:50:04.150
solar system is an inherently unstable

1311
00:50:04.150 --> 00:50:06.990
situation. You're vulnerable to the

1312
00:50:06.990 --> 00:50:08.510
whims of the gravity of all the other

1313
00:50:08.510 --> 00:50:10.070
planets. And that means your orbit gets

1314
00:50:10.070 --> 00:50:11.750
bounced around, you have close encounters

1315
00:50:11.750 --> 00:50:14.400
with the planets. Um, that means that things

1316
00:50:14.400 --> 00:50:17.080
are not stable in that one to one resonance

1317
00:50:17.080 --> 00:50:18.960
with Venus on really long timescales, they'll

1318
00:50:18.960 --> 00:50:21.840
eventually escape and move around. And what

1319
00:50:21.840 --> 00:50:23.880
this study has shown is that uh, for these

1320
00:50:23.880 --> 00:50:25.880
objects that we currently cannot see, they're

1321
00:50:25.880 --> 00:50:27.960
currently most of them hidden from view.

1322
00:50:29.080 --> 00:50:31.440
They are on orbits that can evolve to become

1323
00:50:31.440 --> 00:50:34.000
Earth crossing once again, maybe even within

1324
00:50:34.000 --> 00:50:36.760
just a few thousand years. And so that this

1325
00:50:36.760 --> 00:50:39.520
is a previously, um, unthought of

1326
00:50:39.520 --> 00:50:42.520
reservoir of potentially hazardous asteroids

1327
00:50:43.160 --> 00:50:45.520
that we can't easily detect with our normal

1328
00:50:45.520 --> 00:50:47.760
methods. And um, that Vera Rubin, with all

1329
00:50:47.760 --> 00:50:50.280
its brilliant abilities will be challenged to

1330
00:50:50.280 --> 00:50:53.080
pick up. And so it's flagging up another

1331
00:50:53.080 --> 00:50:55.360
area of objects that uh, they don't pose a

1332
00:50:55.360 --> 00:50:58.040
threat to us right now. Probably

1333
00:50:58.200 --> 00:50:59.840
there might be some of them on orbits that

1334
00:50:59.840 --> 00:51:01.440
just reach the Earth, so they could do. But

1335
00:51:01.440 --> 00:51:03.400
most of these don't pose an immediate threat,

1336
00:51:03.640 --> 00:51:06.520
but they pose a longer term threat. And the

1337
00:51:06.520 --> 00:51:08.320
kind of, I guess, punchline of all of this is

1338
00:51:08.320 --> 00:51:10.760
that we need to become better, we need to be

1339
00:51:10.760 --> 00:51:12.640
creative and think about how we can find

1340
00:51:12.640 --> 00:51:14.760
asteroids like this are hidden in the sun's

1341
00:51:14.760 --> 00:51:17.720
glare. What we can do in order to try

1342
00:51:17.720 --> 00:51:19.480
and quantify the ones that are there and

1343
00:51:19.480 --> 00:51:20.960
figure out if any of them pose a threat,

1344
00:51:20.960 --> 00:51:23.600
that's kind of their punchline. And I think

1345
00:51:23.600 --> 00:51:26.000
it is just a really great reminder of the

1346
00:51:26.000 --> 00:51:27.840
fact that we always think we now know so

1347
00:51:27.840 --> 00:51:30.280
much, we know so much more than we used to

1348
00:51:30.280 --> 00:51:31.840
do. And you always have this niggling

1349
00:51:32.130 --> 00:51:34.130
impression at the back of your mind that our

1350
00:51:34.130 --> 00:51:35.810
knowledge is almost complete. There are no

1351
00:51:35.810 --> 00:51:37.850
surprises still to come. And that's just not

1352
00:51:37.850 --> 00:51:40.170
the case. Uh, part of the reason that I love

1353
00:51:40.170 --> 00:51:41.650
science, part of the reason that most

1354
00:51:41.650 --> 00:51:44.010
scientists still do their job is not because

1355
00:51:44.010 --> 00:51:45.490
we know everything, but because we know

1356
00:51:45.490 --> 00:51:47.929
nothing. We still got so much more to learn.

1357
00:51:47.929 --> 00:51:49.890
And it's the surprises, it's the unknowns

1358
00:51:49.890 --> 00:51:51.410
that really motivate people and get people

1359
00:51:51.410 --> 00:51:53.570
excited. And this is just a really good

1360
00:51:53.570 --> 00:51:55.410
example of that, that here's all these

1361
00:51:55.410 --> 00:51:57.850
objects that uh, we weren't even talking

1362
00:51:57.850 --> 00:52:00.030
about 10 years ago that are a potential

1363
00:52:00.030 --> 00:52:01.630
threat to us and we need to learn more about

1364
00:52:01.630 --> 00:52:03.950
them. How do we do that? And that will drive

1365
00:52:03.950 --> 00:52:05.630
technology and exploration in the years to

1366
00:52:05.630 --> 00:52:05.870
come.

1367
00:52:05.870 --> 00:52:08.230
Andrew Dunkley: Yes, indeed. And, uh, if we've got a few

1368
00:52:08.230 --> 00:52:10.750
thousand years of wiggle room before it

1369
00:52:10.750 --> 00:52:12.950
starts throwing rocks at us, we may be able

1370
00:52:12.950 --> 00:52:15.790
to put probes out there to monitor it

1371
00:52:16.510 --> 00:52:18.990
and get those early warnings. So we may

1372
00:52:18.990 --> 00:52:21.110
develop the technology to, uh, defend

1373
00:52:21.110 --> 00:52:23.790
ourselves down the track. But if you want to

1374
00:52:23.790 --> 00:52:26.590
read about that, uh, the paper is available

1375
00:52:26.670 --> 00:52:28.870
through, uh, Astronomy and Astrophysics, the

1376
00:52:28.870 --> 00:52:31.500
journal, or you can look at it on the

1377
00:52:31.500 --> 00:52:34.460
space.com website. Fascinating

1378
00:52:34.460 --> 00:52:37.260
stuff. And Jonti, thanks for joining us.

1379
00:52:37.260 --> 00:52:39.520
Great to have you back for a few weeks and,

1380
00:52:39.520 --> 00:52:41.380
uh, we'll catch you on the next episode.

1381
00:52:41.700 --> 00:52:42.380
Jonti Horner: Look forward to it.

1382
00:52:42.380 --> 00:52:43.940
Thanks for having me back, professor, uh.

1383
00:52:44.380 --> 00:52:46.780
Andrew Dunkley: Jonti Horner, professor of Astrophysics at

1384
00:52:46.780 --> 00:52:48.780
the University of Southern Queensland. Thanks

1385
00:52:48.780 --> 00:52:51.140
to him. And I, uh, would have thanked Huw in

1386
00:52:51.140 --> 00:52:53.140
the studio, but he forgot to set his clock

1387
00:52:53.140 --> 00:52:54.660
forward for daylight saving in New South

1388
00:52:54.660 --> 00:52:56.620
Wales yesterday and couldn't join us. And

1389
00:52:56.620 --> 00:52:58.260
from me, Andrew Dunkley, thanks for your

1390
00:52:58.260 --> 00:53:00.300
company. See you on the next episode of Space

1391
00:53:00.300 --> 00:53:03.050
Nuts. Until then, bye bye. Uh,

1392
00:53:03.340 --> 00:53:05.540
you'll be listening to the Space Nuts

1393
00:53:05.540 --> 00:53:08.140
podcast, available

1394
00:53:08.220 --> 00:53:10.540
at Apple Podcasts, Spotify,

1395
00:53:10.700 --> 00:53:13.460
iHeartRadio or your favorite podcast

1396
00:53:13.460 --> 00:53:13.820
player.

1397
00:53:13.900 --> 00:53:16.780
Jonti Horner: You can also stream on demand@bytes.com.

1398
00:53:17.180 --> 00:53:19.260
Andrew Dunkley: This has been another quality podcast

1399
00:53:19.260 --> 00:53:21.340
production from sites.um com.