The Black Hole Discovery Revealing the Loudest Gravitational Wave Ever Recorded

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Andrew Dunkley: Hello there. Thanks for joining us. This is

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Space Nuts, where we talk astronomy and

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space science. My name is Andrew Dunkley.

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Great to have your company on this, the

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600 millionth episode. Maybe not that many,

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but we've done quite a few. What is it,

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643 we're up to? Blimey.

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All right, uh, what are we talking about?

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We're talking about, um, an old clapped out,

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uh, telescope. Fred Watson happens to be its

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patron. He's old and clapped out too. Uh,

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we're also going to look, uh, at

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a new black hole discovery which was made

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after, um, two black holes

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collided and they recorded the loudest crash

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of gravitational waves ever. So

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what's it going to tell us? Also, uh, China

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is going to upgrade its space station and

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launch a new space telescope. And a

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star that got close to our sun

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may have caused a bit of a disturbance in the

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force. We'll tell you all about it on this

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episode of space nuts.

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Professor Fred Watson: 15 seconds. Guidance is internal.

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10, 9. Ignition

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sequence.

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Andrew Dunkley: Star.

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Professor Fred Watson: Uh, space nuts. 5, 4, 3, 2. 1.

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2, 3, 4, 5, 5, 4, 3, 2,

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1.

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Andrew Dunkley: Space nuts. Astronauts report it feels

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good. And he's back again. As always,

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it's Professor Fred Watson Watson, astronomer

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at large. Hello, Fred Watson.

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Professor Fred Watson: Hello, Andrew. Hello. Uh, thank you for that

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nice introduction. It's, uh,

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nice to hear welcome like that.

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Andrew Dunkley: You know, I know I only said it a few seconds

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ago, but I forgot what I said. And then it

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dawned on me that I'd actually insulted.

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Professor Fred Watson: Yes. Oh, forget about that. Yeah, no, that's

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all right, that's all right. You're right.

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Andrew Dunkley: Last week.

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Professor Fred Watson: I am old and clapped out. There's no question

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about that.

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Andrew Dunkley: Aren't we all, Aren't we all?

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Um, now, um, before we get into, uh,

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today's storeys, um, the old clapped out

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telescope I referred to is actually a, uh,

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wonderful device, uh, that I've actually seen

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in person when we were down in Melbourne a

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few years ago. Uh, it's the

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Melbourne telescope. Dates back to

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1869. And you're its patron because you

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were there when they put the first screw in

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it. Got you again.

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Professor Fred Watson: Yeah. So the link and the reason why I'm.

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Well, there's a number of reasons why this

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telescope is very close to my heart. One is

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that, uh, I was

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still at school when I found a picture of it

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in Henry King's History of the Telescope, a

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very famous book, uh, on the history of

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telescopes, published, I think in 1955.

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Had a copy of that in the school library. And

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there's this telescope there, the Great

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Melbourne Telescope. And I thought that is.

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That is a telescope. That's what I want one

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like looks.

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Andrew Dunkley: It just looks like you'd expect one to

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look, doesn't it?

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Professor Fred Watson: You can tell it's a telescope. It's got um.

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With decorative bits like the latticework

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tube, which is uh, very unusual, almost

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unique. Anyway, that was my first

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um, encounter with it. Uh, and as

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sort of followed up as much as I could. A

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didn't realise that by then it was actually

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uh, in Canberra at Matt Stromlo. It had been

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refurbished, um, having left Melbourne in

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1944. But, uh,

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100 years

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exactly after work started on

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the manufacture of that telescope in

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1867, 100 years later I

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joined the company that built it.

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So it was uh, its 20th

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century equivalent. It was uh, Howard

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Grubb, Dublin when, uh, the telescope was

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built. By the time I got there it was sir,

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uh, Howard Grubb Parsons Co. Ltd. But

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it was basically the same company amalgamated

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in 1926 with the Parsons company. So,

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um, I continued my kinship with that

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telescope and uh, uh, of course when I came

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to Australia, was interested to see it at

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stromlo. Then in 2003,

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uh, the Stromlo Observatory had that terrible

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fire, bush fire that went through, destroyed

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all the heritage buildings, including the one

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that uh, that telescope sat in,

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uh, and basically melted a lot of

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the. Well, melted the dome onto the

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telescope. The dome was aluminium, uh, and

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the telescope was wrecked, its mirror was

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smashed and all the rest of it. Uh, so I,

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When I. So I wrote a book on the history of

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telescopes which was published I think

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just after that fire because,

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um, I wrote at the end I had a whole chapter

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on this telescope and I wrote something to

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the effect that uh. The best we could hope to

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see would for it to be a static

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exhibit in a museum, just the remnants.

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Uh, but it was for a while. Well it wasn't.

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No, it stayed put in Stromlo. And it was five

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years after the fire, 2008, when this

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consortium of museums, uh, Victoria,

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the Astronomical Society of Victoria, uh,

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Royal Botanic Gardens, Melbourne, because

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that's where it started its career. Uh,

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uh, and uh. I think the Bureau of Meteorology

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were involved as well. Uh, and they

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got together a plan to basically

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restore it. Uh, and

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so I uh, did play a role in that. In

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2015 we actually held

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a workshop which I chaired, which was about

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how you could update the optics of the

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telescope because the mechanical stuff could

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be refurbished. Uh, but the

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optics were a different matter. Uh, and a uh,

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sort of optical prescription was drawn up.

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Now Those optics are still in the process of

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being manufactured. Uh, but

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the telescope itself is now

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essentially mechanically complete. It is

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as complete as it was when it was built.

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And the work that's been done, more than 100

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volunteers and staff from Museums

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Victoria and the Astronomical Society of

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Victoria, well over a hundred have worked on

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it. And so last, uh, week there was a little

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party to celebrate that. And,

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uh, some of the museum's dignitary said a few

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words, I said a few words. The chap who's

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been leading the project, Simon Brink over

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the last few years, he said a few words. He's

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actually coming to lunch with us on Saturday.

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Oh, lovely. Even though he's in Melbourne,

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he's coming up, um, which is nice.

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Um, so we had a celebration and, uh,

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to be honest, what they've done is nothing

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short of miraculous because there weren't any

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diagrams of all the bits and pieces of this

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telescope. There were engineering diagrams of

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the thing complete. They were published in a

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journal. But the individual parts and

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probably thousands of

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components, screws, washers,

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uh, pulleys, cog wheels of various

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different sized, all of that. No

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idea what they looked like. And by

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scouring photographs of the telescope, uh,

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from many sources and

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working out things like the numbers of teeth

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you need on a cogwheel to make the things

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work properly, uh, they've done a great job

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with all that. And now it's in basically in

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perfect working order, except it doesn't have

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its main mirror yet that's being fabricated.

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Um, it's at the moment still at

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Scienceworks, which is the Science M Museum

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in Victoria. And it's a big exhibit which is

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Andrew Dunkley: worth a visit, especially with the kids.

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Professor Fred Watson: Yeah, it's a great place to go. Uh, and

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anybody, uh, who does go to Melbourne and

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sees scienceworks definitely have a look at

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the great Melbourne telescope. The hope is

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that one day it will be in its original

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building, which still exists in the Royal

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Botanic Gardens. Uh, but, um, there's quite a

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bit of work needs to be done to make

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that, uh, oh, s. Uh,

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satisfactory for 2026

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or whenever it happens, compared with

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the, um, you know, the health and safety

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regulations in 1869 when people came and

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went, um, just had a look through the

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telescope. That's the idea that it will

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eventually be a working telescope for the

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public for people to come and look through.

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Andrew Dunkley: Wonderful. And, uh, if you can't get down to

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see it in Melbourne, uh, just do a search for

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the Melbourne telescope online and have a

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look at it and you'll know what we're talking

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about, um, the lattice work is just

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beautiful. It is a glorious piece of

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equipment. And I stumbled across it. I

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didn't even know it was at Science Works when

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we went there. And we just went for a wander

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and found it. And I went, oh, Fred Watson

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will love this. And then it turns out you

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were the patron, so.

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Professor Fred Watson: Yes, that's right. Yeah. Yeah. It's um,

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it is, uh, it's quite staggering.

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It's how big it is, isn't it? When you.

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Andrew Dunkley: Oh yeah.

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Professor Fred Watson: Just when you.

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Andrew Dunkley: It blows your mind.

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Professor Fred Watson: Yes.

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Andrew Dunkley: You just stand there in awe.

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Professor Fred Watson: Telescope. It was the biggest fully

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steerable telescope in the world at the time

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when, um, it was built. It wasn't the

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biggest, but it was. Biggest telescope in the

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world. But it wasn't far off.

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Andrew Dunkley: Yeah. As a good friend of mine often says,

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it's a great piece of kit.

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Professor Fred Watson: It was a great piece of kit. And hopefully it

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will be again one day.

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Andrew Dunkley: Fingers crossed.

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All right, uh, moving on. We're talking black

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holes. Very unusual. We don't usually talk

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things like this, but, uh, this, this is an

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interesting one because they, They've uh,

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made it a bit of a discovery. They've.

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They've recorded the loudest crash of

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gravitational waves ever heard. And it was

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because of two black holes that

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decided, uh, to play billiards with each

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other and boom. Uh, but

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it's what they've discovered from the. In the

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aftermath of all this that's getting

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interesting.

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Professor Fred Watson: Uh, yes, it is. Um, so,

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yep, we black, um, gravitational waves

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from colliding objects have been detectable

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by humans since 2015,

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um, with uh, the LIGO

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Laser Interferometer Gravitational Wave

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Observatory in America. And that now works

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with, uh, virgo, which is an

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Italian, uh, uh, gravitational wave

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observatory, and kagra, which is the

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Kamioka Gravitational Wave Detector in

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Japan. So those three telescopes work

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together to pick up the vibrations of space,

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uh, which are, uh, transmitted from very

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distant collisions usually. And it's usually

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neutron stars and black holes, uh, with

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collisions between either neutron stars and

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neutron stars or black holes and black holes,

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or neutron stars and black holes. Um,

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those all produce gravitational wave signals

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that are actually in the frequency range

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detectable by uh, these telescopes.

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Because that's a key part of it. The amount

258
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of energy that's involved tells, uh, you what

259
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the frequency of the gravitational waves is

260
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going to be. And as we've noted

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before, Andrew, it's curious that, um,

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the gravitational waves that these telescopes

263
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are sensitive to are actually in the audio

264
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frequency regime. They're basically. If you

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just amplified them, uh, you would have an

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audio signal. And that's basically what they

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do, except they're doing it in a very much

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more sophisticated way. Um,

269
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um. The amount of, um,

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shaking of space that they can

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detect is

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absolutely infinitesimal. Uh, but

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these things are sensitive enough that they

274
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can measure a distance that is a

275
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thousandth, I think it's a 10,000th actually,

276
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of the diameter of a proton. Uh, that's

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the accuracy with which they can measure the

278
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distance between two mirrors, which is how

279
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you do all this sort of thing. So that's the

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backstory. Uh, the up storey,

281
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the forward storey. Is that

282
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an object or you don't have an object,

283
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you have a gravitational wave signal. Uh, it

284
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rejoices in the name of

285
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GW25014.

286
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Uh, that tells you that it was picked up, um,

287
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in January, uh, 2025. Uh,

288
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that's where the 25011 comes

289
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from. Um. Uh, and it,

290
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uh, basically, uh, on

291
00:11:56.870 --> 00:11:59.310
analysis, um, has

292
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been, uh, detected to be

293
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a collision between two black holes, each

294
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of which had, uh, around 32 times the

295
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mass of the sun until they collided. And

296
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that set, uh, you know, set the

297
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gravitational waves on their way because it

298
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basically disturbed space, it rippled space.

299
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So what's happened is. And this, as you

300
00:12:23.780 --> 00:12:25.380
mentioned at the beginning, is the loudest

301
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gravitational wave signal that's been

302
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detected, or certainly the most, uh,

303
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intense. The, um, highest amplitude one.

304
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Andrew Dunkley: Yeah.

305
00:12:33.130 --> 00:12:35.540
Professor Fred Watson: Um, so what has happened

306
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is, uh, that researchers, uh, have

307
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analysed the audio signal,

308
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um, and they found in it, um,

309
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basically that it's been described as a

310
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feature, uh, which is uh, something

311
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called a direct wave. It's

312
00:12:53.130 --> 00:12:55.770
a component of the signal, uh,

313
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and it's a direct wave, uh, that

314
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has not. That's been seen before,

315
00:13:01.810 --> 00:13:04.769
but hasn't. Nobody's worked out what it

316
00:13:04.769 --> 00:13:07.570
is, but apparently it

317
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is a feature that

318
00:13:09.890 --> 00:13:12.850
essentially, uh. In

319
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the gravitational wave structure that comes

320
00:13:15.250 --> 00:13:18.200
from this event, you can tell this

321
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direct wave is to do with

322
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the event horizon of the combined

323
00:13:24.080 --> 00:13:26.680
black holes. So you've got two black

324
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holes, each of which has got its own event

325
00:13:29.400 --> 00:13:31.840
horizon. They're spinning around one another,

326
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getting ever closer, as we've seen that sort

327
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of thing before. And the frequency goes up of

328
00:13:36.680 --> 00:13:39.280
the gravitational waves, um, and then

329
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suddenly it all stops because they've

330
00:13:42.200 --> 00:13:44.520
collided and there's no more accelerations,

331
00:13:44.520 --> 00:13:46.760
which is what you need, uh, to set up

332
00:13:46.760 --> 00:13:49.660
gravitational waves. Um, but,

333
00:13:49.870 --> 00:13:52.620
uh, at that point the two, um,

334
00:13:52.860 --> 00:13:55.420
gravitate, sorry, the two event horizons

335
00:13:55.420 --> 00:13:55.980
merge.

336
00:13:56.880 --> 00:13:59.500
Uh, now, a recap on event horizons. That's

337
00:13:59.500 --> 00:14:01.740
the point of no return. Basically,

338
00:14:02.460 --> 00:14:04.620
it's the distance from the black hole,

339
00:14:05.180 --> 00:14:07.660
uh, where the escape velocity

340
00:14:08.320 --> 00:14:11.060
uh, is more than the speed of

341
00:14:11.060 --> 00:14:14.060
light. And so nothing can escape from

342
00:14:14.060 --> 00:14:16.470
within the event horizon. Uh, and in

343
00:14:16.470 --> 00:14:18.230
particular light can't escape. So the event

344
00:14:18.230 --> 00:14:20.230
horizon is black. It's a sphere around the

345
00:14:20.230 --> 00:14:22.510
black hole, uh, through which you can't see

346
00:14:22.510 --> 00:14:24.190
because nothing escapes, including light.

347
00:14:25.230 --> 00:14:28.150
So um, that is what the event horizon

348
00:14:28.150 --> 00:14:30.820
is. In a sense it's imaginary. Uh, uh,

349
00:14:30.820 --> 00:14:33.550
Andrew, you know it's not a real surface,

350
00:14:33.550 --> 00:14:35.870
it's an imaginary surface because it's just

351
00:14:35.870 --> 00:14:38.510
the boundary between what's visible and

352
00:14:38.510 --> 00:14:41.070
what's not visible.

353
00:14:41.550 --> 00:14:44.380
Now we know when black holes

354
00:14:44.380 --> 00:14:47.260
collide. Uh, I don't know that

355
00:14:47.260 --> 00:14:49.660
much about the details of these things but

356
00:14:49.660 --> 00:14:52.500
there is a period immediately after

357
00:14:52.500 --> 00:14:54.500
they've merged which is called the ring down.

358
00:14:54.900 --> 00:14:57.340
And it's a time when they sort of

359
00:14:57.340 --> 00:15:00.340
consolidate as one black hole. And that

360
00:15:00.340 --> 00:15:03.340
means their event horizons also consolidate.

361
00:15:03.340 --> 00:15:06.140
And I think this direct wave that has been

362
00:15:06.140 --> 00:15:08.180
detected is basically

363
00:15:09.290 --> 00:15:12.170
uh, an artefact of that ring

364
00:15:12.170 --> 00:15:14.320
down. Uh, and so um,

365
00:15:15.450 --> 00:15:18.130
what I guess is uh, perhaps the

366
00:15:18.130 --> 00:15:20.730
takeaway message from this work is not

367
00:15:21.210 --> 00:15:24.010
that we've learned something miraculous

368
00:15:24.010 --> 00:15:26.330
and new about the event horizon

369
00:15:26.730 --> 00:15:28.770
but that we've learned that there might be a

370
00:15:28.770 --> 00:15:31.130
way of, in future

371
00:15:31.130 --> 00:15:34.050
gravitational wave events uh, might be

372
00:15:34.050 --> 00:15:36.930
a way of analysing these direct waves to give

373
00:15:36.930 --> 00:15:39.530
us more information on the black hole

374
00:15:39.940 --> 00:15:42.380
event horizon. Because at the moment we don't

375
00:15:42.380 --> 00:15:45.060
know much about it. We've seen them

376
00:15:45.460 --> 00:15:48.140
in the telescopes, you know the

377
00:15:48.140 --> 00:15:50.220
um, observations from the Event Horizon

378
00:15:50.220 --> 00:15:53.140
Telescope that um, amalgam of many radio

379
00:15:53.140 --> 00:15:55.620
telescopes, an Earth sized array,

380
00:15:56.100 --> 00:15:58.780
uh, which has been used to look at the black

381
00:15:58.780 --> 00:16:01.140
holes in centre of our own galaxy. And in

382
00:16:01.140 --> 00:16:03.950
M57 I think it was uh, with um,

383
00:16:05.280 --> 00:16:08.230
uh fairly high degree of

384
00:16:08.230 --> 00:16:10.510
precision. What we've seen is the black

385
00:16:10.510 --> 00:16:13.430
shadow of the event horizon. Um

386
00:16:13.590 --> 00:16:15.830
but perhaps with these gravitational waves,

387
00:16:15.910 --> 00:16:18.750
these direct waves there might be a ah,

388
00:16:18.830 --> 00:16:21.789
way of teasing out even more detail from

389
00:16:21.789 --> 00:16:24.310
these distant and highly enigmatic

390
00:16:24.310 --> 00:16:24.950
objects.

391
00:16:25.030 --> 00:16:27.270
Andrew Dunkley: Yes, indeed. And uh, another interesting

392
00:16:27.270 --> 00:16:29.190
thing that comes out of this storey is that

393
00:16:29.270 --> 00:16:31.950
um, they're suggesting uh, the

394
00:16:31.950 --> 00:16:34.800
measurements that uh, that they've

395
00:16:34.800 --> 00:16:37.080
made could be a step towards

396
00:16:38.120 --> 00:16:40.920
future um, tests of general relativity

397
00:16:41.960 --> 00:16:44.720
using direct waves. So you know there's all

398
00:16:44.720 --> 00:16:46.520
sorts of potential by the sound of it.

399
00:16:46.760 --> 00:16:49.740
Professor Fred Watson: That's right, yeah. I mean exactly. And uh,

400
00:16:49.880 --> 00:16:52.280
of course this is one of the holy grails of

401
00:16:52.920 --> 00:16:55.000
science generally actually certainly physics

402
00:16:55.000 --> 00:16:57.680
to find chinks in general relativity

403
00:16:57.680 --> 00:17:00.570
because uh, at the moment it behaves

404
00:17:00.570 --> 00:17:02.570
exactly as predicted. Everything that we've

405
00:17:02.570 --> 00:17:05.300
seen in the universe Follows, uh,

406
00:17:05.730 --> 00:17:07.490
the rules and regulations of general

407
00:17:07.490 --> 00:17:10.370
relativity, uh, in a perfect way.

408
00:17:11.010 --> 00:17:13.850
So maybe, uh, direct waves will, as you

409
00:17:13.850 --> 00:17:16.210
said, uh, give us a way of testing general

410
00:17:16.210 --> 00:17:19.170
relativity. If we find, um, things

411
00:17:19.170 --> 00:17:22.050
that don't work in general relativity, then

412
00:17:22.050 --> 00:17:23.970
that could be an opening into new physics,

413
00:17:23.970 --> 00:17:26.010
which is certainly a hot topic at the moment.

414
00:17:26.560 --> 00:17:28.680
Andrew Dunkley: Indeed it is. Uh, well, uh, everyone,

415
00:17:28.680 --> 00:17:30.640
including Einstein, thinks something's wrong

416
00:17:30.640 --> 00:17:32.520
with it. They just. Yes, they just can't find

417
00:17:32.520 --> 00:17:34.880
anything at the moment. It keeps coming up

418
00:17:35.280 --> 00:17:37.120
aces every time they test it.

419
00:17:37.280 --> 00:17:38.920
Professor Fred Watson: Yeah, they think something's wrong with it

420
00:17:38.920 --> 00:17:41.080
because it doesn't sit with quantum

421
00:17:41.080 --> 00:17:43.640
mechanics. The two are incompatible and they

422
00:17:43.640 --> 00:17:46.120
both work perfectly well, but they're

423
00:17:46.120 --> 00:17:46.960
incompatible.

424
00:17:48.480 --> 00:17:49.280
Andrew Dunkley: Weird, isn't it?

425
00:17:49.280 --> 00:17:50.720
Professor Fred Watson: Yes, that's very weird. Yeah.

426
00:17:50.720 --> 00:17:52.560
Andrew Dunkley: The other thing that I find fascinating about

427
00:17:52.560 --> 00:17:55.240
this Storey, is that from something as simple

428
00:17:55.240 --> 00:17:57.930
as a, as a gravitational wave,

429
00:17:57.930 --> 00:18:00.770
they're able to break it down and find

430
00:18:00.770 --> 00:18:02.610
information that is

431
00:18:04.690 --> 00:18:07.650
really just. You can't

432
00:18:07.650 --> 00:18:10.130
see any of this. It's all just data, isn't

433
00:18:10.130 --> 00:18:10.330
it?

434
00:18:10.330 --> 00:18:12.290
Professor Fred Watson: Yeah, yeah, that's correct. That's right.

435
00:18:12.290 --> 00:18:14.770
But, uh, the physics is well understood

436
00:18:14.770 --> 00:18:17.090
because general relativity is such a reliable

437
00:18:17.570 --> 00:18:19.930
tool for people to use to analyse these

438
00:18:19.930 --> 00:18:22.370
things. Um, that's how we can make these

439
00:18:22.980 --> 00:18:25.940
statements about it. And yes, um, if we can

440
00:18:25.940 --> 00:18:27.900
find flaws with general relativity, it will

441
00:18:27.900 --> 00:18:30.740
be very exciting indeed it will.

442
00:18:30.740 --> 00:18:33.580
Andrew Dunkley: And you can read all about it@the space.com

443
00:18:33.580 --> 00:18:35.780
website. Uh, they publish their research,

444
00:18:36.370 --> 00:18:39.340
uh, in the journal Nature. This

445
00:18:39.340 --> 00:18:41.860
is Space Nuts with Andrew Dunkley and

446
00:18:41.940 --> 00:18:43.780
Professor Fred Watson Watson.

447
00:18:45.780 --> 00:18:47.820
Professor Fred Watson: I believe that this nation should commit

448
00:18:47.820 --> 00:18:50.050
Andrew Dunkley: itself to achieving the goal,

449
00:18:50.690 --> 00:18:53.610
before this decade is out, of landing a

450
00:18:53.610 --> 00:18:53.810
man

451
00:18:53.810 --> 00:18:56.170
Professor Fred Watson: on the moon and returning him safely to the

452
00:18:56.170 --> 00:18:56.490
Earth.

453
00:18:56.490 --> 00:18:57.330
Andrew Dunkley: These nuts.

454
00:18:58.210 --> 00:19:01.130
Now, Fred Watson, we turn our, uh, attention

455
00:19:01.130 --> 00:19:03.730
towards China. Uh, of course, they've got a

456
00:19:03.970 --> 00:19:06.930
very active space station in operation

457
00:19:06.930 --> 00:19:09.490
at the moment. Uh, the latest news though is

458
00:19:09.490 --> 00:19:12.170
that they intend to, uh, make it

459
00:19:12.170 --> 00:19:14.530
bigger and at the same time they're going to

460
00:19:14.530 --> 00:19:17.190
put a new space telescope into, uh, into

461
00:19:17.190 --> 00:19:19.270
orbit as well. So, uh, they're really going

462
00:19:19.270 --> 00:19:20.950
ahead in leaps and bounds, aren't they?

463
00:19:21.750 --> 00:19:24.110
Professor Fred Watson: They are, yes. Uh, it's, um. You know, this

464
00:19:24.110 --> 00:19:26.630
is part of the Chinese. It's not the China

465
00:19:26.630 --> 00:19:29.260
national, uh, Space Agency.

466
00:19:29.260 --> 00:19:31.350
Uh, I think it's that they've got a separate

467
00:19:31.909 --> 00:19:34.550
space agency for human space flight.

468
00:19:35.040 --> 00:19:37.630
Uh, and that's the organisation that

469
00:19:37.630 --> 00:19:40.550
operates the Tiangong, uh, space Station,

470
00:19:40.550 --> 00:19:43.310
which has been up there since 2021, I think

471
00:19:43.310 --> 00:19:45.980
was when, uh, we started seeing it being

472
00:19:45.980 --> 00:19:48.500
assembled. It was assembled in a very similar

473
00:19:48.500 --> 00:19:50.700
manner to the International Space Station by

474
00:19:51.020 --> 00:19:54.020
building sort of modules that you can stick

475
00:19:54.020 --> 00:19:57.020
together like Lego, uh, up once

476
00:19:57.120 --> 00:19:58.780
uh, these modules are in orbit.

477
00:19:58.940 --> 00:20:01.020
Andrew Dunkley: Yeah. And at the moment it's the China

478
00:20:01.020 --> 00:20:03.820
National Space Administration which handles

479
00:20:03.820 --> 00:20:06.060
the programmes, and the China Manned Space

480
00:20:06.060 --> 00:20:08.380
Agency which um, oversees human

481
00:20:08.380 --> 00:20:09.100
spaceflight.

482
00:20:09.740 --> 00:20:12.100
Professor Fred Watson: That's right. I knew there were two

483
00:20:12.100 --> 00:20:13.980
organisations involved. Thank you for that.

484
00:20:14.140 --> 00:20:14.700
Andrew Dunkley: That's all right.

485
00:20:15.060 --> 00:20:17.670
Professor Fred Watson: Um, so, uh,

486
00:20:17.670 --> 00:20:20.380
yes, so uh, at the moment the,

487
00:20:20.380 --> 00:20:22.700
the Tiangong consists of three

488
00:20:22.780 --> 00:20:25.780
modules and they're arranged in a sort of T

489
00:20:25.780 --> 00:20:27.780
shape, uh, with um.

490
00:20:28.560 --> 00:20:30.940
Uh, two, three. The, the three

491
00:20:31.740 --> 00:20:33.740
end points of the modules if you like,

492
00:20:33.740 --> 00:20:36.020
coming, coming together in a, in a sort of

493
00:20:36.020 --> 00:20:38.420
vestibule where you can uh, tunnel your way

494
00:20:38.420 --> 00:20:40.940
from one to the, to the other with these

495
00:20:41.380 --> 00:20:43.570
uh, basically entry and exit hatches. That

496
00:20:43.900 --> 00:20:46.330
uh, is the way things work on the

497
00:20:46.330 --> 00:20:48.890
International Space Station as well. But as

498
00:20:48.890 --> 00:20:51.130
you've said, uh, what they're now planning to

499
00:20:51.130 --> 00:20:53.490
do is to add three more

500
00:20:53.490 --> 00:20:56.490
modules. Um and the reason they

501
00:20:56.490 --> 00:20:59.470
want to do that is because uh,

502
00:20:59.810 --> 00:21:02.370
they want to do more research up there,

503
00:21:02.980 --> 00:21:05.970
uh, and make more frequent crew and

504
00:21:05.970 --> 00:21:08.930
cargo changes. Um, so they're

505
00:21:08.930 --> 00:21:11.930
actually, I think the way to deal

506
00:21:11.930 --> 00:21:14.170
with that is to make the space station

507
00:21:14.170 --> 00:21:17.170
bigger. Um, and so it's going to be

508
00:21:17.330 --> 00:21:20.210
what they're calling a double T shape, which

509
00:21:20.210 --> 00:21:22.290
I think is probably an H shape

510
00:21:23.410 --> 00:21:25.610
if I can put it that way. Um, well that's

511
00:21:25.610 --> 00:21:25.969
what it.

512
00:21:25.969 --> 00:21:27.570
Andrew Dunkley: Yeah, it would turn into that, wouldn't it?

513
00:21:27.570 --> 00:21:29.970
Professor Fred Watson: You'd expect so. Yes, that's right. Unless

514
00:21:29.970 --> 00:21:32.970
they do something clever, uh, like turn

515
00:21:32.970 --> 00:21:35.730
one of the T's round, uh right angles to the

516
00:21:35.730 --> 00:21:37.770
other one. Anyway, we don't know what's going

517
00:21:37.770 --> 00:21:40.220
to happen there. But um, there is a new

518
00:21:40.780 --> 00:21:43.180
multipurpose um, module and two

519
00:21:43.500 --> 00:21:46.220
new experimental modules that are planned

520
00:21:46.530 --> 00:21:49.200
uh, to um, essentially uh,

521
00:21:49.340 --> 00:21:51.980
you know, allow Chinese

522
00:21:52.230 --> 00:21:54.820
uh, space exploration in low Earth

523
00:21:54.820 --> 00:21:57.660
orbit to continue and be extended.

524
00:21:58.450 --> 00:22:01.020
Um, um, we understand from

525
00:22:01.320 --> 00:22:03.740
um, some of the researchers in China

526
00:22:04.300 --> 00:22:07.290
that uh, it's always been

527
00:22:07.640 --> 00:22:10.170
uh, an expectation that this

528
00:22:10.250 --> 00:22:12.490
would take place, that there'd be this

529
00:22:12.490 --> 00:22:15.330
extension. Uh, and what it will do in

530
00:22:15.330 --> 00:22:18.250
terms of the mass of the um, space

531
00:22:18.250 --> 00:22:20.610
station is take it up from its current 90

532
00:22:20.610 --> 00:22:22.810
tonnes, uh up to

533
00:22:23.690 --> 00:22:26.650
180 tonnes or thereabouts. And there's a

534
00:22:26.650 --> 00:22:28.570
yardstick, if I remember rightly, and you

535
00:22:28.570 --> 00:22:30.530
might be able to correct me here Andrew, but

536
00:22:30.530 --> 00:22:32.370
I think the International Space station is

537
00:22:32.370 --> 00:22:34.890
about 400 tonnes in terms of its mass.

538
00:22:35.530 --> 00:22:38.190
I think that is the case. So uh,

539
00:22:38.310 --> 00:22:41.190
that's uh, the plan and

540
00:22:41.430 --> 00:22:44.270
alongside that, as you've already mentioned

541
00:22:44.270 --> 00:22:46.870
Andrew, is the idea of a new

542
00:22:47.630 --> 00:22:50.270
um, space observatory, an optical

543
00:22:50.270 --> 00:22:53.069
Telescope quite similar in some

544
00:22:53.069 --> 00:22:55.550
ways to the Hubble Space Telescope. A

545
00:22:55.550 --> 00:22:58.150
slightly smaller mirror, 2 metres rather than

546
00:22:58.150 --> 00:22:59.350
2.3 metres,

547
00:23:01.110 --> 00:23:03.950
um, and also with a much wider

548
00:23:03.950 --> 00:23:06.830
field of view. The Hubble has quite a narrow

549
00:23:06.830 --> 00:23:09.490
field of view. Uh, and in fact the Nancy

550
00:23:09.490 --> 00:23:12.370
Grace Roman telescope, which is also very

551
00:23:12.370 --> 00:23:14.930
similar to the Hubble, will have a much wider

552
00:23:14.930 --> 00:23:16.690
field of view than Hubble. That's being

553
00:23:16.690 --> 00:23:18.610
launched later this year, I hope.

554
00:23:19.170 --> 00:23:21.650
Um, this, uh, Chinese

555
00:23:21.650 --> 00:23:24.570
telescope, uh, which has a name, Shuntian,

556
00:23:24.570 --> 00:23:27.450
I think, is probably how it's

557
00:23:27.450 --> 00:23:30.210
pronounced in my,

558
00:23:30.230 --> 00:23:32.850
um, poor Chinese, uh, poor

559
00:23:32.850 --> 00:23:34.530
Mandarin and poor Chinese.

560
00:23:35.690 --> 00:23:38.690
Um, it's got a much bigger field of view and

561
00:23:38.690 --> 00:23:41.690
will actually give new, uh,

562
00:23:41.690 --> 00:23:43.750
surveys to Chinese, uh,

563
00:23:44.200 --> 00:23:46.400
astronomers. We'll see a lot more

564
00:23:46.880 --> 00:23:48.720
information about the universe coming from

565
00:23:48.720 --> 00:23:50.320
this telescope. The more telescopes you've

566
00:23:50.320 --> 00:23:52.650
got on the universe, the better. And, uh,

567
00:23:52.720 --> 00:23:55.690
Shuntian will be one of those, uh,

568
00:23:55.690 --> 00:23:58.560
features when it is launched and actually

569
00:23:58.640 --> 00:24:01.320
commissioned, uh, that will, we hope, um,

570
00:24:01.440 --> 00:24:04.200
really bring new insights into our knowledge

571
00:24:04.200 --> 00:24:04.640
of space.

572
00:24:04.880 --> 00:24:07.440
Andrew Dunkley: Yeah. Apparently its field of view

573
00:24:07.680 --> 00:24:10.520
is going to be massive compared to

574
00:24:10.520 --> 00:24:12.160
Hubble at 300 times.

575
00:24:12.480 --> 00:24:14.920
Professor Fred Watson: Correct? Yes, that's right. So it's a wide

576
00:24:14.920 --> 00:24:17.320
angle telescope rather than the sort of

577
00:24:17.320 --> 00:24:19.360
pinpoint view of the Hubble.

578
00:24:19.520 --> 00:24:21.800
Andrew Dunkley: Yeah, quite incredible. Uh, you were right

579
00:24:21.800 --> 00:24:23.940
about the International space station. Uh,

580
00:24:23.940 --> 00:24:26.720
419,700 kilogrammes

581
00:24:26.720 --> 00:24:29.680
is its mass, or say 420,

582
00:24:30.760 --> 00:24:33.720
um, tonnes. Yes, indeed. Um, the

583
00:24:33.720 --> 00:24:35.720
other interesting thing that China's working

584
00:24:35.720 --> 00:24:38.000
on, uh, is a new,

585
00:24:38.160 --> 00:24:41.130
um, um, delivery system for their. They

586
00:24:41.130 --> 00:24:42.610
call them taika nauts, don't they?

587
00:24:42.850 --> 00:24:44.210
Professor Fred Watson: Yes, they do, yeah.

588
00:24:44.860 --> 00:24:46.450
Andrew Dunkley: Uh, they want to. They want to develop a

589
00:24:46.450 --> 00:24:49.370
rocket system that will send seven up at a

590
00:24:49.370 --> 00:24:49.650
time.

591
00:24:49.650 --> 00:24:52.650
Professor Fred Watson: Yes, yeah, seven up.

592
00:24:52.650 --> 00:24:55.570
Andrew Dunkley: No, I'm joking. But, um, again, yeah, that's

593
00:24:55.570 --> 00:24:57.130
what they're looking at doing at the moment.

594
00:24:57.130 --> 00:24:58.690
They can only send up three at a time.

595
00:24:59.170 --> 00:25:01.460
Professor Fred Watson: Yes. So the Chinese, um,

596
00:25:02.300 --> 00:25:04.130
uh, orbital

597
00:25:04.980 --> 00:25:07.300
vehicle for getting astronauts up,

598
00:25:07.380 --> 00:25:09.220
Taikonauts up there. And

599
00:25:10.180 --> 00:25:11.740
I'm ashamed that I can't remember what it's

600
00:25:11.740 --> 00:25:13.700
called. Uh, is it Shenzhou?

601
00:25:14.100 --> 00:25:16.980
Shenzhou, I can't remember. Um,

602
00:25:16.980 --> 00:25:19.780
but that is basically an adaptation

603
00:25:20.340 --> 00:25:22.420
of the old Soyuts Russian

604
00:25:22.580 --> 00:25:25.020
spacecraft which is still in service in the

605
00:25:25.020 --> 00:25:26.780
International Space Station. Developed in the

606
00:25:26.780 --> 00:25:29.460
1960s. A, uh, three person,

607
00:25:29.820 --> 00:25:32.660
uh, module. Uh, I think I'm right in

608
00:25:32.660 --> 00:25:34.860
saying that the crew Dragon can take up to

609
00:25:34.860 --> 00:25:36.910
seven astronauts as well.

610
00:25:36.990 --> 00:25:38.830
Andrew Dunkley: Interesting. Shenzhou.

611
00:25:38.990 --> 00:25:40.070
Professor Fred Watson: Shenzhou, yeah.

612
00:25:40.070 --> 00:25:41.830
Andrew Dunkley: Is the, um, is the system they

613
00:25:41.830 --> 00:25:42.670
Professor Fred Watson: used at the moment.

614
00:25:43.230 --> 00:25:45.400
You did m. So, uh,

615
00:25:46.110 --> 00:25:48.430
yes. So that will go from three to seven.

616
00:25:48.670 --> 00:25:50.870
It's understandable, you know, if you Want to

617
00:25:50.870 --> 00:25:52.870
keep the crews coming and going. I think this

618
00:25:52.870 --> 00:25:54.750
is a really important development because,

619
00:25:55.410 --> 00:25:58.230
um, if nothing else, it's going to, I

620
00:25:58.230 --> 00:26:00.060
think, spur, uh,

621
00:26:01.080 --> 00:26:03.760
the private sector, um, to pick up the

622
00:26:03.760 --> 00:26:06.360
baton of what you might call Western

623
00:26:06.520 --> 00:26:08.880
International Space Stations or the Western

624
00:26:08.880 --> 00:26:11.040
International Space Station, because that's

625
00:26:11.040 --> 00:26:13.800
scheduled at the moment to be decommissioned

626
00:26:13.800 --> 00:26:16.640
in 2030. That might change. But

627
00:26:16.640 --> 00:26:18.920
it's a possibility that we will lose the ISS

628
00:26:19.160 --> 00:26:22.160
in 2030. And we've seen problems

629
00:26:22.160 --> 00:26:24.960
with the leakage that we had in one of the

630
00:26:24.960 --> 00:26:27.760
modules a couple of weeks ago where the

631
00:26:27.760 --> 00:26:30.440
crew was evacuated, not evacuated, but

632
00:26:30.440 --> 00:26:32.670
moved. The American crew,

633
00:26:33.230 --> 00:26:35.900
uh, the NASA end of the spacecraft

634
00:26:35.900 --> 00:26:38.820
were moved into a crew Dragon capsule

635
00:26:38.820 --> 00:26:41.700
to uh, just be certain that

636
00:26:41.700 --> 00:26:44.530
nothing untoward was going to happen, uh,

637
00:26:44.530 --> 00:26:47.260
if there was a catastrophic

638
00:26:47.260 --> 00:26:49.940
leak, uh, when the Roscosmos,

639
00:26:50.100 --> 00:26:52.220
cosmonauts, they were actually trying to fix

640
00:26:52.220 --> 00:26:54.420
the leak, uh, they moved the other crew,

641
00:26:55.230 --> 00:26:57.940
um, into the crew Dragon capsule for safety.

642
00:26:58.020 --> 00:27:00.690
Andrew Dunkley: Yeah, uh, in terms of replacing the iss,

643
00:27:01.570 --> 00:27:04.210
there are no firm plans at the moment, but

644
00:27:04.450 --> 00:27:06.770
they're kind of thinking about,

645
00:27:07.320 --> 00:27:09.810
um, I think you mentioned it, the commercial

646
00:27:09.810 --> 00:27:11.010
sector getting involved.

647
00:27:12.770 --> 00:27:14.850
And that's probably logical.

648
00:27:15.570 --> 00:27:18.290
I'm pretty sure that, uh, Elon would be

649
00:27:18.290 --> 00:27:21.010
pretty keen to put a space station into orbit

650
00:27:21.010 --> 00:27:23.730
and a few others probably.

651
00:27:23.730 --> 00:27:25.480
There's plenty of people around with uh,

652
00:27:25.480 --> 00:27:26.670
megabucks to do it.

653
00:27:27.300 --> 00:27:30.140
Professor Fred Watson: Yes, that's right. Um, um, but, uh, you

654
00:27:30.140 --> 00:27:32.180
know, you might think, have to think

655
00:27:32.180 --> 00:27:35.180
carefully about whether you, uh, take

656
00:27:35.180 --> 00:27:37.940
over the old, uh, the old tired

657
00:27:38.580 --> 00:27:41.360
and quite dodgy old, uh,

658
00:27:41.620 --> 00:27:43.340
International Space Station or whether you

659
00:27:43.340 --> 00:27:46.060
build something new. Um, and uh, of course

660
00:27:46.060 --> 00:27:47.940
the technology's moved on enormously since

661
00:27:47.940 --> 00:27:50.660
the 1990s when that was put together.

662
00:27:50.820 --> 00:27:53.740
It's been continuously occupied since

663
00:27:53.740 --> 00:27:56.600
2000. Uh, that's 26

664
00:27:56.600 --> 00:27:59.240
years of, um, tenants coming and going. It's

665
00:27:59.240 --> 00:28:01.080
probably taken a fair beating inside.

666
00:28:01.240 --> 00:28:03.000
Andrew Dunkley: Yeah, I'm sure they've had a few parties.

667
00:28:03.000 --> 00:28:04.280
Yeah, no doubt about it.

668
00:28:06.130 --> 00:28:08.430
Uh, if you want to uh, read all about, uh,

669
00:28:08.440 --> 00:28:09.840
China's plans, you can do

670
00:28:09.840 --> 00:28:12.640
that@space.com. uh, this is

671
00:28:12.640 --> 00:28:14.960
Space Nuts with Andrew Dunkley and Professor

672
00:28:14.960 --> 00:28:15.720
Fred Watson Watson.

673
00:28:18.360 --> 00:28:21.080
Space Nuts, our final

674
00:28:21.080 --> 00:28:23.320
storey. Fred Watson takes us close to home.

675
00:28:23.480 --> 00:28:26.440
And this is really quite a fascinating storey

676
00:28:26.520 --> 00:28:29.300
because it talks about a star, not

677
00:28:29.300 --> 00:28:32.220
our sun. Ah, another star that got

678
00:28:32.220 --> 00:28:35.140
up close and personal, um, with

679
00:28:35.140 --> 00:28:38.060
our particular, uh, sun, um, a

680
00:28:38.060 --> 00:28:40.780
little while ago. But the

681
00:28:40.780 --> 00:28:42.820
effects of that interaction,

682
00:28:43.780 --> 00:28:45.860
uh, seem to still exist,

683
00:28:46.580 --> 00:28:47.700
which is very odd.

684
00:28:47.860 --> 00:28:50.500
Professor Fred Watson: Yeah, well, that's right. Uh, yes, it is,

685
00:28:50.500 --> 00:28:53.430
it's an interesting storey. It covers two

686
00:28:53.430 --> 00:28:55.750
quite different bits of astronomy here that

687
00:28:55.750 --> 00:28:57.990
come together to sort of work out what was

688
00:28:57.990 --> 00:29:00.750
going on. So this star in question,

689
00:29:01.230 --> 00:29:02.910
it's got the glorious name of

690
00:29:02.910 --> 00:29:05.670
HD7977. HD

691
00:29:05.670 --> 00:29:07.390
stands for Henry Draper. It's one of the

692
00:29:07.390 --> 00:29:09.910
early star catalogues, uh, from the 19th

693
00:29:09.910 --> 00:29:12.590
century I think, uh, the Henry Draper

694
00:29:12.590 --> 00:29:15.390
catalogue. Uh, and it's a relatively

695
00:29:15.390 --> 00:29:18.150
near star, similar to the

696
00:29:18.150 --> 00:29:20.860
sun. Uh, it's currently in the constellation

697
00:29:20.860 --> 00:29:23.660
of Cassiopeia, which is um, one of my

698
00:29:23.660 --> 00:29:25.300
favourite northern constellations. Actually.

699
00:29:25.300 --> 00:29:27.820
It's one that we don't see from down here in

700
00:29:27.820 --> 00:29:30.740
Australia. Uh, so,

701
00:29:30.930 --> 00:29:33.540
um, how do we know that

702
00:29:33.540 --> 00:29:36.250
HD7977 had um,

703
00:29:36.420 --> 00:29:39.060
a near miss with our solar system?

704
00:29:39.540 --> 00:29:42.380
And the answer is with the Gaia mission.

705
00:29:42.380 --> 00:29:45.380
So Gaia is a spacecraft. Uh,

706
00:29:45.540 --> 00:29:47.790
it sits at the um, uh,

707
00:29:48.890 --> 00:29:51.650
sun, Earth, uh, L2 point, that's

708
00:29:51.650 --> 00:29:54.170
the Lagrange point, on the opposite side of

709
00:29:54.170 --> 00:29:56.890
the Earth from the sun. Um, it's been

710
00:29:57.130 --> 00:29:59.570
working for, I think, certainly more than a

711
00:29:59.570 --> 00:30:02.410
decade. And what it's done is measured

712
00:30:02.490 --> 00:30:05.210
star positions with absolutely

713
00:30:05.210 --> 00:30:07.850
exquisite precision. Uh, you're talking

714
00:30:07.850 --> 00:30:10.210
about, I think it's sort of some

715
00:30:10.210 --> 00:30:12.890
accuracies in the region of 100 millionths of

716
00:30:12.890 --> 00:30:15.180
an arc second. These are phenomenal

717
00:30:15.660 --> 00:30:17.900
accuracies. And an arc second of course is

718
00:30:17.900 --> 00:30:20.600
1-3600th of a degree, uh,

719
00:30:20.620 --> 00:30:23.500
the size of a, here In Australia, a $1 coin

720
00:30:23.500 --> 00:30:25.700
held up at five kilometres. It's a tiny

721
00:30:25.700 --> 00:30:27.900
angle, but this thing's measuring

722
00:30:28.620 --> 00:30:30.620
millionths of that basically, or 100

723
00:30:30.620 --> 00:30:33.500
millions. Uh, and what that does is it

724
00:30:33.500 --> 00:30:35.940
allows you, if you make these measurements at

725
00:30:35.940 --> 00:30:38.500
different times, it allows you to plot the

726
00:30:38.500 --> 00:30:41.210
motions of stars,

727
00:30:41.530 --> 00:30:44.410
uh, not just in our own galaxy and in our own

728
00:30:44.410 --> 00:30:46.890
neighbourhood, but also in the Two

729
00:30:46.890 --> 00:30:49.450
Magellanic Clouds, uh, the two

730
00:30:49.450 --> 00:30:52.250
nearest neighbour dwarf galaxies, the big

731
00:30:52.250 --> 00:30:54.690
ones, Large and Small Magellanic Clouds

732
00:30:54.690 --> 00:30:57.490
165 and 200,000 light

733
00:30:57.490 --> 00:31:00.250
years away respectively. Uh, those,

734
00:31:00.490 --> 00:31:02.850
uh, you can detect the motions of stars in

735
00:31:02.850 --> 00:31:05.810
those galaxies. And even in the Andromeda

736
00:31:05.810 --> 00:31:08.250
galaxy, about 2 1/2 million light years away,

737
00:31:08.250 --> 00:31:10.770
you can see evidence of what we call lateral

738
00:31:10.770 --> 00:31:13.110
motion on the sky, sideways motion of things.

739
00:31:13.190 --> 00:31:15.870
And if you can measure the radial velocity,

740
00:31:15.870 --> 00:31:18.110
that's the velocity along the line of sight,

741
00:31:18.110 --> 00:31:20.430
which is actually much easier if you can do

742
00:31:20.430 --> 00:31:22.910
that as well. You've got, um, the three

743
00:31:22.910 --> 00:31:25.550
dimensional motion of objects in space. And

744
00:31:25.550 --> 00:31:27.570
that is how, uh,

745
00:31:28.070 --> 00:31:30.830
HD7977 was picked

746
00:31:30.830 --> 00:31:33.270
up as having passed close to the sun

747
00:31:33.750 --> 00:31:36.390
about two and a half million years ago.

748
00:31:37.030 --> 00:31:39.150
As both these stars, The sun and

749
00:31:39.150 --> 00:31:42.030
HD7977, as they both orbit around the

750
00:31:42.030 --> 00:31:44.970
centre of our galaxy. Uh, we still

751
00:31:44.970 --> 00:31:47.970
don't know exactly how close. Uh, the data

752
00:31:47.970 --> 00:31:50.290
from Gaia suggests It was between

753
00:31:50.850 --> 00:31:53.250
4,000 and 25,000

754
00:31:53.330 --> 00:31:55.970
astronomical units. And as we've mentioned

755
00:31:55.970 --> 00:31:57.930
before, an astronomical unit is the distance

756
00:31:57.930 --> 00:32:00.770
between the Earth and the sun. Um, convenient

757
00:32:00.770 --> 00:32:03.730
measure it is uh, 150 million kilometres.

758
00:32:04.310 --> 00:32:06.210
Um, they may have

759
00:32:07.050 --> 00:32:09.930
um, we might be able to

760
00:32:09.930 --> 00:32:12.890
tie that close approach down though by other

761
00:32:12.890 --> 00:32:15.610
methods. And the methods in question

762
00:32:16.090 --> 00:32:19.050
have been employed by uh, some

763
00:32:19.050 --> 00:32:21.370
scientists at the University of

764
00:32:21.370 --> 00:32:24.330
Bordeaux. Uh, and basically

765
00:32:24.410 --> 00:32:27.410
what they have done is looked not

766
00:32:27.410 --> 00:32:30.010
at Gaia data to try and refine

767
00:32:30.450 --> 00:32:33.210
uh, this sort of look back in

768
00:32:33.210 --> 00:32:35.810
time as to when these two stars were close

769
00:32:35.810 --> 00:32:38.090
together. They've looked at long period

770
00:32:38.090 --> 00:32:40.890
comets, comets that uh, come in

771
00:32:40.890 --> 00:32:43.250
from the very furthest reaches of the solar

772
00:32:43.250 --> 00:32:45.820
system where we think there is a

773
00:32:45.820 --> 00:32:47.940
reservoir of comets. We call it the Oort

774
00:32:47.940 --> 00:32:50.820
Cloud. Uh, and it turns out that

775
00:32:50.820 --> 00:32:53.060
if you look at long period comets,

776
00:32:53.620 --> 00:32:56.540
uh, which have been measured over the

777
00:32:56.540 --> 00:32:59.540
past hundred years I guess, um, then

778
00:32:59.540 --> 00:33:02.100
you get uh, an idea

779
00:33:02.580 --> 00:33:04.820
of the distribution of their orbits.

780
00:33:05.620 --> 00:33:08.620
And basically there's a quote here

781
00:33:08.620 --> 00:33:11.460
from one of the authors uh, of

782
00:33:11.460 --> 00:33:14.420
the paper that we're talking about uh, who

783
00:33:14.420 --> 00:33:16.340
says the distribution of comet orbits

784
00:33:16.340 --> 00:33:18.800
suggests we living through an unusual time

785
00:33:19.280 --> 00:33:21.800
where HD 7977 has

786
00:33:21.800 --> 00:33:24.560
dominated the generation of new comets

787
00:33:25.040 --> 00:33:27.480
and not the larger gravitational field of the

788
00:33:27.480 --> 00:33:30.080
Milky Way as it usually would. This would

789
00:33:30.080 --> 00:33:31.800
also mean we're living through the late

790
00:33:31.800 --> 00:33:34.640
stages of a pretty rare and powerful

791
00:33:34.640 --> 00:33:37.360
comet shower. And so what they've done

792
00:33:37.360 --> 00:33:40.170
is made computer simulations of uh,

793
00:33:40.560 --> 00:33:43.440
how comet orbits might behave

794
00:33:44.080 --> 00:33:46.760
as a result of being tipped out of the Oort

795
00:33:46.760 --> 00:33:49.500
cloud by the passage of this star HD

796
00:33:49.500 --> 00:33:52.420
7977. They've kicked out the Oort cloud

797
00:33:52.420 --> 00:33:54.780
and heading towards the sun. Uh, they've

798
00:33:54.780 --> 00:33:57.620
measured uh, basically the details of

799
00:33:57.620 --> 00:34:00.500
112 long period comets. Actually they've

800
00:34:00.500 --> 00:34:02.420
chosen ones that have only been observed in

801
00:34:02.420 --> 00:34:05.020
recent years, since 1989 because

802
00:34:05.420 --> 00:34:08.260
that's when we could detect comets coming

803
00:34:08.260 --> 00:34:11.040
from uh, any part of the sky. Uh,

804
00:34:11.500 --> 00:34:13.660
if you only limit yourself to one part of the

805
00:34:13.660 --> 00:34:16.020
sky then you've got uh, as visible for

806
00:34:16.020 --> 00:34:18.700
example by a single observatory, uh, or even

807
00:34:18.700 --> 00:34:20.460
as visible by the Northern Hemisphere

808
00:34:20.460 --> 00:34:23.180
observatory. You're missing uh,

809
00:34:23.180 --> 00:34:25.480
half the objects that you want to see. And

810
00:34:25.480 --> 00:34:27.360
since what you're doing is looking at the

811
00:34:27.360 --> 00:34:29.760
statistical distribution of these things, you

812
00:34:29.760 --> 00:34:32.600
can't afford to um, eliminate

813
00:34:32.600 --> 00:34:34.720
things that way. It's what would be called a

814
00:34:34.720 --> 00:34:37.680
selection effect. Um, so yes these

815
00:34:37.680 --> 00:34:40.120
long period comets they've got very elongated

816
00:34:40.120 --> 00:34:43.120
Orbits, uh, and the suggestion is that the

817
00:34:43.120 --> 00:34:46.000
distribution of those orbits in relation to

818
00:34:46.000 --> 00:34:47.400
the direction that we know

819
00:34:47.640 --> 00:34:50.560
HD7977 went through the solar system or

820
00:34:50.560 --> 00:34:53.259
went close to the solar system. Uh, that's

821
00:34:53.259 --> 00:34:56.019
why they believe, uh, that the two

822
00:34:56.019 --> 00:34:58.659
events, uh, um, the close

823
00:34:58.739 --> 00:35:01.700
passage of 7977, uh,

824
00:35:01.939 --> 00:35:04.939
tipped up the comets and caused a lot more of

825
00:35:04.939 --> 00:35:07.819
these comets to come in. And if you

826
00:35:07.819 --> 00:35:10.790
accept uh, their hypothesis,

827
00:35:10.790 --> 00:35:13.459
um, then what it does is,

828
00:35:13.459 --> 00:35:16.179
ties down rather

829
00:35:16.179 --> 00:35:18.819
better the distance that we estimate

830
00:35:19.219 --> 00:35:21.750
HD7977, uh,

831
00:35:22.259 --> 00:35:25.040
approach the sun at somewhere

832
00:35:25.040 --> 00:35:28.000
between 6,000 and 10,000 astronomical units.

833
00:35:28.240 --> 00:35:30.880
A tighter window compared with the 4,000 to

834
00:35:30.880 --> 00:35:33.360
25,000 astronomical units that Gaia

835
00:35:33.440 --> 00:35:36.400
suggests. Yes, uh, so, uh, it's a nice

836
00:35:36.400 --> 00:35:38.320
tightening up of our uh, understanding of

837
00:35:38.320 --> 00:35:41.080
this hypothesised but probably

838
00:35:41.080 --> 00:35:43.360
real event 2 1/2 million years ago.

839
00:35:43.600 --> 00:35:45.640
Andrew Dunkley: And just to give people a bit of an idea of

840
00:35:45.640 --> 00:35:48.120
the distance, so somewhere between 6 and

841
00:35:48.120 --> 00:35:50.000
10,000 AU is where

842
00:35:50.000 --> 00:35:52.840
HD7977 and kind

843
00:35:52.840 --> 00:35:54.560
of grazed our uh, solar system.

844
00:35:54.560 --> 00:35:55.000
Professor Fred Watson: Yes.

845
00:35:55.320 --> 00:35:57.560
Andrew Dunkley: Voyager 1 is 170

846
00:35:57.800 --> 00:36:00.280
AU from Earth. So

847
00:36:00.600 --> 00:36:02.120
we're talking a fair way out.

848
00:36:02.120 --> 00:36:03.560
Professor Fred Watson: It's a long way off. That's right.

849
00:36:04.040 --> 00:36:06.080
Andrew Dunkley: You're talking probably getting into the

850
00:36:06.080 --> 00:36:08.360
vicinity of the Oort cloud, which makes sense

851
00:36:08.360 --> 00:36:11.280
given what they're hypothesising in

852
00:36:11.280 --> 00:36:11.880
this paper.

853
00:36:12.680 --> 00:36:15.440
Professor Fred Watson: Exactly right. So a star passing nearby the

854
00:36:15.440 --> 00:36:18.360
Oort cloud would definitely upset it and

855
00:36:18.360 --> 00:36:20.770
send stuff in towards the, the inner solar

856
00:36:20.770 --> 00:36:23.610
system. Yes, it's actually um, it's a theory

857
00:36:23.610 --> 00:36:25.930
that, uh, that general mechanism

858
00:36:26.410 --> 00:36:28.610
was proposed by colleagues of mine in the

859
00:36:28.610 --> 00:36:30.370
Royal Observatory in Edinburgh, Victor Klub

860
00:36:30.370 --> 00:36:32.730
and Bill Napier, back in the late 1970s.

861
00:36:33.130 --> 00:36:36.130
The idea that they were suggesting it might

862
00:36:36.130 --> 00:36:38.610
have needed a bit more mass than a single

863
00:36:38.610 --> 00:36:41.570
star to disturb the Oort cloud. And uh, they

864
00:36:41.570 --> 00:36:44.130
suggested the passage nearby, passage of

865
00:36:44.130 --> 00:36:46.610
something called a giant molecular cloud, uh,

866
00:36:46.610 --> 00:36:48.650
a kind of stellar birthplace. If one of those

867
00:36:48.650 --> 00:36:50.850
goes past the solar system, they were

868
00:36:50.850 --> 00:36:53.190
inferring it would disturb the Oort cloud to

869
00:36:53.190 --> 00:36:55.550
the extent that you would get bombardment of

870
00:36:55.550 --> 00:36:57.550
the inner solar system by comets and that

871
00:36:57.550 --> 00:37:00.190
might be visible in the geological record on

872
00:37:00.190 --> 00:37:02.960
Earth. That was basically um, uh,

873
00:37:03.990 --> 00:37:06.510
their principal line of attack. Uh, really

874
00:37:06.510 --> 00:37:09.110
very interesting science. Uh, so this is not

875
00:37:09.110 --> 00:37:11.990
a new idea, but this is new research

876
00:37:12.230 --> 00:37:14.990
that suggests that um, perhaps we can learn

877
00:37:14.990 --> 00:37:16.230
more by pursuing it.

878
00:37:16.790 --> 00:37:19.790
Andrew Dunkley: Indeed, yes. Um, the paper by the way,

879
00:37:19.790 --> 00:37:21.790
has been accepted by the Planetary Science

880
00:37:21.790 --> 00:37:23.500
Journal and is available at the moment,

881
00:37:23.650 --> 00:37:26.290
moment on the Arxiv Preprint server.

882
00:37:26.690 --> 00:37:29.530
You can also read about it at phys.org, p h

883
00:37:29.530 --> 00:37:32.410
y s.org Fred Watson,

884
00:37:32.410 --> 00:37:34.130
that brings us to the end of the show.

885
00:37:34.130 --> 00:37:35.010
Thank you so much.

886
00:37:35.170 --> 00:37:37.330
Professor Fred Watson: Well, that went very quickly. Uh, what a good

887
00:37:37.330 --> 00:37:37.970
time we had.

888
00:37:38.290 --> 00:37:40.450
Andrew Dunkley: We did indeed. Yes. We'll catch you on the

889
00:37:40.450 --> 00:37:40.850
next one.

890
00:37:40.930 --> 00:37:41.650
Professor Fred Watson: Sounds great.

891
00:37:41.890 --> 00:37:43.450
Andrew Dunkley: Thank you very much, Professor Fred Watson

892
00:37:43.450 --> 00:37:45.410
Watson, astronomer at large. And don't forget

893
00:37:45.410 --> 00:37:47.610
between episodes to jump on our website and

894
00:37:47.610 --> 00:37:50.050
have a look around. SpaceNutsPodcast.com you

895
00:37:50.050 --> 00:37:52.290
can click on the AMA button and send us

896
00:37:52.370 --> 00:37:54.410
messages. Even if you want to send us a joke,

897
00:37:54.410 --> 00:37:57.310
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898
00:37:57.390 --> 00:37:59.670
uh, send us a question or, um, you can

899
00:37:59.670 --> 00:38:02.670
comment on a discussion point, whatever

900
00:38:02.670 --> 00:38:04.470
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901
00:38:04.470 --> 00:38:05.750
you are or where you're from. You can send

902
00:38:05.750 --> 00:38:08.030
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903
00:38:08.030 --> 00:38:09.390
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904
00:38:09.390 --> 00:38:12.310
shop. Cheque out. Uh, the, uh, ways

905
00:38:12.310 --> 00:38:14.910
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906
00:38:14.910 --> 00:38:16.790
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907
00:38:16.790 --> 00:38:19.350
You can do all of that on our website. And

908
00:38:19.350 --> 00:38:21.950
thanks to Huw in the studio who, uh, couldn't

909
00:38:21.950 --> 00:38:23.950
be with us today because he saw a passing

910
00:38:23.950 --> 00:38:26.670
star and chased her down for an autograph.

911
00:38:27.450 --> 00:38:29.890
And from and from me, Andrew Dunkley. Thanks

912
00:38:29.890 --> 00:38:31.410
for your company. We'll see you on the next

913
00:38:31.410 --> 00:38:33.530
episode of Space Nuts. Bye. Bye.

914
00:38:34.730 --> 00:38:36.930
You've been listening to the Space Nuts

915
00:38:36.930 --> 00:38:39.930
podcast, available at

916
00:38:39.930 --> 00:38:41.850
Apple Podcasts, Spotify,

917
00:38:42.090 --> 00:38:44.850
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918
00:38:44.850 --> 00:38:46.570
player. You can also stream on

919
00:38:46.570 --> 00:38:48.850
demand@bytes.com this

920
00:38:48.850 --> 00:38:51.210
Professor Fred Watson: has been another quality podcast production

921
00:38:51.210 --> 00:38:52.730
from bytes.com.