The Largest Galaxy in the Universe, Measured at Last

WEBVTT
Kind: captions
Language: en

00:00:00.000 --> 00:00:01.590
Here's


00:00:01.600 --> 00:00:03.590
a question to start your week. [music]


00:00:03.600 --> 00:00:07.349
How big can a single thing actually get?


00:00:07.359 --> 00:00:10.230
Not a country, not [music] an ocean, one


00:00:10.240 --> 00:00:13.030
object held together as one.


00:00:13.040 --> 00:00:14.410
>> And I'm guessing you don't mean my


00:00:14.420 --> 00:00:15.910
[music] inbox.


00:00:15.920 --> 00:00:18.870
>> Bigger. Today, astronomers have finally


00:00:18.880 --> 00:00:20.950
put a tape measure around the largest


00:00:20.960 --> 00:00:23.670
[music] galaxy we know of and found its


00:00:23.680 --> 00:00:26.870
edge for the very first time. Plus, a


00:00:26.880 --> 00:00:28.710
Japanese spacecraft that just set the


00:00:28.720 --> 00:00:31.029
record for the closest asteroid flyby


00:00:31.039 --> 00:00:33.670
ever flown. A British launch put on hold


00:00:33.680 --> 00:00:35.750
at the last minute, and news that our


00:00:35.760 --> 00:00:38.389
nearest big neighbor galaxy is quietly


00:00:38.399 --> 00:00:39.830
powering down.


00:00:39.840 --> 00:00:42.549
>> It's Monday, the 3rd of August. This is


00:00:42.559 --> 00:00:45.110
Astronomy Daily. I'm Anna.


00:00:45.120 --> 00:00:47.350
>> And I'm Avery. Let's get into it.


00:00:47.360 --> 00:00:49.830
>> So, let's start with that tape measure.


00:00:49.840 --> 00:00:51.990
If I asked you to name the biggest


00:00:52.000 --> 00:00:54.389
galaxy in the universe, an astronomer


00:00:54.399 --> 00:00:58.229
would very likely say IC1101.


00:00:58.239 --> 00:01:00.470
And they've been saying it for decades.


00:01:00.480 --> 00:01:03.110
But here's the strange part. Until now,


00:01:03.120 --> 00:01:05.590
nobody could actually tell you where it


00:01:05.600 --> 00:01:06.710
ends.


00:01:06.720 --> 00:01:09.109
>> How do you not know where a galaxy ends?


00:01:09.119 --> 00:01:10.950
It's right there in the pictures.


00:01:10.960 --> 00:01:14.070
>> You'd think so. IC1101


00:01:14.080 --> 00:01:17.190
sits about 1.15 billion lighty years


00:01:17.200 --> 00:01:19.190
away at the heart of a cluster of


00:01:19.200 --> 00:01:22.710
galaxies called Abel 2029. William


00:01:22.720 --> 00:01:25.670
Herschel first logged it back in 1790,


00:01:25.680 --> 00:01:28.149
though of course he had no idea it was a


00:01:28.159 --> 00:01:31.670
galaxy. Nobody did until the 1920s. It's


00:01:31.680 --> 00:01:34.630
what we call a giant elliptical or more


00:01:34.640 --> 00:01:37.749
precisely a brightest cluster galaxy, a


00:01:37.759 --> 00:01:41.670
BCG. And BCGs are the great white sharks


00:01:41.680 --> 00:01:44.149
of the galaxy world. They sit at the


00:01:44.159 --> 00:01:46.389
center of a cluster and they grow by


00:01:46.399 --> 00:01:48.950
swallowing their neighbors one merger at


00:01:48.960 --> 00:01:51.590
a time over billions of years.


00:01:51.600 --> 00:01:53.670
>> So it's basically been eating the other


00:01:53.680 --> 00:01:55.429
galaxies in its cluster


00:01:55.439 --> 00:01:58.149
>> for most of cosmic history. Yes. And


00:01:58.159 --> 00:02:00.950
that's exactly why its edge is so hard


00:02:00.960 --> 00:02:03.510
to find. When a galaxy grows by


00:02:03.520 --> 00:02:06.149
cannibalizing others, it ends up wrapped


00:02:06.159 --> 00:02:09.190
in an enormous faint halo of stars.


00:02:09.200 --> 00:02:11.670
Stars flung out into the space between


00:02:11.680 --> 00:02:15.190
galaxies. That glow is so dim it blurs


00:02:15.200 --> 00:02:16.869
into the background of the cluster


00:02:16.879 --> 00:02:20.309
itself. So, the honest answer to how big


00:02:20.319 --> 00:02:22.790
is IC1101


00:02:22.800 --> 00:02:25.830
has for years been a shrug. You'll see


00:02:25.840 --> 00:02:28.150
figures online anywhere from about


00:02:28.160 --> 00:02:31.990
400,000 lightyear across to a wild 6


00:02:32.000 --> 00:02:34.470
million lightyear. Nobody could pin it


00:02:34.480 --> 00:02:35.270
down.


00:02:35.280 --> 00:02:37.190
>> That's not a rounding error. That's a


00:02:37.200 --> 00:02:39.990
factor of 15. So what changed?


00:02:40.000 --> 00:02:43.270
>> A team led by Carlos Morero de la Roza


00:02:43.280 --> 00:02:45.990
took the deepest images ever captured of


00:02:46.000 --> 00:02:49.270
this galaxy. Ultra deep exposures in two


00:02:49.280 --> 00:02:51.910
colors using the Isaac Newton's wide


00:02:51.920 --> 00:02:54.790
field camera. And when I say deep, I


00:02:54.800 --> 00:02:56.470
mean they were sensitive enough to


00:02:56.480 --> 00:02:59.750
detect a glow 30 magnitudes per square


00:02:59.760 --> 00:03:03.110
arcsec. Faint. In plain terms, they


00:03:03.120 --> 00:03:05.270
could pick out starlight roughly a


00:03:05.280 --> 00:03:07.589
billion times fainter than the night sky


00:03:07.599 --> 00:03:09.509
you'd see with your own eyes.


00:03:09.519 --> 00:03:11.589
>> And the trick is separating that whisper


00:03:11.599 --> 00:03:13.509
of light from everything else.


00:03:13.519 --> 00:03:16.229
>> That's the whole game. Bright foreground


00:03:16.239 --> 00:03:18.949
stars smear light across the image. The


00:03:18.959 --> 00:03:21.750
galaxy scatters its own light, too. So,


00:03:21.760 --> 00:03:24.149
they carefully modeled all that stray


00:03:24.159 --> 00:03:27.190
light and subtracted it using a detailed


00:03:27.200 --> 00:03:29.670
map of how the telescope spreads out a


00:03:29.680 --> 00:03:31.990
point of light. Only then could they


00:03:32.000 --> 00:03:34.710
trace the galaxy's true profile all the


00:03:34.720 --> 00:03:37.430
way out until it finally melts into the


00:03:37.440 --> 00:03:40.070
cluster. And here's what they found.


00:03:40.080 --> 00:03:41.990
IC1101


00:03:42.000 --> 00:03:45.430
reaches an edge about 260,000


00:03:45.440 --> 00:03:47.509
lighty years from its center which gives


00:03:47.519 --> 00:03:51.990
it a diameter of roughly 520 kiloparex.


00:03:52.000 --> 00:03:55.110
That's about 1.7 million lightyear from


00:03:55.120 --> 00:03:58.869
one side to the other holding around 3.4


00:03:58.879 --> 00:04:01.429
trillion suns worth of stars.


00:04:01.439 --> 00:04:03.589
>> Okay, I need a yard stick for that. How


00:04:03.599 --> 00:04:05.830
does it compare to us to the Milky Way?


00:04:05.840 --> 00:04:09.030
Our galaxy is about 100,000 lightyears


00:04:09.040 --> 00:04:12.070
across. So IC1101


00:04:12.080 --> 00:04:15.030
is something like 17 times wider than


00:04:15.040 --> 00:04:18.550
the Milky Way. And on mass, our entire


00:04:18.560 --> 00:04:21.189
galaxy, including all its dark matter,


00:04:21.199 --> 00:04:24.629
comes in around 1 to 1/2 trillion solar


00:04:24.639 --> 00:04:27.670
masses. IC1101


00:04:27.680 --> 00:04:30.469
has more than 3 trillion solar masses in


00:04:30.479 --> 00:04:34.150
its stars alone. It is by any measure we


00:04:34.160 --> 00:04:36.790
can now defend with data the largest


00:04:36.800 --> 00:04:38.390
galaxy known.


00:04:38.400 --> 00:04:41.270
>> You said now defend with data. That word


00:04:41.280 --> 00:04:43.350
now is doing some work.


00:04:43.360 --> 00:04:46.230
>> It is because the second finding is


00:04:46.240 --> 00:04:48.710
almost better than the first. This


00:04:48.720 --> 00:04:52.070
galaxy isn't finished. Beyond that main


00:04:52.080 --> 00:04:54.710
edge, the team spotted a scatter of


00:04:54.720 --> 00:04:58.150
faint lopsided structures. Eight of them


00:04:58.160 --> 00:05:00.310
and two line up neatly with


00:05:00.320 --> 00:05:02.710
disturbances. astronomers had already


00:05:02.720 --> 00:05:05.030
seen in the hot X-ray gas of the


00:05:05.040 --> 00:05:07.670
cluster. That's the fingerprint of


00:05:07.680 --> 00:05:11.590
ongoing feeding. IC 1101 is still


00:05:11.600 --> 00:05:15.189
pulling material in, still assembling,


00:05:15.199 --> 00:05:17.270
probably shaped by a collision with


00:05:17.280 --> 00:05:20.390
another group of galaxies 2 to 3 billion


00:05:20.400 --> 00:05:22.710
years ago that's still settling down


00:05:22.720 --> 00:05:23.590
today.


00:05:23.600 --> 00:05:25.909
>> So, it holds the record and it's still


00:05:25.919 --> 00:05:29.350
growing. That feels almost greedy. Which


00:05:29.360 --> 00:05:31.430
brings us to the real question in the


00:05:31.440 --> 00:05:34.710
paper's title. How large can galaxies


00:05:34.720 --> 00:05:39.029
actually get? Because IC 1101 now sits


00:05:39.039 --> 00:05:41.670
right at the extreme upper end of what


00:05:41.680 --> 00:05:44.550
we call the mass size relation. The


00:05:44.560 --> 00:05:47.110
biggest edge yet measured for any


00:05:47.120 --> 00:05:50.390
galaxy. It's not just a trivia record.


00:05:50.400 --> 00:05:52.550
It's a data point that tells us the


00:05:52.560 --> 00:05:55.749
ceiling for how big a galaxy can grow in


00:05:55.759 --> 00:05:59.590
the present-day universe. And IC 1101 is


00:05:59.600 --> 00:06:02.390
sitting up there brushing against it,


00:06:02.400 --> 00:06:03.990
still reaching.


00:06:04.000 --> 00:06:06.150
>> Can anyone actually see this monster for


00:06:06.160 --> 00:06:07.510
themselves?


00:06:07.520 --> 00:06:09.990
>> You'd want a good telescope. It's a


00:06:10.000 --> 00:06:11.990
faint smudge in the constellation


00:06:12.000 --> 00:06:14.550
serpents near the Virgo border.


00:06:14.560 --> 00:06:16.469
Wellplaced in the evening for both


00:06:16.479 --> 00:06:19.430
hemispheres right now. But honestly, the


00:06:19.440 --> 00:06:22.070
wonder here isn't in the eyepiece. It's


00:06:22.080 --> 00:06:24.870
the idea. Somewhere out there is an


00:06:24.880 --> 00:06:27.909
object nearly 2 million lighty years


00:06:27.919 --> 00:06:31.510
wide, three trillion stars strong, and


00:06:31.520 --> 00:06:34.309
it's still hungry. From the largest


00:06:34.319 --> 00:06:37.270
thing we know to a very small, very fast


00:06:37.280 --> 00:06:40.230
one, Japan's space agency, JAXA, held a


00:06:40.240 --> 00:06:42.150
press conference last Thursday to


00:06:42.160 --> 00:06:44.150
confirm a result that had asteroid


00:06:44.160 --> 00:06:46.870
scientists grinning. Their Hayabusa 2


00:06:46.880 --> 00:06:49.189
spacecraft has just flown the closest


00:06:49.199 --> 00:06:51.990
asteroid flyby ever attempted by any


00:06:52.000 --> 00:06:53.029
mission.


00:06:53.039 --> 00:06:55.270
>> This is the same spacecraft that brought


00:06:55.280 --> 00:06:58.150
samples of asteroid Ryugu back to Earth,


00:06:58.160 --> 00:06:59.110
isn't it?


00:06:59.120 --> 00:07:01.990
>> The very same. Hayabusa 2 launched back


00:07:02.000 --> 00:07:04.790
in 2014, dropped those precious Ryugule


00:07:04.800 --> 00:07:06.550
samples in the Australian outback in


00:07:06.560 --> 00:07:09.110
2020, and then with fuel still in the


00:07:09.120 --> 00:07:11.990
tank, kept going. It's now traveled


00:07:12.000 --> 00:07:14.230
something like 10.7


00:07:14.240 --> 00:07:17.189
billion km on an extended mission. And


00:07:17.199 --> 00:07:19.510
on the 5th of July, it threaded past a


00:07:19.520 --> 00:07:22.309
near-earth asteroid called Torifune.


00:07:22.319 --> 00:07:25.510
>> How close is closest ever?


00:07:25.520 --> 00:07:30.629
>> 400 m from the surface. 400. That's 744


00:07:30.639 --> 00:07:33.110
m from the asteroid center. And they did


00:07:33.120 --> 00:07:35.270
it while both objects were screaming


00:07:35.280 --> 00:07:38.710
along at more than 18,000 km an hour.


00:07:38.720 --> 00:07:41.510
about a 100 million km from Earth.


00:07:41.520 --> 00:07:43.749
They'd plan to pass 800 m from the


00:07:43.759 --> 00:07:45.749
center and beat their own target by


00:07:45.759 --> 00:07:48.950
clean half. At that speed and distance,


00:07:48.960 --> 00:07:51.430
that's absurdly precise.


00:07:51.440 --> 00:07:54.070
>> The operations lead, Yuya Mimasu, put it


00:07:54.080 --> 00:07:56.390
beautifully. He said the difficulty was


00:07:56.400 --> 00:07:58.950
like shooting a oneyen coin up on the


00:07:58.960 --> 00:08:01.430
northern island of Hokkaido from down in


00:08:01.440 --> 00:08:03.189
Okinawa, right at the other end of


00:08:03.199 --> 00:08:05.189
Japan. And they didn't just take


00:08:05.199 --> 00:08:07.830
pictures. Hayabusa 2 pulled off the


00:08:07.840 --> 00:08:10.230
first ever laser ranging of an asteroid


00:08:10.240 --> 00:08:13.029
during a flyby, bouncing a laser off the


00:08:13.039 --> 00:08:15.189
rock to measure the distance in real


00:08:15.199 --> 00:08:16.150
time.


00:08:16.160 --> 00:08:17.990
>> And there was a surprise waiting for


00:08:18.000 --> 00:08:19.110
them, too.


00:08:19.120 --> 00:08:21.830
>> There was toif turned out to be a


00:08:21.840 --> 00:08:24.710
contact binary. Two lumps of rocks stuck


00:08:24.720 --> 00:08:27.670
together, a bit like a cosmic snowman.


00:08:27.680 --> 00:08:31.189
Roughly 450 m of doublelobed asteroid.


00:08:31.199 --> 00:08:33.029
They hadn't expected to look like that


00:08:33.039 --> 00:08:36.949
at all. So why do this beyond the lovely


00:08:36.959 --> 00:08:38.149
images?


00:08:38.159 --> 00:08:40.709
>> Planetary defense. Learning to navigate


00:08:40.719 --> 00:08:43.509
a spacecraft that precisely that close


00:08:43.519 --> 00:08:46.230
to a moving target is exactly the skill


00:08:46.240 --> 00:08:49.430
you'd need to reach or one day nudge a


00:08:49.440 --> 00:08:52.310
genuinely hazardous asteroid. This was a


00:08:52.320 --> 00:08:54.389
rehearsal and the next act is already


00:08:54.399 --> 00:08:57.269
booked. In 2031, Hayabusa 2 will


00:08:57.279 --> 00:08:59.590
rendevous with a tiny asteroid called


00:08:59.600 --> 00:09:02.310
1998 KY26,


00:09:02.320 --> 00:09:05.350
just 11 m across. It might even try to


00:09:05.360 --> 00:09:06.150
land.


00:09:06.160 --> 00:09:08.790
>> A fridge sized probe landing on


00:09:08.800 --> 00:09:11.110
something the size of a house. I love


00:09:11.120 --> 00:09:14.230
this mission. Now to a launch that isn't


00:09:14.240 --> 00:09:16.550
happening quite yet, but when it does,


00:09:16.560 --> 00:09:19.110
it'll be a first. The German company


00:09:19.120 --> 00:09:22.710
rocket factory Oxford RFA is aiming to


00:09:22.720 --> 00:09:25.110
send the first ever rocket to orbit from


00:09:25.120 --> 00:09:28.790
UK soil flying from Saxavord Spaceport


00:09:28.800 --> 00:09:31.190
up on UNST, the most northerly of


00:09:31.200 --> 00:09:33.910
Britain's inhabited islands in Shetland,


00:09:33.920 --> 00:09:36.310
>> the first orbital launch from the UK.


00:09:36.320 --> 00:09:38.150
That's a genuine milestone.


00:09:38.160 --> 00:09:40.710
>> It really is. Britain has never launched


00:09:40.720 --> 00:09:42.630
a satellite to orbit from its own


00:09:42.640 --> 00:09:47.269
ground. RFA's rocket called RFA1 is a 30


00:09:47.279 --> 00:09:49.829
meter three-stage vehicle designed to


00:09:49.839 --> 00:09:53.829
carry up to,300 kg to a sunsynchronous


00:09:53.839 --> 00:09:56.470
orbit. But last Monday, while running a


00:09:56.480 --> 00:09:58.870
test campaign on the pad ahead of a hot


00:09:58.880 --> 00:10:01.190
fire of the engines, the company found


00:10:01.200 --> 00:10:03.750
what it called an issue with the vehicle


00:10:03.760 --> 00:10:06.550
that requires further investigation. So,


00:10:06.560 --> 00:10:09.350
they've made the call to destack, to


00:10:09.360 --> 00:10:11.829
take the fully assembled rocket apart


00:10:11.839 --> 00:10:14.389
stage by stage to get at the problem.


00:10:14.399 --> 00:10:16.069
>> And they've got a history at that pad,


00:10:16.079 --> 00:10:16.870
haven't they?


00:10:16.880 --> 00:10:20.870
>> They do. Back in August 2024, an earlier


00:10:20.880 --> 00:10:23.829
RFA1 first stage was destroyed in a


00:10:23.839 --> 00:10:26.150
fireball during a static fire test at


00:10:26.160 --> 00:10:29.110
that very site. Nobody hurt, the pad


00:10:29.120 --> 00:10:32.790
saved, but the stage lost. RFA are open


00:10:32.800 --> 00:10:34.790
about their philosophy. They develop


00:10:34.800 --> 00:10:37.350
iteratively. They test hard and they


00:10:37.360 --> 00:10:39.990
accept that things sometimes break. This


00:10:40.000 --> 00:10:42.630
latest issue sounds far less dramatic.


00:10:42.640 --> 00:10:44.790
Caught on the ground exactly where you


00:10:44.800 --> 00:10:45.829
want to catch it.


00:10:45.839 --> 00:10:48.150
>> So what does the timeline look like now?


00:10:48.160 --> 00:10:50.389
>> Air certified launch window opens on the


00:10:50.399 --> 00:10:52.710
10th of August. Whether they make that


00:10:52.720 --> 00:10:54.710
depends on what the investigation turns


00:10:54.720 --> 00:10:57.910
up. Saxavord matters here beyond just


00:10:57.920 --> 00:11:00.150
this one flight. It's the first


00:11:00.160 --> 00:11:02.389
fullylicicensed vertical orbital launch


00:11:02.399 --> 00:11:05.190
site in Western Europe and the only UK


00:11:05.200 --> 00:11:07.829
spaceport cleared for vertical launches.


00:11:07.839 --> 00:11:10.069
With satellite demand the way it is,


00:11:10.079 --> 00:11:12.630
Europe is hungry for its own independent


00:11:12.640 --> 00:11:15.030
way to orbit. Though, this is one to


00:11:15.040 --> 00:11:17.269
keep an eye on over the next week. We


00:11:17.279 --> 00:11:18.790
opened with a galaxy that's still


00:11:18.800 --> 00:11:21.190
growing. Let's close the news with one


00:11:21.200 --> 00:11:23.269
that's slowing down. And this one's


00:11:23.279 --> 00:11:25.670
practically a neighbor. New Hubble work


00:11:25.680 --> 00:11:27.590
published last Monday finds star


00:11:27.600 --> 00:11:29.750
formation across the Andromeda galaxy


00:11:29.760 --> 00:11:32.470
has been fading for the last 500 million


00:11:32.480 --> 00:11:35.350
years. Andromeda, that's the closest big


00:11:35.360 --> 00:11:36.630
spiral to us.


00:11:36.640 --> 00:11:39.190
>> The nearest large spiral about 2.5


00:11:39.200 --> 00:11:41.430
million lighty years away, roughly a


00:11:41.440 --> 00:11:44.230
trillion stars. And on a dark night, you


00:11:44.240 --> 00:11:46.470
can see it with your own eyes. A team


00:11:46.480 --> 00:11:48.710
led by Benjamin Williams pieced together


00:11:48.720 --> 00:11:51.030
two enormous Hubble surveys covering


00:11:51.040 --> 00:11:53.509
about 2/3 of Andromeda's disc and


00:11:53.519 --> 00:11:55.750
measured something like 200 million


00:11:55.760 --> 00:11:58.790
individual stars. As Williams put it,


00:11:58.800 --> 00:12:00.790
the stars are the fossil record of the


00:12:00.800 --> 00:12:03.110
galaxy's formation. Read them carefully


00:12:03.120 --> 00:12:05.350
and you can reconstruct its history.


00:12:05.360 --> 00:12:07.990
>> And that history is one of a galaxy


00:12:08.000 --> 00:12:09.509
quieting down


00:12:09.519 --> 00:12:12.069
>> steadily. Yes. Its star forming rate has


00:12:12.079 --> 00:12:13.990
dropped from about one sun's worth of


00:12:14.000 --> 00:12:16.470
new stars a year to roughly a fifth of


00:12:16.480 --> 00:12:18.790
that with the sharpest decline in just


00:12:18.800 --> 00:12:21.110
the last 40 million years. Most of


00:12:21.120 --> 00:12:23.110
what's left is concentrated in a ring


00:12:23.120 --> 00:12:25.430
about 32,000 lighty years out from the


00:12:25.440 --> 00:12:27.990
center. And there may be a culprit, a


00:12:28.000 --> 00:12:31.269
little satellite galaxy called M32.


00:12:31.279 --> 00:12:32.470
>> Pit and run,


00:12:32.480 --> 00:12:34.790
>> possibly a sideswipe. The region of


00:12:34.800 --> 00:12:37.509
Andromeda nearest M32 shows the most


00:12:37.519 --> 00:12:39.509
suppressed star formation. And the


00:12:39.519 --> 00:12:41.430
slowdown there seems to have kicked off


00:12:41.440 --> 00:12:44.069
around 60 million years ago, which could


00:12:44.079 --> 00:12:46.870
actually help pin down when M32 last


00:12:46.880 --> 00:12:49.269
barged through Andromeda's disc. It's a


00:12:49.279 --> 00:12:51.350
reminder that galaxies aren't serene


00:12:51.360 --> 00:12:54.069
islands. They jostle, they collide, and


00:12:54.079 --> 00:12:56.629
sometimes a small neighbor leaves a very


00:12:56.639 --> 00:12:57.590
large mark.


00:12:57.600 --> 00:12:59.509
>> And you can go and look at the scene of


00:12:59.519 --> 00:13:02.389
the crime tonight. You can, which is the


00:13:02.399 --> 00:13:04.550
perfect handover to the skywatch.


00:13:04.560 --> 00:13:07.269
>> Skywatch time. And a heads up before we


00:13:07.279 --> 00:13:09.670
start. We've just had the full buck


00:13:09.680 --> 00:13:12.069
moon, so the moon is a waning gibbus


00:13:12.079 --> 00:13:14.230
this week. Still bright enough early on


00:13:14.240 --> 00:13:16.870
to wash out the faintest targets. It'll


00:13:16.880 --> 00:13:18.629
get easier as the week goes, and the


00:13:18.639 --> 00:13:20.949
moon thins toward last quarter.


00:13:20.959 --> 00:13:23.350
>> First up, a comet with its moment


00:13:23.360 --> 00:13:26.550
tonight. Comet 10p/temple


00:13:26.560 --> 00:13:29.190
2 reached its closest point to the sun


00:13:29.200 --> 00:13:32.389
yesterday. And tonight, Monday the 3rd,


00:13:32.399 --> 00:13:35.430
it makes its closest approach to Earth.


00:13:35.440 --> 00:13:37.750
>> It's not a naked eye showpiece. You'll


00:13:37.760 --> 00:13:40.470
want binoculars or a small telescope and


00:13:40.480 --> 00:13:42.389
dark skies. From the southern


00:13:42.399 --> 00:13:44.629
hemisphere, it rides highest before


00:13:44.639 --> 00:13:47.350
dawn. So, Sydney, early risers have the


00:13:47.360 --> 00:13:49.910
better geometry. From North America,


00:13:49.920 --> 00:13:52.629
it's best hunted in the narrow window of


00:13:52.639 --> 00:13:55.350
true darkness after evening twilight,


00:13:55.360 --> 00:13:58.230
but before that gibbus moon climbs up.


00:13:58.240 --> 00:14:00.550
For midn northern latitudes, roughly


00:14:00.560 --> 00:14:04.389
9:30 to 10:30 p.m. local. Use averted


00:14:04.399 --> 00:14:06.790
vision and let your eyes settle.


00:14:06.800 --> 00:14:09.990
>> Next, an easy one for everyone. Tonight,


00:14:10.000 --> 00:14:12.870
the waning gibbus moon sits right beside


00:14:12.880 --> 00:14:15.990
Saturn. A lovely naked eye pairing up


00:14:16.000 --> 00:14:18.310
through most of the night and into dawn


00:14:18.320 --> 00:14:20.790
and visible from both hemispheres. If


00:14:20.800 --> 00:14:23.030
you've got a scope, swing it to Saturn


00:14:23.040 --> 00:14:25.189
while you're there for the rings. And


00:14:25.199 --> 00:14:27.590
for the early risers, Mercury reached


00:14:27.600 --> 00:14:29.750
its greatest western elongation


00:14:29.760 --> 00:14:32.230
yesterday. So, it's about as well placed


00:14:32.240 --> 00:14:34.230
in the morning sky as it gets this


00:14:34.240 --> 00:14:37.189
round. Look low to the eastern horizon


00:14:37.199 --> 00:14:39.990
roughly an hour before sunrise over


00:14:40.000 --> 00:14:42.949
toward the stars of Gemini with Mars a


00:14:42.959 --> 00:14:45.509
little higher up. Northern observers get


00:14:45.519 --> 00:14:47.990
the cleaner shot at Mercury this time,


00:14:48.000 --> 00:14:49.990
but it's worth a try from the south,


00:14:50.000 --> 00:14:52.790
too. You'll need a flat, clear horizon


00:14:52.800 --> 00:14:55.990
either way. Now, a diary note we flagged


00:14:56.000 --> 00:14:58.870
last week, and it's now just 2 days out.


00:14:58.880 --> 00:15:01.750
On the 5th of August, a spent Falcon 9


00:15:01.760 --> 00:15:04.550
upper stage is on track to impact the


00:15:04.560 --> 00:15:07.269
moon near Einstein crater on the western


00:15:07.279 --> 00:15:10.069
limb at about 0635


00:15:10.079 --> 00:15:13.350
universal time. And this one's squarely


00:15:13.360 --> 00:15:15.670
for our North American listeners. You


00:15:15.680 --> 00:15:17.910
have the best seat in the house. That


00:15:17.920 --> 00:15:21.269
impact time works out to about 2:35


00:15:21.279 --> 00:15:25.110
Eastern, 11:35 Pacific the night before


00:15:25.120 --> 00:15:27.269
with the moon up and the impact region


00:15:27.279 --> 00:15:29.509
on the dark side of the terminator.


00:15:29.519 --> 00:15:31.750
Ideal. You won't see a flash with the


00:15:31.760 --> 00:15:33.829
naked eye, but if you've got a decent


00:15:33.839 --> 00:15:35.990
telescope and a camera trained on that


00:15:36.000 --> 00:15:37.750
limb, you're in the game.


00:15:37.760 --> 00:15:39.750
>> For us in the Southern Hemisphere, the


00:15:39.760 --> 00:15:42.150
timing is unkind. That's midafter


00:15:42.160 --> 00:15:45.269
afternoon in Sydney around 4:35 p.m.


00:15:45.279 --> 00:15:48.069
with the moon not favorably placed. So,


00:15:48.079 --> 00:15:49.990
we'll be waiting on the orbiter after


00:15:50.000 --> 00:15:52.150
images of the impact site rather than


00:15:52.160 --> 00:15:54.470
catching it live. But, it's a great


00:15:54.480 --> 00:15:57.269
excuse to follow along online. And


00:15:57.279 --> 00:15:59.670
looking ahead, a quick flag for the big


00:15:59.680 --> 00:16:02.389
month coming. The 12th of August is a


00:16:02.399 --> 00:16:05.110
huge date. A total solar eclipse


00:16:05.120 --> 00:16:07.670
tracking across Greenland, Iceland, and


00:16:07.680 --> 00:16:10.790
Spain. paired for once with a moonless


00:16:10.800 --> 00:16:13.590
peak of the Percied meteor shower, plus


00:16:13.600 --> 00:16:16.870
a sixplanet lineup in the pre-dawn sky.


00:16:16.880 --> 00:16:19.030
We'll build all of that out closer to


00:16:19.040 --> 00:16:19.990
the day.


00:16:20.000 --> 00:16:22.550
>> One safety word now, though, and we'll


00:16:22.560 --> 00:16:24.949
say it every time. If you're anywhere


00:16:24.959 --> 00:16:27.189
near that eclipse path, you view the


00:16:27.199 --> 00:16:29.670
partial phases only through certified


00:16:29.680 --> 00:16:33.189
ISO12312-2


00:16:33.199 --> 00:16:35.829
eclipse glasses or a properly filtered


00:16:35.839 --> 00:16:38.949
scope. Never look at the an eclipse sun


00:16:38.959 --> 00:16:40.069
without them.


00:16:40.079 --> 00:16:42.069
>> That's your Monday briefing. If you want


00:16:42.079 --> 00:16:43.590
more, everything lives at


00:16:43.600 --> 00:16:45.749
astronomyaily.io.


00:16:45.759 --> 00:16:48.150
The fullback catalog, a news feed that


00:16:48.160 --> 00:16:50.230
updates through the day, and a spot to


00:16:50.240 --> 00:16:52.230
sign up for the daily newsletter.


00:16:52.240 --> 00:16:53.990
>> You can send us a message from the site,


00:16:54.000 --> 00:16:56.710
too. Corrections, questions, what you


00:16:56.720 --> 00:16:58.949
spotted in your own sky. We read them


00:16:58.959 --> 00:17:01.430
and we love them. We even got our first


00:17:01.440 --> 00:17:03.670
voice message today from listener Ian


00:17:03.680 --> 00:17:06.549
Sama in Uganda who said, "Hi there. I'm


00:17:06.559 --> 00:17:08.870
Ian from Uganda and I really enjoy your


00:17:08.880 --> 00:17:11.669
podcast very much. Thanks a lot. Thank


00:17:11.679 --> 00:17:13.909
you, Ian. The feedback is very much


00:17:13.919 --> 00:17:15.029
appreciated.


00:17:15.039 --> 00:17:16.949
>> Yes, thank you Ian. Very much


00:17:16.959 --> 00:17:19.189
appreciated by all of us. We'll be back


00:17:19.199 --> 00:17:21.270
tomorrow with more of today's space


00:17:21.280 --> 00:17:23.990
news. Until then, from Avery and me,


00:17:24.000 --> 00:17:25.270
keep looking up.


00:17:25.280 --> 00:17:27.346
>> Clear skies.


00:17:27.356 --> 00:17:37.669
[music and singing]


00:17:37.679 --> 00:17:40.520
Stories to tell. [music]