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Revealing the Secrets of Space and the Cosmos: Insights from Space Nuts
Join Andrew Dunkley and Professor Fred Watson as they explore the fascinating universe—from a historic telescope in Melbourne to the latest discoveries in black hole physics and our own solar system. This episode offers a blend of awe-inspiring science, historical stories, and future possibilities that make astronomy accessible and thrilling.
In this episode:
The extraordinary history and restoration of the Melbourne Telescope, crafted in 1869, and its cultural significance.
The record-breaking detection of the loudest gravitational wave from colliding black holes and what it reveals about event horizons.
China's ambitious plans to expand its space station, including new modules and a cutting-edge space telescope.
Recent insights into a star passing close to our solar system, potentially disturbing comet orbits and shaping our cosmic history.
Upcoming solar observatories, including the ESA's Solar Orbiter and the Chinese Shun Tian telescope.
The incredible speed of the Parker Solar Probe and future missions to study the Sun's atmosphere.
How scientists analyze lunar impacts and cosmic rays using imagery and human eye observations.
The long-standing mystery of Earth's atmosphere and the role of tectonic cycles in its stability.
Resources & Links:
The Melbourne Telescope's History and Restoration (Note: Placeholder, search for Melbourne Telescope history)
LIGO and Virgo Gravitational Wave Observatory
NASA's Parker Solar Probe
ESA's Solar Orbiter
Chinese Space Station and Modules
The Daniel K. Inouye Solar Telescope
Fiz.org Physics Articles on Black Holes and Gravitational Waves
The Gaia Mission and Star Orbits
Preprint Article on Black Hole Gravitational Waves
Connect with Fred Watson:
Feel inspired by space science's latest breakthroughs and historic stories, knowing that curiosity drives understanding. With a confident yet approachable tone, this episode pushes the boundaries of knowledge while making complex ideas understandable and engaging for all.
Become a supporter of this podcast: https://www.spreaker.com/podcast/space-nuts-astronomy-insights-cosmic-discoveries--2631155/support.
00:00:00 --> 00:00:02 Andrew Dunkley: Hello there. Thanks for joining us. This is
00:00:02 --> 00:00:05 Space Nuts, where we talk astronomy and
00:00:05 --> 00:00:07 space science. My name is Andrew Dunkley.
00:00:07 --> 00:00:10 Great to have your company on this, the
00:00:10 --> 00:00:13 600 millionth episode. Maybe not that many,
00:00:13 --> 00:00:15 but we've done quite a few. What is it,
00:00:15 --> 00:00:17 643 we're up to? Blimey.
00:00:18 --> 00:00:19 All right, uh, what are we talking about?
00:00:19 --> 00:00:22 We're talking about, um, an old clapped out,
00:00:23 --> 00:00:25 uh, telescope. Fred Watson happens to be its
00:00:25 --> 00:00:27 patron. He's old and clapped out too. Uh,
00:00:27 --> 00:00:30 we're also going to look, uh, at
00:00:30 --> 00:00:32 a new black hole discovery which was made
00:00:33 --> 00:00:35 after, um, two black holes
00:00:35 --> 00:00:38 collided and they recorded the loudest crash
00:00:38 --> 00:00:41 of gravitational waves ever. So
00:00:41 --> 00:00:43 what's it going to tell us? Also, uh, China
00:00:43 --> 00:00:45 is going to upgrade its space station and
00:00:45 --> 00:00:48 launch a new space telescope. And a
00:00:48 --> 00:00:51 star that got close to our sun
00:00:51 --> 00:00:53 may have caused a bit of a disturbance in the
00:00:53 --> 00:00:56 force. We'll tell you all about it on this
00:00:56 --> 00:00:58 episode of space nuts.
00:00:58 --> 00:01:00 Professor Fred Watson: 15 seconds. Guidance is internal.
00:01:01 --> 00:01:03 10, 9. Ignition
00:01:04 --> 00:01:04 sequence.
00:01:04 --> 00:01:04 Andrew Dunkley: Star.
00:01:04 --> 00:01:07 Professor Fred Watson: Uh, space nuts. 5, 4, 3, 2. 1.
00:01:07 --> 00:01:10 2, 3, 4, 5, 5, 4, 3, 2,
00:01:10 --> 00:01:10 1.
00:01:10 --> 00:01:13 Andrew Dunkley: Space nuts. Astronauts report it feels
00:01:13 --> 00:01:16 good. And he's back again. As always,
00:01:16 --> 00:01:19 it's Professor Fred Watson Watson, astronomer
00:01:19 --> 00:01:20 at large. Hello, Fred Watson.
00:01:20 --> 00:01:22 Professor Fred Watson: Hello, Andrew. Hello. Uh, thank you for that
00:01:22 --> 00:01:25 nice introduction. It's, uh,
00:01:25 --> 00:01:28 nice to hear welcome like that.
00:01:29 --> 00:01:31 Andrew Dunkley: You know, I know I only said it a few seconds
00:01:31 --> 00:01:33 ago, but I forgot what I said. And then it
00:01:33 --> 00:01:35 dawned on me that I'd actually insulted.
00:01:35 --> 00:01:37 Professor Fred Watson: Yes. Oh, forget about that. Yeah, no, that's
00:01:37 --> 00:01:39 all right, that's all right. You're right.
00:01:39 --> 00:01:40 Andrew Dunkley: Last week.
00:01:40 --> 00:01:42 Professor Fred Watson: I am old and clapped out. There's no question
00:01:42 --> 00:01:43 about that.
00:01:44 --> 00:01:46 Andrew Dunkley: Aren't we all, Aren't we all?
00:01:47 --> 00:01:50 Um, now, um, before we get into, uh,
00:01:50 --> 00:01:52 today's storeys, um, the old clapped out
00:01:52 --> 00:01:54 telescope I referred to is actually a, uh,
00:01:54 --> 00:01:57 wonderful device, uh, that I've actually seen
00:01:57 --> 00:02:00 in person when we were down in Melbourne a
00:02:00 --> 00:02:03 few years ago. Uh, it's the
00:02:03 --> 00:02:05 Melbourne telescope. Dates back to
00:02:05 --> 00:02:08 1869. And you're its patron because you
00:02:08 --> 00:02:10 were there when they put the first screw in
00:02:10 --> 00:02:11 it. Got you again.
00:02:12 --> 00:02:15 Professor Fred Watson: Yeah. So the link and the reason why I'm.
00:02:15 --> 00:02:17 Well, there's a number of reasons why this
00:02:17 --> 00:02:19 telescope is very close to my heart. One is
00:02:19 --> 00:02:22 that, uh, I was
00:02:22 --> 00:02:24 still at school when I found a picture of it
00:02:24 --> 00:02:27 in Henry King's History of the Telescope, a
00:02:27 --> 00:02:30 very famous book, uh, on the history of
00:02:30 --> 00:02:33 telescopes, published, I think in 1955.
00:02:33 --> 00:02:35 Had a copy of that in the school library. And
00:02:35 --> 00:02:37 there's this telescope there, the Great
00:02:37 --> 00:02:39 Melbourne Telescope. And I thought that is.
00:02:39 --> 00:02:42 That is a telescope. That's what I want one
00:02:42 --> 00:02:43 like looks.
00:02:43 --> 00:02:46 Andrew Dunkley: It just looks like you'd expect one to
00:02:46 --> 00:02:46 look, doesn't it?
00:02:46 --> 00:02:48 Professor Fred Watson: You can tell it's a telescope. It's got um.
00:02:48 --> 00:02:51 With decorative bits like the latticework
00:02:51 --> 00:02:54 tube, which is uh, very unusual, almost
00:02:54 --> 00:02:57 unique. Anyway, that was my first
00:02:57 --> 00:03:00 um, encounter with it. Uh, and as
00:03:00 --> 00:03:01 sort of followed up as much as I could. A
00:03:02 --> 00:03:04 didn't realise that by then it was actually
00:03:04 --> 00:03:07 uh, in Canberra at Matt Stromlo. It had been
00:03:07 --> 00:03:10 refurbished, um, having left Melbourne in
00:03:10 --> 00:03:12 1944. But, uh,
00:03:12 --> 00:03:15 100 years
00:03:15 --> 00:03:18 exactly after work started on
00:03:18 --> 00:03:21 the manufacture of that telescope in
00:03:21 --> 00:03:24 1867, 100 years later I
00:03:24 --> 00:03:25 joined the company that built it.
00:03:27 --> 00:03:30 So it was uh, its 20th
00:03:30 --> 00:03:33 century equivalent. It was uh, Howard
00:03:33 --> 00:03:35 Grubb, Dublin when, uh, the telescope was
00:03:35 --> 00:03:37 built. By the time I got there it was sir,
00:03:37 --> 00:03:40 uh, Howard Grubb Parsons Co. Ltd. But
00:03:40 --> 00:03:43 it was basically the same company amalgamated
00:03:43 --> 00:03:46 in 1926 with the Parsons company. So,
00:03:46 --> 00:03:48 um, I continued my kinship with that
00:03:48 --> 00:03:51 telescope and uh, uh, of course when I came
00:03:51 --> 00:03:54 to Australia, was interested to see it at
00:03:54 --> 00:03:57 stromlo. Then in 2003,
00:03:57 --> 00:04:00 uh, the Stromlo Observatory had that terrible
00:04:00 --> 00:04:02 fire, bush fire that went through, destroyed
00:04:02 --> 00:04:05 all the heritage buildings, including the one
00:04:05 --> 00:04:08 that uh, that telescope sat in,
00:04:08 --> 00:04:11 uh, and basically melted a lot of
00:04:11 --> 00:04:13 the. Well, melted the dome onto the
00:04:13 --> 00:04:16 telescope. The dome was aluminium, uh, and
00:04:16 --> 00:04:18 the telescope was wrecked, its mirror was
00:04:18 --> 00:04:21 smashed and all the rest of it. Uh, so I,
00:04:21 --> 00:04:23 When I. So I wrote a book on the history of
00:04:23 --> 00:04:24 telescopes which was published I think
00:04:25 --> 00:04:28 just after that fire because,
00:04:28 --> 00:04:31 um, I wrote at the end I had a whole chapter
00:04:31 --> 00:04:33 on this telescope and I wrote something to
00:04:33 --> 00:04:36 the effect that uh. The best we could hope to
00:04:36 --> 00:04:38 see would for it to be a static
00:04:38 --> 00:04:41 exhibit in a museum, just the remnants.
00:04:42 --> 00:04:45 Uh, but it was for a while. Well it wasn't.
00:04:45 --> 00:04:48 No, it stayed put in Stromlo. And it was five
00:04:48 --> 00:04:50 years after the fire, 2008, when this
00:04:50 --> 00:04:53 consortium of museums, uh, Victoria,
00:04:53 --> 00:04:56 the Astronomical Society of Victoria, uh,
00:04:56 --> 00:04:58 Royal Botanic Gardens, Melbourne, because
00:04:58 --> 00:05:01 that's where it started its career. Uh,
00:05:02 --> 00:05:04 uh, and uh. I think the Bureau of Meteorology
00:05:04 --> 00:05:07 were involved as well. Uh, and they
00:05:07 --> 00:05:10 got together a plan to basically
00:05:10 --> 00:05:12 restore it. Uh, and
00:05:13 --> 00:05:16 so I uh, did play a role in that. In
00:05:16 --> 00:05:19 2015 we actually held
00:05:19 --> 00:05:21 a workshop which I chaired, which was about
00:05:21 --> 00:05:24 how you could update the optics of the
00:05:24 --> 00:05:26 telescope because the mechanical stuff could
00:05:26 --> 00:05:29 be refurbished. Uh, but the
00:05:29 --> 00:05:32 optics were a different matter. Uh, and a uh,
00:05:32 --> 00:05:35 sort of optical prescription was drawn up.
00:05:35 --> 00:05:37 Now Those optics are still in the process of
00:05:37 --> 00:05:39 being manufactured. Uh, but
00:05:40 --> 00:05:43 the telescope itself is now
00:05:43 --> 00:05:45 essentially mechanically complete. It is
00:05:45 --> 00:05:48 as complete as it was when it was built.
00:05:48 --> 00:05:51 And the work that's been done, more than 100
00:05:52 --> 00:05:54 volunteers and staff from Museums
00:05:54 --> 00:05:56 Victoria and the Astronomical Society of
00:05:56 --> 00:05:59 Victoria, well over a hundred have worked on
00:05:59 --> 00:06:01 it. And so last, uh, week there was a little
00:06:01 --> 00:06:04 party to celebrate that. And,
00:06:04 --> 00:06:07 uh, some of the museum's dignitary said a few
00:06:07 --> 00:06:09 words, I said a few words. The chap who's
00:06:09 --> 00:06:11 been leading the project, Simon Brink over
00:06:11 --> 00:06:13 the last few years, he said a few words. He's
00:06:13 --> 00:06:16 actually coming to lunch with us on Saturday.
00:06:16 --> 00:06:18 Oh, lovely. Even though he's in Melbourne,
00:06:18 --> 00:06:21 he's coming up, um, which is nice.
00:06:21 --> 00:06:24 Um, so we had a celebration and, uh,
00:06:24 --> 00:06:26 to be honest, what they've done is nothing
00:06:26 --> 00:06:29 short of miraculous because there weren't any
00:06:30 --> 00:06:32 diagrams of all the bits and pieces of this
00:06:32 --> 00:06:35 telescope. There were engineering diagrams of
00:06:35 --> 00:06:38 the thing complete. They were published in a
00:06:38 --> 00:06:40 journal. But the individual parts and
00:06:40 --> 00:06:43 probably thousands of
00:06:43 --> 00:06:45 components, screws, washers,
00:06:46 --> 00:06:49 uh, pulleys, cog wheels of various
00:06:49 --> 00:06:51 different sized, all of that. No
00:06:51 --> 00:06:54 idea what they looked like. And by
00:06:54 --> 00:06:57 scouring photographs of the telescope, uh,
00:06:57 --> 00:07:00 from many sources and
00:07:00 --> 00:07:03 working out things like the numbers of teeth
00:07:03 --> 00:07:05 you need on a cogwheel to make the things
00:07:05 --> 00:07:08 work properly, uh, they've done a great job
00:07:08 --> 00:07:11 with all that. And now it's in basically in
00:07:11 --> 00:07:13 perfect working order, except it doesn't have
00:07:13 --> 00:07:16 its main mirror yet that's being fabricated.
00:07:16 --> 00:07:19 Um, it's at the moment still at
00:07:19 --> 00:07:21 Scienceworks, which is the Science M Museum
00:07:21 --> 00:07:23 in Victoria. And it's a big exhibit which is
00:07:23 --> 00:07:25 Andrew Dunkley: worth a visit, especially with the kids.
00:07:25 --> 00:07:27 Professor Fred Watson: Yeah, it's a great place to go. Uh, and
00:07:27 --> 00:07:29 anybody, uh, who does go to Melbourne and
00:07:29 --> 00:07:31 sees scienceworks definitely have a look at
00:07:31 --> 00:07:33 the great Melbourne telescope. The hope is
00:07:33 --> 00:07:35 that one day it will be in its original
00:07:35 --> 00:07:37 building, which still exists in the Royal
00:07:37 --> 00:07:40 Botanic Gardens. Uh, but, um, there's quite a
00:07:40 --> 00:07:43 bit of work needs to be done to make
00:07:43 --> 00:07:45 that, uh, oh, s. Uh,
00:07:45 --> 00:07:48 satisfactory for 2026
00:07:48 --> 00:07:51 or whenever it happens, compared with
00:07:51 --> 00:07:53 the, um, you know, the health and safety
00:07:53 --> 00:07:56 regulations in 1869 when people came and
00:07:56 --> 00:07:58 went, um, just had a look through the
00:07:58 --> 00:08:00 telescope. That's the idea that it will
00:08:00 --> 00:08:02 eventually be a working telescope for the
00:08:02 --> 00:08:04 public for people to come and look through.
00:08:05 --> 00:08:07 Andrew Dunkley: Wonderful. And, uh, if you can't get down to
00:08:07 --> 00:08:09 see it in Melbourne, uh, just do a search for
00:08:09 --> 00:08:11 the Melbourne telescope online and have a
00:08:11 --> 00:08:13 look at it and you'll know what we're talking
00:08:13 --> 00:08:15 about, um, the lattice work is just
00:08:15 --> 00:08:17 beautiful. It is a glorious piece of
00:08:17 --> 00:08:20 equipment. And I stumbled across it. I
00:08:20 --> 00:08:22 didn't even know it was at Science Works when
00:08:22 --> 00:08:24 we went there. And we just went for a wander
00:08:24 --> 00:08:26 and found it. And I went, oh, Fred Watson
00:08:26 --> 00:08:28 will love this. And then it turns out you
00:08:28 --> 00:08:29 were the patron, so.
00:08:29 --> 00:08:32 Professor Fred Watson: Yes, that's right. Yeah. Yeah. It's um,
00:08:32 --> 00:08:35 it is, uh, it's quite staggering.
00:08:35 --> 00:08:36 It's how big it is, isn't it? When you.
00:08:36 --> 00:08:37 Andrew Dunkley: Oh yeah.
00:08:37 --> 00:08:37 Professor Fred Watson: Just when you.
00:08:37 --> 00:08:38 Andrew Dunkley: It blows your mind.
00:08:38 --> 00:08:39 Professor Fred Watson: Yes.
00:08:39 --> 00:08:40 Andrew Dunkley: You just stand there in awe.
00:08:40 --> 00:08:43 Professor Fred Watson: Telescope. It was the biggest fully
00:08:43 --> 00:08:45 steerable telescope in the world at the time
00:08:45 --> 00:08:47 when, um, it was built. It wasn't the
00:08:47 --> 00:08:49 biggest, but it was. Biggest telescope in the
00:08:49 --> 00:08:50 world. But it wasn't far off.
00:08:50 --> 00:08:52 Andrew Dunkley: Yeah. As a good friend of mine often says,
00:08:52 --> 00:08:54 it's a great piece of kit.
00:08:54 --> 00:08:56 Professor Fred Watson: It was a great piece of kit. And hopefully it
00:08:56 --> 00:08:57 will be again one day.
00:08:58 --> 00:08:59 Andrew Dunkley: Fingers crossed.
00:08:59 --> 00:09:02 All right, uh, moving on. We're talking black
00:09:02 --> 00:09:04 holes. Very unusual. We don't usually talk
00:09:04 --> 00:09:06 things like this, but, uh, this, this is an
00:09:06 --> 00:09:08 interesting one because they, They've uh,
00:09:08 --> 00:09:09 made it a bit of a discovery. They've.
00:09:09 --> 00:09:11 They've recorded the loudest crash of
00:09:11 --> 00:09:14 gravitational waves ever heard. And it was
00:09:14 --> 00:09:16 because of two black holes that
00:09:16 --> 00:09:19 decided, uh, to play billiards with each
00:09:19 --> 00:09:22 other and boom. Uh, but
00:09:22 --> 00:09:24 it's what they've discovered from the. In the
00:09:24 --> 00:09:26 aftermath of all this that's getting
00:09:26 --> 00:09:27 interesting.
00:09:27 --> 00:09:30 Professor Fred Watson: Uh, yes, it is. Um, so,
00:09:30 --> 00:09:33 yep, we black, um, gravitational waves
00:09:33 --> 00:09:36 from colliding objects have been detectable
00:09:36 --> 00:09:39 by humans since 2015,
00:09:39 --> 00:09:42 um, with uh, the LIGO
00:09:42 --> 00:09:44 Laser Interferometer Gravitational Wave
00:09:44 --> 00:09:47 Observatory in America. And that now works
00:09:47 --> 00:09:50 with, uh, virgo, which is an
00:09:50 --> 00:09:53 Italian, uh, uh, gravitational wave
00:09:53 --> 00:09:55 observatory, and kagra, which is the
00:09:55 --> 00:09:58 Kamioka Gravitational Wave Detector in
00:09:58 --> 00:10:00 Japan. So those three telescopes work
00:10:00 --> 00:10:03 together to pick up the vibrations of space,
00:10:04 --> 00:10:06 uh, which are, uh, transmitted from very
00:10:06 --> 00:10:09 distant collisions usually. And it's usually
00:10:09 --> 00:10:12 neutron stars and black holes, uh, with
00:10:12 --> 00:10:14 collisions between either neutron stars and
00:10:14 --> 00:10:17 neutron stars or black holes and black holes,
00:10:17 --> 00:10:19 or neutron stars and black holes. Um,
00:10:20 --> 00:10:22 those all produce gravitational wave signals
00:10:22 --> 00:10:24 that are actually in the frequency range
00:10:25 --> 00:10:27 detectable by uh, these telescopes.
00:10:27 --> 00:10:30 Because that's a key part of it. The amount
00:10:30 --> 00:10:32 of energy that's involved tells, uh, you what
00:10:32 --> 00:10:35 the frequency of the gravitational waves is
00:10:35 --> 00:10:37 going to be. And as we've noted
00:10:37 --> 00:10:40 before, Andrew, it's curious that, um,
00:10:40 --> 00:10:42 the gravitational waves that these telescopes
00:10:42 --> 00:10:45 are sensitive to are actually in the audio
00:10:45 --> 00:10:48 frequency regime. They're basically. If you
00:10:48 --> 00:10:50 just amplified them, uh, you would have an
00:10:50 --> 00:10:52 audio signal. And that's basically what they
00:10:52 --> 00:10:54 do, except they're doing it in a very much
00:10:54 --> 00:10:56 more sophisticated way. Um,
00:10:57 --> 00:11:00 um. The amount of, um,
00:11:00 --> 00:11:02 shaking of space that they can
00:11:02 --> 00:11:04 detect is
00:11:05 --> 00:11:08 absolutely infinitesimal. Uh, but
00:11:08 --> 00:11:10 these things are sensitive enough that they
00:11:10 --> 00:11:13 can measure a distance that is a
00:11:13 --> 00:11:15 thousandth, I think it's a 10th actually,
00:11:15 --> 00:11:18 of the diameter of a proton. Uh, that's
00:11:19 --> 00:11:21 the accuracy with which they can measure the
00:11:21 --> 00:11:23 distance between two mirrors, which is how
00:11:23 --> 00:11:26 you do all this sort of thing. So that's the
00:11:26 --> 00:11:28 backstory. Uh, the up storey,
00:11:29 --> 00:11:32 the forward storey. Is that
00:11:32 --> 00:11:35 an object or you don't have an object,
00:11:35 --> 00:11:38 you have a gravitational wave signal. Uh, it
00:11:38 --> 00:11:39 rejoices in the name of
00:11:39 --> 00:11:42 GW25014.
00:11:42 --> 00:11:44 Uh, that tells you that it was picked up, um,
00:11:44 --> 00:11:47 in January, uh, 2025. Uh,
00:11:47 --> 00:11:50 that's where the 25011 comes
00:11:50 --> 00:11:53 from. Um. Uh, and it,
00:11:53 --> 00:11:56 uh, basically, uh, on
00:11:56 --> 00:11:59 analysis, um, has
00:12:00 --> 00:12:02 been, uh, detected to be
00:12:02 --> 00:12:05 a collision between two black holes, each
00:12:05 --> 00:12:08 of which had, uh, around 32 times the
00:12:08 --> 00:12:11 mass of the sun until they collided. And
00:12:11 --> 00:12:14 that set, uh, you know, set the
00:12:14 --> 00:12:17 gravitational waves on their way because it
00:12:17 --> 00:12:20 basically disturbed space, it rippled space.
00:12:21 --> 00:12:23 So what's happened is. And this, as you
00:12:23 --> 00:12:25 mentioned at the beginning, is the loudest
00:12:25 --> 00:12:26 gravitational wave signal that's been
00:12:26 --> 00:12:29 detected, or certainly the most, uh,
00:12:29 --> 00:12:31 intense. The, um, highest amplitude one.
00:12:31 --> 00:12:32 Andrew Dunkley: Yeah.
00:12:33 --> 00:12:35 Professor Fred Watson: Um, so what has happened
00:12:35 --> 00:12:38 is, uh, that researchers, uh, have
00:12:38 --> 00:12:41 analysed the audio signal,
00:12:41 --> 00:12:44 um, and they found in it, um,
00:12:45 --> 00:12:47 basically that it's been described as a
00:12:47 --> 00:12:50 feature, uh, which is uh, something
00:12:50 --> 00:12:53 called a direct wave. It's
00:12:53 --> 00:12:55 a component of the signal, uh,
00:12:56 --> 00:12:59 and it's a direct wave, uh, that
00:12:59 --> 00:13:01 has not. That's been seen before,
00:13:01 --> 00:13:04 but hasn't. Nobody's worked out what it
00:13:04 --> 00:13:07 is, but apparently it
00:13:07 --> 00:13:09 is a feature that
00:13:09 --> 00:13:12 essentially, uh. In
00:13:12 --> 00:13:15 the gravitational wave structure that comes
00:13:15 --> 00:13:18 from this event, you can tell this
00:13:18 --> 00:13:20 direct wave is to do with
00:13:21 --> 00:13:24 the event horizon of the combined
00:13:24 --> 00:13:26 black holes. So you've got two black
00:13:26 --> 00:13:29 holes, each of which has got its own event
00:13:29 --> 00:13:31 horizon. They're spinning around one another,
00:13:32 --> 00:13:34 getting ever closer, as we've seen that sort
00:13:34 --> 00:13:36 of thing before. And the frequency goes up of
00:13:36 --> 00:13:39 the gravitational waves, um, and then
00:13:39 --> 00:13:42 suddenly it all stops because they've
00:13:42 --> 00:13:44 collided and there's no more accelerations,
00:13:44 --> 00:13:46 which is what you need, uh, to set up
00:13:46 --> 00:13:49 gravitational waves. Um, but,
00:13:49 --> 00:13:52 uh, at that point the two, um,
00:13:52 --> 00:13:55 gravitate, sorry, the two event horizons
00:13:55 --> 00:13:55 merge.
00:13:56 --> 00:13:59 Uh, now, a recap on event horizons. That's
00:13:59 --> 00:14:01 the point of no return. Basically,
00:14:02 --> 00:14:04 it's the distance from the black hole,
00:14:05 --> 00:14:07 uh, where the escape velocity
00:14:08 --> 00:14:11 uh, is more than the speed of
00:14:11 --> 00:14:14 light. And so nothing can escape from
00:14:14 --> 00:14:16 within the event horizon. Uh, and in
00:14:16 --> 00:14:18 particular light can't escape. So the event
00:14:18 --> 00:14:20 horizon is black. It's a sphere around the
00:14:20 --> 00:14:22 black hole, uh, through which you can't see
00:14:22 --> 00:14:24 because nothing escapes, including light.
00:14:25 --> 00:14:28 So um, that is what the event horizon
00:14:28 --> 00:14:30 is. In a sense it's imaginary. Uh, uh,
00:14:30 --> 00:14:33 Andrew, you know it's not a real surface,
00:14:33 --> 00:14:35 it's an imaginary surface because it's just
00:14:35 --> 00:14:38 the boundary between what's visible and
00:14:38 --> 00:14:41 what's not visible.
00:14:41 --> 00:14:44 Now we know when black holes
00:14:44 --> 00:14:47 collide. Uh, I don't know that
00:14:47 --> 00:14:49 much about the details of these things but
00:14:49 --> 00:14:52 there is a period immediately after
00:14:52 --> 00:14:54 they've merged which is called the ring down.
00:14:54 --> 00:14:57 And it's a time when they sort of
00:14:57 --> 00:15:00 consolidate as one black hole. And that
00:15:00 --> 00:15:03 means their event horizons also consolidate.
00:15:03 --> 00:15:06 And I think this direct wave that has been
00:15:06 --> 00:15:08 detected is basically
00:15:09 --> 00:15:12 uh, an artefact of that ring
00:15:12 --> 00:15:14 down. Uh, and so um,
00:15:15 --> 00:15:18 what I guess is uh, perhaps the
00:15:18 --> 00:15:20 takeaway message from this work is not
00:15:21 --> 00:15:24 that we've learned something miraculous
00:15:24 --> 00:15:26 and new about the event horizon
00:15:26 --> 00:15:28 but that we've learned that there might be a
00:15:28 --> 00:15:31 way of, in future
00:15:31 --> 00:15:34 gravitational wave events uh, might be
00:15:34 --> 00:15:36 a way of analysing these direct waves to give
00:15:36 --> 00:15:39 us more information on the black hole
00:15:39 --> 00:15:42 event horizon. Because at the moment we don't
00:15:42 --> 00:15:45 know much about it. We've seen them
00:15:45 --> 00:15:48 in the telescopes, you know the
00:15:48 --> 00:15:50 um, observations from the Event Horizon
00:15:50 --> 00:15:53 Telescope that um, amalgam of many radio
00:15:53 --> 00:15:55 telescopes, an Earth sized array,
00:15:56 --> 00:15:58 uh, which has been used to look at the black
00:15:58 --> 00:16:01 holes in centre of our own galaxy. And in
00:16:01 --> 00:16:03 M57 I think it was uh, with um,
00:16:05 --> 00:16:08 uh fairly high degree of
00:16:08 --> 00:16:10 precision. What we've seen is the black
00:16:10 --> 00:16:13 shadow of the event horizon. Um
00:16:13 --> 00:16:15 but perhaps with these gravitational waves,
00:16:15 --> 00:16:18 these direct waves there might be a ah,
00:16:18 --> 00:16:21 way of teasing out even more detail from
00:16:21 --> 00:16:24 these distant and highly enigmatic
00:16:24 --> 00:16:24 objects.
00:16:25 --> 00:16:27 Andrew Dunkley: Yes, indeed. And uh, another interesting
00:16:27 --> 00:16:29 thing that comes out of this storey is that
00:16:29 --> 00:16:31 um, they're suggesting uh, the
00:16:31 --> 00:16:34 measurements that uh, that they've
00:16:34 --> 00:16:37 made could be a step towards
00:16:38 --> 00:16:40 future um, tests of general relativity
00:16:41 --> 00:16:44 using direct waves. So you know there's all
00:16:44 --> 00:16:46 sorts of potential by the sound of it.
00:16:46 --> 00:16:49 Professor Fred Watson: That's right, yeah. I mean exactly. And uh,
00:16:49 --> 00:16:52 of course this is one of the holy grails of
00:16:52 --> 00:16:55 science generally actually certainly physics
00:16:55 --> 00:16:57 to find chinks in general relativity
00:16:57 --> 00:17:00 because uh, at the moment it behaves
00:17:00 --> 00:17:02 exactly as predicted. Everything that we've
00:17:02 --> 00:17:05 seen in the universe Follows, uh,
00:17:05 --> 00:17:07 the rules and regulations of general
00:17:07 --> 00:17:10 relativity, uh, in a perfect way.
00:17:11 --> 00:17:13 So maybe, uh, direct waves will, as you
00:17:13 --> 00:17:16 said, uh, give us a way of testing general
00:17:16 --> 00:17:19 relativity. If we find, um, things
00:17:19 --> 00:17:22 that don't work in general relativity, then
00:17:22 --> 00:17:23 that could be an opening into new physics,
00:17:23 --> 00:17:26 which is certainly a hot topic at the moment.
00:17:26 --> 00:17:28 Andrew Dunkley: Indeed it is. Uh, well, uh, everyone,
00:17:28 --> 00:17:30 including Einstein, thinks something's wrong
00:17:30 --> 00:17:32 with it. They just. Yes, they just can't find
00:17:32 --> 00:17:34 anything at the moment. It keeps coming up
00:17:35 --> 00:17:37 aces every time they test it.
00:17:37 --> 00:17:38 Professor Fred Watson: Yeah, they think something's wrong with it
00:17:38 --> 00:17:41 because it doesn't sit with quantum
00:17:41 --> 00:17:43 mechanics. The two are incompatible and they
00:17:43 --> 00:17:46 both work perfectly well, but they're
00:17:46 --> 00:17:46 incompatible.
00:17:48 --> 00:17:49 Andrew Dunkley: Weird, isn't it?
00:17:49 --> 00:17:50 Professor Fred Watson: Yes, that's very weird. Yeah.
00:17:50 --> 00:17:52 Andrew Dunkley: The other thing that I find fascinating about
00:17:52 --> 00:17:55 this Storey, is that from something as simple
00:17:55 --> 00:17:57 as a, as a gravitational wave,
00:17:57 --> 00:18:00 they're able to break it down and find
00:18:00 --> 00:18:02 information that is
00:18:04 --> 00:18:07 really just. You can't
00:18:07 --> 00:18:10 see any of this. It's all just data, isn't
00:18:10 --> 00:18:10 it?
00:18:10 --> 00:18:12 Professor Fred Watson: Yeah, yeah, that's correct. That's right.
00:18:12 --> 00:18:14 But, uh, the physics is well understood
00:18:14 --> 00:18:17 because general relativity is such a reliable
00:18:17 --> 00:18:19 tool for people to use to analyse these
00:18:19 --> 00:18:22 things. Um, that's how we can make these
00:18:22 --> 00:18:25 statements about it. And yes, um, if we can
00:18:25 --> 00:18:27 find flaws with general relativity, it will
00:18:27 --> 00:18:30 be very exciting indeed it will.
00:18:30 --> 00:18:33 Andrew Dunkley: And you can read all about it@the space.com
00:18:33 --> 00:18:35 website. Uh, they publish their research,
00:18:36 --> 00:18:39 uh, in the journal Nature. This
00:18:39 --> 00:18:41 is Space Nuts with Andrew Dunkley and
00:18:41 --> 00:18:43 Professor Fred Watson Watson.
00:18:45 --> 00:18:47 Professor Fred Watson: I believe that this nation should commit
00:18:47 --> 00:18:50 Andrew Dunkley: itself to achieving the goal,
00:18:50 --> 00:18:53 before this decade is out, of landing a
00:18:53 --> 00:18:53 man
00:18:53 --> 00:18:56 Professor Fred Watson: on the moon and returning him safely to the
00:18:56 --> 00:18:56 Earth.
00:18:56 --> 00:18:57 Andrew Dunkley: These nuts.
00:18:58 --> 00:19:01 Now, Fred Watson, we turn our, uh, attention
00:19:01 --> 00:19:03 towards China. Uh, of course, they've got a
00:19:03 --> 00:19:06 very active space station in operation
00:19:06 --> 00:19:09 at the moment. Uh, the latest news though is
00:19:09 --> 00:19:12 that they intend to, uh, make it
00:19:12 --> 00:19:14 bigger and at the same time they're going to
00:19:14 --> 00:19:17 put a new space telescope into, uh, into
00:19:17 --> 00:19:19 orbit as well. So, uh, they're really going
00:19:19 --> 00:19:20 ahead in leaps and bounds, aren't they?
00:19:21 --> 00:19:24 Professor Fred Watson: They are, yes. Uh, it's, um. You know, this
00:19:24 --> 00:19:26 is part of the Chinese. It's not the China
00:19:26 --> 00:19:29 national, uh, Space Agency.
00:19:29 --> 00:19:31 Uh, I think it's that they've got a separate
00:19:31 --> 00:19:34 space agency for human space flight.
00:19:35 --> 00:19:37 Uh, and that's the organisation that
00:19:37 --> 00:19:40 operates the Tiangong, uh, space Station,
00:19:40 --> 00:19:43 which has been up there since 2021, I think
00:19:43 --> 00:19:45 was when, uh, we started seeing it being
00:19:45 --> 00:19:48 assembled. It was assembled in a very similar
00:19:48 --> 00:19:50 manner to the International Space Station by
00:19:51 --> 00:19:54 building sort of modules that you can stick
00:19:54 --> 00:19:57 together like Lego, uh, up once
00:19:57 --> 00:19:58 uh, these modules are in orbit.
00:19:58 --> 00:20:01 Andrew Dunkley: Yeah. And at the moment it's the China
00:20:01 --> 00:20:03 National Space Administration which handles
00:20:03 --> 00:20:06 the programmes, and the China Manned Space
00:20:06 --> 00:20:08 Agency which um, oversees human
00:20:08 --> 00:20:09 spaceflight.
00:20:09 --> 00:20:12 Professor Fred Watson: That's right. I knew there were two
00:20:12 --> 00:20:13 organisations involved. Thank you for that.
00:20:14 --> 00:20:14 Andrew Dunkley: That's all right.
00:20:15 --> 00:20:17 Professor Fred Watson: Um, so, uh,
00:20:17 --> 00:20:20 yes, so uh, at the moment the,
00:20:20 --> 00:20:22 the Tiangong consists of three
00:20:22 --> 00:20:25 modules and they're arranged in a sort of T
00:20:25 --> 00:20:27 shape, uh, with um.
00:20:28 --> 00:20:30 Uh, two, three. The, the three
00:20:31 --> 00:20:33 end points of the modules if you like,
00:20:33 --> 00:20:36 coming, coming together in a, in a sort of
00:20:36 --> 00:20:38 vestibule where you can uh, tunnel your way
00:20:38 --> 00:20:40 from one to the, to the other with these
00:20:41 --> 00:20:43 uh, basically entry and exit hatches. That
00:20:43 --> 00:20:46 uh, is the way things work on the
00:20:46 --> 00:20:48 International Space Station as well. But as
00:20:48 --> 00:20:51 you've said, uh, what they're now planning to
00:20:51 --> 00:20:53 do is to add three more
00:20:53 --> 00:20:56 modules. Um and the reason they
00:20:56 --> 00:20:59 want to do that is because uh,
00:20:59 --> 00:21:02 they want to do more research up there,
00:21:02 --> 00:21:05 uh, and make more frequent crew and
00:21:05 --> 00:21:08 cargo changes. Um, so they're
00:21:08 --> 00:21:11 actually, I think the way to deal
00:21:11 --> 00:21:14 with that is to make the space station
00:21:14 --> 00:21:17 bigger. Um, and so it's going to be
00:21:17 --> 00:21:20 what they're calling a double T shape, which
00:21:20 --> 00:21:22 I think is probably an H shape
00:21:23 --> 00:21:25 if I can put it that way. Um, well that's
00:21:25 --> 00:21:25 what it.
00:21:25 --> 00:21:27 Andrew Dunkley: Yeah, it would turn into that, wouldn't it?
00:21:27 --> 00:21:29 Professor Fred Watson: You'd expect so. Yes, that's right. Unless
00:21:29 --> 00:21:32 they do something clever, uh, like turn
00:21:32 --> 00:21:35 one of the T's round, uh right angles to the
00:21:35 --> 00:21:37 other one. Anyway, we don't know what's going
00:21:37 --> 00:21:40 to happen there. But um, there is a new
00:21:40 --> 00:21:43 multipurpose um, module and two
00:21:43 --> 00:21:46 new experimental modules that are planned
00:21:46 --> 00:21:49 uh, to um, essentially uh,
00:21:49 --> 00:21:51 you know, allow Chinese
00:21:52 --> 00:21:54 uh, space exploration in low Earth
00:21:54 --> 00:21:57 orbit to continue and be extended.
00:21:58 --> 00:22:01 Um, um, we understand from
00:22:01 --> 00:22:03 um, some of the researchers in China
00:22:04 --> 00:22:07 that uh, it's always been
00:22:07 --> 00:22:10 uh, an expectation that this
00:22:10 --> 00:22:12 would take place, that there'd be this
00:22:12 --> 00:22:15 extension. Uh, and what it will do in
00:22:15 --> 00:22:18 terms of the mass of the um, space
00:22:18 --> 00:22:20 station is take it up from its current 90
00:22:20 --> 00:22:22 tonnes, uh up to
00:22:23 --> 00:22:26 180 tonnes or thereabouts. And there's a
00:22:26 --> 00:22:28 yardstick, if I remember rightly, and you
00:22:28 --> 00:22:30 might be able to correct me here Andrew, but
00:22:30 --> 00:22:32 I think the International Space station is
00:22:32 --> 00:22:34 about 400 tonnes in terms of its mass.
00:22:35 --> 00:22:38 I think that is the case. So uh,
00:22:38 --> 00:22:41 that's uh, the plan and
00:22:41 --> 00:22:44 alongside that, as you've already mentioned
00:22:44 --> 00:22:46 Andrew, is the idea of a new
00:22:47 --> 00:22:50 um, space observatory, an optical
00:22:50 --> 00:22:53 Telescope quite similar in some
00:22:53 --> 00:22:55 ways to the Hubble Space Telescope. A
00:22:55 --> 00:22:58 slightly smaller mirror, 2 metres rather than
00:22:58 --> 00:22:59 2.3 metres,
00:23:01 --> 00:23:03 um, and also with a much wider
00:23:03 --> 00:23:06 field of view. The Hubble has quite a narrow
00:23:06 --> 00:23:09 field of view. Uh, and in fact the Nancy
00:23:09 --> 00:23:12 Grace Roman telescope, which is also very
00:23:12 --> 00:23:14 similar to the Hubble, will have a much wider
00:23:14 --> 00:23:16 field of view than Hubble. That's being
00:23:16 --> 00:23:18 launched later this year, I hope.
00:23:19 --> 00:23:21 Um, this, uh, Chinese
00:23:21 --> 00:23:24 telescope, uh, which has a name, Shuntian,
00:23:24 --> 00:23:27 I think, is probably how it's
00:23:27 --> 00:23:30 pronounced in my,
00:23:30 --> 00:23:32 um, poor Chinese, uh, poor
00:23:32 --> 00:23:34 Mandarin and poor Chinese.
00:23:35 --> 00:23:38 Um, it's got a much bigger field of view and
00:23:38 --> 00:23:41 will actually give new, uh,
00:23:41 --> 00:23:43 surveys to Chinese, uh,
00:23:44 --> 00:23:46 astronomers. We'll see a lot more
00:23:46 --> 00:23:48 information about the universe coming from
00:23:48 --> 00:23:50 this telescope. The more telescopes you've
00:23:50 --> 00:23:52 got on the universe, the better. And, uh,
00:23:52 --> 00:23:55 Shuntian will be one of those, uh,
00:23:55 --> 00:23:58 features when it is launched and actually
00:23:58 --> 00:24:01 commissioned, uh, that will, we hope, um,
00:24:01 --> 00:24:04 really bring new insights into our knowledge
00:24:04 --> 00:24:04 of space.
00:24:04 --> 00:24:07 Andrew Dunkley: Yeah. Apparently its field of view
00:24:07 --> 00:24:10 is going to be massive compared to
00:24:10 --> 00:24:12 Hubble at 300 times.
00:24:12 --> 00:24:14 Professor Fred Watson: Correct? Yes, that's right. So it's a wide
00:24:14 --> 00:24:17 angle telescope rather than the sort of
00:24:17 --> 00:24:19 pinpoint view of the Hubble.
00:24:19 --> 00:24:21 Andrew Dunkley: Yeah, quite incredible. Uh, you were right
00:24:21 --> 00:24:23 about the International space station. Uh,
00:24:23 --> 00:24:26 419 kilogrammes
00:24:26 --> 00:24:29 is its mass, or say 420,
00:24:30 --> 00:24:33 um, tonnes. Yes, indeed. Um, the
00:24:33 --> 00:24:35 other interesting thing that China's working
00:24:35 --> 00:24:38 on, uh, is a new,
00:24:38 --> 00:24:41 um, um, delivery system for their. They
00:24:41 --> 00:24:42 call them taika nauts, don't they?
00:24:42 --> 00:24:44 Professor Fred Watson: Yes, they do, yeah.
00:24:44 --> 00:24:46 Andrew Dunkley: Uh, they want to. They want to develop a
00:24:46 --> 00:24:49 rocket system that will send seven up at a
00:24:49 --> 00:24:49 time.
00:24:49 --> 00:24:52 Professor Fred Watson: Yes, yeah, seven up.
00:24:52 --> 00:24:55 Andrew Dunkley: No, I'm joking. But, um, again, yeah, that's
00:24:55 --> 00:24:57 what they're looking at doing at the moment.
00:24:57 --> 00:24:58 They can only send up three at a time.
00:24:59 --> 00:25:01 Professor Fred Watson: Yes. So the Chinese, um,
00:25:02 --> 00:25:04 uh, orbital
00:25:04 --> 00:25:07 vehicle for getting astronauts up,
00:25:07 --> 00:25:09 Taikonauts up there. And
00:25:10 --> 00:25:11 I'm ashamed that I can't remember what it's
00:25:11 --> 00:25:13 called. Uh, is it Shenzhou?
00:25:14 --> 00:25:16 Shenzhou, I can't remember. Um,
00:25:16 --> 00:25:19 but that is basically an adaptation
00:25:20 --> 00:25:22 of the old Soyuts Russian
00:25:22 --> 00:25:25 spacecraft which is still in service in the
00:25:25 --> 00:25:26 International Space Station. Developed in the
00:25:26 --> 00:25:29 1960s. A, uh, three person,
00:25:29 --> 00:25:32 uh, module. Uh, I think I'm right in
00:25:32 --> 00:25:34 saying that the crew Dragon can take up to
00:25:34 --> 00:25:36 seven astronauts as well.
00:25:36 --> 00:25:38 Andrew Dunkley: Interesting. Shenzhou.
00:25:38 --> 00:25:40 Professor Fred Watson: Shenzhou, yeah.
00:25:40 --> 00:25:41 Andrew Dunkley: Is the, um, is the system they
00:25:41 --> 00:25:42 Professor Fred Watson: used at the moment.
00:25:43 --> 00:25:45 You did m. So, uh,
00:25:46 --> 00:25:48 yes. So that will go from three to seven.
00:25:48 --> 00:25:50 It's understandable, you know, if you Want to
00:25:50 --> 00:25:52 keep the crews coming and going. I think this
00:25:52 --> 00:25:54 is a really important development because,
00:25:55 --> 00:25:58 um, if nothing else, it's going to, I
00:25:58 --> 00:26:00 think, spur, uh,
00:26:01 --> 00:26:03 the private sector, um, to pick up the
00:26:03 --> 00:26:06 baton of what you might call Western
00:26:06 --> 00:26:08 International Space Stations or the Western
00:26:08 --> 00:26:11 International Space Station, because that's
00:26:11 --> 00:26:13 scheduled at the moment to be decommissioned
00:26:13 --> 00:26:16 in 2030. That might change. But
00:26:16 --> 00:26:18 it's a possibility that we will lose the ISS
00:26:19 --> 00:26:22 in 2030. And we've seen problems
00:26:22 --> 00:26:24 with the leakage that we had in one of the
00:26:24 --> 00:26:27 modules a couple of weeks ago where the
00:26:27 --> 00:26:30 crew was evacuated, not evacuated, but
00:26:30 --> 00:26:32 moved. The American crew,
00:26:33 --> 00:26:35 uh, the NASA end of the spacecraft
00:26:35 --> 00:26:38 were moved into a crew Dragon capsule
00:26:38 --> 00:26:41 to uh, just be certain that
00:26:41 --> 00:26:44 nothing untoward was going to happen, uh,
00:26:44 --> 00:26:47 if there was a catastrophic
00:26:47 --> 00:26:49 leak, uh, when the Roscosmos,
00:26:50 --> 00:26:52 cosmonauts, they were actually trying to fix
00:26:52 --> 00:26:54 the leak, uh, they moved the other crew,
00:26:55 --> 00:26:57 um, into the crew Dragon capsule for safety.
00:26:58 --> 00:27:00 Andrew Dunkley: Yeah, uh, in terms of replacing the iss,
00:27:01 --> 00:27:04 there are no firm plans at the moment, but
00:27:04 --> 00:27:06 they're kind of thinking about,
00:27:07 --> 00:27:09 um, I think you mentioned it, the commercial
00:27:09 --> 00:27:11 sector getting involved.
00:27:12 --> 00:27:14 And that's probably logical.
00:27:15 --> 00:27:18 I'm pretty sure that, uh, Elon would be
00:27:18 --> 00:27:21 pretty keen to put a space station into orbit
00:27:21 --> 00:27:23 and a few others probably.
00:27:23 --> 00:27:25 There's plenty of people around with uh,
00:27:25 --> 00:27:26 megabucks to do it.
00:27:27 --> 00:27:30 Professor Fred Watson: Yes, that's right. Um, um, but, uh, you
00:27:30 --> 00:27:32 know, you might think, have to think
00:27:32 --> 00:27:35 carefully about whether you, uh, take
00:27:35 --> 00:27:37 over the old, uh, the old tired
00:27:38 --> 00:27:41 and quite dodgy old, uh,
00:27:41 --> 00:27:43 International Space Station or whether you
00:27:43 --> 00:27:46 build something new. Um, and uh, of course
00:27:46 --> 00:27:47 the technology's moved on enormously since
00:27:47 --> 00:27:50 the 1990s when that was put together.
00:27:50 --> 00:27:53 It's been continuously occupied since
00:27:53 --> 00:27:56 2000. Uh, that's 26
00:27:56 --> 00:27:59 years of, um, tenants coming and going. It's
00:27:59 --> 00:28:01 probably taken a fair beating inside.
00:28:01 --> 00:28:03 Andrew Dunkley: Yeah, I'm sure they've had a few parties.
00:28:03 --> 00:28:04 Yeah, no doubt about it.
00:28:06 --> 00:28:08 Uh, if you want to uh, read all about, uh,
00:28:08 --> 00:28:09 China's plans, you can do
00:28:09 --> 00:28:12 that@space.com. uh, this is
00:28:12 --> 00:28:14 Space Nuts with Andrew Dunkley and Professor
00:28:14 --> 00:28:15 Fred Watson Watson.
00:28:18 --> 00:28:21 Space Nuts, our final
00:28:21 --> 00:28:23 storey. Fred Watson takes us close to home.
00:28:23 --> 00:28:26 And this is really quite a fascinating storey
00:28:26 --> 00:28:29 because it talks about a star, not
00:28:29 --> 00:28:32 our sun. Ah, another star that got
00:28:32 --> 00:28:35 up close and personal, um, with
00:28:35 --> 00:28:38 our particular, uh, sun, um, a
00:28:38 --> 00:28:40 little while ago. But the
00:28:40 --> 00:28:42 effects of that interaction,
00:28:43 --> 00:28:45 uh, seem to still exist,
00:28:46 --> 00:28:47 which is very odd.
00:28:47 --> 00:28:50 Professor Fred Watson: Yeah, well, that's right. Uh, yes, it is,
00:28:50 --> 00:28:53 it's an interesting storey. It covers two
00:28:53 --> 00:28:55 quite different bits of astronomy here that
00:28:55 --> 00:28:57 come together to sort of work out what was
00:28:57 --> 00:29:00 going on. So this star in question,
00:29:01 --> 00:29:02 it's got the glorious name of
00:29:02 --> 00:29:05 HD7977. HD
00:29:05 --> 00:29:07 stands for Henry Draper. It's one of the
00:29:07 --> 00:29:09 early star catalogues, uh, from the 19th
00:29:09 --> 00:29:12 century I think, uh, the Henry Draper
00:29:12 --> 00:29:15 catalogue. Uh, and it's a relatively
00:29:15 --> 00:29:18 near star, similar to the
00:29:18 --> 00:29:20 sun. Uh, it's currently in the constellation
00:29:20 --> 00:29:23 of Cassiopeia, which is um, one of my
00:29:23 --> 00:29:25 favourite northern constellations. Actually.
00:29:25 --> 00:29:27 It's one that we don't see from down here in
00:29:27 --> 00:29:30 Australia. Uh, so,
00:29:30 --> 00:29:33 um, how do we know that
00:29:33 --> 00:29:36 HD7977 had um,
00:29:36 --> 00:29:39 a near miss with our solar system?
00:29:39 --> 00:29:42 And the answer is with the Gaia mission.
00:29:42 --> 00:29:45 So Gaia is a spacecraft. Uh,
00:29:45 --> 00:29:47 it sits at the um, uh,
00:29:48 --> 00:29:51 sun, Earth, uh, L2 point, that's
00:29:51 --> 00:29:54 the Lagrange point, on the opposite side of
00:29:54 --> 00:29:56 the Earth from the sun. Um, it's been
00:29:57 --> 00:29:59 working for, I think, certainly more than a
00:29:59 --> 00:30:02 decade. And what it's done is measured
00:30:02 --> 00:30:05 star positions with absolutely
00:30:05 --> 00:30:07 exquisite precision. Uh, you're talking
00:30:07 --> 00:30:10 about, I think it's sort of some
00:30:10 --> 00:30:12 accuracies in the region of 100 millionths of
00:30:12 --> 00:30:15 an arc second. These are phenomenal
00:30:15 --> 00:30:17 accuracies. And an arc second of course is
00:30:17 --> 00:30:20 1-3600th of a degree, uh,
00:30:20 --> 00:30:23 the size of a, here In Australia, a $1 coin
00:30:23 --> 00:30:25 held up at five kilometres. It's a tiny
00:30:25 --> 00:30:27 angle, but this thing's measuring
00:30:28 --> 00:30:30 millionths of that basically, or 100
00:30:30 --> 00:30:33 millions. Uh, and what that does is it
00:30:33 --> 00:30:35 allows you, if you make these measurements at
00:30:35 --> 00:30:38 different times, it allows you to plot the
00:30:38 --> 00:30:41 motions of stars,
00:30:41 --> 00:30:44 uh, not just in our own galaxy and in our own
00:30:44 --> 00:30:46 neighbourhood, but also in the Two
00:30:46 --> 00:30:49 Magellanic Clouds, uh, the two
00:30:49 --> 00:30:52 nearest neighbour dwarf galaxies, the big
00:30:52 --> 00:30:54 ones, Large and Small Magellanic Clouds
00:30:54 --> 00:30:57 165 and 200 light
00:30:57 --> 00:31:00 years away respectively. Uh, those,
00:31:00 --> 00:31:02 uh, you can detect the motions of stars in
00:31:02 --> 00:31:05 those galaxies. And even in the Andromeda
00:31:05 --> 00:31:08 galaxy, about 2 1/2 million light years away,
00:31:08 --> 00:31:10 you can see evidence of what we call lateral
00:31:10 --> 00:31:13 motion on the sky, sideways motion of things.
00:31:13 --> 00:31:15 And if you can measure the radial velocity,
00:31:15 --> 00:31:18 that's the velocity along the line of sight,
00:31:18 --> 00:31:20 which is actually much easier if you can do
00:31:20 --> 00:31:22 that as well. You've got, um, the three
00:31:22 --> 00:31:25 dimensional motion of objects in space. And
00:31:25 --> 00:31:27 that is how, uh,
00:31:28 --> 00:31:30 HD7977 was picked
00:31:30 --> 00:31:33 up as having passed close to the sun
00:31:33 --> 00:31:36 about two and a half million years ago.
00:31:37 --> 00:31:39 As both these stars, The sun and
00:31:39 --> 00:31:42 HD7977, as they both orbit around the
00:31:42 --> 00:31:44 centre of our galaxy. Uh, we still
00:31:44 --> 00:31:47 don't know exactly how close. Uh, the data
00:31:47 --> 00:31:50 from Gaia suggests It was between
00:31:50 --> 00:31:53 4 and 25
00:31:53 --> 00:31:55 astronomical units. And as we've mentioned
00:31:55 --> 00:31:57 before, an astronomical unit is the distance
00:31:57 --> 00:32:00 between the Earth and the sun. Um, convenient
00:32:00 --> 00:32:03 measure it is uh, 150 million kilometres.
00:32:04 --> 00:32:06 Um, they may have
00:32:07 --> 00:32:09 um, we might be able to
00:32:09 --> 00:32:12 tie that close approach down though by other
00:32:12 --> 00:32:15 methods. And the methods in question
00:32:16 --> 00:32:19 have been employed by uh, some
00:32:19 --> 00:32:21 scientists at the University of
00:32:21 --> 00:32:24 Bordeaux. Uh, and basically
00:32:24 --> 00:32:27 what they have done is looked not
00:32:27 --> 00:32:30 at Gaia data to try and refine
00:32:30 --> 00:32:33 uh, this sort of look back in
00:32:33 --> 00:32:35 time as to when these two stars were close
00:32:35 --> 00:32:38 together. They've looked at long period
00:32:38 --> 00:32:40 comets, comets that uh, come in
00:32:40 --> 00:32:43 from the very furthest reaches of the solar
00:32:43 --> 00:32:45 system where we think there is a
00:32:45 --> 00:32:47 reservoir of comets. We call it the Oort
00:32:47 --> 00:32:50 Cloud. Uh, and it turns out that
00:32:50 --> 00:32:53 if you look at long period comets,
00:32:53 --> 00:32:56 uh, which have been measured over the
00:32:56 --> 00:32:59 past hundred years I guess, um, then
00:32:59 --> 00:33:02 you get uh, an idea
00:33:02 --> 00:33:04 of the distribution of their orbits.
00:33:05 --> 00:33:08 And basically there's a quote here
00:33:08 --> 00:33:11 from one of the authors uh, of
00:33:11 --> 00:33:14 the paper that we're talking about uh, who
00:33:14 --> 00:33:16 says the distribution of comet orbits
00:33:16 --> 00:33:18 suggests we living through an unusual time
00:33:19 --> 00:33:21 where HD 7977 has
00:33:21 --> 00:33:24 dominated the generation of new comets
00:33:25 --> 00:33:27 and not the larger gravitational field of the
00:33:27 --> 00:33:30 Milky Way as it usually would. This would
00:33:30 --> 00:33:31 also mean we're living through the late
00:33:31 --> 00:33:34 stages of a pretty rare and powerful
00:33:34 --> 00:33:37 comet shower. And so what they've done
00:33:37 --> 00:33:40 is made computer simulations of uh,
00:33:40 --> 00:33:43 how comet orbits might behave
00:33:44 --> 00:33:46 as a result of being tipped out of the Oort
00:33:46 --> 00:33:49 cloud by the passage of this star HD
00:33:49 --> 00:33:52 7977. They've kicked out the Oort cloud
00:33:52 --> 00:33:54 and heading towards the sun. Uh, they've
00:33:54 --> 00:33:57 measured uh, basically the details of
00:33:57 --> 00:34:00 112 long period comets. Actually they've
00:34:00 --> 00:34:02 chosen ones that have only been observed in
00:34:02 --> 00:34:05 recent years, since 1989 because
00:34:05 --> 00:34:08 that's when we could detect comets coming
00:34:08 --> 00:34:11 from uh, any part of the sky. Uh,
00:34:11 --> 00:34:13 if you only limit yourself to one part of the
00:34:13 --> 00:34:16 sky then you've got uh, as visible for
00:34:16 --> 00:34:18 example by a single observatory, uh, or even
00:34:18 --> 00:34:20 as visible by the Northern Hemisphere
00:34:20 --> 00:34:23 observatory. You're missing uh,
00:34:23 --> 00:34:25 half the objects that you want to see. And
00:34:25 --> 00:34:27 since what you're doing is looking at the
00:34:27 --> 00:34:29 statistical distribution of these things, you
00:34:29 --> 00:34:32 can't afford to um, eliminate
00:34:32 --> 00:34:34 things that way. It's what would be called a
00:34:34 --> 00:34:37 selection effect. Um, so yes these
00:34:37 --> 00:34:40 long period comets they've got very elongated
00:34:40 --> 00:34:43 Orbits, uh, and the suggestion is that the
00:34:43 --> 00:34:46 distribution of those orbits in relation to
00:34:46 --> 00:34:47 the direction that we know
00:34:47 --> 00:34:50 HD7977 went through the solar system or
00:34:50 --> 00:34:53 went close to the solar system. Uh, that's
00:34:53 --> 00:34:56 why they believe, uh, that the two
00:34:56 --> 00:34:58 events, uh, um, the close
00:34:58 --> 00:35:01 passage of 7977, uh,
00:35:01 --> 00:35:04 tipped up the comets and caused a lot more of
00:35:04 --> 00:35:07 these comets to come in. And if you
00:35:07 --> 00:35:10 accept uh, their hypothesis,
00:35:10 --> 00:35:13 um, then what it does is,
00:35:13 --> 00:35:16 ties down rather
00:35:16 --> 00:35:18 better the distance that we estimate
00:35:19 --> 00:35:21 HD7977, uh,
00:35:22 --> 00:35:25 approach the sun at somewhere
00:35:25 --> 00:35:28 between 6 and 10 astronomical units.
00:35:28 --> 00:35:30 A tighter window compared with the 4 to
00:35:30 --> 00:35:33 25 astronomical units that Gaia
00:35:33 --> 00:35:36 suggests. Yes, uh, so, uh, it's a nice
00:35:36 --> 00:35:38 tightening up of our uh, understanding of
00:35:38 --> 00:35:41 this hypothesised but probably
00:35:41 --> 00:35:43 real event 2 1/2 million years ago.
00:35:43 --> 00:35:45 Andrew Dunkley: And just to give people a bit of an idea of
00:35:45 --> 00:35:48 the distance, so somewhere between 6 and
00:35:48 --> 00:35:50 10 AU is where
00:35:50 --> 00:35:52 HD7977 and kind
00:35:52 --> 00:35:54 of grazed our uh, solar system.
00:35:54 --> 00:35:55 Professor Fred Watson: Yes.
00:35:55 --> 00:35:57 Andrew Dunkley: Voyager 1 is 170
00:35:57 --> 00:36:00 AU from Earth. So
00:36:00 --> 00:36:02 we're talking a fair way out.
00:36:02 --> 00:36:03 Professor Fred Watson: It's a long way off. That's right.
00:36:04 --> 00:36:06 Andrew Dunkley: You're talking probably getting into the
00:36:06 --> 00:36:08 vicinity of the Oort cloud, which makes sense
00:36:08 --> 00:36:11 given what they're hypothesising in
00:36:11 --> 00:36:11 this paper.
00:36:12 --> 00:36:15 Professor Fred Watson: Exactly right. So a star passing nearby the
00:36:15 --> 00:36:18 Oort cloud would definitely upset it and
00:36:18 --> 00:36:20 send stuff in towards the, the inner solar
00:36:20 --> 00:36:23 system. Yes, it's actually um, it's a theory
00:36:23 --> 00:36:25 that, uh, that general mechanism
00:36:26 --> 00:36:28 was proposed by colleagues of mine in the
00:36:28 --> 00:36:30 Royal Observatory in Edinburgh, Victor Klub
00:36:30 --> 00:36:32 and Bill Napier, back in the late 1970s.
00:36:33 --> 00:36:36 The idea that they were suggesting it might
00:36:36 --> 00:36:38 have needed a bit more mass than a single
00:36:38 --> 00:36:41 star to disturb the Oort cloud. And uh, they
00:36:41 --> 00:36:44 suggested the passage nearby, passage of
00:36:44 --> 00:36:46 something called a giant molecular cloud, uh,
00:36:46 --> 00:36:48 a kind of stellar birthplace. If one of those
00:36:48 --> 00:36:50 goes past the solar system, they were
00:36:50 --> 00:36:53 inferring it would disturb the Oort cloud to
00:36:53 --> 00:36:55 the extent that you would get bombardment of
00:36:55 --> 00:36:57 the inner solar system by comets and that
00:36:57 --> 00:37:00 might be visible in the geological record on
00:37:00 --> 00:37:02 Earth. That was basically um, uh,
00:37:03 --> 00:37:06 their principal line of attack. Uh, really
00:37:06 --> 00:37:09 very interesting science. Uh, so this is not
00:37:09 --> 00:37:11 a new idea, but this is new research
00:37:12 --> 00:37:14 that suggests that um, perhaps we can learn
00:37:14 --> 00:37:16 more by pursuing it.
00:37:16 --> 00:37:19 Andrew Dunkley: Indeed, yes. Um, the paper by the way,
00:37:19 --> 00:37:21 has been accepted by the Planetary Science
00:37:21 --> 00:37:23 Journal and is available at the moment,
00:37:23 --> 00:37:26 moment on the Arxiv Preprint server.
00:37:26 --> 00:37:29 You can also read about it at phys.org, p h
00:37:29 --> 00:37:32 y s.org Fred Watson,
00:37:32 --> 00:37:34 that brings us to the end of the show.
00:37:34 --> 00:37:35 Thank you so much.
00:37:35 --> 00:37:37 Professor Fred Watson: Well, that went very quickly. Uh, what a good
00:37:37 --> 00:37:37 time we had.
00:37:38 --> 00:37:40 Andrew Dunkley: We did indeed. Yes. We'll catch you on the
00:37:40 --> 00:37:40 next one.
00:37:40 --> 00:37:41 Professor Fred Watson: Sounds great.
00:37:41 --> 00:37:43 Andrew Dunkley: Thank you very much, Professor Fred Watson
00:37:43 --> 00:37:45 Watson, astronomer at large. And don't forget
00:37:45 --> 00:37:47 between episodes to jump on our website and
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00:38:16 --> 00:38:19 You can do all of that on our website. And
00:38:19 --> 00:38:21 thanks to Huw in the studio who, uh, couldn't
00:38:21 --> 00:38:23 be with us today because he saw a passing
00:38:23 --> 00:38:26 star and chased her down for an autograph.
00:38:27 --> 00:38:29 And from and from me, Andrew Dunkley. Thanks
00:38:29 --> 00:38:31 for your company. We'll see you on the next
00:38:31 --> 00:38:33 episode of Space Nuts. Bye. Bye.
00:38:34 --> 00:38:36 You've been listening to the Space Nuts
00:38:36 --> 00:38:39 podcast, available at
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00:38:48 --> 00:38:51 Professor Fred Watson: has been another quality podcast production
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