Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / The Black Hole Discovery Revealing the Loudest Gravitational Wave Ever Recorded

Transcript

The Black Hole Discovery Revealing the Loudest Gravitational Wave Ever Recorded · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Andrew Dunkley: Hello there. Thanks for joining us. This is
• 0:02
  Space Nuts, where we talk astronomy and
• 0:05
  space science. My name is Andrew Dunkley.
• 0:07
  Great to have your company on this, the
• 0:10
  600 millionth episode. Maybe not that many,
• 0:13
  but we've done quite a few. What is it,
• 0:15
  643 we're up to? Blimey.
• 0:18
  All right, uh, what are we talking about?
• 0:19
  We're talking about, um, an old clapped out,
• 0:23
  uh, telescope. Fred Watson happens to be its
• 0:25
  patron. He's old and clapped out too. Uh,
• 0:27
  we're also going to look, uh, at
• 0:30
  a new black hole discovery which was made
• 0:33
  after, um, two black holes
• 0:35
  collided and they recorded the loudest crash
• 0:38
  of gravitational waves ever. So
• 0:41
  what's it going to tell us? Also, uh, China
• 0:43
  is going to upgrade its space station and
• 0:45
  launch a new space telescope. And a
• 0:48
  star that got close to our sun
• 0:51
  may have caused a bit of a disturbance in the
• 0:53
  force. We'll tell you all about it on this
• 0:56
  episode of space nuts.
• 0:58
  Professor Fred Watson: 15 seconds. Guidance is internal.
• 1:01
  10, 9. Ignition
• 1:04
  sequence.
• 1:04
  Andrew Dunkley: Star.
• 1:04
  Professor Fred Watson: Uh, space nuts. 5, 4, 3, 2. 1.
• 1:07
  2, 3, 4, 5, 5, 4, 3, 2,
• 1:10
  1.
• 1:10
  Andrew Dunkley: Space nuts. Astronauts report it feels
• 1:13
  good. And he's back again. As always,
• 1:16
  it's Professor Fred Watson Watson, astronomer
• 1:19
  at large. Hello, Fred Watson.
• 1:20
  Professor Fred Watson: Hello, Andrew. Hello. Uh, thank you for that
• 1:22
  nice introduction. It's, uh,
• 1:25
  nice to hear welcome like that.
• 1:29
  Andrew Dunkley: You know, I know I only said it a few seconds
• 1:31
  ago, but I forgot what I said. And then it
• 1:33
  dawned on me that I'd actually insulted.
• 1:35
  Professor Fred Watson: Yes. Oh, forget about that. Yeah, no, that's
• 1:37
  all right, that's all right. You're right.
• 1:39
  Andrew Dunkley: Last week.
• 1:40
  Professor Fred Watson: I am old and clapped out. There's no question
• 1:42
  about that.
• 1:44
  Andrew Dunkley: Aren't we all, Aren't we all?
• 1:47
  Um, now, um, before we get into, uh,
• 1:50
  today's storeys, um, the old clapped out
• 1:52
  telescope I referred to is actually a, uh,
• 1:54
  wonderful device, uh, that I've actually seen
• 1:57
  in person when we were down in Melbourne a
• 2:00
  few years ago. Uh, it's the
• 2:03
  Melbourne telescope. Dates back to
• 2:05
  1869. And you're its patron because you
• 2:08
  were there when they put the first screw in
• 2:10
  it. Got you again.
• 2:12
  Professor Fred Watson: Yeah. So the link and the reason why I'm.
• 2:15
  Well, there's a number of reasons why this
• 2:17
  telescope is very close to my heart. One is
• 2:19
  that, uh, I was
• 2:22
  still at school when I found a picture of it
• 2:24
  in Henry King's History of the Telescope, a
• 2:27
  very famous book, uh, on the history of
• 2:30
  telescopes, published, I think in 1955.
• 2:33
  Had a copy of that in the school library. And
• 2:35
  there's this telescope there, the Great
• 2:37
  Melbourne Telescope. And I thought that is.
• 2:39
  That is a telescope. That's what I want one
• 2:42
  like looks.
• 2:43
  Andrew Dunkley: It just looks like you'd expect one to
• 2:46
  look, doesn't it?
• 2:46
  Professor Fred Watson: You can tell it's a telescope. It's got um.
• 2:48
  With decorative bits like the latticework
• 2:51
  tube, which is uh, very unusual, almost
• 2:54
  unique. Anyway, that was my first
• 2:57
  um, encounter with it. Uh, and as
• 3:00
  sort of followed up as much as I could. A
• 3:02
  didn't realise that by then it was actually
• 3:04
  uh, in Canberra at Matt Stromlo. It had been
• 3:07
  refurbished, um, having left Melbourne in
• 3:10
  1944. But, uh,
• 3:12
  100 years
• 3:15
  exactly after work started on
• 3:18
  the manufacture of that telescope in
• 3:21
  1867, 100 years later I
• 3:24
  joined the company that built it.
• 3:27
  So it was uh, its 20th
• 3:30
  century equivalent. It was uh, Howard
• 3:33
  Grubb, Dublin when, uh, the telescope was
• 3:35
  built. By the time I got there it was sir,
• 3:37
  uh, Howard Grubb Parsons Co. Ltd. But
• 3:40
  it was basically the same company amalgamated
• 3:43
  in 1926 with the Parsons company. So,
• 3:46
  um, I continued my kinship with that
• 3:48
  telescope and uh, uh, of course when I came
• 3:51
  to Australia, was interested to see it at
• 3:54
  stromlo. Then in 2003,
• 3:57
  uh, the Stromlo Observatory had that terrible
• 4:00
  fire, bush fire that went through, destroyed
• 4:02
  all the heritage buildings, including the one
• 4:05
  that uh, that telescope sat in,
• 4:08
  uh, and basically melted a lot of
• 4:11
  the. Well, melted the dome onto the
• 4:13
  telescope. The dome was aluminium, uh, and
• 4:16
  the telescope was wrecked, its mirror was
• 4:18
  smashed and all the rest of it. Uh, so I,
• 4:21
  When I. So I wrote a book on the history of
• 4:23
  telescopes which was published I think
• 4:25
  just after that fire because,
• 4:28
  um, I wrote at the end I had a whole chapter
• 4:31
  on this telescope and I wrote something to
• 4:33
  the effect that uh. The best we could hope to
• 4:36
  see would for it to be a static
• 4:38
  exhibit in a museum, just the remnants.
• 4:42
  Uh, but it was for a while. Well it wasn't.
• 4:45
  No, it stayed put in Stromlo. And it was five
• 4:48
  years after the fire, 2008, when this
• 4:50
  consortium of museums, uh, Victoria,
• 4:53
  the Astronomical Society of Victoria, uh,
• 4:56
  Royal Botanic Gardens, Melbourne, because
• 4:58
  that's where it started its career. Uh,
• 5:02
  uh, and uh. I think the Bureau of Meteorology
• 5:04
  were involved as well. Uh, and they
• 5:07
  got together a plan to basically
• 5:10
  restore it. Uh, and
• 5:13
  so I uh, did play a role in that. In
• 5:16
  2015 we actually held
• 5:19
  a workshop which I chaired, which was about
• 5:21
  how you could update the optics of the
• 5:24
  telescope because the mechanical stuff could
• 5:26
  be refurbished. Uh, but the
• 5:29
  optics were a different matter. Uh, and a uh,
• 5:32
  sort of optical prescription was drawn up.
• 5:35
  Now Those optics are still in the process of
• 5:37
  being manufactured. Uh, but
• 5:40
  the telescope itself is now
• 5:43
  essentially mechanically complete. It is
• 5:45
  as complete as it was when it was built.
• 5:48
  And the work that's been done, more than 100
• 5:52
  volunteers and staff from Museums
• 5:54
  Victoria and the Astronomical Society of
• 5:56
  Victoria, well over a hundred have worked on
• 5:59
  it. And so last, uh, week there was a little
• 6:01
  party to celebrate that. And,
• 6:04
  uh, some of the museum's dignitary said a few
• 6:07
  words, I said a few words. The chap who's
• 6:09
  been leading the project, Simon Brink over
• 6:11
  the last few years, he said a few words. He's
• 6:13
  actually coming to lunch with us on Saturday.
• 6:16
  Oh, lovely. Even though he's in Melbourne,
• 6:18
  he's coming up, um, which is nice.
• 6:21
  Um, so we had a celebration and, uh,
• 6:24
  to be honest, what they've done is nothing
• 6:26
  short of miraculous because there weren't any
• 6:30
  diagrams of all the bits and pieces of this
• 6:32
  telescope. There were engineering diagrams of
• 6:35
  the thing complete. They were published in a
• 6:38
  journal. But the individual parts and
• 6:40
  probably thousands of
• 6:43
  components, screws, washers,
• 6:46
  uh, pulleys, cog wheels of various
• 6:49
  different sized, all of that. No
• 6:51
  idea what they looked like. And by
• 6:54
  scouring photographs of the telescope, uh,
• 6:57
  from many sources and
• 7:00
  working out things like the numbers of teeth
• 7:03
  you need on a cogwheel to make the things
• 7:05
  work properly, uh, they've done a great job
• 7:08
  with all that. And now it's in basically in
• 7:11
  perfect working order, except it doesn't have
• 7:13
  its main mirror yet that's being fabricated.
• 7:16
  Um, it's at the moment still at
• 7:19
  Scienceworks, which is the Science M Museum
• 7:21
  in Victoria. And it's a big exhibit which is
• 7:23
  Andrew Dunkley: worth a visit, especially with the kids.
• 7:25
  Professor Fred Watson: Yeah, it's a great place to go. Uh, and
• 7:27
  anybody, uh, who does go to Melbourne and
• 7:29
  sees scienceworks definitely have a look at
• 7:31
  the great Melbourne telescope. The hope is
• 7:33
  that one day it will be in its original
• 7:35
  building, which still exists in the Royal
• 7:37
  Botanic Gardens. Uh, but, um, there's quite a
• 7:40
  bit of work needs to be done to make
• 7:43
  that, uh, oh, s. Uh,
• 7:45
  satisfactory for 2026
• 7:48
  or whenever it happens, compared with
• 7:51
  the, um, you know, the health and safety
• 7:53
  regulations in 1869 when people came and
• 7:56
  went, um, just had a look through the
• 7:58
  telescope. That's the idea that it will
• 8:00
  eventually be a working telescope for the
• 8:02
  public for people to come and look through.
• 8:05
  Andrew Dunkley: Wonderful. And, uh, if you can't get down to
• 8:07
  see it in Melbourne, uh, just do a search for
• 8:09
  the Melbourne telescope online and have a
• 8:11
  look at it and you'll know what we're talking
• 8:13
  about, um, the lattice work is just
• 8:15
  beautiful. It is a glorious piece of
• 8:17
  equipment. And I stumbled across it. I
• 8:20
  didn't even know it was at Science Works when
• 8:22
  we went there. And we just went for a wander
• 8:24
  and found it. And I went, oh, Fred Watson
• 8:26
  will love this. And then it turns out you
• 8:28
  were the patron, so.
• 8:29
  Professor Fred Watson: Yes, that's right. Yeah. Yeah. It's um,
• 8:32
  it is, uh, it's quite staggering.
• 8:35
  It's how big it is, isn't it? When you.
• 8:36
  Andrew Dunkley: Oh yeah.
• 8:37
  Professor Fred Watson: Just when you.
• 8:37
  Andrew Dunkley: It blows your mind.
• 8:38
  Professor Fred Watson: Yes.
• 8:39
  Andrew Dunkley: You just stand there in awe.
• 8:40
  Professor Fred Watson: Telescope. It was the biggest fully
• 8:43
  steerable telescope in the world at the time
• 8:45
  when, um, it was built. It wasn't the
• 8:47
  biggest, but it was. Biggest telescope in the
• 8:49
  world. But it wasn't far off.
• 8:50
  Andrew Dunkley: Yeah. As a good friend of mine often says,
• 8:52
  it's a great piece of kit.
• 8:54
  Professor Fred Watson: It was a great piece of kit. And hopefully it
• 8:56
  will be again one day.
• 8:58
  Andrew Dunkley: Fingers crossed.
• 8:59
  All right, uh, moving on. We're talking black
• 9:02
  holes. Very unusual. We don't usually talk
• 9:04
  things like this, but, uh, this, this is an
• 9:06
  interesting one because they, They've uh,
• 9:08
  made it a bit of a discovery. They've.
• 9:09
  They've recorded the loudest crash of
• 9:11
  gravitational waves ever heard. And it was
• 9:14
  because of two black holes that
• 9:16
  decided, uh, to play billiards with each
• 9:19
  other and boom. Uh, but
• 9:22
  it's what they've discovered from the. In the
• 9:24
  aftermath of all this that's getting
• 9:26
  interesting.
• 9:27
  Professor Fred Watson: Uh, yes, it is. Um, so,
• 9:30
  yep, we black, um, gravitational waves
• 9:33
  from colliding objects have been detectable
• 9:36
  by humans since 2015,
• 9:39
  um, with uh, the LIGO
• 9:42
  Laser Interferometer Gravitational Wave
• 9:44
  Observatory in America. And that now works
• 9:47
  with, uh, virgo, which is an
• 9:50
  Italian, uh, uh, gravitational wave
• 9:53
  observatory, and kagra, which is the
• 9:55
  Kamioka Gravitational Wave Detector in
• 9:58
  Japan. So those three telescopes work
• 10:00
  together to pick up the vibrations of space,
• 10:04
  uh, which are, uh, transmitted from very
• 10:06
  distant collisions usually. And it's usually
• 10:09
  neutron stars and black holes, uh, with
• 10:12
  collisions between either neutron stars and
• 10:14
  neutron stars or black holes and black holes,
• 10:17
  or neutron stars and black holes. Um,
• 10:20
  those all produce gravitational wave signals
• 10:22
  that are actually in the frequency range
• 10:25
  detectable by uh, these telescopes.
• 10:27
  Because that's a key part of it. The amount
• 10:30
  of energy that's involved tells, uh, you what
• 10:32
  the frequency of the gravitational waves is
• 10:35
  going to be. And as we've noted
• 10:37
  before, Andrew, it's curious that, um,
• 10:40
  the gravitational waves that these telescopes
• 10:42
  are sensitive to are actually in the audio
• 10:45
  frequency regime. They're basically. If you
• 10:48
  just amplified them, uh, you would have an
• 10:50
  audio signal. And that's basically what they
• 10:52
  do, except they're doing it in a very much
• 10:54
  more sophisticated way. Um,
• 10:57
  um. The amount of, um,
• 11:00
  shaking of space that they can
• 11:02
  detect is
• 11:05
  absolutely infinitesimal. Uh, but
• 11:08
  these things are sensitive enough that they
• 11:10
  can measure a distance that is a
• 11:13
  thousandth, I think it's a 10,000th actually,
• 11:15
  of the diameter of a proton. Uh, that's
• 11:19
  the accuracy with which they can measure the
• 11:21
  distance between two mirrors, which is how
• 11:23
  you do all this sort of thing. So that's the
• 11:26
  backstory. Uh, the up storey,
• 11:29
  the forward storey. Is that
• 11:32
  an object or you don't have an object,
• 11:35
  you have a gravitational wave signal. Uh, it
• 11:38
  rejoices in the name of
• 11:39
  GW25014.
• 11:42
  Uh, that tells you that it was picked up, um,
• 11:44
  in January, uh, 2025. Uh,
• 11:47
  that's where the 25011 comes
• 11:50
  from. Um. Uh, and it,
• 11:53
  uh, basically, uh, on
• 11:56
  analysis, um, has
• 12:00
  been, uh, detected to be
• 12:02
  a collision between two black holes, each
• 12:05
  of which had, uh, around 32 times the
• 12:08
  mass of the sun until they collided. And
• 12:11
  that set, uh, you know, set the
• 12:14
  gravitational waves on their way because it
• 12:17
  basically disturbed space, it rippled space.
• 12:21
  So what's happened is. And this, as you
• 12:23
  mentioned at the beginning, is the loudest
• 12:25
  gravitational wave signal that's been
• 12:26
  detected, or certainly the most, uh,
• 12:29
  intense. The, um, highest amplitude one.
• 12:31
  Andrew Dunkley: Yeah.
• 12:33
  Professor Fred Watson: Um, so what has happened
• 12:35
  is, uh, that researchers, uh, have
• 12:38
  analysed the audio signal,
• 12:41
  um, and they found in it, um,
• 12:45
  basically that it's been described as a
• 12:47
  feature, uh, which is uh, something
• 12:50
  called a direct wave. It's
• 12:53
  a component of the signal, uh,
• 12:56
  and it's a direct wave, uh, that
• 12:59
  has not. That's been seen before,
• 13:01
  but hasn't. Nobody's worked out what it
• 13:04
  is, but apparently it
• 13:07
  is a feature that
• 13:09
  essentially, uh. In
• 13:12
  the gravitational wave structure that comes
• 13:15
  from this event, you can tell this
• 13:18
  direct wave is to do with
• 13:21
  the event horizon of the combined
• 13:24
  black holes. So you've got two black
• 13:26
  holes, each of which has got its own event
• 13:29
  horizon. They're spinning around one another,
• 13:32
  getting ever closer, as we've seen that sort
• 13:34
  of thing before. And the frequency goes up of
• 13:36
  the gravitational waves, um, and then
• 13:39
  suddenly it all stops because they've
• 13:42
  collided and there's no more accelerations,
• 13:44
  which is what you need, uh, to set up
• 13:46
  gravitational waves. Um, but,
• 13:49
  uh, at that point the two, um,
• 13:52
  gravitate, sorry, the two event horizons
• 13:55
  merge.
• 13:56
  Uh, now, a recap on event horizons. That's
• 13:59
  the point of no return. Basically,
• 14:02
  it's the distance from the black hole,
• 14:05
  uh, where the escape velocity
• 14:08
  uh, is more than the speed of
• 14:11
  light. And so nothing can escape from
• 14:14
  within the event horizon. Uh, and in
• 14:16
  particular light can't escape. So the event
• 14:18
  horizon is black. It's a sphere around the
• 14:20
  black hole, uh, through which you can't see
• 14:22
  because nothing escapes, including light.
• 14:25
  So um, that is what the event horizon
• 14:28
  is. In a sense it's imaginary. Uh, uh,
• 14:30
  Andrew, you know it's not a real surface,
• 14:33
  it's an imaginary surface because it's just
• 14:35
  the boundary between what's visible and
• 14:38
  what's not visible.
• 14:41
  Now we know when black holes
• 14:44
  collide. Uh, I don't know that
• 14:47
  much about the details of these things but
• 14:49
  there is a period immediately after
• 14:52
  they've merged which is called the ring down.
• 14:54
  And it's a time when they sort of
• 14:57
  consolidate as one black hole. And that
• 15:00
  means their event horizons also consolidate.
• 15:03
  And I think this direct wave that has been
• 15:06
  detected is basically
• 15:09
  uh, an artefact of that ring
• 15:12
  down. Uh, and so um,
• 15:15
  what I guess is uh, perhaps the
• 15:18
  takeaway message from this work is not
• 15:21
  that we've learned something miraculous
• 15:24
  and new about the event horizon
• 15:26
  but that we've learned that there might be a
• 15:28
  way of, in future
• 15:31
  gravitational wave events uh, might be
• 15:34
  a way of analysing these direct waves to give
• 15:36
  us more information on the black hole
• 15:39
  event horizon. Because at the moment we don't
• 15:42
  know much about it. We've seen them
• 15:45
  in the telescopes, you know the
• 15:48
  um, observations from the Event Horizon
• 15:50
  Telescope that um, amalgam of many radio
• 15:53
  telescopes, an Earth sized array,
• 15:56
  uh, which has been used to look at the black
• 15:58
  holes in centre of our own galaxy. And in
• 16:01
  M57 I think it was uh, with um,
• 16:05
  uh fairly high degree of
• 16:08
  precision. What we've seen is the black
• 16:10
  shadow of the event horizon. Um
• 16:13
  but perhaps with these gravitational waves,
• 16:15
  these direct waves there might be a ah,
• 16:18
  way of teasing out even more detail from
• 16:21
  these distant and highly enigmatic
• 16:24
  objects.
• 16:25
  Andrew Dunkley: Yes, indeed. And uh, another interesting
• 16:27
  thing that comes out of this storey is that
• 16:29
  um, they're suggesting uh, the
• 16:31
  measurements that uh, that they've
• 16:34
  made could be a step towards
• 16:38
  future um, tests of general relativity
• 16:41
  using direct waves. So you know there's all
• 16:44
  sorts of potential by the sound of it.
• 16:46
  Professor Fred Watson: That's right, yeah. I mean exactly. And uh,
• 16:49
  of course this is one of the holy grails of
• 16:52
  science generally actually certainly physics
• 16:55
  to find chinks in general relativity
• 16:57
  because uh, at the moment it behaves
• 17:00
  exactly as predicted. Everything that we've
• 17:02
  seen in the universe Follows, uh,
• 17:05
  the rules and regulations of general
• 17:07
  relativity, uh, in a perfect way.
• 17:11
  So maybe, uh, direct waves will, as you
• 17:13
  said, uh, give us a way of testing general
• 17:16
  relativity. If we find, um, things
• 17:19
  that don't work in general relativity, then
• 17:22
  that could be an opening into new physics,
• 17:23
  which is certainly a hot topic at the moment.
• 17:26
  Andrew Dunkley: Indeed it is. Uh, well, uh, everyone,
• 17:28
  including Einstein, thinks something's wrong
• 17:30
  with it. They just. Yes, they just can't find
• 17:32
  anything at the moment. It keeps coming up
• 17:35
  aces every time they test it.
• 17:37
  Professor Fred Watson: Yeah, they think something's wrong with it
• 17:38
  because it doesn't sit with quantum
• 17:41
  mechanics. The two are incompatible and they
• 17:43
  both work perfectly well, but they're
• 17:46
  incompatible.
• 17:48
  Andrew Dunkley: Weird, isn't it?
• 17:49
  Professor Fred Watson: Yes, that's very weird. Yeah.
• 17:50
  Andrew Dunkley: The other thing that I find fascinating about
• 17:52
  this Storey, is that from something as simple
• 17:55
  as a, as a gravitational wave,
• 17:57
  they're able to break it down and find
• 18:00
  information that is
• 18:04
  really just. You can't
• 18:07
  see any of this. It's all just data, isn't
• 18:10
  it?
• 18:10
  Professor Fred Watson: Yeah, yeah, that's correct. That's right.
• 18:12
  But, uh, the physics is well understood
• 18:14
  because general relativity is such a reliable
• 18:17
  tool for people to use to analyse these
• 18:19
  things. Um, that's how we can make these
• 18:22
  statements about it. And yes, um, if we can
• 18:25
  find flaws with general relativity, it will
• 18:27
  be very exciting indeed it will.
• 18:30
  Andrew Dunkley: And you can read all about it@the space.com
• 18:33
  website. Uh, they publish their research,
• 18:36
  uh, in the journal Nature. This
• 18:39
  is Space Nuts with Andrew Dunkley and
• 18:41
  Professor Fred Watson Watson.
• 18:45
  Professor Fred Watson: I believe that this nation should commit
• 18:47
  Andrew Dunkley: itself to achieving the goal,
• 18:50
  before this decade is out, of landing a
• 18:53
  man
• 18:53
  Professor Fred Watson: on the moon and returning him safely to the
• 18:56
  Earth.
• 18:56
  Andrew Dunkley: These nuts.
• 18:58
  Now, Fred Watson, we turn our, uh, attention
• 19:01
  towards China. Uh, of course, they've got a
• 19:03
  very active space station in operation
• 19:06
  at the moment. Uh, the latest news though is
• 19:09
  that they intend to, uh, make it
• 19:12
  bigger and at the same time they're going to
• 19:14
  put a new space telescope into, uh, into
• 19:17
  orbit as well. So, uh, they're really going
• 19:19
  ahead in leaps and bounds, aren't they?
• 19:21
  Professor Fred Watson: They are, yes. Uh, it's, um. You know, this
• 19:24
  is part of the Chinese. It's not the China
• 19:26
  national, uh, Space Agency.
• 19:29
  Uh, I think it's that they've got a separate
• 19:31
  space agency for human space flight.
• 19:35
  Uh, and that's the organisation that
• 19:37
  operates the Tiangong, uh, space Station,
• 19:40
  which has been up there since 2021, I think
• 19:43
  was when, uh, we started seeing it being
• 19:45
  assembled. It was assembled in a very similar
• 19:48
  manner to the International Space Station by
• 19:51
  building sort of modules that you can stick
• 19:54
  together like Lego, uh, up once
• 19:57
  uh, these modules are in orbit.
• 19:58
  Andrew Dunkley: Yeah. And at the moment it's the China
• 20:01
  National Space Administration which handles
• 20:03
  the programmes, and the China Manned Space
• 20:06
  Agency which um, oversees human
• 20:08
  spaceflight.
• 20:09
  Professor Fred Watson: That's right. I knew there were two
• 20:12
  organisations involved. Thank you for that.
• 20:14
  Andrew Dunkley: That's all right.
• 20:15
  Professor Fred Watson: Um, so, uh,
• 20:17
  yes, so uh, at the moment the,
• 20:20
  the Tiangong consists of three
• 20:22
  modules and they're arranged in a sort of T
• 20:25
  shape, uh, with um.
• 20:28
  Uh, two, three. The, the three
• 20:31
  end points of the modules if you like,
• 20:33
  coming, coming together in a, in a sort of
• 20:36
  vestibule where you can uh, tunnel your way
• 20:38
  from one to the, to the other with these
• 20:41
  uh, basically entry and exit hatches. That
• 20:43
  uh, is the way things work on the
• 20:46
  International Space Station as well. But as
• 20:48
  you've said, uh, what they're now planning to
• 20:51
  do is to add three more
• 20:53
  modules. Um and the reason they
• 20:56
  want to do that is because uh,
• 20:59
  they want to do more research up there,
• 21:02
  uh, and make more frequent crew and
• 21:05
  cargo changes. Um, so they're
• 21:08
  actually, I think the way to deal
• 21:11
  with that is to make the space station
• 21:14
  bigger. Um, and so it's going to be
• 21:17
  what they're calling a double T shape, which
• 21:20
  I think is probably an H shape
• 21:23
  if I can put it that way. Um, well that's
• 21:25
  what it.
• 21:25
  Andrew Dunkley: Yeah, it would turn into that, wouldn't it?
• 21:27
  Professor Fred Watson: You'd expect so. Yes, that's right. Unless
• 21:29
  they do something clever, uh, like turn
• 21:32
  one of the T's round, uh right angles to the
• 21:35
  other one. Anyway, we don't know what's going
• 21:37
  to happen there. But um, there is a new
• 21:40
  multipurpose um, module and two
• 21:43
  new experimental modules that are planned
• 21:46
  uh, to um, essentially uh,
• 21:49
  you know, allow Chinese
• 21:52
  uh, space exploration in low Earth
• 21:54
  orbit to continue and be extended.
• 21:58
  Um, um, we understand from
• 22:01
  um, some of the researchers in China
• 22:04
  that uh, it's always been
• 22:07
  uh, an expectation that this
• 22:10
  would take place, that there'd be this
• 22:12
  extension. Uh, and what it will do in
• 22:15
  terms of the mass of the um, space
• 22:18
  station is take it up from its current 90
• 22:20
  tonnes, uh up to
• 22:23
  180 tonnes or thereabouts. And there's a
• 22:26
  yardstick, if I remember rightly, and you
• 22:28
  might be able to correct me here Andrew, but
• 22:30
  I think the International Space station is
• 22:32
  about 400 tonnes in terms of its mass.
• 22:35
  I think that is the case. So uh,
• 22:38
  that's uh, the plan and
• 22:41
  alongside that, as you've already mentioned
• 22:44
  Andrew, is the idea of a new
• 22:47
  um, space observatory, an optical
• 22:50
  Telescope quite similar in some
• 22:53
  ways to the Hubble Space Telescope. A
• 22:55
  slightly smaller mirror, 2 metres rather than
• 22:58
  2.3 metres,
• 23:01
  um, and also with a much wider
• 23:03
  field of view. The Hubble has quite a narrow
• 23:06
  field of view. Uh, and in fact the Nancy
• 23:09
  Grace Roman telescope, which is also very
• 23:12
  similar to the Hubble, will have a much wider
• 23:14
  field of view than Hubble. That's being
• 23:16
  launched later this year, I hope.
• 23:19
  Um, this, uh, Chinese
• 23:21
  telescope, uh, which has a name, Shuntian,
• 23:24
  I think, is probably how it's
• 23:27
  pronounced in my,
• 23:30
  um, poor Chinese, uh, poor
• 23:32
  Mandarin and poor Chinese.
• 23:35
  Um, it's got a much bigger field of view and
• 23:38
  will actually give new, uh,
• 23:41
  surveys to Chinese, uh,
• 23:44
  astronomers. We'll see a lot more
• 23:46
  information about the universe coming from
• 23:48
  this telescope. The more telescopes you've
• 23:50
  got on the universe, the better. And, uh,
• 23:52
  Shuntian will be one of those, uh,
• 23:55
  features when it is launched and actually
• 23:58
  commissioned, uh, that will, we hope, um,
• 24:01
  really bring new insights into our knowledge
• 24:04
  of space.
• 24:04
  Andrew Dunkley: Yeah. Apparently its field of view
• 24:07
  is going to be massive compared to
• 24:10
  Hubble at 300 times.
• 24:12
  Professor Fred Watson: Correct? Yes, that's right. So it's a wide
• 24:14
  angle telescope rather than the sort of
• 24:17
  pinpoint view of the Hubble.
• 24:19
  Andrew Dunkley: Yeah, quite incredible. Uh, you were right
• 24:21
  about the International space station. Uh,
• 24:23
  419,700 kilogrammes
• 24:26
  is its mass, or say 420,
• 24:30
  um, tonnes. Yes, indeed. Um, the
• 24:33
  other interesting thing that China's working
• 24:35
  on, uh, is a new,
• 24:38
  um, um, delivery system for their. They
• 24:41
  call them taika nauts, don't they?
• 24:42
  Professor Fred Watson: Yes, they do, yeah.
• 24:44
  Andrew Dunkley: Uh, they want to. They want to develop a
• 24:46
  rocket system that will send seven up at a
• 24:49
  time.
• 24:49
  Professor Fred Watson: Yes, yeah, seven up.
• 24:52
  Andrew Dunkley: No, I'm joking. But, um, again, yeah, that's
• 24:55
  what they're looking at doing at the moment.
• 24:57
  They can only send up three at a time.
• 24:59
  Professor Fred Watson: Yes. So the Chinese, um,
• 25:02
  uh, orbital
• 25:04
  vehicle for getting astronauts up,
• 25:07
  Taikonauts up there. And
• 25:10
  I'm ashamed that I can't remember what it's
• 25:11
  called. Uh, is it Shenzhou?
• 25:14
  Shenzhou, I can't remember. Um,
• 25:16
  but that is basically an adaptation
• 25:20
  of the old Soyuts Russian
• 25:22
  spacecraft which is still in service in the
• 25:25
  International Space Station. Developed in the
• 25:26
  1960s. A, uh, three person,
• 25:29
  uh, module. Uh, I think I'm right in
• 25:32
  saying that the crew Dragon can take up to
• 25:34
  seven astronauts as well.
• 25:36
  Andrew Dunkley: Interesting. Shenzhou.
• 25:38
  Professor Fred Watson: Shenzhou, yeah.
• 25:40
  Andrew Dunkley: Is the, um, is the system they
• 25:41
  Professor Fred Watson: used at the moment.
• 25:43
  You did m. So, uh,
• 25:46
  yes. So that will go from three to seven.
• 25:48
  It's understandable, you know, if you Want to
• 25:50
  keep the crews coming and going. I think this
• 25:52
  is a really important development because,
• 25:55
  um, if nothing else, it's going to, I
• 25:58
  think, spur, uh,
• 26:01
  the private sector, um, to pick up the
• 26:03
  baton of what you might call Western
• 26:06
  International Space Stations or the Western
• 26:08
  International Space Station, because that's
• 26:11
  scheduled at the moment to be decommissioned
• 26:13
  in 2030. That might change. But
• 26:16
  it's a possibility that we will lose the ISS
• 26:19
  in 2030. And we've seen problems
• 26:22
  with the leakage that we had in one of the
• 26:24
  modules a couple of weeks ago where the
• 26:27
  crew was evacuated, not evacuated, but
• 26:30
  moved. The American crew,
• 26:33
  uh, the NASA end of the spacecraft
• 26:35
  were moved into a crew Dragon capsule
• 26:38
  to uh, just be certain that
• 26:41
  nothing untoward was going to happen, uh,
• 26:44
  if there was a catastrophic
• 26:47
  leak, uh, when the Roscosmos,
• 26:50
  cosmonauts, they were actually trying to fix
• 26:52
  the leak, uh, they moved the other crew,
• 26:55
  um, into the crew Dragon capsule for safety.
• 26:58
  Andrew Dunkley: Yeah, uh, in terms of replacing the iss,
• 27:01
  there are no firm plans at the moment, but
• 27:04
  they're kind of thinking about,
• 27:07
  um, I think you mentioned it, the commercial
• 27:09
  sector getting involved.
• 27:12
  And that's probably logical.
• 27:15
  I'm pretty sure that, uh, Elon would be
• 27:18
  pretty keen to put a space station into orbit
• 27:21
  and a few others probably.
• 27:23
  There's plenty of people around with uh,
• 27:25
  megabucks to do it.
• 27:27
  Professor Fred Watson: Yes, that's right. Um, um, but, uh, you
• 27:30
  know, you might think, have to think
• 27:32
  carefully about whether you, uh, take
• 27:35
  over the old, uh, the old tired
• 27:38
  and quite dodgy old, uh,
• 27:41
  International Space Station or whether you
• 27:43
  build something new. Um, and uh, of course
• 27:46
  the technology's moved on enormously since
• 27:47
  the 1990s when that was put together.
• 27:50
  It's been continuously occupied since
• 27:53
  2000. Uh, that's 26
• 27:56
  years of, um, tenants coming and going. It's
• 27:59
  probably taken a fair beating inside.
• 28:01
  Andrew Dunkley: Yeah, I'm sure they've had a few parties.
• 28:03
  Yeah, no doubt about it.
• 28:06
  Uh, if you want to uh, read all about, uh,
• 28:08
  China's plans, you can do
• 28:09
  that@space.com. uh, this is
• 28:12
  Space Nuts with Andrew Dunkley and Professor
• 28:14
  Fred Watson Watson.
• 28:18
  Space Nuts, our final
• 28:21
  storey. Fred Watson takes us close to home.
• 28:23
  And this is really quite a fascinating storey
• 28:26
  because it talks about a star, not
• 28:29
  our sun. Ah, another star that got
• 28:32
  up close and personal, um, with
• 28:35
  our particular, uh, sun, um, a
• 28:38
  little while ago. But the
• 28:40
  effects of that interaction,
• 28:43
  uh, seem to still exist,
• 28:46
  which is very odd.
• 28:47
  Professor Fred Watson: Yeah, well, that's right. Uh, yes, it is,
• 28:50
  it's an interesting storey. It covers two
• 28:53
  quite different bits of astronomy here that
• 28:55
  come together to sort of work out what was
• 28:57
  going on. So this star in question,
• 29:01
  it's got the glorious name of
• 29:02
  HD7977. HD
• 29:05
  stands for Henry Draper. It's one of the
• 29:07
  early star catalogues, uh, from the 19th
• 29:09
  century I think, uh, the Henry Draper
• 29:12
  catalogue. Uh, and it's a relatively
• 29:15
  near star, similar to the
• 29:18
  sun. Uh, it's currently in the constellation
• 29:20
  of Cassiopeia, which is um, one of my
• 29:23
  favourite northern constellations. Actually.
• 29:25
  It's one that we don't see from down here in
• 29:27
  Australia. Uh, so,
• 29:30
  um, how do we know that
• 29:33
  HD7977 had um,
• 29:36
  a near miss with our solar system?
• 29:39
  And the answer is with the Gaia mission.
• 29:42
  So Gaia is a spacecraft. Uh,
• 29:45
  it sits at the um, uh,
• 29:48
  sun, Earth, uh, L2 point, that's
• 29:51
  the Lagrange point, on the opposite side of
• 29:54
  the Earth from the sun. Um, it's been
• 29:57
  working for, I think, certainly more than a
• 29:59
  decade. And what it's done is measured
• 30:02
  star positions with absolutely
• 30:05
  exquisite precision. Uh, you're talking
• 30:07
  about, I think it's sort of some
• 30:10
  accuracies in the region of 100 millionths of
• 30:12
  an arc second. These are phenomenal
• 30:15
  accuracies. And an arc second of course is
• 30:17
  1-3600th of a degree, uh,
• 30:20
  the size of a, here In Australia, a $1 coin
• 30:23
  held up at five kilometres. It's a tiny
• 30:25
  angle, but this thing's measuring
• 30:28
  millionths of that basically, or 100
• 30:30
  millions. Uh, and what that does is it
• 30:33
  allows you, if you make these measurements at
• 30:35
  different times, it allows you to plot the
• 30:38
  motions of stars,
• 30:41
  uh, not just in our own galaxy and in our own
• 30:44
  neighbourhood, but also in the Two
• 30:46
  Magellanic Clouds, uh, the two
• 30:49
  nearest neighbour dwarf galaxies, the big
• 30:52
  ones, Large and Small Magellanic Clouds
• 30:54
  165 and 200,000 light
• 30:57
  years away respectively. Uh, those,
• 31:00
  uh, you can detect the motions of stars in
• 31:02
  those galaxies. And even in the Andromeda
• 31:05
  galaxy, about 2 1/2 million light years away,
• 31:08
  you can see evidence of what we call lateral
• 31:10
  motion on the sky, sideways motion of things.
• 31:13
  And if you can measure the radial velocity,
• 31:15
  that's the velocity along the line of sight,
• 31:18
  which is actually much easier if you can do
• 31:20
  that as well. You've got, um, the three
• 31:22
  dimensional motion of objects in space. And
• 31:25
  that is how, uh,
• 31:28
  HD7977 was picked
• 31:30
  up as having passed close to the sun
• 31:33
  about two and a half million years ago.
• 31:37
  As both these stars, The sun and
• 31:39
  HD7977, as they both orbit around the
• 31:42
  centre of our galaxy. Uh, we still
• 31:44
  don't know exactly how close. Uh, the data
• 31:47
  from Gaia suggests It was between
• 31:50
  4,000 and 25,000
• 31:53
  astronomical units. And as we've mentioned
• 31:55
  before, an astronomical unit is the distance
• 31:57
  between the Earth and the sun. Um, convenient
• 32:00
  measure it is uh, 150 million kilometres.
• 32:04
  Um, they may have
• 32:07
  um, we might be able to
• 32:09
  tie that close approach down though by other
• 32:12
  methods. And the methods in question
• 32:16
  have been employed by uh, some
• 32:19
  scientists at the University of
• 32:21
  Bordeaux. Uh, and basically
• 32:24
  what they have done is looked not
• 32:27
  at Gaia data to try and refine
• 32:30
  uh, this sort of look back in
• 32:33
  time as to when these two stars were close
• 32:35
  together. They've looked at long period
• 32:38
  comets, comets that uh, come in
• 32:40
  from the very furthest reaches of the solar
• 32:43
  system where we think there is a
• 32:45
  reservoir of comets. We call it the Oort
• 32:47
  Cloud. Uh, and it turns out that
• 32:50
  if you look at long period comets,
• 32:53
  uh, which have been measured over the
• 32:56
  past hundred years I guess, um, then
• 32:59
  you get uh, an idea
• 33:02
  of the distribution of their orbits.
• 33:05
  And basically there's a quote here
• 33:08
  from one of the authors uh, of
• 33:11
  the paper that we're talking about uh, who
• 33:14
  says the distribution of comet orbits
• 33:16
  suggests we living through an unusual time
• 33:19
  where HD 7977 has
• 33:21
  dominated the generation of new comets
• 33:25
  and not the larger gravitational field of the
• 33:27
  Milky Way as it usually would. This would
• 33:30
  also mean we're living through the late
• 33:31
  stages of a pretty rare and powerful
• 33:34
  comet shower. And so what they've done
• 33:37
  is made computer simulations of uh,
• 33:40
  how comet orbits might behave
• 33:44
  as a result of being tipped out of the Oort
• 33:46
  cloud by the passage of this star HD
• 33:49
  7977. They've kicked out the Oort cloud
• 33:52
  and heading towards the sun. Uh, they've
• 33:54
  measured uh, basically the details of
• 33:57
  112 long period comets. Actually they've
• 34:00
  chosen ones that have only been observed in
• 34:02
  recent years, since 1989 because
• 34:05
  that's when we could detect comets coming
• 34:08
  from uh, any part of the sky. Uh,
• 34:11
  if you only limit yourself to one part of the
• 34:13
  sky then you've got uh, as visible for
• 34:16
  example by a single observatory, uh, or even
• 34:18
  as visible by the Northern Hemisphere
• 34:20
  observatory. You're missing uh,
• 34:23
  half the objects that you want to see. And
• 34:25
  since what you're doing is looking at the
• 34:27
  statistical distribution of these things, you
• 34:29
  can't afford to um, eliminate
• 34:32
  things that way. It's what would be called a
• 34:34
  selection effect. Um, so yes these
• 34:37
  long period comets they've got very elongated
• 34:40
  Orbits, uh, and the suggestion is that the
• 34:43
  distribution of those orbits in relation to
• 34:46
  the direction that we know
• 34:47
  HD7977 went through the solar system or
• 34:50
  went close to the solar system. Uh, that's
• 34:53
  why they believe, uh, that the two
• 34:56
  events, uh, um, the close
• 34:58
  passage of 7977, uh,
• 35:01
  tipped up the comets and caused a lot more of
• 35:04
  these comets to come in. And if you
• 35:07
  accept uh, their hypothesis,
• 35:10
  um, then what it does is,
• 35:13
  ties down rather
• 35:16
  better the distance that we estimate
• 35:19
  HD7977, uh,
• 35:22
  approach the sun at somewhere
• 35:25
  between 6,000 and 10,000 astronomical units.
• 35:28
  A tighter window compared with the 4,000 to
• 35:30
  25,000 astronomical units that Gaia
• 35:33
  suggests. Yes, uh, so, uh, it's a nice
• 35:36
  tightening up of our uh, understanding of
• 35:38
  this hypothesised but probably
• 35:41
  real event 2 1/2 million years ago.
• 35:43
  Andrew Dunkley: And just to give people a bit of an idea of
• 35:45
  the distance, so somewhere between 6 and
• 35:48
  10,000 AU is where
• 35:50
  HD7977 and kind
• 35:52
  of grazed our uh, solar system.
• 35:54
  Professor Fred Watson: Yes.
• 35:55
  Andrew Dunkley: Voyager 1 is 170
• 35:57
  AU from Earth. So
• 36:00
  we're talking a fair way out.
• 36:02
  Professor Fred Watson: It's a long way off. That's right.
• 36:04
  Andrew Dunkley: You're talking probably getting into the
• 36:06
  vicinity of the Oort cloud, which makes sense
• 36:08
  given what they're hypothesising in
• 36:11
  this paper.
• 36:12
  Professor Fred Watson: Exactly right. So a star passing nearby the
• 36:15
  Oort cloud would definitely upset it and
• 36:18
  send stuff in towards the, the inner solar
• 36:20
  system. Yes, it's actually um, it's a theory
• 36:23
  that, uh, that general mechanism
• 36:26
  was proposed by colleagues of mine in the
• 36:28
  Royal Observatory in Edinburgh, Victor Klub
• 36:30
  and Bill Napier, back in the late 1970s.
• 36:33
  The idea that they were suggesting it might
• 36:36
  have needed a bit more mass than a single
• 36:38
  star to disturb the Oort cloud. And uh, they
• 36:41
  suggested the passage nearby, passage of
• 36:44
  something called a giant molecular cloud, uh,
• 36:46
  a kind of stellar birthplace. If one of those
• 36:48
  goes past the solar system, they were
• 36:50
  inferring it would disturb the Oort cloud to
• 36:53
  the extent that you would get bombardment of
• 36:55
  the inner solar system by comets and that
• 36:57
  might be visible in the geological record on
• 37:00
  Earth. That was basically um, uh,
• 37:03
  their principal line of attack. Uh, really
• 37:06
  very interesting science. Uh, so this is not
• 37:09
  a new idea, but this is new research
• 37:12
  that suggests that um, perhaps we can learn
• 37:14
  more by pursuing it.
• 37:16
  Andrew Dunkley: Indeed, yes. Um, the paper by the way,
• 37:19
  has been accepted by the Planetary Science
• 37:21
  Journal and is available at the moment,
• 37:23
  moment on the Arxiv Preprint server.
• 37:26
  You can also read about it at phys.org, p h
• 37:29
  y s.org Fred Watson,
• 37:32
  that brings us to the end of the show.
• 37:34
  Thank you so much.
• 37:35
  Professor Fred Watson: Well, that went very quickly. Uh, what a good
• 37:37
  time we had.
• 37:38
  Andrew Dunkley: We did indeed. Yes. We'll catch you on the
• 37:40
  next one.
• 37:40
  Professor Fred Watson: Sounds great.
• 37:41
  Andrew Dunkley: Thank you very much, Professor Fred Watson
• 37:43
  Watson, astronomer at large. And don't forget
• 37:45
  between episodes to jump on our website and
• 37:47
  have a look around. SpaceNutsPodcast.com you
• 37:50
  can click on the AMA button and send us
• 37:52
  messages. Even if you want to send us a joke,
• 37:54
  we don't mind, we love jokes. Or you can,
• 37:57
  uh, send us a question or, um, you can
• 37:59
  comment on a discussion point, whatever
• 38:02
  you like. Just don't forget to tell us who
• 38:04
  you are or where you're from. You can send
• 38:05
  text and audio questions and while you're
• 38:08
  there, have a look around. Cheque out the
• 38:09
  shop. Cheque out. Uh, the, uh, ways
• 38:12
  you could become a supporter, uh, or sign up
• 38:14
  for the Astronomy AstroDailyPod News feed.
• 38:16
  You can do all of that on our website. And
• 38:19
  thanks to Huw in the studio who, uh, couldn't
• 38:21
  be with us today because he saw a passing
• 38:23
  star and chased her down for an autograph.
• 38:27
  And from and from me, Andrew Dunkley. Thanks
• 38:29
  for your company. We'll see you on the next
• 38:31
  episode of Space Nuts. Bye. Bye.
• 38:34
  You've been listening to the Space Nuts
• 38:36
  podcast, available at
• 38:39
  Apple Podcasts, Spotify,
• 38:42
  iHeartRadio or your favourite podcast
• 38:44
  player. You can also stream on
• 38:46
  demand@bytes.com this
• 38:48
  Professor Fred Watson: has been another quality podcast production
• 38:51
  from bytes.com.