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"Jupiter's not quite as big as we thought." · Space Nuts: Astronomy Insights & Cosmic Discoveries

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Speaker 1: Hello there, thanks for joining us yet again. This is
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Speaker 1: Space Nuts. My name is Andrew Dunkley. We're here to
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Speaker 1: talk astronomy and space science. And on today's program, we're
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Speaker 1: going to look at a tiny weeni itsy bitsy Jupiter. Yes,
0:13
Speaker 1: it's not nearly as big as they thought it was.
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Speaker 1: In fact, it could lose status as a consequence of this.
0:20
Speaker 1: Maybe not, but we'll talk about that. We're also going
0:23
Speaker 1: to look at a flipping interesting comet and solar gravitational
0:28
Speaker 1: lens focal points. Could we visit them and what will
0:31
Speaker 1: that mean? We'll find out on this episode of Space Nuts.
0:36
Speaker 2: Fifteen second in channel ten nine ignition sequence Space Nuts
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Speaker 2: or three two.
0:48
Speaker 3: Space Nuts, as can I report it.
0:50
Speaker 1: Bills good and joining us again to talk about all
0:54
Speaker 1: of that stuff and probably a lot more as Professor
0:57
Speaker 1: Fred Watson, Astronomer at Large, Hello Fred.
0:59
Speaker 3: Hello Andrew, good to see you again, to see you.
1:02
Speaker 3: Always love the hoopy shirt. Oh yeah, sorry, it's very
1:08
Speaker 3: tutty old on this shirt.
1:11
Speaker 1: This one's nasty, tatty, but it's white and it's got
1:14
Speaker 1: more food on it than I've ever put in his stomach.
1:16
Speaker 3: So has he got the has he got the space not?
1:18
Speaker 3: His logo on it.
1:19
Speaker 1: Hang on, I've got one here somewhere, a spacent logo
1:25
Speaker 1: to know I have, but it's not on not on
1:27
Speaker 1: this shirt. It's on the other wide shirt. Where did
1:31
Speaker 1: that logo go? I've lost my logo.
1:35
Speaker 3: Anyway, we'll fight losing losing mojo.
1:38
Speaker 1: That's true too. Yes, indeed, let's begin because we've got
1:43
Speaker 1: a lot to talk about. This first story looks at Jupiter,
1:47
Speaker 1: the biggest planet in our solar system until we find
1:50
Speaker 1: planet nine. And this is a story that's suggesting that
1:56
Speaker 1: Jupiter is not quite as big as we thought it was.
2:00
Speaker 3: Yeah, it's it's shrunk by well eight kilometers at the
2:06
Speaker 3: equator and twenty four kilometers at the poles. So what
2:10
Speaker 3: this is all about? And I should just give you
2:13
Speaker 3: the numbers. So the revised radius of Jupiter at its
2:19
Speaker 3: equator is seventy four hundred and eighty eight kilometers, which
2:23
Speaker 3: is actually I think four kilometers less than we thought before,
2:31
Speaker 3: which doubles up to up to eight kilometers when you're
2:34
Speaker 3: talking about diameter. But it's polar radius, which is sixty
2:40
Speaker 3: six thousand, eight hundred and forty two, And those two
2:43
Speaker 3: numbers are quite different, which is why Jupiter's flattened at
2:47
Speaker 3: its poles, just as Saturn is. But that's actually twenty
2:51
Speaker 3: four kilometers less than the previous estimations. So for the diameter,
2:57
Speaker 3: so it's not a huge, huge amount, but it's.
3:02
Speaker 1: Not when you're talking about the size of the planet.
3:04
Speaker 3: That's exactly that's what I mean. Yeah, seventy one thousand
3:07
Speaker 3: and four. So it's what one one hundred and forty
3:10
Speaker 3: thousand kilometers or thereabouts in diameter, which is eleven Earth diameters,
3:17
Speaker 3: which is what we always say. So why, well, first
3:21
Speaker 3: of all, how have these measurements been made? And the
3:24
Speaker 3: answer is that the old measurements actually go back a
3:27
Speaker 3: long way. They come from the voyager and pioneer era
3:31
Speaker 3: of the exploration of the outer planets, and that goes
3:35
Speaker 3: back to the seventies and eighties. They So what led
3:41
Speaker 3: to the diameter or the size of Jupiter that we've
3:44
Speaker 3: been using since then is what's called a radio occultation.
3:49
Speaker 3: So the spacecraft is behind As it passes behind Jupiter,
3:55
Speaker 3: its signals get refracted actually by the atmosphere of the planet,
4:00
Speaker 3: probably scattered as well, but you can time it very
4:03
Speaker 3: accurately in time when the spacecraft disappears behind the planet,
4:07
Speaker 3: and you know it's trajectory. You can then time when
4:11
Speaker 3: it reappears, and from that you can calculate the and
4:14
Speaker 3: knowing about Jupiter's motion and the spacecraft's motion, you can
4:17
Speaker 3: calculate what the diameter is. So that those are the
4:20
Speaker 3: values that we've been using ever since.
4:23
Speaker 1: I think I know where all of this went wrong.
4:25
Speaker 1: They didn't a layer for it, stopping for gas.
4:29
Speaker 3: The planet or the spacecraft. Well, it's a gas giant,
4:34
Speaker 3: that's right, Yeah, the planet's a gas giant. So yes,
4:36
Speaker 3: it's a good point. Anyway, I let that one pass.
4:41
Speaker 1: So moving off wasn't very good.
4:44
Speaker 3: It was all right for the start of the show.
4:46
Speaker 3: They usually get better, as we call it's the new
4:50
Speaker 3: measurements come, of course from the spacecraft that is currently
4:54
Speaker 3: in orbit and working away very hard at Jupiter in
4:58
Speaker 3: orbit around the planet, and that is JUNO, that says
5:01
Speaker 3: JUNO Mission, which has been orbiting Jupiter since twenty sixteen
5:07
Speaker 3: and doing pretty well. It's yes, for the decades since
5:09
Speaker 3: we've had Juno, which gosh it, time flies, doesn't it anyway,
5:14
Speaker 3: So that's allowed much more accurate measurements because the space
5:18
Speaker 3: that JUNO spacecraft. Its orbit is very well understood. It's
5:22
Speaker 3: fairly close to Jupiter. But you might think, you know, well,
5:27
Speaker 3: why are we so keen to know the damage of
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Speaker 3: the planet to such a high degree of accuracy, And
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Speaker 3: the answer is to do with our model because it is. Yeah,
5:42
Speaker 3: that's right, it's to do with our modeling of the
5:45
Speaker 3: planet's interior because a small difference like that can make
5:50
Speaker 3: a big difference to what we imagine the interior of
5:55
Speaker 3: the planet is like. And remember, of course, everybody that
5:58
Speaker 3: Jupiter all wes see is it's cloud belts. When we
6:00
Speaker 3: look at the planet, we don't see any surface or
6:04
Speaker 3: any hint of a surface. So the internal structure of
6:07
Speaker 3: Jupiter is something we have to deduce from other measurements,
6:11
Speaker 3: and the an accurate measurement of the diameter of the
6:14
Speaker 3: planet comes into that. So that's the reason it Also,
6:19
Speaker 3: you know, one of the other things that's of interest
6:21
Speaker 3: in Jupiter is the behavior of the atmosphere itself and
6:25
Speaker 3: the winds that blow in Jupiter's atmosphere, and that also
6:29
Speaker 3: needs an accurate understanding of the diameter of the planet.
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Speaker 1: Yeah, I actually I was just looking at that diagram
6:38
Speaker 1: that shows the different potential diameter situations based on the
6:44
Speaker 1: behavior of the planet. And yeah, without wind it loses
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Speaker 1: another what fourteen kilometers.
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Speaker 3: Yes, that's right, it does. If you if you imagine
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Speaker 3: the winds aren't there, it does. It shrinks, so by
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Speaker 3: fourteen kilometers exactly. That's the radius the not the diameter.
7:02
Speaker 3: So we we have, you know, a tiny figure that
7:10
Speaker 3: looks minuscule compared with the diameters of the planet itself,
7:14
Speaker 3: but it is important in understanding the upper atmosphere. It's
7:18
Speaker 3: if there were no winds, then what we will be
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Speaker 3: seeing will be fourteen kilometers smaller.
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Speaker 1: I'm surprised that it's taken us a decade to figure
7:27
Speaker 1: it out, and Juno as they have been there nearly
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Speaker 1: ten years.
7:31
Speaker 3: Yeah, but maybe you know, the accuracy that we're getting
7:37
Speaker 3: with this relies on many passages of Juno around Jupiter.
7:45
Speaker 3: There were and because you're always you know that the
7:48
Speaker 3: cord that of the Jupiter's disc that the planet that
7:53
Speaker 3: the spacecraft flies behind is different every time, and so
7:57
Speaker 3: we you probably need to build up a statistically significant
8:03
Speaker 3: sample of entry and egress times when you're looking at
8:07
Speaker 3: you know, the object disappearing by behind the planet. Occultation
8:11
Speaker 3: is what we call it an occultation, is when one
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Speaker 3: object hides another, and that's how you're measuring these diameters.
8:18
Speaker 3: So yeah, it's probably it's probably taken ten years, partly
8:22
Speaker 3: to a mass the data to give us this kind
8:24
Speaker 3: of level of accuracy.
8:26
Speaker 1: So, okay, how accurate do you think it is now
8:29
Speaker 1: compared to those early flybys with Voyager and Pioneer.
8:35
Speaker 3: That's a really good question. Actually, I haven't seen any
8:39
Speaker 3: error estimates on and as you know in physics and
8:44
Speaker 3: certainly in astronomy too, you always need a plus or
8:47
Speaker 3: minus an error estimate as to you know what the
8:51
Speaker 3: likelihood of your measurement being that number is, and I'm
8:56
Speaker 3: seen it for these so I don't know the answer
8:59
Speaker 3: to that. But my guess is that we're talking about
9:01
Speaker 3: in the region of a kilometer, which is pretty impressive
9:05
Speaker 3: for something that diameter, and something that's that far away
9:09
Speaker 3: have a billion kilometers away, So.
9:12
Speaker 1: Does this mean that air estimations of other planets in
9:16
Speaker 1: the Solar System are probably a bit off as well?
9:19
Speaker 1: When you consider that Neptune, for example, I think we've
9:22
Speaker 1: only visited once, would that be right?
9:25
Speaker 3: Yeah, Yeah, that's right. So yes, I think you're right,
9:30
Speaker 3: You know you certainly the estimates of the planets beyond
9:36
Speaker 3: Jupiter and Saturn in terms of their diameter and physical
9:39
Speaker 3: characteristics will have much bigger error limits on them, just
9:43
Speaker 3: because we can't make the measurements as accurate as you
9:46
Speaker 3: can when you've got a spacecraft in orbits around.
9:49
Speaker 1: One of them. Okay, so that's that's work in progress.
9:54
Speaker 1: Whenever we go back, we might be able to fix that.
9:57
Speaker 1: But yeah, they've got any missions plan and for Nepturing
10:01
Speaker 1: and Urinus or anything.
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Speaker 3: There's always calls for them because they're such interesting worlds. Yeah,
10:07
Speaker 3: but I don't think I mean, I think there are
10:10
Speaker 3: there are lots of proposals, but I don't think there's
10:12
Speaker 3: anything FUNDED might be wrong about that. Maybe our listeners
10:15
Speaker 3: can tell me if I'm wrong about.
10:16
Speaker 1: They may well, because a lot of it. Actually, We've
10:20
Speaker 1: got one fellow on Facebook who regularly researches some of
10:24
Speaker 1: the things we talk about, and he publishes his findings
10:26
Speaker 1: on the Facebook podcast group. Yeah, and I think it's great.
10:31
Speaker 1: I've read a few of his explanations and they're very good.
10:35
Speaker 1: So we're probably going to get sacked, but.
10:38
Speaker 3: It's surprise them sectors or.
10:44
Speaker 1: Well they can afford us. That's why we're still here.
10:47
Speaker 3: Well, that's true. Yes, that's true, very true.
10:50
Speaker 1: No, it's a really good discussion point. So it sort
10:53
Speaker 1: of keeps the momentum going when we discuss these things.
10:56
Speaker 1: So I'm sure it'll work on our tiny Jupiter story,
11:00
Speaker 1: which good, yes, which you can read about at the
11:03
Speaker 1: Daily Galaxy dot com website, or you can read the
11:06
Speaker 1: paper at Nature Astronomy. This is space Nuts with Andrew
11:10
Speaker 1: Dunkley and Professor Fred Watson.
11:17
Speaker 4: That's a that's agreement, is that if the goodness say,
11:20
Speaker 4: I'm really sorry, Okay, he gets very enthusiastic.
11:31
Speaker 3: Space nuts.
11:33
Speaker 1: I couldn't help it. Turn that into a link.
11:36
Speaker 3: It's it's yeah, brilliant.
11:37
Speaker 1: I'll tell him, gosh, it's just too good. It's just
11:41
Speaker 1: too good. He was going off his nut that day, wasn't.
11:43
Speaker 3: He He was? Yes, he's very highly strung.
11:49
Speaker 1: Well, that that's how he That's how he greeted us
11:51
Speaker 1: when we visited you late last year. He came tearing down.
11:54
Speaker 3: The stairs doing his rooster impersonation. No one could ever
11:58
Speaker 3: rob your Fred. The one good thing about it, yes,
12:03
Speaker 3: is the one good thing.
12:04
Speaker 1: They don't have to be big aggressive dogs they just
12:07
Speaker 1: have to be loud.
12:09
Speaker 3: Or even you know, a brush turkey going past the
12:11
Speaker 3: window in the middle of the night. That's enough as well.
12:15
Speaker 1: Yes, that's it's all that takes sometimes. Now let's move
12:19
Speaker 1: on to our next story. And this is a story
12:22
Speaker 1: that's got scientists really well. The headline says, scientists stunned.
12:27
Speaker 1: We're talking about a comet that has done something really,
12:32
Speaker 1: really unusual. Unusual. We're talking about comet forty one P.
12:37
Speaker 1: What's it done this time? Because it keeps making the
12:40
Speaker 1: news this one, Yes.
12:42
Speaker 3: It does. Tuttle. Jacobini cressak is its full name, better
12:48
Speaker 3: known as forty one P. It's an object probably a
12:53
Speaker 3: kilometer across a flying iceberg like basically like comets are,
12:58
Speaker 3: and it orbits the I think about every five and
13:01
Speaker 3: a half years, so it's in what we would call
13:03
Speaker 3: a short period comet orbit, and it's when it passes
13:09
Speaker 3: near the Sun. Of course, it does what comets do.
13:11
Speaker 3: It out gases, produces basically plumes of gas leaving its surface.
13:20
Speaker 3: It's usually water ice being converted directly to water vapor
13:25
Speaker 3: by the process known as sublimation. But what has been
13:30
Speaker 3: recorded in in fact, in quite a while ago actually,
13:37
Speaker 3: I think this is eight years ago by a NASA
13:39
Speaker 3: spacecraft observations made by NASA Swift spacecraft measuring its rotation
13:46
Speaker 3: and basically over sixty days, what's that sort of nine
13:52
Speaker 3: weeks or something like that, it slowed down from rotating
13:58
Speaker 3: once every twenty hours to once every fifty three hours.
14:03
Speaker 3: So that is a you know, it's almost a three
14:05
Speaker 3: factor of three in the level of spin that this
14:10
Speaker 3: commet has got. Ye, and it's there's suggestion that maybe
14:18
Speaker 3: it's now rotating in the other direction from what it
14:23
Speaker 3: was before that there has been some sort of reverse.
14:26
Speaker 1: It hasn't slided down to about one third, it's it's reversed.
14:30
Speaker 1: So it's it's slowed down well five times.
14:34
Speaker 3: Yeah, if the other way it could be, I mean,
14:38
Speaker 3: part of it could be due to how you measure
14:41
Speaker 3: the rotation, because it could be tumbling as well, so
14:43
Speaker 3: you might be seeing it going the other way around.
14:45
Speaker 3: But it does seem to be I think you're right.
14:47
Speaker 3: It's I think what you've just said is correct that
14:49
Speaker 3: it's a it's a reversal and genuine reversal of its
14:53
Speaker 3: rotation direction. So yes, it's it's got much more than
14:57
Speaker 3: a factor of three. That's right.
14:59
Speaker 1: That kill my theory because my first thought was, well,
15:02
Speaker 1: this must just be an observational era. But an observational
15:06
Speaker 1: era wouldn't get it the wrong way around. Less, of
15:09
Speaker 1: course you're talking about the color of the universe, but
15:11
Speaker 1: we won't get there. But it was so, yeah, what
15:20
Speaker 1: else could be causing this change behind?
15:23
Speaker 3: Well, I think if it was anything other than a comet,
15:27
Speaker 3: you know, if it was an asteroid doing this, or
15:30
Speaker 3: a planetismal, or a distant one of the distant Couiper
15:35
Speaker 3: Belt objects or something like that. If it was any
15:37
Speaker 3: of those, we would be utterly gobsmacked because there's no
15:42
Speaker 3: physical mechanism to do that other than an interaction with
15:45
Speaker 3: another body. You know, if you had two bodies gravitating
15:50
Speaker 3: close together, it could have an effect on the rotation,
15:54
Speaker 3: but in fact, more especially a collision that would do
15:57
Speaker 3: it as well. But with a comet, you've got this
16:00
Speaker 3: process that outgases what I was saying earlier, as it
16:03
Speaker 3: gets near the sun there they're basically the ices start
16:08
Speaker 3: to vaporize and you get a thrust from the from
16:12
Speaker 3: the outgasing material, which is what we call a non
16:17
Speaker 3: gravitational perturbation. It's when when you know, the outgasing material
16:22
Speaker 3: is acting like a rocket engine and it's changing the
16:26
Speaker 3: dynamics of the object as it's orbiting the Sun. And
16:31
Speaker 3: you can imagine that if there was a formation of
16:35
Speaker 3: ice on the on the surface of the comet that
16:39
Speaker 3: essentially tilted the blast of the of the escaping material
16:45
Speaker 3: as as it's sublimated as the as the the material
16:50
Speaker 3: that water mostly went straight from a solid to a gas.
16:54
Speaker 3: It's like having a you know, a sort of Vernia thruster.
16:58
Speaker 3: It's like where you've got a thrust that is changing
17:01
Speaker 3: the rotation of a spacecraft because it's not going the
17:05
Speaker 3: line of the of the thrust is not going through
17:08
Speaker 3: the center of gravity of the comet. If it's off
17:10
Speaker 3: the center of gravity, then it's going to impart a
17:12
Speaker 3: rotation on it, and if it's strong enough, then it
17:15
Speaker 3: might be enough to slow it down and perhaps even
17:17
Speaker 3: reverse its reverse its rotation. So that's what the thinking is.
17:21
Speaker 3: But it's never been seen before.
17:23
Speaker 1: No, like retro rockets.
17:26
Speaker 3: Yeah, that's right, it's a retro rocket, but one that's
17:30
Speaker 3: not slowing it down in its orbit. It's changing its
17:33
Speaker 3: rotation because if the angle that the rocket, if you
17:36
Speaker 3: want to call it that the rocket exhaust is coming out.
17:40
Speaker 1: At the moment, it's seven hundred and seventy four million
17:43
Speaker 1: kilometers from Earth by point one out astronomical units, And
17:50
Speaker 1: as you mentioned, this unusual behavior was checked back in
17:54
Speaker 1: twenty seventeen and they've only just sort of put a
17:59
Speaker 1: paper together to try and explain it. It's got a
18:02
Speaker 1: five point four year orbit, so it comes back quite often.
18:05
Speaker 3: Yeah, that's right. It's it's it's captured, basically captured by Jupiter,
18:11
Speaker 3: so its orbit is dictated. It would have been in
18:14
Speaker 3: its early history, it would have been a comet coming
18:16
Speaker 3: into the Inner Solar System from the Oort Cloud, this
18:19
Speaker 3: spherical sort of reservoir of comets, but would have had
18:23
Speaker 3: its orbit modified maybe several times by the influence of Jupiter,
18:27
Speaker 3: which is why it's now in this really short, such
18:31
Speaker 3: short period orbit five point four years. There has been
18:36
Speaker 3: a suggestion that if you've got these sort of oblique
18:39
Speaker 3: out gassing that we've just been talking about that would
18:42
Speaker 3: change the rotation of the object, that that might also
18:46
Speaker 3: signal that there might be weaknesses in the comet structure,
18:49
Speaker 3: and it may even be a precursor to it breaking up,
18:52
Speaker 3: which is something that I think will be observed with
18:56
Speaker 3: great interest as to how it progresses since since this
19:00
Speaker 3: change of spin.
19:01
Speaker 1: Yeah maybe, and we will find We could find out
19:04
Speaker 1: as late as or as soon as late twenty twenty eight,
19:08
Speaker 1: I think, is its next appearance near the Sun or
19:12
Speaker 1: near us.
19:12
Speaker 3: Or whatever you like.
19:13
Speaker 1: So I'll keep an eye on forty one P. I
19:18
Speaker 1: guess you P.
19:19
Speaker 3: That's right. There was a proposal long and long ago
19:25
Speaker 3: to send a spacecraft to it because it's a short
19:28
Speaker 3: period comet, so it's always in the inner Solar System,
19:31
Speaker 3: and that was what was then called EZRA, the European
19:34
Speaker 3: Space Research Organization, the precursor of ISSA, the European Space Agency.
19:40
Speaker 3: This is in the nineteen sixties. They looked at sending
19:42
Speaker 3: a probe to that comet, but they changed their mind
19:45
Speaker 3: so it never went.
19:47
Speaker 1: Ah, yes, I'm sure that happens a lot in astronomy.
19:51
Speaker 1: I mean not an easy, not an easy thing to
19:56
Speaker 1: do to you know, set up a mission and actually
20:00
Speaker 1: execute it, and you're going to come up with the dollars
20:02
Speaker 1: and yeah, you know, it's only so many ten cent
20:06
Speaker 1: pieces confider on a jar on the mantelpiece. So yeah,
20:11
Speaker 1: that's right, Yeah, all right. You can read all about
20:16
Speaker 1: comment forty one p at it's at the Daily Galaxy
20:21
Speaker 1: dot com website. But you can also read the paper.
20:24
Speaker 1: I think it's just been pre published or pre there's
20:28
Speaker 1: a pre print available on the archive. This is Space
20:33
Speaker 1: Nuts Andrew Dunkley here with Professor Fred what's a bolt?
20:42
Speaker 3: If I'm promund.
20:50
Speaker 1: Piece Nuts, I've read to our final story on this episode.
20:55
Speaker 1: We've talked many times about gravitational lensing and some of
20:59
Speaker 1: the strain things that it does. You can watch something
21:02
Speaker 1: happen two, three, four times over the course of many
21:05
Speaker 1: years because of gravitational lensing, because the light is redirected
21:10
Speaker 1: and takes longer to get here, and so you can
21:12
Speaker 1: see something and go, oh, what was that? Hang on,
21:15
Speaker 1: I'll know again in a couple of years because not quite.
21:19
Speaker 1: But what we're talking about, what we're talking about in
21:24
Speaker 1: this particular case though, is actually going out to a
21:29
Speaker 1: solar gravitational lens focal point. Is that the crux of
21:33
Speaker 1: the story.
21:34
Speaker 3: It is, That's right. So this is a really interesting
21:37
Speaker 3: kind of assay really on the Universe Today website by
21:42
Speaker 3: Thomas Wick about about the solar gravitational lens and about
21:47
Speaker 3: how you'd get there. But the solar gravitational lens itself
21:51
Speaker 3: is really interesting. So the idea is exactly as you've said.
21:55
Speaker 3: If you've got an object of any mass, and it
21:58
Speaker 3: happens with planets as well stars, it's going to bend
22:03
Speaker 3: the light passing around it because it's distorting space under
22:08
Speaker 3: the protocols introduced by not sorry, as we understand it,
22:13
Speaker 3: by the protocols introduced by Einstein's general theory of relativity.
22:18
Speaker 3: That's what lets us do all the calculations about this
22:21
Speaker 3: sort of thing. So you've got an object in space,
22:23
Speaker 3: it's bending the light around it, which means it acts
22:25
Speaker 3: kind of like a lens. It's a very odd sort
22:28
Speaker 3: of lens, though. I've seen a glass kind of interpretation
22:33
Speaker 3: of a gravitational lens. There's a specialist who works on
22:38
Speaker 3: this stuff in Melbourne who showed me her glass version
22:42
Speaker 3: of a gravitational lens, and it resembles, you know, the
22:46
Speaker 3: bottom of a wineglass where the stalk comes up out
22:49
Speaker 3: of the middle of that.
22:50
Speaker 1: I know them very well for it.
22:52
Speaker 3: Yeah, Well, if you break the wine glass off and
22:56
Speaker 3: you're left with that sort of flared part at the bottom,
22:59
Speaker 3: that's more less the same as a gravitational lens in
23:02
Speaker 3: the way it would act on the light going around it.
23:04
Speaker 3: So it's not like a magnifying loss, which is what
23:07
Speaker 3: you'd like it to be. It's this very peculiar cusp
23:10
Speaker 3: shaped lens, and so it gives you a focus that
23:16
Speaker 3: is blurred, but it's because you know the properties of
23:20
Speaker 3: the object that's doing the lensing, and in this case
23:23
Speaker 3: we're talking about the Sun. Because you know the properties
23:27
Speaker 3: of the Sun, you can calculate what that blurring does
23:30
Speaker 3: to the image and you can essentially compensate it. So
23:34
Speaker 3: you could recreate the light coming from a very distant
23:38
Speaker 3: object and recreate the image that the Sun is forming
23:43
Speaker 3: as though it was a proper lens rather than a
23:45
Speaker 3: peculiar cusp lens. And that's what's sort of being proposed.
23:50
Speaker 3: Could we send a spacecraft to the solar gravitational lens
23:55
Speaker 3: focus where you could look directly back at a planet
24:02
Speaker 3: on the other side of the Sun around a distant star,
24:07
Speaker 3: so you're looking into another Solar system a long way away,
24:10
Speaker 3: but you're using the Sun's gravity to bend that light
24:14
Speaker 3: by relativity and focus it to a point. And if
24:18
Speaker 3: you put a spacecraft there with a camera and a
24:21
Speaker 3: fancy computer, you might be able to reveal continents on
24:25
Speaker 3: an exoplanet, for example, or even cities. That's the sort
24:30
Speaker 3: of thing that people are thinking of. So here's the
24:33
Speaker 3: snag though. That's a great idea, but a snag.
24:36
Speaker 1: I think I just read that exact paragraph as you're
24:40
Speaker 1: about to say it. I might blow the whistle.
24:43
Speaker 3: Yeah, well you can now you do it. It's the distance,
24:47
Speaker 3: isn't it. It's yeah, about somewhere between six hundred and
24:52
Speaker 3: fifty and nine hundred astronomical units is what's quoted in
24:55
Speaker 3: this in this article. In an astronomical unit is one
24:58
Speaker 3: hundred and fifty million, killer me. So it is a
25:01
Speaker 3: number with a lot of zeros after it in kilometers,
25:06
Speaker 3: and you know it's getting your spacecraft that is the
25:10
Speaker 3: issue we're talking about. Well, the estimate here is four
25:14
Speaker 3: times further than Voyager one has traveled, and that, as
25:17
Speaker 3: we know, is twenty three light hours away. They reckon
25:22
Speaker 3: that it would be more than another one hundred and
25:25
Speaker 3: thirty years to for Voyager one to get to the
25:31
Speaker 3: Sun's gravitational lens point.
25:33
Speaker 1: By my calculation, and this is probably way wrong. Ninety
25:37
Speaker 1: seven five hundred million kilometers.
25:41
Speaker 3: Sounds about right. Yeah, it sounds like a lot.
25:43
Speaker 1: Yep. I didn't think my calculator could fit that many
25:46
Speaker 1: numbers on it. Remember the old calculators when they first
25:50
Speaker 1: came out. If you gave it too big a problem
25:52
Speaker 1: and it would just give you a little EVA era.
25:56
Speaker 1: Now I can't do that. Sorry.
25:57
Speaker 3: Yeah, yeah, this computer says no. Really, that's right.
26:01
Speaker 1: Yeah, that's a long way away and very difficult to achieve.
26:05
Speaker 1: But I think one day maybe we could do yes.
26:08
Speaker 3: So that that's really the thrust of this article. How
26:11
Speaker 3: about you know what's the way to do it? Can you?
26:14
Speaker 3: Can you get to that point? And they the author's
26:19
Speaker 3: got some nice calculations which have checked these are correct,
26:23
Speaker 3: I should check them. But anyway, if you were trying
26:27
Speaker 3: to get to that solar gravitational lens point focal point
26:31
Speaker 3: in twenty years, then you need your spacecraft to travel
26:35
Speaker 3: at about one hundred and fifty kilometers per second. It's
26:41
Speaker 3: which is very hard when you're pointing away from the sum.
26:45
Speaker 3: The Parker solar probe, they point out, and we kind
26:48
Speaker 3: of know this because we've talked about it, has actually
26:50
Speaker 3: got to nearly two hundred kilometers per second but that's
26:54
Speaker 3: only when it's a what we call perihelium. It's at
26:56
Speaker 3: its closest point to the Sun where it's going fast.
27:01
Speaker 3: And what we're talking about here is something going in
27:03
Speaker 3: the opposite direction, going away from the Sun. For it
27:06
Speaker 3: to travel at that sort of speed, you need an
27:08
Speaker 3: extraordinary amount of thrust. I don't think you're talking about
27:13
Speaker 3: chemical rockets to get up tow one hundred and fifty
27:15
Speaker 3: kilometers per second. Lights, So the light sales, Yeah, that's
27:20
Speaker 3: one of the things that you and I've spoken about before.
27:23
Speaker 3: If you can beam out laser lights to a solar
27:27
Speaker 3: sale or gigantic piece of you know, something very thin
27:32
Speaker 3: like MYLA that's reflective, then the light itself pushes it
27:35
Speaker 3: along and you just keep going so that it just
27:38
Speaker 3: keeps up, building up speed.
27:41
Speaker 1: There are trouble is when you get there, how do
27:45
Speaker 1: you stop it?
27:46
Speaker 3: Yeah, you don't.
27:46
Speaker 1: You just keep going, That's right, unless it had something
27:50
Speaker 1: on board to like you turn off the light and
27:54
Speaker 1: reverse something.
27:56
Speaker 3: I don't know, you're never going to slow it down
27:58
Speaker 3: because even if you turn the light, it stops it accelerating,
28:02
Speaker 3: but it's still going at that speed. That's right. There's
28:06
Speaker 3: a a possibility that, you know, could you do the
28:14
Speaker 3: solar sale trick and basically make it successful. The problem
28:23
Speaker 3: with solar sales is you can only carry objects that
28:27
Speaker 3: are very light in weight or have low mass. And
28:30
Speaker 3: you might remember we've looked at this with what was it,
28:34
Speaker 3: the Breakthrough star Shot program, which I think has now ceased.
28:38
Speaker 3: Breakthrough star Shop looked at the feasibility of using a
28:41
Speaker 3: solar sale to send a spacecraft to proximate Centauri, which
28:45
Speaker 3: is only four light years away, and it could be done,
28:50
Speaker 3: but your spacecraft would basically consist of one what's it
28:57
Speaker 3: called printed circuit board and a detector. There's not really
29:00
Speaker 3: room for anything else. It will be so it'd have
29:03
Speaker 3: to be so light in weight it will be measured
29:05
Speaker 3: in grams rather than kilograms or tons. So that will
29:10
Speaker 3: be the problem with your you know, with sending a
29:12
Speaker 3: spacecraft to the solar gravitational lens using a solar sale.
29:17
Speaker 3: So you're talking then about nuclear sources and things of
29:20
Speaker 3: that sort. That this very nice article goes into some
29:25
Speaker 3: of the niceties of nuclear thermal propulsion and things of
29:29
Speaker 3: that sort. Even so, it's still a very tough ask
29:34
Speaker 3: to send a spacecraft to that interesting part of the
29:39
Speaker 3: Sun's environment where you've got the solar gravity forming a
29:46
Speaker 3: focus to get there. It's really to get there in
29:51
Speaker 3: you know, twenty years or so. You're talking about really
29:54
Speaker 3: new technologies that we simply don't have at the moment.
29:56
Speaker 1: Yeah, well one day it might be a long way off,
29:59
Speaker 1: but the time may come, and then again we might
30:03
Speaker 1: have figured everything out by then, so yeah.
30:07
Speaker 3: Yeah, I mean, you know, the other thing is you'd
30:10
Speaker 3: want to choose. So you've got to choose the direction
30:13
Speaker 3: that you go in to be in the opposite direction
30:16
Speaker 3: to the planet that you want to observe, the exoplanet.
30:20
Speaker 3: And if you get that wrong, if you choose a
30:22
Speaker 3: planet that's completely boring and has no surface features whatsoever,
30:27
Speaker 3: then you don't really contribute much to our knowledge, particularly
30:32
Speaker 3: our knowledge of whether we're alone or not, whether it's
30:34
Speaker 3: life and dowhere else.
30:34
Speaker 1: It's sort of like leaving the lens cap on the
30:37
Speaker 1: camera when you land on birdness. Yes, actually they didn't
30:41
Speaker 1: leave it on. It melted on. I think.
30:44
Speaker 3: Yeah, well one of them fell off as well, didn't
30:46
Speaker 3: it fall off some top of the on top of
30:49
Speaker 3: the scale that was going to give the you know,
30:52
Speaker 3: as a ruler that they jettison to give the camera
30:56
Speaker 3: something to look at so you could measure the size
30:58
Speaker 3: of things, and the lens cap landed right and top
31:00
Speaker 3: of it. I think that's what happens.
31:01
Speaker 1: They've had quite a few venus disasters over the years.
31:05
Speaker 1: But yeah, you're right, this would be very, very difficult
31:09
Speaker 1: to swallow if you buging it up, because you couldn't
31:12
Speaker 1: go and fix it, not.
31:13
Speaker 3: Like honey, that's right. You can't move it in any direction.
31:16
Speaker 3: You're stuck on one plate. Really.
31:18
Speaker 1: Indeed, it's food for thought though, but one day we'll
31:23
Speaker 1: figure out a way. If you'd like to read about
31:25
Speaker 1: that story, it is at Universe today dot com, as
31:29
Speaker 1: Fred said, and we're done, Fred, thank you very much.
31:32
Speaker 3: Oh yeah, that was great to talk about all those things.
31:35
Speaker 3: So I hope you do it again sometimes.
31:37
Speaker 1: One topic, so I'm sure we will. If you would
31:40
Speaker 1: like to visit us in the meantime, don't forget to
31:44
Speaker 1: visit our website, space nuts podcast dot com or space
31:47
Speaker 1: nuts dot io, or visit our social media platforms the
31:50
Speaker 1: official space nuts Facebook page or Instagram page or YouTube
31:54
Speaker 1: channel or whatever you like. Or if you want to
31:57
Speaker 1: talk to like minded space nuts, you can do that
32:01
Speaker 1: on the Space Nuts podcast group on Facebook, which is
32:04
Speaker 1: always a lot of fun. Thanks Red, We'll see you soon.
32:07
Speaker 3: Yes, I hope so Bill he said that.
32:10
Speaker 1: And thanks to HEU in the studio who couldn't be
32:13
Speaker 1: with us today. He was invited by a friend to
32:16
Speaker 1: see a comet. He couldn't wait, so he ran over there.
32:19
Speaker 1: It turned out to be Goldfish. Some people will get
32:22
Speaker 1: that and from me Andrew Dunkley, thanks for your company.
32:27
Speaker 1: See you on the next episode of Space Nuts. Bye
32:29
Speaker 1: Bye snus.
32:30
Speaker 5: You'll be listening to the Space Nuts podcast available at
32:35
Speaker 5: Apple Podcasts, Spotify, iHeartRadio, or your favorite podcast player.
32:41
Speaker 1: You can also stream on demand at guides dot com.
32:44
Speaker 1: This has been another quality podcast production from nights dot com.