Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Expanding Universes, Space Elevators & the Enigma of Gale Crater

Transcript

Expanding Universes, Space Elevators & the Enigma of Gale Crater · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Hello again. This is Space Nuts. It's a Q and
0:03
A edition. This is where we take questions
0:05
from the audience, throw them in the bin and
0:08
discuss other things amongst ourselves. No,
0:10
we do answer questions from the audience and
0:12
we've got a bunch. Um, we've got a question
0:14
about the uh, naming of the
0:17
increase in the expansion of the universe
0:20
rate. Although last episode, if you
0:23
were listening, that might not be happening,
0:25
but we will still try and tackle it. Uh,
0:27
there's a question about space elevators.
0:30
We've got uh, a question about an object that
0:32
has been getting a lot of attention
0:34
TOI6894B. And
0:37
a very different kind of question, I
0:39
will say, uh, regarding Gale Crater.
0:43
That's all coming up on this, uh, edition of
0:45
space nuts. 15 seconds. Guidance is
0:48
internal. 10, 9.
0:51
Ignition sequence start.
0:53
Jonti Horner: Space nuts. 5, 4, 3, 2.
0:55
Andrew Dunkley: 1. 2, 3, 4, 5, 5, 4, 3,
0:58
2, 1. Space nuts. Astronauts report
1:01
it feels good. He's back again for
1:04
more. He is Jonti Horner, professor of
1:06
Astrophysics at the University of Southern
1:08
Queensland. Jonti, hello.
1:10
Jonti Horner: Good afternoon. How are you going?
1:12
Andrew Dunkley: I'm well, I'm very well.
1:14
Uh, we've got a lot of questions and this
1:17
very first one, we'll jump straight in. Comes
1:19
from Rusty in Donnybrook in Western
1:22
Australia.
1:22
Andrew Dunkley: Johnny and Andrew. G'.
1:24
Jonti Horner: Day.
1:24
Andrew Dunkley: It's Rusty in Donnybrook and I'm wondering
1:26
what the, the term um, for
1:30
an increase in the acceleration
1:32
rate for the expansion of the universe is.
1:35
We've known about. Well we've had this
1:37
concept for quite a few years now. And
1:39
recently we um, we're now looking at
1:42
a reduction in the acceleration of the
1:44
expansion rate of the universe as well. So
1:46
there's a positive and a negative aspect to
1:49
this. And um, since we've had all this time,
1:51
someone may have come up with ah, a better
1:53
term than jolt or jerk, which seem
1:56
to apply to very short term changes
1:59
and not very gradual changes that
2:02
we theorize uh, in the expansion of the
2:05
universe. Thank you.
2:07
Andrew Dunkley: Thanks Rusty. Always good to hear from you.
2:10
Uh, he's always got a
2:12
curveball type question, has Rusty. Although
2:15
we might have been able to curve the ball
2:16
back to him because last uh, episode we
2:19
were talking about this very subject, the
2:21
expand, increasing rate of the
2:24
expansion of the universe. And uh, he wants
2:26
to know what it should be called. But um, the
2:29
expansion of the universe theory might be
2:31
tipped on its head because of the research we
2:33
were talking about last time. So if you
2:35
haven't listened to the previous
2:37
episode573, go back and have a Listen to
2:40
the last story because it, it's
2:42
suggesting that, uh, things may not be as
2:45
they seem. Jonti.
2:47
Jonti Horner: Absolutely. And it's, you know, this advert
2:49
brought to you by the developing nature of
2:51
science. Essentially it, uh, is how science
2:54
evolves. You know, we get new observations
2:56
and we revisit our theories. It's a really
2:58
good question and it's a really good point. I
3:00
have never actually heard any
3:02
nickname or any kind of easy roll off
3:05
the tongue phrase to talk about the
3:07
accelerating expansion of the universe.
3:10
Cosmologists talk about things in the context
3:12
of the lambda CDM model. And, um, I don't
3:14
really understand what that is because I'm
3:16
not a cosmologist, but that is not an easy
3:18
roll off the tongue nickname. Now, if you go
3:21
back to the very, very, very, very early
3:23
youth of the universe, there was
3:26
a period where there was this incredibly
3:29
accelerated expansion that is hypothesized
3:32
called inflation. And, um, that was
3:35
very, very, very early on. That's called the
3:38
inflationary period. That's a little bit
3:39
different. What Russ is talking about here is
3:42
the, uh, evidence which won the Nobel
3:45
Prize in 1998, I think, for the fact that,
3:48
that the universe may be expanding at an
3:51
accelerating rate. So in other words, the
3:53
expansion is getting quicker rather than
3:54
slowing down. And if gravity was winning,
3:57
you'd expect the expansion to slow down over
3:59
time as gravity pulls back on the expansion.
4:01
So this was the great evidence for the
4:04
existence of dark energy, which people
4:05
hypothesize contributes something like
4:08
68% of all that there is in the universe.
4:11
It's basically we're a dark energy universe
4:13
with a fair chunk of dark matter and a tiny
4:15
little bit of normal matter on the side, like
4:17
less than 2%. That,
4:20
as we talked about in the previous episode,
4:22
may be a paradigm that is about to change.
4:24
There's growing evidence that the universe is
4:26
perhaps a bit more complex than that. But in
4:29
terms of Rusty's question, I have never come
4:31
across a simple term or nickname
4:34
or something like that for this theory.
4:37
People just talk about the accelerating
4:38
expansion rate of the universe. So
4:41
unfortunately, Rusty, I can't help you there.
4:43
To the best of my knowledge, there is no
4:45
really snappy roll off your tongue thing. I.
4:48
The model that tries to explain it, like,
4:49
say, is a lambda CDM model. But that is
4:52
not a snappy, um,
4:54
public article, BBC documentary
4:57
type name that will capture people's
5:00
imaginations. That's just a working
5:02
terminology in the industry kind of thing.
5:04
Yeah.
5:04
Andrew Dunkley: Well, while you've been talking, I asked
5:06
Chatgpt what we
5:09
should call it. It came up with a whole
5:11
bunch, uh, accelerating universe hypothesis,
5:15
uh, cosmic expansion theory, uh,
5:17
inflation continuum theory, dark energy
5:20
paradigm. You use that word. Uh,
5:23
that's a more scientific style. But uh, it
5:26
came up with some, uh, conceptual names. The
5:28
great unbinding, uh,
5:31
external expansion
5:33
hypothesis, uh, runaway cosmos
5:36
model, uh, the horizon drift
5:39
theory. I like that one. Metric
5:41
unfolding principle, the lambda drive and the
5:44
everflight theory. That's what ChatGPT's come
5:47
up with. Probably just found stuff that
5:49
people have published.
5:50
Jonti Horner: I think a lot of those are things that are
5:51
linked to this but are other hypotheses and
5:53
stuff like that. Yeah, I mean I have to admit
5:56
that I didn't really want to Google things
5:58
there because I wasn't all that keen on
6:00
seeing the Google autocorrect coming back
6:01
saying, did you mean expanding wasteland?
6:06
Andrew Dunkley: Yeah, it does come up with some. Really what
6:08
I hate is when I know exactly what I'm
6:10
searching for. I put it in, I've uh, spelled
6:11
it right and an autocorrect and finds me
6:13
something else. Yeah, that's not what I asked
6:16
for. I told you to look for, you know,
6:18
lemonade, not lemons. Anyway,
6:22
thanks Rusty. Uh, maybe you've got a name you
6:24
can send through to us or maybe um, somebody
6:26
could pose the question on the Facebook group
6:28
or the podcast group on Facebook and uh,
6:31
come up with some names. I'd be interested to
6:34
see what you think of.
6:36
Uh, our next question comes from Barry. Uh,
6:38
Barry said, I, uh, recently read a sci fi
6:41
book called First Ascent. Based on a space
6:44
element. The elevator had six stations, one
6:46
being Earth, uh, two at 300 kilometers, five
6:49
at 6200 kilometers and six being
6:52
geostationary orbit at
6:53
35,786 kilometers. I
6:56
know the International Space Station's about
6:58
400 kilometers and the crew are in free
7:01
fall. This is due to the forward motion of
7:04
the iss, which is constantly falling and is
7:06
in orbit. In the book they discuss that at
7:09
Station 1 at 300 km the travellers are still
7:12
at about 1G. Station 5, uh,
7:15
at 6200 km they're at 1 quarter G,
7:18
they're on the moon, they be at 1/6 and free
7:21
fall, weightless, is at station 6,
7:24
35,000 and a bit kilometers. Can you
7:27
discuss with accuracy of feeling
7:30
gravity if and when a space elevator is
7:33
built? Of course, this is totally
7:35
hypothetical for at least the next few
7:37
hundred or thousand years. Yes it is. It's
7:40
not something we can do yet. And even if we
7:43
could, I don't know if it would be the
7:46
Logical way to do things. But you know, we
7:49
don't know what reasons in the future we
7:50
might need one. So um, we'll just leave it
7:53
hanging in the air. Boom.
7:54
Jonti Horner: Boom.
7:55
Andrew Dunkley: Um, so, uh, yeah. So can you discuss the
7:57
accuracy of feeling gravity if and when a
8:00
space.
8:01
Jonti Horner: Uh, elevator is built?
8:03
Yeah, it's a fabulous question. And it does
8:05
sound like this book is hard sci fi in
8:08
the sense that it's based on real world
8:10
physics is what I'd say. It sounds like the
8:12
numbers are right to me. Now the argument is
8:14
that a space elevator, once you can get it
8:16
built, it's an incredibly challenging thing
8:18
to do beyond us at the minute. But once
8:20
you've got it, it's suddenly it makes it much
8:23
easier to access space. And part of the
8:25
argument there is that we will be extracting
8:28
resources off Earth. And so it's likely that
8:31
there'll be more stuff coming down the
8:32
elevator than going up. So effectively you
8:34
can ride up for free, just, you know, as a
8:37
side effect of it. So it's one of those
8:39
things that has become a staple of kind of
8:42
relatively near futureish science fiction.
8:45
The numbers here about the acceleration that
8:47
you'd feel are accurate. So there's two ways
8:50
that you can get gravity if you're on a space
8:52
elevator. One is that you would feel
8:55
a pseudo gravity based on the acceleration
8:58
of the lift going upwards. And you
9:01
get this when your lift goes up or when it
9:04
falls. If you're in a building that has one
9:06
of those ultra fast lifts, you feel a little
9:08
bit more weightless. If it's going down, you
9:09
feel a little bit heavier when it's pulling
9:11
up initially because the flow will be
9:13
accelerating up to meet you or
9:16
accelerating down away from you. And that
9:18
will mean that you will get a change to the
9:21
gravity you would otherwise feel if you were
9:23
stationary at that altitude. So
9:26
some sci fi books I've seen with kind of far
9:29
future type technology have
9:32
your space elevator, uh, able to accelerate,
9:35
ah, or in excess of 1g, very hard
9:38
acceleration. And what they do is they
9:40
accelerate slowly going up through the
9:42
atmosphere and then speed up once you're in
9:44
vacuum with the acceleration
9:46
offsetting the drop in gravity you get as you
9:49
get higher, keeping you at a comfortable
9:51
level of gravity. And then when you're
9:52
halfway to the end point, it turns around,
9:55
you have a brief period of pseudo
9:57
weightlessness and then you accelerate in the
9:59
other direction, slow down. So that's one way
10:01
that you could get kind of constant gravity
10:03
throughout almost the entire trip. And that
10:05
will get you to your uh, End point pretty
10:07
quickly. So if you're accelerating at 1G, you
10:10
actually accelerate very quickly. And that's
10:11
why you wait till you're out of the
10:12
atmosphere to do that. But the other thing
10:15
is, as you ride up on a space elevator, the
10:17
higher you get, you will still feel gravity
10:20
pulling you down through the soles of your
10:22
feet, but the strength of the gravitational
10:25
pull you feel will weaken. Now,
10:27
when you're at the end point, which is
10:30
a space station in geostationary orbit, you
10:33
are moving around the Earth, ah, at orbital
10:35
velocity. And, um, the space station around
10:38
you is moving around the Earth at orbital
10:39
velocity. So that's why you'd be weightless,
10:42
because you're accelerating at exactly the
10:44
same rate as your surroundings.
10:47
So compared to you, there is no acceleration
10:50
pulling you down because the flow's falling
10:51
away at exactly the speed that you're falling
10:54
down effectively. So that's what you'd
10:56
experience very briefly if you were in an
10:58
elevator on Earth and the wires were cut when
11:01
you started to fall, you'd be weightless, but
11:03
you wouldn't be enjoying the experience. No,
11:05
not much worrying about what happens at the
11:06
bottom. Although, thanks to a very, very
11:09
silly TV series that's quite swearing
11:12
offensive called Archer, my understanding is
11:14
that lifts, uh, have been designed in such a
11:17
way that if the cables break, there are
11:19
safety mechanisms in so you won't just splat
11:21
at the bottom. There was a whole episode
11:23
based where they were stuck in the lift and
11:24
they were worried about that. It's bizarre
11:26
what you learn from random TV cartoons.
11:28
Anyway, so you have,
11:31
at the upper limit, effectively
11:34
zero G, you are weightless. You're actually,
11:37
you are experiencing the Earth's gravity, but
11:39
so is the space station around you. When
11:40
you're falling together, just like mentioned
11:42
with the International Space Station
11:45
at, uh, that point, if you had some way of
11:49
sitting stationary in space, so in other
11:51
words, you were not orbiting the Earth, you
11:54
were motionless, but you had a rocket holding
11:56
you up. You would still feel the Earth's
11:58
gravity pulling you down because the rocket
12:00
would be pushing up against your feet
12:02
essentially, and you'd feel the strength of
12:04
gravity there. You're, uh, at
12:06
36,000 kilometers, which means you're 42,000
12:09
kilometers from the center of the earth,
12:11
which means you're seven times further from
12:13
the middle of the Earth, uh, than we are
12:15
here. The strength of gravity falls off as 1
12:17
over distance squared. So you'd feel about 1
12:20
50th of a G there. So if
12:23
you were able to sit still rather than
12:25
falling with the Space station, you would
12:26
feel a little bit of gravity there, but it
12:28
wouldn't be that intense at the lower
12:31
altitudes. The effect
12:34
is dominated not by your rotation movement,
12:36
because you're going much slower than orbital
12:38
speed, but by the fact that gravity is
12:41
pulling you down, but the
12:43
lift is being winched upwards.
12:46
So if you lifted your space elevator up and
12:49
you stopped at one of these stops, and that's
12:52
why they talk about the stops, I suspect if
12:54
you stopped at 300 km at a station just above
12:57
the atmosphere, attached to the tether,
12:59
moving around at the same speed the Earth's
13:02
rotating underneath you, you'd feel an
13:05
acceleration due to gravity that is a little
13:07
bit smaller than that we feel at the surface
13:08
of the Earth. Now, if you're at the top of
13:11
Mount Everest, technically you feel a
13:13
slightly lower acceleration due to gravity
13:14
than you do at the sea level because
13:17
you're further from the center of the Earth.
13:19
So that one over R squared component in
13:22
the acceleration due to gravity equation is
13:25
a slightly bigger number on the R squared,
13:27
which means your acceleration due to gravity
13:29
is a slightly smaller number. But that's
13:31
imperceptible to humans. But we can measure
13:33
it with instrumentation. That, incidentally,
13:35
is why, if you really wanted to, to,
13:38
um, lose weight, um, but
13:41
you're being lazy. If you want to get weighed
13:43
in the place where you will wear the least on
13:45
the Earth, you go to the top of that mountain
13:47
near the equator. Is it anaconda? I think it
13:49
is. Which is a point on the Earth that is
13:52
furthest from the Earth's core. Because
13:54
you've got the bulge of the Earth's equator
13:55
on top of the height of the mountain.
13:59
And you will feel a slightly smaller
14:00
acceleration due to gravity there because
14:02
you're further from the Earth's core. So at
14:04
300km up, you've only changed your distance
14:07
from the center of the earth by about 5%. And
14:10
so you've probably changed the acceleration
14:11
due to gravity by less than 10%. It's
14:13
probably enough that you'd be able to notice
14:15
it. Walking around would feel slightly
14:17
unusual, but it wouldn't be a problem. The
14:20
station number five that is mentioned here,
14:22
at 6200km, that means
14:25
you're nearly twice as far away from the
14:27
center of the Earth now as we are on the
14:29
surface of the Earth. Surface of the Earth,
14:30
we're about 6,380 kilometers from the middle.
14:34
Varies a little depending on your altitude
14:35
above sea level and where you are on the
14:37
globe. Yeah. Add another 6200
14:39
km, you've effectively doubled the distance,
14:42
which means 1 upon r squared is 1 over 2
14:45
times 1 over 2 is 1 over 4. So the
14:48
acceleration is a quarter of a g. So we've
14:50
dropped the strength of gravitude field by a
14:52
factor of four. And at that point that is
14:54
hugely noticeable. It's a little bit stronger
14:57
gravity than you'd have on the moon, but not
14:59
by much. Now, I guess this is the kind of
15:02
thing where you could, if you were sending
15:03
people to Mars and you wanted them to
15:06
experience Martian gravity and see if they
15:09
could cope with it, you know, you had a
15:11
training and a testing program and anybody
15:13
that got too travel sick or whatever and
15:15
couldn't adapt was bumped out of the program.
15:17
What you do is you take this space elevator,
15:20
you figure out exactly at what height above
15:22
the ground, you would emulate Martian gravity
15:24
perfectly and you build a training station
15:26
there. Because at the end of the day, if
15:28
you've got a space elevator, you know, you
15:29
may as well put an extra level on it. Um, and
15:32
that way you can train people up for Mars.
15:34
And I could almost imagine a future where
15:35
they have one for the moon as well. You know,
15:37
go up there, spend a few weeks training in
15:39
lunar gravity and see if you can hack it on
15:41
the surface of the M moon. And anybody who
15:43
can't, no shame. We all have slightly
15:45
different balance systems and all the rest of
15:47
it, if you can't adjust, that's fine, you can
15:50
work on Earth, no problem. But so it
15:52
does sound like the science in this
15:55
book is robust. In other words, it's hard,
15:58
hard sci fi.
15:59
It's based on our current understanding of
16:01
physics and that's how it would work on space
16:03
elevator. So hopefully that makes sense. And
16:05
it is a really good example of how you can
16:08
use a science fiction book to t to teach
16:10
people science fact.
16:12
Andrew Dunkley: Yeah, absolutely. Yeah. Thanks, Barry. Um,
16:14
just a side question, Jonti. Do you think
16:17
we ever will build such a thing?
16:21
Jonti Horner: I'd be a fool to say no on it. I really hope
16:23
that we do. And um, given the impact we've
16:26
seen both good and bad, from the
16:29
advent of reusable spacecraft and the growth
16:31
of commercial space, that's dropped the cost
16:33
of launching kilogram of material to space by
16:36
between a factor of 10 and factor of 100. And
16:38
it's been revolutionary. If you could drop
16:40
that cost to essentially nothing. What
16:43
that enables is an enormous expansion in
16:46
our use of space. It also enables the kind of
16:49
space tourism type stuff because if you
16:52
have a docking station at geostationary
16:54
orbit, you've Already done a hell of a lot of
16:57
the work of getting out of Earth's gravity.
17:00
So it's much easier to launch to Mars or the
17:02
moon or pick your tourist destination from
17:05
there. Pick your research destination, you
17:08
hugely reduce the cost of doing
17:10
both. Research, commerce, tourism.
17:13
By getting people up to that altitude. You
17:15
don't have to get through the atmosphere, but
17:17
you also don't have to burn your rocket to
17:19
get up, uh, through that hardest, steepest
17:21
part of Earth's gravity well. So once it is
17:24
technologically feasible, I suspect what
17:27
you'll have is it'll become technologically
17:28
feasible. Then not too long after that, it
17:31
will become commercially feasible. And that's
17:33
the point people look at doing it. And, uh,
17:35
the big caveat there would be, is it actually
17:37
ever going to be technologically feasible?
17:40
But it's near enough future science that
17:42
people have already had suggestions about the
17:44
kind of materials you could use to make
17:47
the cable. Because that's a big
17:50
constraint is actually making the cable, um,
17:53
would need to be a lot stronger than spider
17:55
silk, for example. But it is
17:58
not so far beyond what we can make now that
18:01
people think it's impossible. Rather, people
18:03
think it could be feasible, but we don't know
18:05
how yet. And in that kind of context, we're
18:07
incredibly good at doing the impossible and
18:09
the improbable as a species. So, uh, so long
18:12
as we don't wipe each other out, so long as
18:15
the shutdown eventually ends, then perhaps
18:18
we'll be able to figure this out. And, you
18:20
know, probably not in our lifetime, but may
18:23
well not be as far beyond that as you'd
18:24
think.
18:25
Andrew Dunkley: Well, uh, if you go back 200 years and tell
18:27
people, hey, I, you know, where I come from,
18:29
we've been to the moon, they'd think you were
18:31
a witch. They just wouldn't believe
18:34
it. So, uh, who knows what's possible in 200
18:37
years time?
18:37
Jonti Horner: Yeah, the thing that makes my head hurt with
18:39
that, uh, is we're almost at the point. In
18:41
fact, I think we possibly are at the point
18:43
now where it is longer since the first
18:45
moonwalk than that moonwalk was from the
18:48
first powered flight.
18:49
Andrew Dunkley: I know. Isn't it amazing?
18:52
It's incredible how far we've come in such a
18:54
short period of time. M thank you, Barry. Um,
18:57
great question.
18:58
Uh, our next question coming up in a moment
19:00
on Space Nuts.
19:06
Space Nuts. And you're with Andrew Dunkley
19:09
and John T. Horner. Um, this one comes from
19:11
Casey in Colorado. I was hoping that you
19:14
could Please explain why TOI
19:17
6894B is such a big deal
19:20
and what it means for our understanding of
19:23
the universe. Love the show, and I hope
19:24
you're both well.
19:25
Jonti Horner: Thanks.
19:26
Andrew Dunkley: Thank you, Casey. Yeah. So I did a bit of
19:28
research on this, uh, particular planet,
19:30
TOI 6894. It's a massive,
19:34
massive gas giant planet. But what makes it
19:36
unusual is that its star
19:39
is, um, a bit of a mouse.
19:42
So they're trying to figure out how such a
19:45
massive planet can exist
19:47
next to such a tiny star. I think that's the
19:50
guts of it, isn't it?
19:51
Jonti Horner: It is. And it's a really good example, again,
19:54
of the detective story side of
19:57
astronomy, the way that we can't really
20:00
do experiments, so we have to learn through
20:01
observation. And so the interplay is not
20:03
experiment and theory like it is in other
20:05
disciplines, but it's observation and the.
20:07
And, um, that leads to our science being
20:09
different in subtle ways, even down to the
20:11
structure of how we write and how we
20:13
communicate. It's less about testing
20:15
hypotheses than other disciplines. You know,
20:16
there's a lot of complexity in that. Now,
20:19
if you go back to when I was a kid and I was
20:22
learning all about astronomy, we didn't know
20:23
of any planet from any other star. And we
20:26
thought we had a very good feeling of how the
20:27
solar system formed and therefore, by
20:29
extension, what kind of planets we would
20:31
find. Yeah, and we expected that you'd find
20:33
giant planets like Jupiter out beyond the
20:36
snow line, you know, several astronomical
20:38
units from their star, going around on orbits
20:39
that are measured in decades, and rocky
20:41
planets in the interior. And that's how
20:43
planetary systems would form and the solar
20:44
system would be typical. We then found
20:47
51 Pegasi B, which is a planet comparable to
20:50
Jupiter, going around its star every four
20:52
days. And that kind of threw everything out.
20:55
And we had to improve our theories. Now what
20:57
it led to was a refinement of the theories of
21:00
planets forming in disks rather than them
21:02
being totally chucked out on something new.
21:04
But that first discovery of a planet around a
21:06
sun like star really set the scene for the
21:08
fact that the diversity of planets we find
21:11
around other stars is overwhelmingly
21:14
greater than we could have ever imagined.
21:16
Planets are ubiquitous. Every star has them.
21:18
That's what we've learned. But the variety of
21:20
planets is much greater than we could have
21:22
imagined. And all of that data has been
21:25
a fabulous resource for scientists trying to
21:27
understand the process of planet formation
21:29
and the variety of ways that that process can
21:32
proceed effectively. Every planetary system
21:35
will be unique in the same way every human's
21:37
unique. You know, they're the product of the
21:39
environment that they form in. The mass of
21:41
the disk is important, the mass of the star,
21:43
but also the cluster environment they form
21:44
in. There's a lot of things going on that
21:47
mean if you have two identical stars with two
21:49
identical disks, you'll still get different
21:51
planetary systems at the end. So we're
21:53
learning more about planet formation. And
21:55
it's the outliers and the oddities that
21:58
really drive that science forward.
22:00
Which brings us to TOI 6894. What we
22:03
found typically is that, uh, giant planets
22:05
are common in the cosmos. We find them easier
22:08
than everything else because they're more
22:09
obvious. So our discovery techniques are
22:12
biased towards finding planets the size of
22:14
Jupiter and Saturn and against finding
22:16
planets the size of the Earth. That's why we
22:18
find a lot more of them. And, um, what the
22:20
results have shown is that, uh, giant
22:22
planets, massive planets like Jupiter and
22:24
Saturn, are, um, more common the more massive
22:27
the star is. They're also more common the
22:30
higher the metallicity of the star is. So the
22:32
higher the amount of solid material would
22:33
have been around that star. And typically
22:36
we don't find giant planets like Jupiter
22:39
and Saturn around the lowest mass stars.
22:42
And the argument has always been that low
22:44
mass stars form from low mass disks where
22:46
there's just not simply enough for planets to
22:48
form there. Then you get
22:51
TOI 6894B. So the
22:54
star TOI 6894 is a little red dwarf.
22:57
It's only about 20% the mass of the sun,
22:59
about 238 light years away. The
23:02
planet going round it is a little bit bigger
23:05
than Saturn, but about half the mass of our
23:07
giant planet. So it's another one of these
23:09
superpuff planets that we've talked about
23:11
before. It's heavily irradiated, has been
23:13
inflated, and that probably suggests that
23:15
it's migrated in in the recent past. Now
23:18
people who've looked at data from Kepler
23:21
and TESS more recently, which looked at so
23:23
many stars, have been able to do a kind of
23:25
statistical study. And what they've found is,
23:28
uh, for red dwarfs like TOI,
23:31
um, 6894, only about
23:33
1.5% of all red dwarfs harbor any giant
23:36
planets. And TOI
23:38
6894 is the least massive star to be found
23:41
with an orbiting giant planet around it. So
23:44
that's why it's really, really interesting.
23:46
Now there's a number of different processes
23:48
that go on in planet formation and, um, star
23:51
formation. And we've talked before about the
23:53
Blurred lines between planets and
23:56
brown dwarfs and stars. And back in the day,
23:58
we thought we had a very clear rational
24:00
explanation that they're formed in different
24:01
ways. But now we see brown
24:04
dwarfs being discovered free floating that
24:06
are lower mass than the canonical traditional
24:09
13 Jupiter mass limit. Anything smaller than
24:11
13 Jupiter mass used to be thought of as a
24:13
planet. Similarly, we're finding things that
24:15
they're calling planets that are more than 13
24:16
Jupiter masses. So the lines are getting
24:18
blurred.
24:19
Andrew Dunkley: Yeah.
24:19
Jonti Horner: And I think we may see a bit of a
24:22
paradigm shift in years and decades to come,
24:25
where part of what defines whether you're a
24:27
planet or a brown dwarf at the top end is
24:29
actually how you formed and by extension,
24:31
what's buried deep in your core. So a
24:34
planet like Jupiter has a massive,
24:37
you know, 20, 30 earth mass, solid core at
24:40
the middle because it formed from a process
24:41
of core accretion. You get solid material
24:44
agglomerating, forming bigger and bigger
24:46
bits, until you form things kilometers
24:47
across, then thousands of kilometers across
24:50
objects like the Earth. And the more they
24:52
eat, the bigger they get. Eventually you get
24:54
to 20 or 30 times the mass of the earth,
24:56
well, 10 or 12 times the mass of the Earth to
24:58
start the process. When you're at that point,
25:00
your gravity is strong enough to start
25:02
capturing hydrogen and helium gas from the
25:04
nebula that previously would have escaped,
25:06
you finally can hold onto, um, it. And, um,
25:08
because there's more of hydrogen and helium
25:10
than everything else combined by a couple of
25:12
orders of magnitude, 98% of everything is
25:15
hydrogen or helium. Suddenly you've got this
25:17
enormous new untapped food source. You can
25:19
quickly devour all there is, and your mass
25:21
grows really rapidly until you open a gap in
25:23
the disk, and voila, you've got a giant
25:25
planet in a gap. And we talked about this a
25:27
bit last week. That's core accretion.
25:30
That leads to giant planets that are planets
25:32
with a solid core and a thick atmosphere. And
25:34
that atmosphere can be the bulk of their
25:36
mass. You've then got a
25:38
method called gravitational instability,
25:40
where your disk is sufficiently massive
25:42
compared to the star in the middle, that it
25:44
can become unstable itself. And you can get
25:47
it essentially globbing together to form
25:49
massive objects on a very short time scale.
25:51
And that's probably, to be honest, the
25:53
process by which binary stars form, where you
25:56
get a second star forming on a quite wide,
25:58
elongated orbit, whatever. And I've always
26:00
had a suspicion back from when earlier in my
26:03
career I was at the University of Bern, and
26:05
this is 20 years ago now, there was this kind
26:07
of conflict for giant Planets where people
26:09
said one of these two methods will be right
26:12
and the other one will be wrong. And you've
26:13
got core accretion or, uh, gravitational
26:15
instability. And it was a big kind of which
26:16
one of them is right. And I've always had the
26:18
feeling that in the right conditions both of
26:20
them can happen. And this suspicion that
26:23
brown dwarfs and stellar companions
26:26
probably form through this gravitational
26:28
instability process, which leads to more
26:31
instability and kind of lowers the likelihood
26:32
of planets then forming in the system. And
26:34
you'd form an object there, ah, that doesn't
26:36
have that massive core in the center. It's
26:38
basically the composition will match the
26:41
composition of the material in the universe.
26:44
This is a really interesting one because this
26:46
planet is so much so massive compared to
26:48
its star. This is kind of equivalent to the
26:51
sun having a 5 or 10 Jupiter mass planet,
26:54
probably something like that, because m more
26:56
massive star would have more mass and you
26:57
wouldn't just five times the mass of the star
26:59
is five times the mass of the planet. It will
27:01
go a bit more than that. So it's a real
27:03
surprise and there's a lot of investigation
27:06
to be done to try and figure out what the
27:07
formation process of this object is. The fact
27:10
it's a super puff, it's puffed up, it's
27:13
bigger than Saturn, but less massive than
27:14
Saturn, suggests that, um, either
27:17
it's very close into the star and it's
27:19
getting hugely irradiated. If that's the
27:22
case and it's been losing mass, it was
27:23
probably more massive in the past. Um, which
27:26
adds further weight to maybe this was a
27:28
bigger thing in the past and maybe it could
27:30
have been a very low mass brown dwarf rather
27:32
than a very high mass planet. Or maybe it's
27:34
telling us that you can get M dwarfs, red
27:37
dwarfs, which have a disk massive enough to
27:39
form giant planets on occasion in the right
27:41
setup, and we just need to learn more.
27:45
Um, but it seems very unlikely
27:48
that if the properties of the disk
27:51
around this star, uh, were similar to the
27:53
bulk of disk we found, there should not have
27:55
been enough solid material to get the core
27:58
accretion process to go quickly enough for
28:00
you to get a giant planet, never mind one
28:02
close enough in like this one, to then become
28:04
a bit of a superpuff. So there's a lot to
28:07
learn. It's very close to its star. It's only
28:09
3.9 million kilometers out from the
28:12
star. So it's much more
28:14
comparable to the Jovian moons. If you
28:17
imagine the star being where Jupiter is, this
28:19
is comparable to some of the moons of Jupiter
28:20
and distance. And that's another of the
28:23
reasons it's just really hard to imagine how
28:24
it could been have form so close in.
28:27
There's a lot to dig into in this. They're
28:29
looking at the chemistry of the atmosphere
28:30
because this planet's close enough in to be
28:32
hot enough that we can actually get light
28:34
from it and we can look at its atmosphere
28:36
seems to be kind of methane dominated, I
28:38
think, which is really, really odd. Um,
28:40
there's all sorts of weird stuff going on.
28:43
Um, but because red dwarf
28:46
stars are so common, even though giant
28:47
planets like this are rare per red dwarf,
28:50
there's probably a hell of a lot of them out
28:52
there. You know, red dwarfs are the most
28:53
common star in the galaxy by far. You know,
28:56
some estimates are, you know, up to three
28:58
quarters of all gas in our size in our galaxy
29:01
will count as red dwarfs. Which means he
29:02
could have 100, 200,
29:05
300 billion of them out there. So even if
29:08
only 1% of those stars have a giant planet
29:11
like this, you know, 1% of,
29:14
you know, 100 billion stars is still a
29:16
billion stars.
29:17
Jonti Horner: Yes.
29:18
Jonti Horner: Now maybe this planet is both rare and common
29:20
at the same time.
29:21
Andrew Dunkley: Yeah, that sounds like a very good
29:24
theory actually. Um, Casey, thanks
29:27
for the question. If you'd like to read up on
29:29
it, uh, you can go to uh, Psy News,
29:32
the website, because they've got a great
29:34
article on it, uh, but they've also published
29:35
a recent paper, uh, in the
29:38
journal Nature Astronomy.
29:43
Jonti Horner: 3, 2, 1.
29:46
Space.
29:48
Andrew Dunkley: Our uh, final question.
29:50
Jonti. Uh, I don't know how to introduce
29:52
this, so I'm just going to let it speak for
29:55
itself.
29:55
Jonti Horner: Hello, space nuts.
29:57
Andrew Dunkley: This is Philip McCrackpipe, future Nobel
29:59
Prize winner, here again. This time I've got
30:02
my bony lassie.
30:03
Jonti Horner: The famous English soprano. I need a fix here
30:06
with me.
30:07
Jonti Horner: That's a neater fix. F I C K S.
30:10
Thank you. Not if F I X.
30:13
So many people get that wrong. I have this
30:16
question about Gale Crater on Mars and what
30:19
kind of life it might have supported. Being
30:21
a famous soprano, I'd like uh, to sing it
30:24
to you. Pardon my voice today
30:27
I have a slight touch of the anthrax.
30:32
How many lovely life old might have grown
30:35
in an ancient Martian crater?
30:38
Could they have thrived or only just survived
30:41
in an ancient Martian?
30:45
Were they all just single soul? Did they fly
30:47
like Tinkerbell and laugh and sing and play
30:50
a microscopic trees?
30:53
How, um, many lovely life forms made grown in
30:56
an ancient Martian crater?
30:59
Jonti Horner: Ah.
30:59
Jonti Horner: Did they breathe the atmosphere where the
31:02
predators, the fear elucidate your views,
31:04
ecosystem.
31:10
Thank lovely space nuts for listening to this
31:12
tripe about an ancient Martian
31:15
creator.
31:22
Andrew Dunkley: Uh, um, I hope you get over the antlex real
31:25
soon. Thanks, Anita. Um, I
31:28
think I need a very.
31:29
Jonti Horner: Different kind of musical ensemble. If I
31:31
remember rightly.
31:32
Andrew Dunkley: Yes, I think I need a fix.
31:34
Jonti Horner: Uh.
31:36
Andrew Dunkley: Bottom line, was there, or
31:39
could there still be life in Gale Crater and
31:42
what would it be like?
31:43
Jonti Horner: Lots of places to go with this. I mean, two
31:46
immediate diversions just spring to mind
31:48
listening to that. It's lovely to get a
31:49
musical entry from such a storied soprano,
31:51
but reminds me, probably my favorite group,
31:55
Finnish symphonic metal group called
31:57
Nightwish. And this is relevant, I promise.
32:00
Um, symphonic metal is this weird fusion of
32:03
metal and opera, so you could describe it as
32:05
operatic met. And the lead singer is a very
32:08
storied classical soprano called Flo
32:11
Jansen, who's just ridiculously awesome in
32:13
many, many ways. Um, reason it's relevant is
32:16
we were talking earlier on about Eugene
32:17
Shoemaker, um, in the previous episode about
32:20
Asher's going to the moon, things like this.
32:23
Um, Nightwish, on their most recent
32:26
no album before last had a track called
32:29
Shoemaker, which was a eulogy, a tribute to
32:31
Eugene Shoemaker, which has a lot of rocky
32:34
stuff at the start, but from about 3 minutes
32:36
50 onwards has a very, very operatic,
32:39
classical, um, Latin funeral mass,
32:42
um, which is utterly astonishing. So I do
32:44
recommend people. I don't know if we can play
32:46
it on the podcast. I don't know if we can
32:47
play out because I don't know how rights
32:49
issues work.
32:50
Andrew Dunkley: Um, but, yeah, there are rights issues
32:53
which precludes us, I'm afraid. I did
32:56
listen to what you sent me. You sent me a
32:58
link, uh, on YouTube Music, so we could
33:00
probably send people there.
33:02
Jonti Horner: But, yeah, it's a bit of a musical tour de
33:04
force because it's got bits from William
33:06
Shakespeare in there, which is the epitaph on
33:09
Schumacher's tomb. That's why you've got the
33:11
bit of Shakespeare's book and what in that.
33:13
It's unusual, but it's incredibly touching
33:16
anyway, so. Love a bit of musical science.
33:18
The other thing that occurs without casting
33:20
any aspersions on Anita there is the ability
33:23
to sing while saying in character, which is
33:25
good. And it reminds me of another thing I
33:28
listened to, and I've listened to multiple
33:30
times now, the phenomenon that is Dungeon
33:32
Crawler Carl. Um, and at the end of the
33:35
first audiobook, I was a bit put
33:38
aback because there wasn't a cast list. And I
33:40
thought, hang on, this is a bit Dodged.
33:43
There's multiple people involved with this
33:45
who are not getting credit. There's just this
33:46
one guy getting credit for doing all the
33:48
voice work and all the rest of it. And it
33:49
really is just one guy. And it's
33:52
remarkable how certain
33:54
performers can voice multiple different
33:57
characters to a degree of distinction that
34:00
um, you assume that there's multiple people
34:02
involved in the voicing. So, you know,
34:04
incredible ability to sing well in character
34:07
and stuff like that. So huge uh, credit on
34:09
that in terms of the question and
34:12
questions.
34:13
It's all about life on Mars. Now we know that
34:15
Mars in its youth was both
34:18
warm and wet. It was an ocean planet that's
34:21
fairly well established. Uh, and the
34:23
transition from warm, wet Mars to cool, dry
34:25
Mars would have been very slow and gradual.
34:27
So any life that did get going will have had
34:30
time to adapt and move potentially. That's a
34:32
big part of the focus of the search for life
34:34
on Mars. Both looking for evidence of past
34:37
life and um, that's part of what the rovers
34:39
are doing, driving around in gray in Gale and
34:41
Jezero Crater, or Jezero Crater I think it's
34:44
pronounced. It's also why we're interested,
34:46
for example in the lakes of permanent liquid
34:48
water at Mars south pole. But we
34:51
don't know for a fact that there was life on
34:52
Mars. It still was there, wasn't there? We're
34:55
trying to find out. The idea though is that
34:58
when Mars was young it was warm and wet, it
35:01
had oceans. There may have been icy, slushy
35:03
oceans, more like what you get in the Arctic
35:05
than what you get near the equator. We don't
35:07
fully know on that yet. But there was a
35:09
vast expanse of liquid water on Mars surface
35:12
for an incredibly long protracted period.
35:15
All the conditions that on Earth would lead
35:17
to life establishing and thriving. So
35:20
there's a very real possibility that Gale
35:22
Krata, this ancient Martian creator, was
35:25
teeming with life in the past. It is,
35:28
I think. So the challenge here is that
35:31
we've only got one example of life in the
35:33
universe to go off, which is life on the
35:35
Earth. So we tend to form all our
35:37
assumptions about the pathway that life will
35:39
follow and how it will develop based on that
35:41
example. Now just with the last question, we
35:44
were talking about our ideas on the formation
35:47
of planets when we only had one planetary
35:49
system to go on and how wrong they were when
35:51
we found the second planetary system around a
35:53
sun like star. So the caveat to everything
35:56
I'm about to say is that currently we know of
35:58
one place with life and one planet with life.
36:00
So I'm basing it off assumptions based on how
36:03
things developed on Earth. And on Earth, we
36:06
had simple life from about three and a
36:08
half thousand million years ago. The evidence
36:11
of, so the oldest fossils on Earth that are
36:13
widely accepted, it's about 3.5 billion years
36:16
ago, found in the Pilbara region in Western
36:18
Australia. There are some fossils that are
36:20
arguably older, but they're still
36:21
controversial. For
36:24
the first 3 billion years of life on Earth,
36:27
all you had was single celled life. You had
36:29
an incredible diversity and variety of simple
36:31
life, but that's all you had. So only about
36:34
500 million years ago, give or take, that,
36:36
you start to get complex life. So the
36:39
argument following that would be if
36:41
Mars had life and, um, if that
36:44
life followed a similar pathway to the Earth,
36:47
then you would expect that that ancient life
36:49
would all have been simple life. Now, the
36:51
other thing that argues for that is if you
36:52
look around on the Earth today, we've got
36:54
life in abundance all over the place. But the
36:56
more complex the life is, the more limited
36:58
the variety of environments that it can exist
37:00
in, if that makes sense.
37:02
Andrew Dunkley: Yeah.
37:03
Jonti Horner: So obviously simple life can exist in a
37:06
wider variety of conditions and, um, will
37:09
exist earlier than complex life. And
37:12
so the argument then would be with all those
37:15
assumptions, and I know I'm doing a lot of
37:16
COVID your own ass here, but with the
37:18
assumption that everything followed the way
37:20
that things went on Earth, my expectation
37:22
would have been that Gale Crater could well
37:24
have been teeming with life, but it would
37:26
have been simple life. It would have been
37:27
single celled life. Now, single celled life
37:29
still lives, a very vibrant and
37:32
diverse set of lives. So there will be things
37:34
interfering with each other and eating each
37:36
other and all that kind of happy stuff going
37:38
on. But it's likely that there
37:41
weren't giant sharks or octo sharks
37:44
or whatever you know, swimming around in the
37:46
ocean in Gale Crater. And I suspect that if
37:49
there had have been, we'd already possibly be
37:51
finding evidence in the form of fossils. I
37:53
may be wrong on that, but I suspect that the
37:56
fact we haven't yet got definitive proof of
37:58
ancient life on Mars suggests that the life
38:01
that was there, if it was there, uh, was
38:03
simple life and single celled life rather
38:05
than complex stuff. But I stand to be
38:08
corrected on that. I look forward to the
38:09
confirmation of the discovery of ancient
38:12
fossils on Mars, if we ever get there.
38:14
Confirmation of life elsewhere will be
38:15
awesome. So it might be worth getting Anita
38:18
back on the show, uh, in a decade or so
38:21
to sing the sequel is now that we know there
38:23
Was life there? What was it like? Yeah, yeah.
38:25
Andrew Dunkley: Um, but I think we will
38:28
find something somewhere. Probably Mars,
38:31
but maybe on some of the ice moons
38:34
further out. But there's got to be
38:37
something. Uh, I think it'll be microbial, as
38:39
you said. But it's just,
38:43
you look how life just grabs on
38:46
on Earth given
38:49
minimal opportunity. And
38:51
I think that that same
38:55
thing exists in the universe
38:57
elsewhere. Um, life, if there is
39:00
just a small opportunity, it will grow
39:03
and I think that's what we will find. But,
39:06
uh, whether or not we find another
39:10
so called intelligent
39:13
place in the universe or an intelligent
39:16
species, that's a bigger call
39:19
and a completely different ball game indeed.
39:21
Uh, thank you for the question, Anita. And if
39:23
you would like to listen to the music that
39:25
Jonti, uh, was referring to, you can go to
39:27
YouTube Music, do a search for Nightwish,
39:30
Shoemaker, uh, the official lyric video.
39:33
Um, they've got 1.82 million
39:35
subscribers. Yeah, it's extraordinary.
39:38
Jonti Horner: It's a style of music that isn't really
39:41
widely known in Australia. So when I've gone
39:43
to see them on the odd occasion, they've come
39:44
over here. We've been down at the Tivoli in
39:46
Brisbane, which is kind of a thousand people.
39:49
When they go anywhere else in the world,
39:50
they're doing packed stadiums with a hundred
39:52
thousand plus. So it's a different genre.
39:55
Um, they, along with a group called Epica and
39:58
a male group called Camelot, are probably the
40:00
three leading light groups in that genre of
40:02
symphonic metal, which is the interface of
40:05
opera and rock effectively. Um,
40:07
but they've had a number of scientifically
40:10
themed songs over the years. In fact, there's
40:12
one that I have as recommended reading stroke
40:14
listening for my undergrad students. That's
40:16
kind of of a 20 odd minute long story of the
40:19
evolution of the planetary system and life on
40:21
Earth and all the rest of it. So they've done
40:23
interesting things.
40:24
Andrew Dunkley: I'm sure they have.
40:25
Jonti Horner: All right. Shoemakers are good. Listen.
40:27
Andrew Dunkley: Excellent. All right, uh, thanks to everyone
40:29
who contributed. If you would like to send a
40:32
question into, um, the Space
40:35
Nuts website, just go to
40:36
spacenutspodcast.com or spacenuts
40:39
IO and click on the AMA
40:42
button at the top and send us your, uh, text
40:44
or audio question. Don't forget to tell us,
40:47
tell us who you are and where you're from,
40:49
uh, and leave your email address so we can
40:51
spam the hell out of you. No, I'm only
40:52
kidding. Although I think that is part of the
40:55
deal. M. We'll see. But, um,
40:58
yes. And, uh, uh, Guess what? Huw in the
41:00
studio just turned up. Hi, Huw. Bye,
41:03
Huw. And thanks to you,
41:06
Jonti. We'll catch you on the next episode.
41:08
Jonti Horner: It's a pleasure. Looking forward to it.
41:10
Andrew Dunkley: Uh, Johnny Horner, professor of astrophysics,
41:12
uh, at the University of Southern Queensland.
41:15
And we thank him. We thank everybody and
41:18
thank you. Uh, uh, and from me, Andrew
41:20
Dunkley, thank you for your company. We'll
41:23
catch you on the very next episode of Space
41:24
Nuts.
41:25
Jonti Horner: Bye. Bye.
41:27
You'll be listening to the Space Nuts
41:29
podcast, available at
41:32
Apple Podcasts, Spotify,
41:34
iHeartRadio, or your favorite podcast
41:37
player. You can also stream
41:39
ondemand@bytes.com.
41:41
Andrew Dunkley: This has been another quality podcast
41:43
production from bytes.
41:45
Jonti Horner: Com.
41:45
Jonti Horner: Um.