Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Megastructures, Exoplanet Myths & Satellite Showers: #495 - The Quipu Conundrum and More

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Megastructures, Exoplanet Myths & Satellite Showers: #495 - The Quipu Conundrum and More · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Hi there, thanks for joining us. This is
0:01
Space Nuts. Andrew Dunkley here. Good to have
0:03
your company. And on this episode we
0:06
have a lot to talk
0:09
about.
0:09
The uh, first thing will be a megastructure
0:12
of epic proportions discovered in the
0:15
universe. Now this is not a uh, uh, something
0:17
that was manufactured by some incredible
0:20
race because uh, we have talked about
0:23
megastructures in the past. Now this is
0:24
natural and it's called Quipu.
0:28
What's that mean? We'll tell you soon. Um,
0:30
this is uh, one of um, the biggest bugbears
0:33
that Jonti has to deal with the overselling
0:36
of the potential for life on exoplanets. Yes,
0:38
there is one in the news at the moment. We'll
0:41
do an update on M20, 24 yr, uh
0:43
4. The odds of it hitting us have
0:46
halved and SpaceX satellites
0:49
raining down on our atmosphere. Uh, what does
0:52
that mean? We'll tell you on this episode
0:54
of space. Space nuts.
0:56
Generic: 15 seconds. Guidance is internal.
0:59
10, 9. Ignition
1:02
sequence start. Uh, space nuts. 5, 4, 3,
1:04
2. 1, 2, 3, 4, 5, 5, 4,
1:07
3, 2, 1. Space nuts. Astronauts
1:10
report it feels good.
1:12
Andrew Dunkley: And he's back again, surprisingly.
1:13
It's Jonti Horner, professor of Astrophysics
1:16
at the University of Southern Queensland.
1:17
Jonti. Hello.
1:19
Jonti Horner: G'day. How are you going?
1:20
Andrew Dunkley: I am well. How are you?
1:22
Jonti Horner: I'm getting there. I've never got the hang of
1:24
mornings. I think I'm a bit like the um,
1:26
characters from the Hitchhiker's Guide.
1:27
Except for me it's mornings. It's not
1:29
Mondays, it's mornings.
1:30
Andrew Dunkley: Yes, I, I used to be like that and then
1:33
I started in breakfast radio and did it for
1:35
30 years. So I, I eventually got used to
1:38
being up at Sparrows.
1:41
Jonti Horner: The breakfast shift does not sound fun.
1:44
Andrew Dunkley: Uh, I enjoyed it but that was just me. I
1:47
don't know if anyone else did, especially the
1:48
audience. Boom, boom.
1:50
Jonti Horner: Uh.
1:52
Andrew Dunkley: All right, uh, let us get into it and we're
1:54
going to start off with this discovery, um,
1:57
of a megastructure which has uh,
1:59
been uh, in the news
2:02
over the last week or so and it's,
2:05
it's called Quipu. We'll explain why it's
2:08
called that soon. But this is a
2:10
megastructure, uh, of natural formation in
2:12
the universe. The enormity of this
2:15
is mind splittingly
2:17
amazing.
2:19
Jonti Horner: Yes, yes it is. It's one of those things that
2:21
just makes your head hurt like a lot of
2:23
things in cosmology. Now I'll happily hold my
2:26
hands up right at the start and say my
2:27
expertise is on the parts of the universe
2:29
that are a lot closer than this. So I'm not a
2:32
cosmologist, and if there are cosmologists
2:34
listening in or people who are cosmology
2:35
enthusiasts and I get something wrong, please
2:38
don't be too critical. Um, because, you
2:41
know, the size of the things that I don't
2:43
know in cosmology is enormous. M just like
2:45
the subject itself. But this is a really
2:48
interesting one. When we think about the
2:51
universe, you see all these wonderful
2:53
simulations that come out of our models of
2:56
how the universe works that people produce
2:58
all the time. And, um, you can almost see
3:01
videos on fabulous documentary series where
3:03
they start at the scale of an atom and keep
3:05
zooming out, and you eventually get to the
3:07
person and keep zooming out. And the scale of
3:10
cosmology is roughly the
3:13
same scale compared to a human being, that a
3:15
human being is compared to an atom. So that's
3:17
the kind of size scale we're talking about
3:19
here, which is the study of the ridiculously
3:22
big. But as you zoom out from that human
3:24
being on the earth, you get the solar system,
3:26
then you get the local stars, then you get
3:28
our galaxy. And then as you move out, you get
3:31
structures of galaxies together. So you get
3:33
small clusters of galaxies, and those small
3:36
clusters hang together in bigger clusters
3:38
that gather together in superclusters. And
3:41
they, for a long time, were kind of the
3:43
biggest structures we saw in the universe.
3:44
But then as you zoom out further, you start
3:47
seeing these structures like walls and
3:50
filaments, where those clusters and super
3:53
clusters of galaxies are themselves forming
3:55
structures with huge voids in between. So on
3:58
this kind of scale, when you see those
3:59
simulations, it looks almost like a view of
4:02
a sponge. So if you've had
4:05
a sponge in your bath, the sponge
4:08
is a lot of open air spaces
4:11
surrounded by lots of solid material. And all
4:13
the solid material is in contact with all the
4:15
solid material, but all the air is in contact
4:17
with all the air. So you could put a bit of
4:19
string and go all the way through the sponge,
4:20
through the air holes, and come out the other
4:22
side and m that's kind of what this view
4:25
of the universe looks like. It sees long
4:27
filaments and walls all connected
4:30
to one another with these enormous voids of
4:32
empty space between them. That's the context
4:35
we're talking about here. So the team of
4:37
researchers who studied this have been
4:39
carrying out observations using an X ray
4:42
survey looking at very high energy
4:44
electromagnetic radiation that's produced
4:47
from incredibly hot gas in the most massive
4:49
clusters of galaxies. Enormous structures
4:52
themselves, and they've looked at a region
4:55
about 250 million parsecs across in
4:58
all directions, maybe a bit more,
5:00
looking for the biggest structures they can
5:03
find in that region. And they've identified
5:05
four of these, what they're calling
5:07
superstructures. And their superstructures
5:09
are megastructures because they are bigger
5:11
than normal structures. They're structures
5:13
made of structures made of superclusters made
5:15
of clusters made of local clusters made of
5:18
galaxies. On we go all the way down
5:21
again. Now, these four structures that
5:24
they found between them contain
5:26
45% of all the galaxy clusters. They could
5:29
see 30% of all the galaxies and 25%
5:32
of all the matter, but they only occupy about
5:35
13% of the volume. So that gives you the idea
5:37
of lots of empty space with these filaments
5:40
around it. The biggest of these, this is
5:43
someone quipu that's getting all the
5:45
attention is ridiculous. They talk
5:48
about it being 2000-000000-00000
5:51
times the mass of the sun. So if you
5:54
remember. So for listeners in countries that
5:56
do things differently, we're using the kind
5:58
of British scale million billion system here.
6:01
So a million is 10 to the six one with six
6:03
zeros after it. A billion is a thousand
6:06
million. So that's 10 to the 9. A trillion
6:09
is a thousand billion or a million million.
6:12
That's 10 to the 12. A quadrillion
6:14
is a thousand trillion or a million billion
6:17
or a billion million. So it's 10 to the 15,
6:20
200 of those means this is 2 times 10
6:23
to the 17 or 2 with 17
6:26
zeros after it times the mass of the Sun. Now
6:29
that's a number that is bound to make your
6:31
head hurt. So I converted that down by
6:33
looking at how many Milky Ways that would be.
6:36
And that would be something like 130,000
6:39
times the mass of our galaxy.
6:42
So stupidly big numbers it is
6:45
spread over a distance. It's a big long
6:47
feature, about 400 megaparsecs
6:50
long. So one parsec is
6:53
perversely the distance
6:55
that an object would be away from
6:58
the Earth if its parallax, as
7:01
the Earth goes around the sun, was 1/ arc
7:03
second. It's a really obscure unit of
7:05
measurement. It makes sense when you're doing
7:08
the maths of measuring distance, but it's not
7:10
particularly user friendly. It's a bit like
7:12
talking in feet. Light years is a bit like
7:15
talking in meters. Same kind of thing. Most
7:17
people find light years more straightforward
7:19
to visualize, but where one light year is the
7:21
time it takes light to travel in one year,
7:24
and there are 3.26 light years in one
7:27
parsec. So 400
7:29
megaparsecs is 1.3
7:32
billion light years long. So in other words,
7:35
light leaving one end of this structure will
7:37
take 1.3 billion years
7:40
or, uh, 1300 million years to go from one end
7:43
to the other. So it's an enormous, enormous
7:45
structure. Now, that's all well and good, and
7:48
it's fabulous cataloging the biggest and the
7:50
most massive and the brightest. And I know a
7:52
lot of people, I do this occasionally. Look
7:54
up Wikipedia articles like, what's the most
7:56
massive star? What's the most luminous star?
7:58
Things like that. But it's also really
8:00
valuable to know this kind of stuff because
8:02
if you study these big structures, that gives
8:05
us information that we can compare to the
8:06
models that are based on our current
8:09
understanding of the universe to see if those
8:12
models make sense. And, uh, the good thing is
8:14
that the current models of how the universe
8:16
work predict structures like this. So this
8:19
is very much in line with what people
8:21
expected to see. And that's a really good
8:23
part of how science works. It's very much a
8:26
case of our models predicted this and now
8:28
you've seen it, that makes us happy because
8:30
it means the models are working correctly. It
8:33
also is the kind of information that's really
8:35
useful for people studying the Big Bang and
8:38
more ancient universe. Because structures
8:40
like this are sufficiently massive, then they
8:43
will influence our view of what is beyond.
8:45
You get gravitational lensing from the big
8:47
objects. You also even get. And, um, I don't
8:50
fully understand how this works, but you also
8:52
get the pollution of the cosmic microwave
8:55
background, which is the last hiss of the Big
8:58
Bang. It's our image of the
9:01
last surface 300,000 years after the Big
9:04
Bang, where the universe became transparent.
9:06
And we found little bits of structure in that
9:09
which are important for us understanding how
9:11
the modern structure of the universe formed.
9:14
But that structure is polluted by the
9:17
influence of these foreground objects
9:20
by something called the integrated Sachs
9:22
Wolfe effect. And I have no idea how that
9:23
works, to be brutally honest. But
9:26
if you've got something like that, that
9:28
pollutes our view of what's beyond. And we
9:31
want to understand what's beyond. The better
9:33
we can see the foreground, the better we can
9:35
account for it when we're studying the
9:36
background. So getting studies of this a.
9:39
It's fascinating. It's a really good test for
9:41
our models. But it also allows us in the
9:44
future to get a better handle on how things
9:47
like the cosmic microwave background really
9:49
look when you filter out the foreground mess.
9:52
And I guess the equivalent here will be like
9:54
having a light pollution filter for people
9:56
who are astronomy photography enthusiasts.
9:59
You've got a murky, light polluted sky, but
10:01
if you put a light pollution filter on the
10:03
front of your lens, you can cancel out that
10:05
foreground mess and get a much better view of
10:07
what's beyond. This will enable us to do that
10:10
same kind of filtering when we're looking at
10:12
the microwave background.
10:13
So I think it's a fabulous story, full of
10:16
numbers what make your head hurt. Quite.
10:19
Andrew Dunkley: They're massive numbers. It's just uh,
10:22
just incredible. Now why is
10:25
it called Quipu?
10:27
Jonti Horner: This is partially because of the structure.
10:29
So it looks like a long thick filament with
10:32
thinner filaments branching off the sides of
10:34
it. The authors of this paper
10:36
noticed that this looks very similar to the
10:39
traditional counting instrument of the Incan
10:41
people in Peru. Um, which was essentially
10:44
they did their counting using knotted ropes
10:46
and ah, that knotted rope counting device was
10:48
a Quipu. So it's quite a nice nod to the
10:51
traditional culture of that area in
10:54
Peru. Again, I'm not an anthropologist or an
10:56
archaeologist, I don't really know much more
10:58
about it than that, but I think it is a
11:00
really nice nod to a different culture.
11:03
And as we've talked about in previous weeks,
11:05
this idea of embracing all the cultures of
11:07
the Earth in our studies going forward is
11:09
really gaining traction. It's a really nice
11:11
way of doing things, I think.
11:12
Andrew Dunkley: Absolutely, yes, I'd agree. And uh, the
11:15
Incans have a, um, strong history
11:18
with astronomy so uh, that ties
11:21
in well too. So yeah, fascinating.
11:24
If you would like to chase up that story. It
11:26
was published in Astronomy and Astrophysics,
11:29
the journal. You can also read about
11:31
it at the
11:32
arxiv.org website. That's
11:35
arXiv. I learned that last week.
11:38
arxiv.org uh, yes,
11:41
there was um, um, a lot of involvement from
11:43
the Max Planck Institute in um, in
11:46
running this. The author was Hans
11:49
Boehringer. So uh, you might want to look
11:51
that up.
11:56
Space nuts.
11:57
Uh, now, uh, let's move on to our next
12:00
story. This is a pet peeve peeve story,
12:03
um, which Jonti wanted to talk about. And
12:05
look, I'm not surprised that
12:08
bothers some people, uh, because I, I
12:11
have often referred to the popular press
12:14
when doing this podcast and how they latch
12:16
onto something that isn't quite the story
12:20
but it makes a great headline and that's what
12:22
this is. Overselling the potential for life
12:25
on exoplanets.
12:26
Jonti Horner: Yeah, yeah, it's.
12:28
Andrew Dunkley: And one in particular in the news at the
12:29
moment.
12:30
Jonti Horner: Well it's something that's niggled at me for
12:31
a while. It should be said that the criticism
12:33
here is not of the research done by these
12:35
authors. They've done a fabulous bit of
12:37
research and if you look at the paper,
12:39
they've got the balance right. That's fine.
12:41
But there is a very common trend,
12:44
particularly among press offices at
12:45
universities and also around
12:48
a lot of media sites that rely on clicks for
12:50
their income, to talk about
12:54
the most habitable planet ever discovered. We
12:56
found the most Earth, uh, like, planet ever.
12:58
And the reports on this planet are not quite
13:00
that bad, but they have been talking about
13:02
potentially habitable planet discovered
13:04
around nearby star, because that gets the
13:06
clicks. And before we dig into this story,
13:09
the reason that this niggles at me is that
13:11
people are getting exo Earth fatigue and also
13:14
life elsewhere fatigue. So
13:17
by reporting things when we haven't actually
13:20
found what the reports are saying, it creates
13:21
this opinion that the science is already
13:23
done. We've already discovered the autumn
13:26
stuff. So when we finally find a planet that
13:28
really does have life on it, or when we
13:30
finally find a planet that genuinely is
13:31
Earth, ah, 2.0. That'll be exciting.
13:34
I'll be thrilled. We've finally got something
13:36
to talk about and everybody will be kind of
13:37
the boy who cried wolf. Well, you've told us
13:39
that you've done this a million times
13:40
already. Yeah, and it's easy. Why are you
13:43
interested? You know, it's
13:45
also the fact that we
13:48
basically don't know enough to make these
13:50
statements yet. So when you see a headline
13:52
like, we found the most Earth, uh, like,
13:54
planet ever. What it's actually telling you
13:56
is we found a planet that's about the same
13:58
diameter as the Earth, and that's it.
14:01
So it's like me being an alien and visiting
14:03
the Earth and scanning the oceans and saying,
14:05
I found the most human, like, creature ever.
14:07
It's about the same length and it's about the
14:09
same weight and it's about the same size.
14:11
It's called a dolphin. Nothing like a
14:14
human whatsoever, but it's about the same
14:15
size and about the same mass. So it's the
14:18
most human, like, animal ever. So I get a
14:21
bit grumpy. And there's a lot that goes into
14:23
habitability that I can talk about a little
14:25
bit later on, which is why I think this is a
14:27
much more complex problem. And for me, that
14:30
makes it much more interesting, a lot more
14:31
research to do. But it does mean that when
14:34
you get a claim saying, potentially habitable
14:36
planet, or the most habitable planet we've
14:38
ever found yet People even publishing
14:40
articles about super habitable planets that
14:42
are more suitable for life than Earth. I
14:44
don't think you can say any of that. Aha.
14:46
Uh, in this particular case, it is an
14:49
interesting story. There is a star called 82
14:51
Erudani, which also goes by the name HD
14:54
20794. You know, astronomers love
14:57
our acronyms and our barcodes. This
15:00
is a star that you can see with the naked eye
15:02
in the constellation of Eridanus, but it's
15:03
not particularly bright. It's about magnitude
15:05
4, 4 and a half. And for a while we've known
15:08
it had two planets around it. But it's been
15:10
monitored by the High Accuracy Radial
15:13
Velocity Planet Search for Spectrograph HARPS
15:15
in Chile. And HARPS is an incredible
15:18
instrument. It allows you to measure
15:21
the velocity of a star. So you take the
15:24
light from a star, you break it up into its
15:26
component colors, and laced across that
15:28
spectrum is a series of dark lines. And
15:31
those dark lines, which we call the
15:32
Fraunhofer absorption lines, are, uh, the
15:35
fingerprint of all the different atoms and
15:37
molecules in the star's outer atmosphere.
15:39
Every atomic species, every molecular species
15:41
absorbs light at a very specific, unique set
15:44
of wavelengths. And it imprints this dark set
15:47
of lines across the star spectrum. Now, if
15:49
the star's moving towards us, its light will
15:52
be blue shifted. So all of those lines will
15:54
move a little bit to the blue because of the
15:56
Doppler effect. If it's moving away from us,
15:58
the light will be redshifted. So it'll move a
16:00
bit to the red again with the Doppler effect.
16:02
And I've talked about this before, this is
16:04
the equivalent of having the siren coming
16:06
towards you and hearing it high pitched and
16:08
fast with Nino, Nino, Nino and uh, then it
16:11
moving away and you're hearing it low pitched
16:13
and slow with Nino, Nino to do with the
16:16
waves getting stretched or compressed
16:18
essentially. Now what that means is if we
16:21
measure the positions of these lines
16:22
accurately enough, we can measure the change
16:24
in the speed of the star as it moves around
16:27
by seeing those lines move. So we can look at
16:30
stars and see them wobbling and infer the
16:32
presence of planets that we can't see by how
16:34
those planets pull those stars around. But
16:37
there are limits to this. There's a lot of
16:38
challenges involved. So facility like the one
16:41
we've got at the University of Southern
16:42
Queensland, which is actually the Southern
16:45
hemisphere's only dedicated exoplanet search
16:47
facility, we can get an accuracy
16:50
where we can measure the wobble of stars down
16:52
to about two or three Meters a second. So we
16:55
could see a star, ah, changing in speed by
16:57
about as much as someone going at a very
16:59
gentle jog. What that means is we
17:02
could not find these particular planets,
17:04
they're just much too hard. But the HAARP
17:06
spectrograph is on a much bigger telescope in
17:09
a much better location and it's an incredibly
17:12
accurate piece of kit. So it lets you get
17:15
down to sub meter per second measurements,
17:18
which is breathtaking. Put that in
17:20
perspective. We're looking at stars here
17:22
whose distances are quadrillions ah, of
17:24
kilometers away. Again using the units from
17:26
before. These are stars where the light has
17:29
taken decades to reach us and we are
17:32
able to measure their velocity so accurately
17:34
that we can see changes in that velocity of
17:37
50 centimeters a second. Wow, that's just
17:40
astonishing precision and that's what the
17:43
team have done. So they've observed this
17:45
star, uh, HD 20794
17:48
for a number of years with haps getting more
17:50
and more data tracking how the speed changes.
17:53
And in the past they'd found two planets and
17:55
hints of a third and they've now confirmed
17:57
that third one. That third planet, HD2.0, uh,
18:00
794-D is making the star
18:03
wobble with its speed changing by just
18:06
50cm a second plus and minus
18:09
over a period of about 700 days. So
18:12
you're watching for 700 days, you get rid of
18:14
all the other noise, the star wobbling around
18:16
itself, just oscillating like a shruk
18:19
bell. You get rid of the orbits of the two
18:21
inner planets which are causing it to wobble
18:23
by a similar amount with a different period
18:25
and you're left with a tiny wobble of plus or
18:28
minus 50cm a second that takes 700 days
18:31
to complete once. And that's what they found.
18:33
So this is our planet. It's a planet about
18:36
six times the mass of the Earth, at least
18:39
might be more than that. We don't know how
18:41
edge on or tilted the orbit is because we're
18:43
not seeing it transit. If it's tilted by 30
18:46
degrees, the mass of this planet will be
18:48
higher. If it's tilted by 60 degrees instead
18:50
of being 6 earth masses, it'll be 12 earth
18:52
masses. So this is a minimum mass.
18:56
So it's what we call a super Earth, ah, or a
18:58
mini Neptune. It's much more massive than our
19:01
planet and certainly larger than our planet.
19:04
It's moving on an orbit that if you
19:07
calculated its semi major axis,
19:09
the length of the ellipse, half the length of
19:12
the ellipse, which sets a period that will
19:15
put it in the habitable zone, um, that's what
19:17
the paper says. Now, the habitable zone I'll
19:19
get into in a second. But this planet moves
19:22
on a very elongated orbit, so its distance
19:24
from its star is changing by a factor of two
19:27
from its closest to the star to the furthest
19:29
away. Now, if you scale that up to the solar
19:31
system and put it in the same place,
19:33
temperature wise, as it is in its system.
19:35
Now, if you put it in the solar system so
19:37
that its orbit had that same temperature
19:39
range, that would mean when it's closest to
19:42
its star, it's as close as Venus. When it's
19:44
furthest from its star, it's further out than
19:46
Mars. You're going to have
19:48
extreme, extreme temperature variability on
19:51
this planet. Now, the habitable zone, um,
19:54
is always thrown out for these planets. It's
19:56
that Goldilocks idea. If you have a planet
19:59
that's at the right distance from a star, the
20:01
temperature will be not too hot and not too
20:03
cold, and it'll be just right for liquid
20:05
water on the surface. The subtle
20:07
implication buried in this is not actually
20:11
what I just said, but it's rather. If you
20:13
took the Earth as the Earth is
20:15
today, and dropped it where this planet is,
20:18
would the Earth, uh, still have liquid water
20:20
on its surface? Now, that's a subtle
20:23
difference. But to illustrate it, if you
20:24
think about the solar system, the
20:27
boundaries of the habitable zone are usually
20:29
set by looking at Venus and Mars. That's
20:31
what's motivated this. The calculations are
20:33
more robust, uh, now, but that's about where
20:35
it washes out. Venus, closer to the sun than
20:38
us, is super hot. 450 degrees centigrade on
20:41
the surface and clearly not habitable. Mars
20:43
is super cold. It's too cold for life. It's
20:45
outside the habitable zone. The Earth's in
20:47
the middle, and it's just right. But to
20:49
illustrate why it's not so simple, imagine a
20:52
thought experiment where you swap Venus and
20:53
Mars around. If you put Mars where Venus is,
20:56
it's got a thinner atmosphere than we do, so
20:59
it's got less of a greenhouse effect. So it
21:01
would probably remain clement where Venus
21:04
would overheat. Similarly, if you put Venus
21:06
where Mars is, Venus has this incredibly
21:08
thick atmosphere with an incredibly strong
21:10
greenhouse. It will probably still be
21:13
habitable. It would still be warm enough
21:15
where Mars wouldn't. So this habitable zone
21:17
is a much woollier concept than I think most
21:20
people realize. And it's
21:23
just not really a guideline. It's just an
21:26
indication that this could be somewhere worth
21:28
looking at. It's not more than that, but it
21:29
tends to get played up as being the Holy
21:31
Grail. And one is in the habitable zone. It
21:34
must therefore have the potential to be
21:36
habitable. Whereas in fact, what you're
21:38
saying is if you put the Earth on the orbit
21:40
that this planet is on, it might still look
21:42
like the Earth, except with the planet we're
21:45
talking about at the minute. If you put the
21:46
Earth on that orbit at, um,
21:49
perihelion, when it was closest to the sun,
21:51
it would receive a flux from the sun as high
21:53
as Venus does. So the oceans would start to
21:55
boil. Fortunately, it doesn't spend long at
21:58
perihelion. We move quickest when we're
22:00
closest to the object. We swing out through
22:02
the habitable zone, probably everything's
22:04
fine. But you've got bonkers weather because
22:06
you're dealing with all that heat you've just
22:08
been given. Then you get to your furthest
22:10
point from the star and that's when you move
22:12
the slowest. So this planet spends probably
22:14
more than 50% of its time further from
22:17
its star than the outer edge of that
22:19
habitable zone by calculation. So those
22:21
oceans would freeze and you get this deep,
22:24
Game of Thrones style winter. You'd have
22:25
everybody going, oh, look, winter is coming.
22:28
Everybody's doomed. And then it would swing
22:30
back into the star and have a brief furnace
22:32
like summer, and then a long cold winter
22:34
again. It doesn't sound particularly clement.
22:37
You add to that, though, the fact that this
22:38
planet is six times the mass of the Earth
22:41
means it's going to have a very substantial
22:43
atmosphere, and I should say at least six
22:45
times the mass of the Earth. A much thicker
22:47
atmosphere means a much stronger greenhouse
22:49
effect, which means the results of
22:52
that extreme insolation, the extreme
22:54
radiation at, uh, pericentre when it's
22:56
closest to the star, is even more pronounced.
22:59
So I don't think it's at all fair to say that
23:01
this planet could be potentially habitable.
23:03
And in fact, the authors of the paper
23:05
themselves don't really say that. What they
23:07
do say is, is that this planet crosses the
23:09
habitable zone. And, um, because it's a bit
23:11
bigger and, um, because it has this big
23:13
variation in existence from the star and, um,
23:16
because it's around a nearby star, could be a
23:18
really good test case for us to practice our
23:21
observation techniques to learn more about
23:23
atmospheres of planets this size before we
23:25
really look at ones that could be habitable
23:27
enough like. But this planet certainly isn't
23:30
it. And even then there's a whole heap of
23:33
Other things that will impact habitability,
23:34
which we may or may not have time to go into
23:36
today. But the habitable zone really is just
23:39
the first of an incredibly long list of
23:42
variables that you can slide around that
23:45
could influence a habitability. Because all
23:46
it's saying is, how hot would the Earth be if
23:48
you put it there? Essentially?
23:50
Andrew Dunkley: Yeah, yeah. And at six times the size of the
23:53
Earth, at least gravity has to be a factor
23:55
as well, doesn't it?
23:57
Jonti Horner: It does. I mean, if you estimate that
24:00
this thing is twice the Earth's diameter and
24:01
M, we don't know that because this thing
24:04
doesn't transit its star, or we've never seen
24:06
it transit its star. So its orbit is almost
24:08
certainly not edron, which means its mass is
24:10
probably a bit higher than we say that
24:12
minimum is. But it means we have no way of
24:14
measuring the size. Now, at six Earth
24:17
masses or a bit heavier, it's near this
24:19
boundary between what we call super Earth or
24:21
mini Neptune. Super Earth is a rocky
24:23
object with a big thick atmosphere, and mini
24:26
Neptune is a big thick atmosphere with a
24:28
rocky core. So you can see how that
24:29
transitions between them. But if you estimate
24:32
for a minute that it is a super Earth with a
24:34
bit of a thick atmosphere, you could say,
24:36
well, maybe it's twice the diameter of the
24:38
Earth. Uh, and, uh, that would kind of make
24:40
sense density wise. That would place it a
24:42
little bit less dense than the Earth. But
24:44
that might make sense because it's a little
24:46
bit cooler for a lot of its orbit.
24:49
Even in that scenario, the acceleration due
24:51
to gravity on its surface will be 50% higher
24:54
than that we have on the Earth right now. You
24:57
know, so gravity will be stronger. We'd
24:58
probably all, if we were there, be squat and
25:01
dumpy and grumbling about how heavy we feel
25:03
and all the rest of it. You know, I'm heavy
25:05
enough already without giving me 50%.
25:08
Andrew Dunkley: Yes, no, that's a fair point. But,
25:11
uh, yeah, these, these stories are not
25:13
uncommon now. And you make a very valid point
25:15
that people will just, you know, when the day
25:17
comes that we've genuinely got an Earth like
25:20
planet Earth 2.0, uh, that could
25:23
harbor life. People will go, yeah, right.
25:26
Oh, ah, heard it all before.
25:28
Jonti Horner: And it's dangerous. And quite often the
25:31
researchers involved don't have control of
25:33
that story. That's one of the reasons I
25:35
love working with websites, like the
25:37
conversation, where I control the narrative
25:39
when I write articles. But it's also why I
25:41
really appreciate our media team here at
25:43
unisq because they actually talk to us
25:46
when they're writing media releases and a lot
25:48
of the bigger universities, the media team
25:50
get hold of a paper and they write their own
25:52
interpretation of it with, with a couple of
25:54
quotes from the authors, but they don't let
25:56
the authors read the release. Then you get
25:58
journalists who read the media release and
26:00
spin it further and you end up from an
26:02
article that says, we found a planet that is
26:04
interesting to being new. Earth planet has
26:06
been found. Life 2.0 is there.
26:09
And that's not what anybody actually said.
26:12
Andrew Dunkley: No, no, but it's a good way.
26:13
Jonti Horner: To get hits and links to your university's
26:15
website.
26:16
Andrew Dunkley: Exactly. Yeah. Okay. If you'd like to
26:18
read up on that, uh, the genuine article I'm
26:21
talking about, uh, you can find it in the
26:23
journal Astronomy and Astrophys.
26:26
You feel better now that you've got that off
26:28
your chest, Jon?
26:29
Jonti Horner: This is a perpetual rant of mine. I actually
26:32
did with my former mentor, Barry Jones, who
26:35
passed away about a decade ago now. Um, we
26:38
wrote my first ever review paper back in 2010
26:40
where I dug into this. So it always used to
26:43
bug me that it was just, it's in the
26:45
habitable zone, right? That's job done. And
26:48
so we wrote this paper where we looked at all
26:50
of the other things people have proposed that
26:51
could make a planet more habitable or less
26:53
habitable, more suitable. And for me, the
26:56
thing here is, when we get to do observations
26:59
to look for life on these planets, which is
27:01
still a bit beyond us, but we're getting
27:03
towards that point, those observations are
27:06
going to be the hardest observations
27:07
humanity's ever had to carry out. You're
27:09
talking hundreds or thousands of hours on the
27:11
biggest space telescopes, really competitive
27:14
time. You're not going to be able to look at
27:16
them all. So you're going to have to find a
27:18
way to pick the best target. You're going to
27:20
have to find a way to whittle down a list of
27:21
hundreds or thousands into the best two or
27:23
three. And you can't just use the habitables
27:26
on there. So I thought, let's look at all the
27:28
different things that can impact habitability
27:30
to see if you can turn them almost into the
27:32
volume sliders on the mixing desk of the
27:34
dj, right? You can turn them up, turn them
27:36
down, and see which planet gets the best
27:39
score overall when you factor all of them in.
27:42
And, um, some of them are things we can't yet
27:43
observe. Some of them are things you might
27:45
have to model with computer modeling, like I
27:47
do. But it can be everything from the nature
27:50
of the star itself, how Variable it is all
27:53
the way through to the other planets in the
27:54
system, what their gravity does, how much
27:56
debris there is, and even down to the planet
27:59
itself. Whether it has plate tectonics,
28:00
whether it has a magnetic field, all of these
28:02
things will factor in. It's not just as
28:04
simple as where do you place it? Is it in the
28:07
right spot?
28:09
Andrew Dunkley: Valid point. All right. Uh, yeah, as
28:12
I said, you can uh, chase that story up at
28:14
Astronomy and Astrophysics. Uh, you could
28:16
probably find it just about anywhere online.
28:18
Uh, there's an article on Space.com as
28:21
well. This is Space Nuts with Andrew Dunkley
28:24
and John Horner.
28:30
Space Nuts, right.
28:31
Our next story, which uh,
28:34
we've uh, done before, we did it a week
28:36
ago, uh, about uh, the comet
28:39
2024 yr. Uh 4. I happen to be
28:42
playing our uh, podcast in the car.
28:45
I always like to listen to it just to see how
28:47
it sounds and you know, decide whether or not
28:50
I'm doing a good job or not. Did it in radio,
28:53
do it with the podcast. But I, I was picking
28:55
up our grandchildren from school and
28:58
uh, Nathaniel who um,
29:01
is 10, uh, years old,
29:04
um, he was listening and he said to me, is
29:07
a comet going to hit Earth? And I
29:09
had to kind of explain to him what was going
29:12
on without alarming him.
29:15
Uh, and now an update on the story. Last week
29:17
we were saying um, there was
29:20
a 70 to 77% chance of this
29:23
thing, um, hitting the atmosphere in
29:26
2032.
29:28
Uh, sorry, yeah, see that's,
29:31
that was a popular press comment. One in
29:33
seven. But now that number's dropped as
29:36
at now. But that could change
29:38
again.
29:39
Jonti Horner: Absolutely. So as of today, so when I sent
29:42
you notes through yesterday, it was at 1 in
29:44
43. It's now fallen back to 1 in 48.
29:47
This number is changing every day. And what
29:50
we will see and what we'll continue to see is
29:52
most likely those odds of an impact
29:55
gradually increasing until
29:58
eventually they most likely drop to zero. Ah.
30:01
And the reason for that is we're getting more
30:03
observations with every day that passes. And
30:05
so with every day that passes we get a
30:07
refined estimate of the orbit of this
30:09
thing. That then means that uh, the
30:12
exact location of the object on 22nd of
30:15
December 2032 has a smaller
30:17
uncertainty. So that big area of space that
30:20
we think it will be in with each day's
30:22
observations get smaller and smaller. Now if
30:25
the Earth is still in that area of space, the
30:28
Earth is a bigger fraction of that total
30:30
volume of space. And so the probability of
30:33
impact is going up because we're a bigger
30:35
fraction of the total area that thing could
30:37
be in. But at some point, as that volume of
30:39
space shrinks down, the Earth could fall out
30:42
of it. And at that point, the probability
30:43
immediately drops to zero. So it isn't a
30:46
reason to panic at all. This is exactly the
30:48
behavior you would expect to see. But
30:51
that probability will continue to change day
30:53
by day. It wouldn't surprise me if it keeps
30:55
getting higher. Now, this asteroid we're
30:58
probably going to lose track of in about
31:00
April. It'll be too far away to observe, but
31:03
then we won't see it again till 2028. People
31:05
are digging back through archival
31:07
observations from 2016,
31:10
2012, 2008, because this thing comes
31:13
roughly near the earth every four years or
31:14
so. If we find it by chance
31:17
on one photograph from one of those previous
31:19
years, this probability will change
31:22
dramatically and we'll probably drop to zero
31:24
straight away. If not, we'll have to wait
31:26
till 2028. And until then we'll see this
31:28
continual slight more wobbling around as each
31:31
day's observations come in and it gets
31:32
recalculated. So fundamentally,
31:35
nothing has changed. This thing still poses a
31:38
threat. Do not panic. Even if it were to hit
31:40
us, it's not really going to cause a problem
31:41
anyway, to be brutally honest. But it is
31:44
fascinating to watch this happen and to see
31:46
that evolution in real time.
31:49
Andrew Dunkley: Absolutely. Yeah. I think I said comet, I
31:51
meant asteroid. But, um, yeah, 2024,
31:54
uh, if you do a search on Google or
31:57
whatever your favorite search engine is,
31:59
you'll find plenty of information.
32:01
And you. I would advise filtering the
32:04
popular press comments because,
32:08
uh, they've been going hammer and tongs on
32:09
this one.
32:10
Jonti Horner: Absolutely.
32:11
Andrew Dunkley: Um, but, yeah, uh, like, uh,
32:13
Jonti said on the previous story, it's
32:16
clickbait, isn't it? Um, that's really
32:19
it. But, uh, I did reassure my grandson
32:22
because as soon as I finished explaining it,
32:24
he wanted to talk about Pokemon. So I think I
32:26
was successful in deflecting him there.
32:30
To, uh, our final story, Jonti, and this
32:33
one is about stuff that's hitting the
32:34
atmosphere. We're talking specifically
32:37
about the, um, turnover of
32:40
SpaceX satellites. They've
32:43
been starting to rain down on
32:46
Earth, uh, fairly regularly. In fact, uh, the
32:48
Space Nuts podcast group on
32:51
Facebook has been, um, discussing
32:54
this. They put an article on there that the
32:56
listeners were discussing, and
32:59
some were quite surprised by the kinds
33:02
of numbers we're talking about. But this is
33:04
just going to get more and more significant
33:07
as time goes on because they haven't finished
33:09
deploying their entire, uh, fleet
33:12
or whatever. You want to call them of, uh,
33:14
SpaceX satellites.
33:16
Jonti Horner: Yeah. This is yet another multifaceted story.
33:19
So I know a lot of people who get very
33:21
passionate in their defense of SpaceX and
33:23
Elon Musk and many others who have very
33:25
negative views of them. And I always try and
33:27
be somewhere in the middle. It's like
33:29
in literature if you ever read a book, very
33:32
few people are purely evil or purely good.
33:35
Everybody's somewhere in the middle unless
33:36
it's a bad book. And it's the same with
33:39
things like this. There's a lot of good about
33:41
this and a lot of bad about it. Now SpaceX
33:43
are putting up their Starlink satellites to
33:46
deliver Internet access, which is
33:49
a great benefit to people in the regions.
33:52
I've heard plenty of stories of people who
33:54
are living remotely in Australia who can't
33:56
get a good Internet connection on Starlink as
33:57
been revolutionary to them.
33:59
Andrew Dunkley: Yeah. And cruise ships use Starlink.
34:02
Jonti Horner: Absolutely. Because they're always.
34:04
Andrew Dunkley: They're in remote areas a lot.
34:06
Jonti Horner: Yeah, it is a really incredible
34:08
technological development. On the other hand,
34:10
you've got all the concerns about the light
34:12
pollution from these things and the
34:14
fact that they launched them without anybody
34:17
really being able to regulate it or say boot
34:19
about it. It's a
34:22
multifaceted problem and there's good things
34:24
and bad things about it. In much the same
34:26
way, this story is both a good and bad story.
34:29
You've got all these satellites up there and
34:32
they have finite lifetimes. They are
34:35
low down because you need them to be in low
34:37
Earth orbit in order to get good latency. If
34:39
you put these at geostationary orbit, you've
34:42
got the light travel time there and back
34:43
again, you've got a long way to go and that
34:46
puts a significant ping, which means for the
34:48
people playing Twitch games and first person
34:51
shooter games, they can't play and sulk. Um,
34:54
but everybody wants a faster Internet
34:56
connection with the lowest latency possible.
34:57
So these things are in low Earth orbit, which
35:00
means that they are moving through a
35:02
significant chunk of the Earth's atmosphere.
35:04
The Earth's atmosphere doesn't just stop, it
35:05
just gets thinner and thinner and thinner the
35:07
further you go away. Technically, the moon is
35:09
still encountering bits of the Earth's
35:11
atmosphere. It should by that point it's so
35:12
thin as to be irrelevant. But at the altitude
35:15
of these Starlink satellites, they are
35:17
actually traveling into a headwind. So
35:20
without something to bump them up, they would
35:22
eventually come down naturally anyway. But
35:24
also they are a fixed term
35:27
thing. They typically, I think thinking about
35:29
an individual satellite having about A five
35:31
year lifetime.
35:32
Andrew Dunkley: Yeah.
35:33
Jonti Horner: Now it's about five years since the Starlink
35:35
satellite started getting launched, which
35:37
means the very first generation of them are
35:39
now in their retirement phase.
35:42
What is really good about this is
35:45
that SpaceX and Starlink are being
35:48
very aggressive in the retirement in that
35:50
they are controlling these things and
35:52
deliberately putting them back in the
35:54
atmosphere to burn up in a controlled
35:55
fashion. So they're controlling where they
35:57
drop them into the atmosphere to minimize the
35:59
risk to air travel and the risk of them
36:02
dropping on a city and things like this. And
36:05
that is really good governance. It's really
36:07
important to say that there's a lot of stuff
36:08
up there that will come down of its own
36:11
accord, at its own time, with no control over
36:13
it. And that's a risk. And people are
36:16
talking about the fact that there's probably
36:17
as high as a 26% chance that in a given
36:20
year from now on space debris will fall
36:23
through a populated airspace
36:26
m which is problematic. There's even studies
36:28
saying there's a 1 in 10 chance that within
36:30
the next decade somebody will die as a result
36:32
of space debris hitting them. So that's a
36:35
concern. And by deliberately deorbiting
36:38
these things in a controlled fashion, they're
36:40
mitigating those risks, putting things down
36:42
in a safe fashion. But because of how many
36:45
satellites they're putting up there, that
36:47
means we've got an increasing number of them
36:48
coming back down. There are currently
36:51
7,000 Starlink satellites up there. The
36:54
goal is to get up to 42,000. That is their
36:57
stated end. So that's the factor of six times
36:59
more.
37:00
Andrew Dunkley: Yeah, that's just Starlink, because there are
37:03
many others.
37:04
Jonti Horner: There are. If you look at all of the proposed
37:06
mega constellations, I think the current
37:08
number is that there could be as many as
37:10
550,000 satellites in orbit within a decade.
37:12
Which makes me, as an amateur astronomer, the
37:15
kind of part of me that goes out and observes
37:17
meteor showers and stuff just makes me weep
37:19
because we'll lose the night sky to such a
37:21
degree. But that's a slightly separate thing.
37:24
With 7,000 up there at the minute, the
37:26
retirements of those first gen ones are now
37:28
coming at a rate of four or five satellites
37:30
per day. So that means four or five
37:33
satellites are burning up somewhere over the
37:35
Earth, uh, every single day of the
37:38
calendar year. That's only going to go up
37:40
because if you increase the number of
37:42
satellites up there by a factor of six times,
37:44
then you'll increase that number of reentries
37:46
per day by a factor of six times. So within
37:49
five Years, we could well be looking at
37:52
something nearer to 25 or even 30 satellites
37:54
per day coming back into the atmosphere. Now,
37:57
these are coming in in a controlled fashion.
37:59
So, uh, they're trying to drop them in the
38:01
atmosphere away from things that would be
38:03
threatened by lumps of metal hitting the
38:05
Earth's atmosphere, essentially. Yeah. But
38:08
there is now a growing concern about the
38:09
pollution side of this.
38:11
Andrew Dunkley: That's the thing that I was getting. Yeah,
38:13
that's the. That's the big if, isn't it?
38:16
Jonti Horner: And it's a difficult one because it's not an
38:18
experiment that's ever been done before.
38:19
Things have re entered. Um, but in the past,
38:22
we've not been putting much up in space. So
38:24
it's been a very rare thing. A little bit of
38:26
extra material dumped into the atmosphere. A
38:29
tiny amount compared to the amount that comes
38:31
in naturally through meteors and meteorites,
38:34
um, stuff hitting the Earth's atmosphere,
38:36
naturally. But we're now getting to a stage
38:37
where this is a significant amount of
38:39
material entering the Earth's atmosphere.
38:41
Each of these Generation 1 satellites is
38:43
several hundred kilos of material.
38:46
So when you've got five of them coming in a
38:48
day, that's a couple of tons of material
38:50
being ablated and added to the atmosphere,
38:53
mainly in the form of heavy metals. There
38:56
is a fact that I've pulled out of an
38:58
interesting article. India Today of all
39:00
places, have got a fairly good article about
39:02
this. And, um, one thing they point out is
39:04
that each individual one of these Generation
39:07
1 Starlink satellites, when it burns up in
39:09
the atmosphere, when it ablates, deposits
39:11
about 30 kilos of aluminum oxide
39:14
into the upper atmosphere, about where the
39:16
ozone layer is. Now that's a problem because
39:19
aluminium oxide is a compound that is known
39:22
to be very devastating to the ozone layer.
39:25
It's a real problem. Now, if each satellite
39:27
is dumping 30 kg into the atmosphere,
39:30
that has a potential to destroy a large
39:32
amount of ozone. If you're suddenly dumping
39:35
five of them in per day, that's 150
39:37
kilos per day. We go up
39:40
to the 25. Obviously, that goes up
39:43
again from 150 kilos to what, five times
39:45
150, 750. 50 nil. Your
39:48
ton of aluminium oxide per day.
39:52
Something that can damage the ozone layer.
39:53
And we've only just got out of the time where
39:55
we did an incredible job of preventing us
39:57
killing the ozone layer. Yeah, we're about to
39:59
start it again. People have tried
40:02
to do some computational studies of the
40:04
effects of adding all this metal to the upper
40:06
atmosphere. And, uh, nobody really knows
40:08
what's going to happen? Some studies have
40:10
said that it could accidentally help to
40:13
slightly mitigate climate change because it
40:15
might increase the albedo of the Earth's
40:16
atmosphere.
40:17
It might cause more clouds to form, so it
40:19
could reflect a bit more sunlight or could be
40:21
good. But other studies have suggested the
40:23
opposite, that it could actually lower the
40:24
amount of clouds we've got and also add a bit
40:27
more greenhouse nastiness to the mix. So it
40:30
could have an impact on our climate. We don't
40:31
know which way it'll go. It could have an
40:33
impact on the ozone layer. We just don't know
40:36
yet. And so what's happening with this is
40:38
we're effectively running a science
40:40
experiment like the ones you do in the lab,
40:42
the ones you do at school without ever done
40:44
it, without ever having done it before. And
40:47
we're running it on the planet that is our
40:49
own home. Um, so I guess it's a bit like,
40:52
you know, you've got two unruly toddlers
40:54
running around with, um, insects, prey.
40:56
Like the stuff you've got to get rid of. The
40:58
mosquitoes. Yeah. Running around emptying can
41:01
after can of that in your house. And you just
41:02
said, yeah, well, let's do it. What's the
41:04
worst that can happen? And you just don't
41:05
know.
41:06
Andrew Dunkley: Yeah. Uh, 42,000
41:09
satellites, when they're ultimately all up
41:10
there, coming back down into the atmosphere,
41:13
will deposit 1.26 million
41:15
kg of aluminium oxide.
41:18
So, and that's going to be continuous
41:21
because it's not just 42,000.
41:24
Uh, as they come down, they'll replace them
41:26
and add more to get to their full
41:28
structure. So it'll be an ongoing
41:31
thing, multiplied by however many
41:34
constellations are created to do the same
41:36
thing. So.
41:37
Jonti Horner: But it isn't also like, that is easily
41:39
recoverable. That's a lot of resources that
41:41
we're just losing.
41:42
Andrew Dunkley: Yeah, exactly.
41:43
Jonti Horner: Um, now, I could imagine a much further
41:46
future where instead of things being retired
41:48
by deorbiting them, you retire them by
41:51
boosting them to kind of graveyard orbits and
41:53
have something there collecting them and
41:55
melting them down for the materials. That's
41:58
why in the future, because that will be a lot
41:59
more expensive. It's cheaper at the minute m
42:01
to just throw them away. I mean, we see with
42:04
recycling efforts that there's not much
42:05
motivation to recycle when making things from
42:08
new products is still cheaper.
42:11
Andrew Dunkley: Yeah, well, if they could solve the latency
42:13
problem, that would maybe help cure it
42:16
as well. But how do you do that? Relay
42:19
stations on Earth? I don't know. I Don't
42:20
know. But, uh, yeah, that's a really
42:23
fascinating story. I know Fred and I have
42:25
talked about it before, but it's worth
42:26
revisiting. And, uh, yeah, the information
42:28
just keeps evolving over time
42:31
and we're not nearly at
42:34
capacity yet with these constellations. If
42:36
you'd like to read it, uh, as Jonti said,
42:38
it's, uh, on the website India
42:40
today.in that brings
42:43
us to the end of the show. Don't forget to
42:45
visit our website or our social media sites.
42:47
Plenty of things to see and do there. Uh, if
42:50
you have any thoughts on any of the things
42:52
we've discussed, by all means, uh, send us a
42:54
message via our website. Just, there's a
42:56
little, uh, button up the top of our
42:57
homepage, um, ama, where you can
43:00
send us messages and audio questions or
43:03
whatever you like. Uh,
43:04
spacenutspodcast.com or
43:07
spacenuts IO is the place to
43:10
go. John D. Thank you so much. We're at the
43:12
end. We'll catch up with you real soon.
43:14
Jonti Horner: It's absolute pleasure. Thank you for having
43:16
me.
43:17
Andrew Dunkley: Uh, John D. Horner, professor of Astrophysics
43:19
at the University of Southern Queensland.
43:21
Thanks to Huw in the studio, who, um.
43:23
Well, he couldn't be with us today because he
43:26
got hit by a piece of SpaceX
43:28
satellite. Uh, no. No, he
43:31
didn't. Maybe he did. I don't know. I haven't
43:33
seen him for ages. And from me, Andrew
43:35
Dunkley, thanks very much for your company.
43:37
We'll catch you on the next episode of Space
43:39
Nuts. Bye for now.
43:42
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