Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Snowball Earth Theories, High-Energy Neutrinos & The Fascinating MWC349A

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Snowball Earth Theories, High-Energy Neutrinos & The Fascinating MWC349A · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Hi there. Thanks for joining us on a Q and A
0:02
edition of Space Nuts. My name is Andrew
0:05
Dunkley and this is the. The show we do each
0:07
week where you supply the agenda
0:10
and we pretend we know what we're talking
0:12
about. And questions are coming in,
0:15
for this week's show from Peter, who's asking
0:18
about climate change.
0:20
Jonti Horner: Paul is.
0:21
Andrew Dunkley: Well, I suppose it's a similar story.
0:24
Snowball, Earth and, a couple of
0:26
objects of interest. Casey is asking about
0:29
KM M3230213A.
0:32
Know all about it. And an even more obscure
0:35
thing. Henrik has asked about
0:38
MWC3498, which I just did a
0:41
Google search for and it came up blank.
0:45
Anyway, it's an A at the end, not an A. I had
0:48
fun with that. Ah, is that the one? All
0:50
right. And that's what we're talking about
0:52
with that little voice you just heard in the
0:54
background on this edition of space
0:57
nuts.
0:57
Voice Over Guy: 15 seconds. Guidance is internal.
1:00
10, 9. Ignition
1:03
sequence start. Space nuts. 5, 4, 3,
1:06
2. 1. 2, 3, 4, 5, 5, 4,
1:09
3, 2, 1. Space nuts. Astronauts
1:12
report it feels good.
1:14
Andrew Dunkley: And that voice belongs to none other than
1:16
Professor Jonti T. Horner, professor of
1:18
Astrophysics at the University of Southern
1:21
Queensland, Jonti. Hello again.
1:23
Jonti Horner: Good afternoon. Yeah, clearly professor of
1:25
interruptions. This is what happens when I've
1:26
had enough time for the coffee to kick in.
1:29
Andrew Dunkley: yes, it's been, what, four days and
1:31
we're still wearing the same clothes.
1:33
Jonti Horner: Absolutely.
1:34
Andrew Dunkley: Yeah, I get a lot of mileage out of that
1:35
joke. Yeah.
1:38
Jonti Horner: but you've been done.
1:39
Had a musical interlude. Haven't I have.
1:40
Andrew Dunkley: Look, I,
1:42
Jonti Horner: It.
1:43
Andrew Dunkley: It was just. Last weekend was a long weekend,
1:45
in New South Wales, and I think it was in
1:48
Queensland too. But, it was the weekend that
1:50
Taylor Swift released her latest album.
1:54
And, I've got three
1:56
granddaughters, all of Taylor's
1:59
swifty age. And we.
2:02
Yeah, we took them to see the launch of her
2:04
new album. and, I. Look, I've got to
2:07
tell you, I really did, I did. I enjoy
2:10
it. Yes.
2:12
It's not aimed at me or my demographic, but,
2:16
it was, it was interesting to
2:19
watch some of the thinking behind the artist
2:21
and some of the creativity that went into
2:23
film clips and things like that. That's the,
2:26
that's what I got out of it. But what, an
2:28
extraordinary.
2:29
Jonti Horner: It's one of the things I love.
2:30
I know we've gone totally off topic straight
2:32
away, but my favorite critic, and the kind of
2:35
only one I pay attention to, really is a guy
2:37
called Mark commodity in the UK who's, they
2:39
used to be on BBC Radio 5 live and now
2:41
they've got their own independent, thing. And
2:43
it's one of those things that's like comfort
2:45
food for the soul that you can listen to and
2:47
just makes your children relax. But part of
2:49
what's nice about him is that you get a lot
2:51
of film critics who, if a film's not made for
2:53
them, are in some misdiabos about it. Right.
2:56
And you know, I remember this with the
2:58
Twilight films, which I'm not the target
2:59
audience, they're not my cup of tea, but they
3:01
got panned because they're made for
3:04
teenage girls and film critics are elderly
3:06
men and there's a slightly different
3:07
demographic there. And this guy's brilliant
3:10
because he'll m. Make the point. You know,
3:11
I'm not the target audience for this. I'm
3:13
very clearly not it and I enjoyed it. Okay.
3:16
But you look around the room at the people
3:17
who are the target audience and they love it.
3:19
So it's obviously doing well. I think it's
3:21
the same with what you're saying by the
3:23
Taylor Swift stuff. We're not the target
3:24
audience. But you can appreciate that this is
3:26
someone who's awesomely talented and ah, for
3:29
the target audience, it's really
3:30
fundamentally awesome, you know.
3:33
Andrew Dunkley: Yeah. I was still working on radio,
3:36
when she was, announced by Time magazine as
3:39
Person of the Year. And I did a big, big
3:42
statement at the time as far as I was
3:45
concerned, about why she deserved it
3:47
because she brought light into the world
3:51
at a very dark time towards the end of COVID
3:54
And but then they went and
3:57
made Donaldjohanson Trump the, Person of the
3:58
Year. So anyway, whatever.
4:01
Jonti Horner: can't see the light without having darkness.
4:03
Right.
4:03
Andrew Dunkley: And I will say one of the songs on the new
4:06
album has got to be about Donaldjohanson
4:08
Trump. So anyway, he's after
4:11
a Nobel priest Peace Prize and the word on
4:14
the hill is that, you might just get it.
4:18
we won't go there. It's not our agenda. But,
4:20
we will go to some questions. Why don't we
4:22
try and tackle this very first one?
4:25
And this one comes from Peter.
4:27
With all this climate change happening, I,
4:29
was wondering how CO2 is warming the
4:32
planet when it's heavy. Heavier than air.
4:35
Maybe the problem is the axis of the planet
4:37
has moved because of all the millions of tons
4:40
of minerals that have been moved. Maybe
4:43
someone should check the axis angle.
4:45
Geez, Peter, I think I've heard this
4:48
theory Once before. I doubt that the
4:51
amount of stuff we take out of the ground and
4:53
move around the planet is going to make that
4:56
big a difference to the tilt.
4:59
Jonti Horner: No, and the beauty is we can measure the
5:01
tilt. I mean, I grew up in the north
5:04
of England, and high in the sky was
5:06
Polaris, the pole star, which is the
5:08
direction that the northern end of the
5:10
Earth's, spin axis points to. I'm very, very
5:13
close to that star. So we can see exactly
5:15
where the spin axis of the Earth is pointing.
5:18
We can measure its spin rate. And it is
5:21
right that moving material around on the
5:24
Earth will to some degree change its spin
5:26
and change its spin axis tilt.
5:29
but, and it's a very big but the amount of
5:32
change that you get from human activity is
5:35
very, very, very, very small. A much
5:38
bigger shift in mass, for example, happens
5:40
with melting of the polar caps. Yeah, if you
5:43
melt the polar caps, you move the water. The
5:45
water settles all around the Earth, so you're
5:46
effectively moving mass from near the poles
5:48
to near the equator. And that changes the
5:51
Earth's rotational angular momentum and will
5:52
change the Earth's spin very, very, very,
5:55
very slightly. But we're now incredibly
5:58
technologically capable, so we can measure
6:00
things that are that small. And a good
6:01
example of that was the big Indian Ocean
6:04
tsunami. The earthquake that caused that, on
6:06
the Pacific Rim had a measurable effect on
6:08
the Earth's spin. But if I remember rightly,
6:11
and I stand to be corrected here, that
6:13
measurable effect was something like one, one
6:15
millionth of a second in the spin rate or
6:17
something like that. And we can measure that,
6:19
but it's not like you'd notice it in your day
6:21
to day life. And it's not like that would be
6:23
big enough to cause the impact on the climate
6:26
that we see today. Now, I understand
6:28
that, thanks to, decades of
6:31
discussion, that climate change is still a
6:33
bit of a controversial topic with some
6:35
people. And I'm quite
6:38
fundamentally comfortable saying climate
6:39
change is a real thing, that the climate is
6:41
changing. I spent three years early in my
6:43
career living in Switzerland, and when I was
6:46
in Switzerland, I used to go skiing, because
6:48
skiing's awesome. And if you're in
6:49
Switzerland, why wouldn't you? And all these
6:51
beautiful little towns that I went to in the
6:53
winter, and then you went back in the summer
6:55
and you went walking in the hills instead of
6:57
skiing because all the snow had gone. They
6:59
all have these photos from 50 or 100 years
7:01
ago where you have the village in the
7:03
foreground and the glacier in the background
7:05
winding out of the hills. And then if you're
7:07
up there in the summer, you go out and look,
7:09
and it isn't there anymore. It's retreated
7:11
that far. And I think that's fundamentally
7:14
why in a lot of those countries with Alpine
7:16
regions, climate change has been accepted for
7:18
much, much longer, because you can really
7:20
physically see the effects. And so it's very
7:23
clear that it's happening. And the argument
7:25
that it's caused by humor rather than
7:26
something natural, the strongest evidence for
7:29
that, to be honest, is the speed at which
7:31
it's happening is unprecedented. The natural
7:34
effects that could cause it, like the
7:36
transition from the ice ages to the
7:38
interglacials, and we'll talk about this a
7:39
bit more later on, are, much more gradual.
7:42
Changes in brightness of the sun are much
7:44
more gradual. And in fact, the sun has dimmed
7:45
a little bit over the time that we've been
7:47
measuring climate change due to little bits
7:49
of tweaks in its behavior. So if
7:52
the climate wasn't changing, we'd actually be
7:54
slightly cooler now than we were a couple of
7:55
hundred years ago, only very slightly. But
7:58
that leads to this perverse and confusing
8:00
statistic that 110% of all climate change is
8:03
caused by humans because we're not just
8:05
making it warmer, but we're offsetting the
8:07
cooling as well. Yeah, so that's all the
8:09
background to it here, how carbon dioxide
8:12
plays a role. Even though it's, you know,
8:15
heavier than air, it's still gas, it still
8:16
floats around up there. It's not like it all
8:18
sits at ankle level on the Earth. But even if
8:20
it did, it would still be fairly effective
8:22
because what carbon dioxide is in a really
8:25
broad sense is it's like a good winter doona
8:27
that you've got. The way that
8:30
I can understand this as an astronomer most
8:32
obviously is, I think back m to again. When I
8:34
was a kid, 1983, when I was five years old,
8:37
there was this satellite launch called the
8:38
infrared astronomical satellite IRAs. And
8:41
that was really foundational for a lot of
8:43
what we've learned about planets around other
8:45
stars, because it was a tool that first
8:47
allowed us to find debris disks around stars,
8:50
which are, the leftovers from planet
8:51
formation. And that was a bit of a shock
8:54
because stars didn't look how they were
8:56
expected to. Three of them in particular.
8:58
Vega, Fomalkauten, Beta Pictoris. They were
9:01
brighter in the infrared wavelengths than we
9:02
expected. They thought the satellite was
9:04
broken. Then they realized that, no, really,
9:06
the stars just had all this debris around
9:08
them that was getting hot, warming up, and
9:10
Giving off radiation and infrared
9:11
wavelengths. So this tells us that
9:14
when you heat something up, it radiates that
9:17
energy away in infrared. And that's why
9:19
thermal imaging cameras work. You can see
9:21
people at night if you're using a thermal
9:23
imaging camera because they're warmer than
9:25
the surrounding area, so they give off more
9:27
infrared radiation. You can see that. But the
9:29
reason we had to launch IRAs was that you
9:32
can't do infrared astronomy from the ground
9:34
except a couple of very specific wavelengths.
9:37
And the reason that you can't do infrared
9:38
astronomy from the ground is that the
9:39
atmosphere is fundamentally opaque at
9:42
infrared wavelengths. And a big part of that
9:44
is carbon dioxide. So if you've got a photon
9:47
of infrared radiation, it coming into our
9:49
atmosphere, we'll essentially see our
9:51
atmosphere as utterly thick cloud. It will be
9:53
absorbed and re emitted back out.
9:56
Optical light, visible light makes it through
9:59
the atmosphere intact. And that's why if I
10:00
look out of the window at the minute, we've
10:02
got a lovely sunny day and I can see what I'm
10:03
doing. And, that solar radiation comes in and
10:06
it warms the Earth up. And what does the
10:08
Earth do? It radiates that energy back
10:10
outward at infrared wavelengths. But because
10:12
the atmosphere is opaque at infrared
10:14
wavelengths, that energy gets absorbed and re
10:16
emitted. And it'll be re emitted randomly in
10:18
any given direction. So the odds are it'll
10:21
come back down. So in other words, that
10:22
radiation gets trapped. And that's how the
10:25
doona works. That's how the carbon dioxide's
10:27
working. Now the carbon dioxide
10:30
we've got in our atmosphere is really
10:32
effective as a greenhouse gas. It's actually
10:35
mostly saturated. So adding
10:37
some carbon dioxide from no carbon dioxide
10:40
would have a much bigger effect than adding
10:42
carbon dioxide to the atmosphere. Now, when
10:44
we've got a fair bit of it in there already,
10:46
but it's not totally saturated. So what that
10:48
means is as we add more carbon dioxide, it
10:51
can still have a bigger effect. And, that's
10:53
why as we put more carbon dioxide into the
10:55
atmosphere, the Earth gets warmer because the
10:57
Dooner gets more effective.
10:59
There are other gases that are effective
11:01
greenhouse gases as well. Methane is a really
11:03
good example. Methane is actually much more
11:05
effective than carbon dioxide. But the
11:07
difference is methane's fairly short lived in
11:09
the atmosphere. Methane molecules on average
11:12
will be removed from the atmosphere within
11:13
400 years by interacting with oxygen.
11:16
Carbon dioxide is only removed by life
11:19
or by weathering. You know, if you get lots
11:22
of rain on the continents, that breaks up the
11:24
rocks, the rocks crumble down. Chemistry
11:27
happens. Carbon dioxide can be pulled out
11:28
into the rocks and locked up in the surface.
11:31
They're the mechanisms that get rid of carbon
11:33
dioxide and they're slower. So that's part of
11:36
why carbon dioxide is a problem, because when
11:37
we put it in the atmosphere, it's going to
11:39
hang around for a good long time. But that
11:41
hopefully kind of answers that question, that
11:43
I am respectful of the fact that it's hard
11:46
for people to comprehend how we
11:48
can change the world's environment. Because
11:50
you think of yourself and your friends and
11:51
you think the Earth's so big and we're so
11:54
small, how can we have that much of an
11:56
effect? And it's hard to come to terms with
11:58
just how many people there are and just how
12:00
much stuff we're doing and pumping stuff into
12:02
the atmosphere. Yeah, it's a bit
12:04
misleading to say, you know, if you change to
12:07
an EV rather than a petrol car, you'll save
12:09
the world, but it'll contribute a little drop
12:12
in the ocean towards lessening climate
12:15
change potentially in the long term. And,
12:18
that's kind of what people are looking at.
12:19
But fundamentally, this is what's happening.
12:22
It's very, very well established. Nothing
12:24
astronomically can even come close to
12:26
explaining what we're seeing. So when you
12:29
rule out all the other options, the only
12:30
thing that's left is human influence. And
12:32
that's kind of sad, but shows what an
12:35
effective species we are at changing our
12:36
environment, you know?
12:38
Andrew Dunkley: Well, hopefully we can be just as effective
12:39
in finding a solution, but I think, to do
12:42
that, everybody has to be on the same page,
12:44
and that's just not the case at the moment.
12:46
Jonti Horner: I'm an optimist. I mean, there's.
12:49
There's real challenges here. I remember
12:51
there was an incredible article by a guy
12:53
called Jeff Masters who used to run the
12:56
Weather Underground site, used to write blogs
12:57
there. yeah. and he wrote about. I think it
13:00
was book review, actually. But he wrote about
13:01
something called Manufactured Doubt, which is
13:04
a whole industry that has sprung up to
13:07
sow confusion over something that should be
13:09
settled science in order to allow business
13:12
to operate without being restricted
13:14
effectively. And, it first came about with
13:16
smoking. So cigarette smoking. Tobacco
13:19
smoking was known to be very harmful to
13:21
people going back 100 years from now. But
13:24
even when I was growing up in the 1980s, he
13:26
still had smoking in public places. You still
13:28
had it everywhere. You still have adverts on
13:29
TV and tobacco sponsorship. Because there'd
13:32
been this very cleverly managed marketing
13:35
strategy of casting doubt on the science and
13:37
casting doubt on the scientists involved,
13:39
effectively slandering them. And you have
13:41
things like, you know, top sportsmen in the
13:43
world, footballers and cricketers and things
13:45
like this being sponsored by tobacco
13:47
companies and smoking cigarettes and
13:49
interviews and giving this impression. Can't
13:51
be harmful, can it? I mean, look, here's one
13:52
of the fittest athletes in the world and they
13:54
smoke and that makes them a great athlete.
13:56
You shouldn't see children. And
13:59
what was interesting in this article from
14:00
Jeff Masters, who's a very powerful advocate
14:03
for knowledge, about climate change, was
14:05
that, there is a lot of evidence that the
14:07
companies that used to do that for tobacco
14:09
through the 1980s were brought on board by
14:12
the big oil companies to do the same kind of
14:15
strategy. And it's been incredibly effective.
14:18
And I think it's led to this wider thing of
14:22
diminishing trust in science and greater
14:24
doubt in it, which has led to the challenges
14:26
we face now with things like vaccines, with,
14:28
you know, flat earthing to some degree, with
14:31
places where people are skeptical and
14:34
don't trust scientists and don't trust
14:36
science, even though science is so
14:37
fundamental and foundational for our day to
14:39
day lives. And it's really sad. But the flip
14:42
side is we got cigarettes banned,
14:45
people's health has improved. We, you know,
14:47
no longer do you go to a pub and the walls
14:49
are grimy and the windows are dark because of
14:51
all the cigarette smoke. No longer do you get
14:52
on a train and have to cough your way to your
14:55
destination. Things have changed and I think
14:57
we're starting to see the same change with
14:59
climate change and, with the actions that we
15:01
can take. And it's not happening out of the
15:03
goodness of people's hearts. It's happening
15:04
because commercially it's now becoming viable
15:07
to make the changes. Yes, electric vehicles
15:10
are a really good example. Back in the early
15:12
1900s you had electric vehicles, we had
15:15
electric milk floats in the uk, but they were
15:16
an oddity and there were specific use. But
15:19
it's finally got to the point where those
15:20
kind of vehicles can be competitive with
15:23
combustion engine vehicles, can even possibly
15:25
work out cheaper and more efficient and
15:27
suddenly there's an incentive for people to
15:29
get them, not because they're doing good for
15:30
the planet, but because it's a better option
15:32
for them. And that's the kind of change that
15:34
hopefully is going to improve things.
15:35
Andrew Dunkley: Yes, yes, I hope you're right. I
15:38
suppose the other difficulty that comes into
15:41
play with trying to change the minds of
15:44
people and get the right thinking happening
15:47
is social media, because there's so much
15:50
scandal going through social media and as
15:52
I mentioned, in the last program,
15:56
we now have artificial intelligence, so
15:59
you don't even know what you're looking at is
16:01
real anymore.
16:02
Speaker C: It's.
16:02
Jonti Horner: Yeah, it's all saying that. And
16:05
I know it from a Terry Pratchett. But like
16:07
many things, Terry Pratchett, he was probably
16:10
referencing people before. But this whole
16:12
idea that a lie can run around the world
16:13
before the truth can get its boots on, it's
16:16
very easy to tell a convenient lie. And
16:18
people are naturally biased as
16:21
humans, with all the different cognitive
16:22
biases we've got, there's a confirmation bias
16:25
that you remember the things that fit in well
16:26
with your lived experience and not the things
16:28
that disagree with it. And, my lived
16:30
experience is that I don't change the world
16:32
when I go around. I'm not fundamentally
16:34
altering the world around me, which I live
16:36
in. So it's very easy when somebody says,
16:38
we're not changing the world. Climate change
16:40
can't be real, because how could you change
16:42
the world for people to really empathize with
16:44
that and fit in with it in just the same way
16:47
that people who are getting vaccinated,
16:49
they'll remember that their anti ulcer had a
16:51
bad reaction to the vaccine, but they don't
16:53
remember that many people who have had the
16:56
vaccine and not had a reaction, but didn't
16:58
die from the thing they were vaccinated
17:00
against because they were vaccinated. So you
17:02
get that confirmation bias that feels like it
17:04
supports the idea that vaccines are bad
17:07
when in fact they're not. And fundamentally,
17:09
this is why as scientists, we use statistics
17:11
for all these things. Lies down, blind
17:14
statistics. We use statistics to try and
17:16
avoid falling into the trap of our own biases
17:19
because we think we've seen a pattern, but
17:20
statistics will give us a hint as to whether
17:22
it's really there or not.
17:24
Andrew Dunkley: Yeah. Gosh, we could talk forever on this.
17:28
It's like opening that can of worms and just
17:30
letting it spill out and everybody has a go.
17:33
thank you, Peter. We're going to sort of
17:34
continue on to this type of, angle, with a,
17:37
question from Paul.
17:39
Speaker C: G', day, Space nuts. Paul Feen from Sunny
17:41
Bridges, Vegas here. Quick question. If
17:44
our Earth were to suddenly or not suddenly
17:47
become a snowball, as
17:50
might have happened if our, scientific
17:52
theories are correct, you know, back in our
17:55
deep, distant past, what effect
17:57
would that have on oxygen levels in our
18:00
atmosphere? Would they
18:03
stay the same? would they drop? Because
18:05
plants don't grow really well down in
18:07
Antarctica. I'd be curious to
18:10
know your thoughts on this. Also
18:13
what kind of events would actually trigger
18:15
that in the first place? Anyway, keep doing a
18:18
great job. Whoever happens to be at helm of
18:19
the good ship Space Huts, big shout out to
18:22
Heidi Campo. Wow, what a great job he
18:25
did. Thank you. And Jonti, wherever you are,
18:28
would love to hear from you again if Fred
18:31
goes off gallivanting over to, I don't know,
18:34
Norway or somewhere like that to see the
18:36
northern lights. Cheers.
18:39
Andrew Dunkley: Thank you, Paul. Well, guess what, that's
18:41
exactly what's happened. And Jonti is
18:44
with us because of Fred's gallivanting.
18:47
So, yes, you get to answer Paul's question
18:50
about snowball Earth. the effect on O2 levels
18:52
and what sort of, events would trigger it.
18:55
Jonti Horner: That's great. And there's a lot to this and
18:56
it's good to hear from a local. So, yeah,
18:58
thank you. And hi from.
19:00
Andrew Dunkley: You're just up the road.
19:01
Jonti Horner: I'm just up the road. Only a couple of
19:02
hundred Ks inland. So, yeah, good hear from a
19:05
local. This is. This sent me down some
19:07
rabbit holes actually. I was digging into
19:09
this and it's fascinating. So I've never
19:11
actually had that thought of how snowball
19:13
Earth episodes could link to oxygen before.
19:16
And it's a really, really, really good
19:17
question. So almost answer these kind of
19:19
things in a bit of reverse order.
19:22
The idea is, for those who aren't familiar
19:24
with it, that at a couple of occasions in the
19:26
past, one a bit more than 2 billion years
19:28
ago, 1, 600, 500 million years ago,
19:32
the Earth's climate went across a tipping
19:34
point and like the ice age began, but the
19:37
glaciers just kept advancing and you ended up
19:39
with pretty much the entire planet clad in
19:42
ice. And conditions at the equator at
19:45
that point could even have been colder than
19:46
we see in Antarctica right now. So really
19:49
kind of dramatic conditions. And that lasted
19:52
for a few million, even tens of millions of
19:54
years before that condition got broken.
19:57
And it makes perfect sense now. The climate
19:59
of the, Earth is relatively stable at the
20:02
minute. We've just talked about our impact on
20:04
it. But, on geological timescales, our
20:07
climate tends to sit around a fairly stable
20:09
point. But what the snowball Earth idea
20:12
is reminding us of is that you have a
20:15
few possible stable scenarios for the Earth's
20:17
climate, of which we are one, we're one,
20:20
which is essentially the warm version. But
20:22
equally, if you turn the Earth into a
20:24
snowball, it will remain a snowball for a
20:27
very long time. And the reason for that is
20:29
that, if you make the Earth a snowball, it
20:31
becomes incredibly More reflective. And so
20:34
therefore it absorbs less energy and so it
20:36
stays cold. You get this kind of feedback
20:38
that keeps the Earth cold. And the idea is
20:41
when you flip from one state to another, you
20:43
can be locked in that new state for a very
20:45
long time until something changes. Now what
20:47
could cause that? One thing that could cause
20:50
that is life on our
20:53
planet. Removing carbon dioxide from the
20:54
atmosphere and weathering on the continents.
20:56
Removing carbon dioxide from the atmosphere
20:59
at, ah, a rate that cools a planet quicker
21:01
than the sun getting brighter, warms a
21:03
planet. So the sun, when the Earth was very
21:05
young, was probably about 30% dimmer. And the
21:08
sun is thought to brighten by about 6 or
21:11
7% every billion years. So it's 30%
21:13
brighter now than it was when the Earth
21:15
formed. So the question is, if the sun was so
21:17
dim when the Earth was young, how were we
21:19
warm enough to have liquid water? And the
21:21
answer is, at that point we had a hugely rich
21:24
atmosphere of greenhouse gases, things like
21:26
carbon dioxide and methane and no oxygen. And
21:29
so the atmosphere was very, very rich in
21:31
things that would create a really thick doona
21:33
and we were very, very pleasantly warm.
21:36
Over time, the sun has got brighter, but
21:39
life and weathering have removed the
21:41
greenhouse gases from the atmosphere and
21:44
averaged over the entire age of the Earth,
21:46
those two things have roughly balanced out.
21:48
And so we still have a temperate climate. Now
21:51
if we had the atmosphere the Earth had when
21:52
it was young, the Earth would be like Venus
21:54
now. The oceans would have boiled and we
21:56
wouldn't be having this conversation. Yeah,
21:58
but the climate has kind of fortunately
22:01
stayed for most of its time in the kind
22:04
of warm, stable version. But there have
22:07
been these two big occasions that have had
22:09
the snowball Earth scenario. Now
22:12
there's some debate over, exactly what
22:13
triggered that. And it's likely there were a
22:15
few things. There was life and increased
22:17
weathering, pulling carbon dioxide out of the
22:19
atmosphere. So you weaken the greenhouse
22:21
effect and cool the planet down. That is
22:24
most likely. You also have a scenario,
22:26
incidentally, where if you make the Earth
22:29
more reflective around the equator, you lower
22:32
the amount of heat that's absorbed by the
22:33
Earth, increase the amount reflected and you
22:35
cool the Earth as well. So what are the
22:37
scenarios that's proposed to explain how we
22:39
got into the snowball Earth periods? At first
22:42
was that you got a period where you got one
22:44
of these supercontinents where all the
22:45
continental material on the Earth kind of
22:47
smushed together, like we had with Pangea,
22:49
like was proposed with Pangaea. Previous
22:51
episode of that. We have most of the Earth's
22:54
continents around the Earth's, equator,
22:57
continental material, rock and, vegetation
23:00
and everything else is more reflective than
23:02
water. And in fact, most of the energy coming
23:05
into the Earth these, ah, days is absorbed by
23:07
the water. The water is the main thing that
23:09
locks in the heat and keeps us warm. And
23:11
that, of course, is why Brisbane gets so warm
23:13
and humid in the summers. It's why Western
23:15
Europe is so pleasant in the winters compared
23:18
to the middle of Canada. The water carries a
23:21
lot of heat, holds onto it for a long, long
23:22
time. So you have this speculative scenario
23:25
where all the continents end up smushed up
23:28
and near the Earth's equator. So the Earth's
23:30
albedo gets more reflective, a higher
23:33
albedo, so the Earth would naturally cool
23:35
because it's absorbing less heat and
23:36
reflecting more. Added to which, if you put
23:39
the continents nearer the equator, you're in
23:41
a location which gets much higher rainfall
23:43
and much higher weather levels because the
23:45
water at that latitude is hotter, so
23:47
evaporates more. The atmosphere can hold more
23:49
water, so you get more weathering, which
23:51
drives more chemistry, which also acts to
23:53
pull more carbon dioxide out of the
23:54
atmosphere. And, that exacerbates this and
23:57
we, you know, removes the greenhouse effect
23:59
as well. So you've got more energy being
24:01
reflected and less absorbed. So the Earth
24:03
cools more carbon dioxide pulled out of the
24:05
atmosphere, so the greenhouse effect weakens,
24:07
so the Earth cools. That then causes the
24:10
Earth to start entering ice ages where the
24:12
water near the poles freezes and the ice
24:15
expands towards the equator. That ice is more
24:18
reflective than the water that it sits on is.
24:21
So less energy is absorbed and more is
24:22
reflected. And so the Earth cools. And so you
24:24
get this feedback effect where the ice
24:26
gradually reaches down towards the equator.
24:28
And once you're in that scenario, you're in a
24:31
position where even if you put all the carbon
24:33
dioxide back in the atmosphere, the Earth is
24:35
so reflective that it will stay cold.
24:38
You're locked into this other stable state.
24:41
However, longer term, what happens is that,
24:43
you've got the ice sheet now sat over all of
24:45
the rocks. So you prevent the weathering that
24:48
was removing carbon dioxide from the
24:50
atmosphere. You turn that off, you've still
24:52
got things putting carbon dioxide back in the
24:54
atmosphere.
24:54
You've still got volcanoes erupting and all
24:56
the sources of gases that were putting it
24:59
back into the atmosphere and eventually
25:00
return the weather, material, weather gases
25:02
into the atmosphere. So you're in the
25:04
snowball, Earth setup. But gradually over
25:06
time, then your greenhouse gas levels rise
25:08
and rise and rise until eventually you start
25:11
to melt the ice and you get this other
25:13
tipping point where suddenly you're warm
25:16
enough for the ice to melt and retreat, which
25:18
means you expose more water, more water is
25:21
exposed, which means more area to absorb the
25:23
heat, which means the Earth will warm up
25:25
more, which means more ice melts, and you go
25:27
back to being this kind of warmer, Earth.
25:30
That brings with it, though, a time when
25:33
you've had the continents crunched up under
25:35
ice sheets, broken up into kind of gravelly
25:37
small bits of debris. And then when you start
25:39
raining on that again, you get a huge amount
25:42
of weathering water washing out
25:44
minerals and putting it into the ocean.
25:47
And that means that suddenly all that life
25:49
that has been starved through the snowball
25:51
Earth epoch is suddenly going, hey, look, the
25:54
Earth's nice and warm. It's a nice place to
25:55
live again. Brilliant. And, oh, look, there's
25:58
suddenly all this food in the oceans. And so
26:00
the papers that I came across when I was
26:02
looking into this as a result of Paul's
26:04
question, it seems that after both of the big
26:07
snowball Earth eras, there was a massive
26:09
oxygenation event on Earth. So after the
26:12
first one, you went from effectively no
26:13
oxygen in Earth's atmosphere to Earth's
26:16
atmosphere being about 2%
26:18
oxygen, which is a big jump from nothing to
26:20
2%. And, then
26:23
6,500 million years ago,
26:25
you had the end of the most recent snowball
26:28
Earth thing, and you got another mass
26:29
oxygenation event. Why suddenly you've
26:32
got all this nutrient and all this stuff
26:34
washing off into the oceans, prime conditions
26:36
for things to grow and a huge amount of
26:39
oxygen released. And, that is thought to have
26:41
been what drove oxygen up to something
26:43
comparable to its current levels relatively
26:45
quickly. And that then led to there
26:48
being sufficient free evidence for what's
26:50
called, I think, the Cambrian explosion,
26:52
where suddenly you've got an Earth that has
26:54
all these different niches suddenly freed up
26:57
and the source of ready oxygen, and
26:59
everything goes crazy evolving to fill the
27:02
available opportunities. And
27:05
so all of that kind of gives you an idea how
27:07
we think snowball Earth episodes could
27:09
happen. And, what would happen to oxygen
27:11
afterwards? Which seems to be the accepted
27:13
scientific wisdom, that after a snowball
27:15
Earth episode, when it ends, you can get the
27:18
oxygen suddenly getting significantly more
27:20
oxygen rich as life takes advantage of the
27:22
new conditions. What would happen to
27:25
oxygen now that there's a lot of it in the
27:27
atmosphere during the snowball Earth period,
27:29
I couldn't find any speculation on. So
27:32
it's a really interesting question. Now, it
27:33
doesn't mean there's no speculation out
27:35
there. It just means that I couldn't find any
27:37
of his. Big difference there. But
27:40
there's a few things that are going on that I
27:41
think could be interesting. Firstly, there's
27:43
a huge amount of oxygen in the atmosphere. So
27:45
even if you stop producing it and you manage
27:48
to keep alive the things that use it, it will
27:51
probably go down very slowly just because
27:52
there's so much of it. And if you were
27:54
killing off a lot of life, then
27:57
to be honest, there's not as much using it
27:59
anyway. Volcanoes erupting, carbon
28:02
dioxide and particularly methane that's been
28:04
erupted and outgassed, particularly towards
28:07
the end of the ice age kind of period,
28:10
getting lots of methane released into the
28:12
atmosphere would remove the oxygen as the
28:14
methane and the oxygen interact with each
28:15
other. And if that was happening quicker than
28:18
life was putting new oxygen into the
28:19
atmosphere, then you can imagine that leading
28:21
to a bit of a dip in the amount of oxygen in
28:23
the atmosphere at the time. But my
28:26
guess would be that probably during the
28:28
snowball Earth period, the oxygen levels
28:31
wouldn't change all that much. You might be
28:33
producing less oxygen, but you'd also be
28:35
using less. So that will balance out. But
28:37
what you would get over time is, particularly
28:40
if you killed off a lot of life, you get this
28:42
slow, steady increase in
28:45
greenhouse gas levels because you're still
28:47
pumping out the same amount in terms of
28:49
volcanism, but you've removed the weathering
28:51
that's taking it away again. And so that
28:53
would lead to the greenhouse gas level rising
28:56
slowly over time until it got to the point
28:59
where it turned it back over the tipping
29:00
point and allowed the Earth to warm up again.
29:02
And that will probably then be a very bad
29:04
thing because the sun is now much more
29:06
luminous than it ever has been in the past.
29:08
If you get a runaway greenhouse effect now,
29:11
that's a lot more problematic than it was 500
29:13
million years ago. And maybe that could lead
29:15
to conditions where you don't hit our current
29:18
stable level, but you go past that and you
29:20
end up hurrying the end of the Earth, as a
29:23
habitable world, effectively.
29:25
Andrew Dunkley: Oh, fun. Yeah.
29:26
Jonti Horner: Careful path.
29:28
Andrew Dunkley: I, just did a.
29:31
I'll get some negative press for this, but, I
29:34
just did a, put a question into chat. GPT
29:38
Would, current oxygen levels on Earth reduce
29:40
if Earth were to freeze over? And it's come
29:42
up with a few scenarios, but basically says
29:44
most, he he. It says most oxygen
29:47
on Earth comes from photosynthetic organisms,
29:50
mainly marine plankton and land plants. If
29:52
Earth froze over ocean, surfaces
29:55
would be sealed under thick ice, preventing
29:57
sunlight from reaching most marine
29:59
photosynthesizers. Land plants would die or
30:02
go dormant due to cold or lack of liquid
30:04
water. So oxygen production would drop
30:07
dramatically.
30:08
Jonti Horner: And that makes sense, but I'd argue that
30:10
oxygen use will drop dramatically as well
30:12
because you kill the things that are using
30:14
the oxygen. Yes. The other thing that I've
30:16
stumb across in my reading actually, and that
30:17
just reminded me of was one of the things
30:20
that tied into this idea of the snowball
30:22
earth stuff was how on earth did life make it
30:24
through. And one of the things that people's
30:27
modeling found was that even though you'd get
30:28
ice all the way down to the equator, the
30:31
processes that happen at the equator will
30:33
probably prevent that ice being more than
30:35
about 10 meters thick. And studies have shown
30:37
that enough light can make it through ice for
30:39
photosynthesis to continue unless the ice is
30:42
20 meters thick or more. And so there'd
30:45
likely be a band where you could continue
30:46
photosynthesis under the ice because the ice
30:48
is not thick enough to block all the
30:50
sunlight. That seemed to be the argument.
30:52
There was some discussions of where the
30:54
pockets of life holding on through the
30:56
hellish times would be and that was quite
30:58
interesting. But like I said, I'm not a
30:59
biologist, so that is straining my expertise
31:02
to look at exactly how life would adapt to
31:04
those conditions.
31:05
Andrew Dunkley: Indeed. All right, Paul, thanks for the
31:07
question. Great one. And there might be more
31:09
to talk about that, in regard to that down
31:12
the track. This is Space Nuts with Andrew
31:14
Dunkley and Jonti Horner.
31:19
Speaker C: Three, two, one.
31:22
Jonti Horner: Space Nuts.
31:23
Andrew Dunkley: Now Jonti, a couple of questions have come in
31:26
about objects or events that
31:29
have happened in space. Casey
31:32
has messaged, us. Hello again, this is Casey
31:35
from Colorado. I recently read a little bit
31:37
about the record breaking KM
31:39
M32302 213A.
31:43
Please correct me if I'm wrong, but detecting
31:46
a 220 PETA electron
31:49
volt neutrino is pretty crazy
31:51
considering that that's like 30 times more
31:54
energetic than the previous record holder.
31:57
what could possibly be its source? Love the
31:59
podcast and hope you're both well. Thanks
32:02
from Casey in Colorado and she hopes you're
32:04
well too, Jonti.
32:06
Speaker C: Yes.
32:07
Andrew Dunkley: Then again she might be talking about Fred
32:08
and Heidi. I don't know.
32:13
Jonti Horner: So this is a really interesting one. I must
32:15
say that I hadn't seen this announcement and
32:17
so this was a really interesting thing to
32:19
read about. this is a neutrino that according
32:22
to the name was seen in 2023, on
32:25
February 13th. And, it was detected
32:28
by this huge array of detectors on the bottom
32:31
of the Mediterranean Ocean, Mediterranean
32:33
Sea, about 3 and a half kilometers below sea
32:36
level, in the pitch black of the deep ocean,
32:38
where they have all these detectors that have
32:41
the job of detecting incredibly faint flashes
32:44
of light that occur when cosmic rays
32:46
or neutrinos collide with an atom in the
32:49
ocean and cause a cascade of light as
32:52
this whole collision chain of, particles
32:55
being formed and energy being released as the
32:57
energy from those things is dumped into the
32:59
ocean. And this occurred before they'd
33:02
finished building and testing this array. So
33:04
it was during the testing phase, and it is
33:07
reliably says on all of these websites, by
33:09
far the most energetic neutrino ever
33:12
detected. And it is so energetic
33:15
that there is no source within our galaxy
33:18
that could generate a neutrino that energetic
33:21
that we know of. And if it had been generated
33:23
by something nearby, we'd have seen other
33:25
things happening. You might have seen a very
33:27
powerful gamma ray burst or something like
33:30
that. And, no counterpart was detected. There
33:33
was nothing that happened at this time that
33:36
synced up with when this happened. Now should
33:38
be said that when I search for this, there's
33:39
a nice little article describing it by the
33:42
Astrobytes website, which is a website run by
33:45
graduate students in astrophysics in the US
33:48
that tries to be a literature review journal
33:51
club for other graduate students
33:54
and, to give students an opportunity to
33:56
practice science writing about things out of
33:58
their field. And there's a bit of a
33:59
description of it. There's and that's a nice
34:01
little website if you're interested in
34:02
getting a little snapshot summary of research
34:04
papers to try and do one a day. But I also
34:08
stumbled across the official page for this
34:10
event, which is published by the network
34:14
that are running these detectors. And that's
34:16
got a lovely little YouTube Music video right
34:18
at the top that you can watch. It's about two
34:20
and a half minutes long that describes this
34:22
thing, how it's detected, and some of the
34:24
possible suggestions for its formation. Now,
34:27
going beyond that to what could have created
34:30
it is really pushing beyond the bounds of my
34:33
knowledge and expertise. So I'm afraid,
34:36
Casey, you're going to have to accept a
34:37
journeyman's explanation based on what I was
34:40
able to read around about this, which digs
34:43
into things that I honestly don't fully
34:44
understand. But the argument is, because of
34:47
the incredibly high energy of this thing, it
34:49
couldn't have been generated locally. And
34:52
that points to an origin in the very distant
34:54
and therefore very early universe.
34:57
Now, there's some theories that fall
35:00
under the branch of what I think is called
35:01
quantum field theory that talk
35:04
about there being photon
35:07
fields permeating space. And
35:10
I don't fully understand what that is and
35:11
what that means, in all honesty. But
35:14
the idea seems to be here that you've got
35:17
radiation from the cosmic microwave
35:18
background, or from very early in the
35:20
universe that includes incredibly high energy
35:23
radiation at, that time,
35:26
because that's a heat from the big Bang. Now,
35:28
nowadays we see that as a cosmic microwave
35:30
background. It's very low energy levels
35:32
because it's been redshifted. But at the
35:35
time, the energy levels were incredibly,
35:36
incredibly high. And that means that these
35:39
photon fields, if you follow the, quantum
35:42
field theory ideas, were incredibly intense.
35:45
Now, one of the ways that you can produce
35:47
neutrinos that is predicted by this
35:50
predicts what are called cosmogenic
35:52
neutrinos. Now, it should be said that
35:54
none of these have ever been detected until
35:56
potentially this one. But it's one of the
35:59
predictions that quantum field theory makes
36:02
is that you should see these cosmogenic
36:04
neutrinos that are generated by
36:06
cosmic radiation rather than a specific event
36:09
like a gamma ray burst or a supernova or
36:11
something like that. And the idea is that in
36:14
the very early universe, you've got these
36:15
incredibly high amounts of energy. And that
36:18
means that these photon fields, I think
36:21
they're called, can interact with
36:23
particles of matter. And, when you get this
36:26
interaction, that can lead to the production
36:28
of an incredibly high energy neutrino.
36:31
Now, the very high energy neutrino, as
36:34
we know, neutrinos, are, about the weakest
36:36
interacting things we know of. So
36:39
once you produce a very high energy neutrino
36:42
that can pass across the entire universe
36:44
without interacting with anything, we've got
36:47
millions of these things passing through our
36:48
bodies as we speak, and we just don't feel
36:50
them. Which incidentally, is why to detect
36:52
them, you want to be at the bottom of the
36:53
ocean or in a huge volume of water so that
36:56
you maximize the number of atoms available
36:58
for one of these to by chance collide with
37:00
and give you the light show. Because you need
37:02
a huge volume of water to get even one
37:04
neutrino to hit something and give you a
37:06
show, because they're that weakly
37:07
interacting.
37:07
Andrew Dunkley: Yeah.
37:08
Jonti Horner: Once you produce these cosmogenic neutrinos,
37:10
they then carry on through the universe
37:12
forevermore at ridiculously high energies.
37:15
Now, the bit I quite honestly don't
37:17
understand with this, and none of the things
37:19
I've read have been able to explain to me is
37:22
the fact that if this thing was
37:24
created with the cosmic microwave
37:27
background, I would have thought it should be
37:29
redshifted by the expansion of the universe
37:32
in the same way that photons are
37:35
the light we see it. And doing a bit of
37:37
reading around it does seem that neutrinos
37:39
can be gravitationally redshifted. So if you
37:41
get a neutrino produced at the surface of a
37:43
neutron star, that is one energy, by the
37:46
time it escapes from the neutron star's
37:48
gravity, it's lost energy and it's
37:49
effectively redshifted. What I haven't been
37:52
able to find out though is whether the
37:53
expansion of the universe would redshift
37:56
neutrinos and therefore lower their energy.
38:00
Now if the expansion of the
38:03
universe doesn't lower the energies then this
38:05
makes perfect sense. You know, you've got
38:07
this incredibly high energy neutrino that's
38:09
tied to how high the energies were when the
38:11
universe was young and it's only just reached
38:13
us now. If they are redshifted then
38:16
that makes this even more head scratchingly
38:18
awesome because if it has been
38:20
redshifted and its energy dropped by an
38:23
incredible amount and it's still 220peta
38:25
electron volts, what was its energy when it
38:28
was formed? And I just don't fully understand
38:30
that. So my knowledge is limited of this.
38:33
I've done my best to read around it and get
38:35
an understanding of what they think is going
38:37
on. But I guess what
38:40
comes out of this for me a, it's just a very
38:42
cool detection. But if you want to push
38:45
the boundaries of what we know and build
38:46
theories of how the universe works, our
38:49
theories will eventually go
38:52
beyond our level to observe the things that
38:54
they predict. A good example of this I always
38:57
go back to because it's my own wheelhouse, is
38:59
Newton's theories of gravitation which he
39:01
published in like in Principia Mathematica in
39:04
1680, 1682. Around then, and that
39:07
gave us mathematical tools that allowed us to
39:09
work how things moved in gravitational
39:11
fields, allowed us to work out orbits and
39:13
predict things in the future. And that's been
39:15
incredibly powerful. By the
39:17
1800s observations were
39:20
starting to show that the orbit of Mercury
39:23
was behaving slightly different to how
39:25
Newton's gravitation will predict it would
39:27
work. That effectively led to the precession
39:30
of Mercury's orbit, the wobble of the orbit
39:33
wobbling at a slightly different rate. And
39:35
nobody could explain that. It led to people
39:36
speculating that maybe there's an unseen
39:38
planet closer to the sun than Mercury.
39:40
Because we'd seen for the planet Uranus that
39:43
an unseen planet pulling it around could
39:44
change its orbit. And that was Neptune. But
39:46
that didn't work. We never found anything.
39:48
And it wasn't until Einstein came up with the
39:51
general theory of relativity that, as a
39:54
byproduct of that, his method for
39:56
understanding how gravity works accurately
39:59
Models the precession of Mercury's orbit With
40:01
incredible precision. So when Newton came up
40:03
with his ideas, the predictions you
40:06
would make with Newton's gravity Were so
40:09
accurate that it was only 150 years or so
40:11
before our observations got good enough to
40:13
show that Newton's theories were wrong. They
40:15
disproved those theories, but we still use
40:18
them because they are so accurate. They're
40:20
slightly off, but they're so accurate and
40:22
easy to use that they're easier for me to use
40:24
in my modeling than general relativity, when
40:27
the uncertainties in the things I model are
40:29
so great that the difference between those
40:31
two is lost in the noise. So it's just easier
40:33
for me to use Newton's laws. But it's a
40:35
really good example of how theory makes
40:38
predictions that are verified for a very long
40:39
time. But eventually you get to the point
40:42
where you go beyond what theory explains,
40:45
and that leads to new theories. And in this
40:47
case, it's a case where there are these set
40:48
of theories that, are very much at the
40:50
cutting edge of science, where the
40:53
predictions that they make are predictions of
40:55
things we have not yet seen. Because it's
40:57
fairly pointless to only predict the things
40:59
we have seen and not go beyond that. So they
41:01
predict things we haven't yet seen. One of
41:04
those things is the existence of cosmogenic
41:06
neutrinos. And, it may well be that this is
41:08
the first detection of a cosmogenic neutrino,
41:11
which then adds credence to the idea that
41:13
these quantum field theories work and make
41:15
sense. So it's that interplay between theory
41:18
and observation, an experiment that I think
41:20
is really interesting, Even if, to be honest,
41:23
I really don't understand it.
41:24
Andrew Dunkley: And what, Jonti is saying, Casey, is that
41:27
it'll be 150 years before someone comes up
41:30
with a model that actually explains it.
41:33
Possibly it could happen that way. You never
41:35
know. and thanks for the question. Casey and
41:38
I assumed female, but, looking at the
41:40
spelling of Casey could be male. Apologies if
41:43
I got that the wrong way around.
41:47
Jonti Horner: Roger, your lots are here. Also space nuts.
41:50
Andrew Dunkley: Our final question today comes from young
41:53
Henrik.
41:54
Jonti Horner: Hello, It's Henrique from Portugal again.
41:58
This time I'd like to ask about the
42:01
object NWC,
42:03
349A. What makes it so
42:06
extreme? How does it emit
42:08
lasers and lasers. Can you
42:11
explain to my dad what's masers are?
42:14
Thank you. Bye.
42:16
Andrew Dunkley: Thank you. Henrik. yes,
42:18
MWC349A.A for Apple
42:21
M, not eight. That's what I thought he said.
42:23
But yeah, this is ah, this is a,
42:26
a mysterious emission line star and
42:29
radio bright object in the constellation of
42:31
Cygnus.
42:32
Jonti Horner: Yes.
42:33
Andrew Dunkley: And it's it's, it's suffered an intensive
42:36
mass loss.
42:38
Jonti Horner: Yeah, it's a really interesting object. Now I
42:41
wasn't familiar with this object before the
42:43
question came in and it's probably something
42:44
that when I was Henrik's age, I'd have heard
42:47
of and come across and would have really
42:49
found fascinating, just like Henrik does.
42:51
It's fabulous question as best we
42:53
understand that this is something that is a
42:55
very luminous, very bright star,
42:59
much younger than the Sun. It's probably at
43:01
most 5 million years old. But it could either
43:03
be a baby star that's still forming
43:06
or a very massive star that's just coming to
43:08
the end of its life, even though it's only 5
43:10
million years old. And there's been a lot of
43:11
debate of that over the years. It
43:14
is famous and it's prominent because it's one
43:16
of the most bright things in the sky at
43:19
millimeter and radio wavelengths. It's very,
43:22
very bright, very obviously visible, even
43:23
though it's way too faint to see with the
43:25
naked eye. Part of the reason it's too faint
43:28
to see with the naked eye though, is that
43:29
there's a lot of dust and gas around both
43:32
where the object is. We found that it's got a
43:35
disk of dust and gas around it. Let's edge
43:37
onto us and is blocking some of the light.
43:39
Plus it's in the spiral arm of the Milky Way,
43:41
so there's a lot of dust and gas between us.
43:43
So this thing has an apparent magnitude of
43:45
about 13, but there are about 10
43:48
magnitudes of extinction along the line of
43:50
sight between us and it, which means that for
43:52
every 10,000 photons it emits, only one
43:54
reaches us. In other words, if you could
43:57
clear all the dust and gas out, this will be
43:59
a third magnitude star and easy to see with a
44:01
naked eye.
44:01
Andrew Dunkley: Right.
44:02
Jonti Horner: So that's intrinsically how luminous it is.
44:04
It's thought to be about 1300 parsecs away.
44:07
So that's 39004000 light years. So
44:10
the light we receive from it we're seeing it
44:12
how it was 4,000 years ago when that light
44:14
was emitted. And because it's so
44:17
luminous in radio wavelengths, it's been
44:19
fairly well studied. And in particular, it
44:22
gives off a lot of energy at, wavelengths
44:24
linked to molecular hydrogen. And it's known
44:27
as one of the few hydrogen masers that we see
44:30
in the sky. Which leads to Henrik's question
44:32
about what is a maser? The very
44:35
simple answer to that, which doesn't tell you
44:37
anything, is that a maser is a laser,
44:40
but happening at millimeter wavelengths. So
44:41
in the infrared, on radio. But it's the
44:44
same physical process. And in fact, masers
44:46
were what we developed before we could do
44:49
lasers, because lasers are the same
44:51
phenomenon happening at visible wavelengths
44:53
in the optical. That is a very accurate
44:55
description that tells you actually nothing
44:57
about what's going on. And I dug into this a
44:59
bit because like a lot of people, I use
45:01
lasers and think about them, but never really
45:04
remind myself how they work. Laser
45:06
stands for light activated.
45:10
Simulated Emission of radiation. Sorry,
45:13
Light Amplification by Simulated Emission of
45:15
radiation. It's an acronym. And MESA stands
45:18
for Microwave Amplification by Stimulated
45:20
Emission of Radiation. So it's the same
45:22
process just happening at longer wavelengths.
45:25
What's happening effectively is that when
45:28
atoms are excited, when energy is
45:31
pumped into atoms and that energy is
45:34
absorbed by them, it makes the electrons in
45:36
those atoms jump from one level to a higher
45:38
energy level. And they are very specific
45:41
jumps in energy. It can only jump by a
45:43
certain amount. It can't miss a gap. It's got
45:45
to get exactly the right jump to jump from
45:48
one level to the next. So those energy levels
45:51
have very specific wavelengths and we
45:52
actually calculate them at universities, part
45:54
of our undergrad quantum mechanics courses
45:56
and things like this. It's one of the tasks
45:57
you have is work out the energy levels of a
45:59
hydrogen atom and they are
46:02
quantized such that, when you're at an energy
46:04
level, if you want to jump down to another
46:05
one, you can only do that by emitting a
46:07
single photon. You can't emit multiple
46:10
photons that add up to that level. You can
46:12
only emit one photon. And you have to hit the
46:14
right energy level to get the gap.
46:17
And so that's why excited hydrogen glows at
46:20
very specific colors. So the photo behind me,
46:23
which won't be visible if you're listening to
46:24
this as a podcast, but the photo behind me
46:26
shows the Helix Nebula, which is a star
46:29
forming, sorry, the Trifid Nebula, which, is
46:32
a star forming region in the middle of It's a
46:34
very distinctive pink color. And that pink
46:36
color is hydrogen alpha emission, which,
46:39
which is hydrogen atoms jumping from the
46:41
third energy level to the second, emitting
46:43
light, and all emitting light of exactly the
46:45
same color. So that's known as
46:48
spontaneous emission. That's where the atom
46:50
sheds its energy by emitting light of a
46:52
certain color. Simulated emission is where
46:55
something happens to trigger that emission,
46:58
specifically at a specific time. So you've
47:01
got an atom, that is excited, is sat at a
47:03
higher energy level, and something gives it a
47:05
nudge and causes it to emit energy. And the
47:08
way that that works is that it absorbs a
47:10
photon of the same energy of the energy level
47:13
difference that it was going to emit anyway,
47:15
and then immediately emits two photons of
47:17
that energy. So you get one photon in and two
47:20
photons out. Two photons out can hit two
47:22
atoms and trigger them to emit, which means
47:25
you get four photons out and so on. So you
47:26
can get this cascade. So what makes it work
47:29
is that there are many ways of exciting the
47:31
atoms in the first place. They don't have to
47:33
just absorb photons. They can be excited
47:36
through magnet magnetic fields, or all sorts
47:37
of different things going on. And so a maser
47:40
is effectively somewhere where
47:43
emission is being stimulated by
47:45
incoming photons of a given wavelength, which
47:48
results in more photons being emitted of that
47:50
wavelength than are coming in. And so you get
47:53
this amplification effect. So in this
47:55
case, this being a hydrogen maser means that
47:57
you've got a lot of hydrogen gas there. That
48:00
hydrogen gas is being irradiated by emission
48:02
of a specific wavelength by this object.
48:05
and that is stimulating the emission of more
48:07
photons, which means you get an extremely
48:09
bright emission at that wavelength because
48:12
you're getting this amplification effect. And
48:14
so that's how these things works as a maser.
48:16
And that has been very useful in allowing us
48:18
to study it because it means we get a
48:20
stronger signal, we get more light, so
48:22
there's more we can study.
48:24
What my research around it this morning
48:27
kind of found out was that there is some
48:29
significant debate historically over whether
48:32
this is firstly a binary star, or on its own,
48:35
there's another very hot blue star very close
48:37
to it in the sky that for a long time was
48:39
thought to be a binary companion. And that's
48:42
why this is MWC349A,
48:45
because there's a star MWC349B.
48:48
Now, recent studies that have measured the
48:50
radial velocity of the two stars suggests
48:53
that the star B is moving 35
48:56
kilometers per second compared to star A. So
48:59
they're not gravitationally held together
49:00
anymore. So they're probably not now a
49:02
binary. Though there is some debate whether
49:06
they were in the past, whether they were held
49:08
together by gravity. And then those two stars
49:10
have shed mass. As we said, this star seems
49:12
to have thrown mass away in recent times, may
49:15
even have lost half its mass. It may have
49:17
gone from 40 solar masses to 20. That
49:19
weakens its gravitational pull until
49:21
eventually the binary falls apart. So that's
49:23
one part of the debate. But the recent
49:25
results seem to suggest that even if they
49:27
were a binary in the past, they no longer
49:29
are. The other debate is
49:32
whether this is a very young star that's only
49:34
just forming now. Or whether it's a star that
49:37
formed a few million years ago and is coming
49:39
to the end of its life. And, you'd have
49:41
thought that was obvious. But for stars like
49:43
this, it's quite hard to tell, especially
49:44
when they're so obscured by gas and dust.
49:47
Now, if it was a baby star, the really
49:50
odd part of that would be, why are there no
49:52
other baby stars around it? Stars kind of
49:54
form in big nurseries. And particularly
49:56
massive stars don't tend to form alone. They
49:59
tend to form in big associations where lots
50:01
of stars are forming at once. And there's one
50:04
relatively near this called Cygnus OB2.
50:07
And, one of the suggestions for this star, if
50:09
it's an older star that's coming to the end
50:11
of its life, is that it formed in that
50:13
association and was ejected in an encounter
50:15
with other stars and flung outwards. And,
50:17
we're seeing it quite far away because it's
50:18
traveled that distance through its lifetime.
50:21
So it formed there, but it's escaped.
50:23
If it's a baby star, we have the problem of
50:26
how is it only just forming in an area where
50:28
there's not really any other stars forming
50:29
around it. Recent studies have suggested,
50:32
by looking over all things, the balance
50:35
between carbon 13 and carbon 12, these two
50:38
different carbon isotopes in the gas that
50:41
has been shed by this star. Recent,
50:44
measurements of that have suggested it's
50:45
actually an old star. Well, old for its mass,
50:49
you know, about 5 million years old. But
50:50
coming to the end of its life, that has been
50:53
shedding mass. And, that is explained by the
50:55
balance of the isotopes in the gases that it
50:57
has emitted. Which fits in a bit better with
51:00
the idea that it may have formed in that
51:01
Cygnus LB2 association a few million years
51:04
ago, have been flung outwards and escaped.
51:06
Would also fit A little bit with the idea
51:08
that the star, B next to it, was once held
51:11
to it as a binary. But with the mass loss,
51:13
they've separated and they're going their
51:15
separate ways. You know, that happens all the
51:17
time. And so that all kind of, as a narrative
51:20
seems to fit together. But it's got a disk of
51:22
material around it that's nearly edge on.
51:24
It's got jets of material coming out of it.
51:26
There is a suggestion that it's probably shed
51:29
something like 20 times the mass of the sun
51:31
over the last few hundred thousand years.
51:33
And, that it's shedding something like
51:35
1/100,000th of a solar mass per year,
51:39
which doesn't sound like a lot, but that's a
51:41
huge amount of mass to be throwing away in
51:43
every given year, which means it would throw
51:45
away a mass equ, the mass of the sun in just
51:47
100,000 years. That's really significant
51:50
mass loss going on as this star comes to the
51:52
end of its life. And it's a really
51:54
interesting case study of that detective
51:57
story again, of how we gather clues from
52:00
all these different types of observations
52:02
about a star that for us, at optical
52:04
wavelengths is so heavily concealed from us
52:07
that only one part in 10,000 of the light it
52:09
emits actually reaches as the rest of it gets
52:11
absorbed en route. and that's why it's been
52:14
such a challenging problem for astronomy for
52:16
so many years, because it's really hard to
52:17
see what's going on. But by looking at the
52:20
masers emitting this light, by looking at all
52:23
the different things going on around it, by
52:24
doing clever studies of the chemistry of the
52:27
gases around it, we can start to piece
52:30
together its life story and figure out what
52:31
it is. I don't think that story of
52:34
discovery is finished yet, by any means. And
52:37
it may well be, Henrik, that when you're
52:38
older, you can actually work on this object
52:39
and learn more about it yourself. I suspect
52:41
people will still be discovering things about
52:44
this object in decades to come. But
52:46
it's a really fascinating object, and I'm
52:49
just so delighted that you brought it to my
52:50
attention because I'd never stumbled across
52:52
it before, and it's really, really cool.
52:53
Andrew Dunkley: Yes, it's, Sorry for this. It's amazing.
52:56
but, Henrik, thanks for the question, and you
52:59
do sound, very astute, and maybe, maybe you
53:01
will be the one that will solve it in years
53:04
to come. Lovely to hear from you. And if
53:06
you have questions for us, please send them
53:09
through. We can take, your questions on our
53:11
website. So, Space Nuts podcast.com spacenuts
53:14
IO click on that little AMA
53:17
link up the top and you can send us text
53:20
or audio questions or both. Some people have
53:22
done that. And don't forget to tell us who
53:25
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53:26
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53:29
parallel with the number of questions we need
53:32
each week. So, we haven't got a big stockpile
53:34
at the moment. So it's a good time to send
53:36
some questions into us. So please do. Would
53:39
love to hear from you. Don't even worry if
53:41
you think it's dumb, because there's no dumb
53:44
questions in astronomy and space science.
53:47
There's weird questions, but there aren't any
53:49
dumb questions. And, while you're on our
53:51
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54:12
None of it's mandatory. And, we appreciate
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all the support we get, so thank you. And
54:17
Jonti, thank you so much. it's been great to
54:19
talk to you and, we'll see you on the next
54:21
episode.
54:22
Jonti Horner: Yeah. Thank you for having me. It's good to
54:23
be back.
54:24
Andrew Dunkley: Always a pleasure. Jonti, Horner, professor
54:27
of Astrophysics at the University of Southern
54:29
Queensland. And, thanks to Huw in the studio
54:32
who, couldn't be with us today because
54:34
they're going to hate me for this one. He got
54:37
lost in a maser. Oh, dear. And from me,
54:40
Andrew Dunkley. Thanks for your company.
54:41
We'll see you on the next episode of Space
54:43
Nuts. Bye. Bye.
54:45
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