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SpaceX Tests Space-Ready Nuclear Power Using Tritium-Driven CubeSat · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Professor Fred Watson: Hi there.
0:00
Andrew Dunkley: Thanks again for joining us. This is Space
0:02
Nuts. My name is Andrew Dunkley and every
0:05
week we talk astronomy and space science
0:08
and we answer audience questions in our
0:10
alternative show, which, uh, happens,
0:13
um, well, wherever you are. I mean, we
0:16
release it on a Monday, but that doesn't mean
0:17
you listen to it on a Monday. Uh, coming up
0:20
today we've got, uh, a couple of
0:23
nuclear explosive storeys. Uh,
0:26
SpaceX is involved in one of those and
0:29
the other storey is about, uh, blowing things
0:31
up with atomic weapons from space.
0:34
Yes, highly guaranteed. Very, very, uh,
0:36
effective as well. Uh, but I think there's
0:39
probably a reason not to. We'll look at all
0:41
of that. Uh, we're also going to talk about
0:44
where Earth's, uh, dust came from. Quite a
0:47
bit of it, which might come as a bit of a
0:48
surprise. Uh, you just have to look under
0:50
just about every bed and kitchen table in the
0:53
world to find as much dust as there is in the
0:55
world. But we'll see where that, uh, is
0:58
headed. And our galaxy, uh, reaches
1:00
out further than we thought. Apparently, uh,
1:03
there's some interesting science behind that.
1:05
We'll talk about it all on this edition of
1:08
space nuts.
1:09
Professor Fred Watson: 15 seconds. Guidance is internal.
1:11
10, 9. Ignition
1:14
sequence start.
1:15
Professor Fred Watson: Space nuts.
1:16
Professor Fred Watson: 5, 4, 3, 2. 1, 2, 3, 4,
1:19
5, 5, 4, 3, 2, 1.
1:21
Andrew Dunkley: Space nuts.
1:22
Professor Fred Watson: Astronauts report it feels good.
1:25
Andrew Dunkley: And joining us again to talk about all of
1:27
that and more is Professor Fred Watson
1:29
Watson, astronomer at large. Hello,
1:31
Fred Watson.
1:32
Professor Fred Watson: Hello, Andrew. Good to see you. Good to see
1:34
you. Yes.
1:35
We sort of missed a few days, haven't we?
1:38
Yes.
1:40
Andrew Dunkley: Uh, you've been off conferencing.
1:41
Professor Fred Watson: Yes. So the annual science meeting,
1:44
as it's called, of the National Astronomy
1:47
Society, the Astronomical Society of
1:48
Australia, it's where all the professional
1:50
astronomers get together and, uh, talk about
1:53
what they've been doing, their research. Uh,
1:55
it was a big meeting. There were, I would
1:58
have guessed, maybe a couple of hundred
2:01
people there altogether. Uh, that's quite big
2:03
for astronomers in a country that's only got
2:05
700 astronomers in it.
2:07
Professor Fred Watson: Yeah.
2:08
Professor Fred Watson: Uh, but, um, what was interesting and
2:10
what was very, I think,
2:13
heartening for me was the number of
2:16
youngsters that were there. I call them
2:17
youngsters, you know, people under 50
2:20
people, um, the new generation of
2:23
astronomers, uh, most of them whom I didn't
2:26
know and they've no idea who I am, and that's
2:28
fine. Uh, that all was okay. It
2:31
just contrasts with a few years ago. So when
2:33
I was the astronomer in charge of the
2:35
observatory at, uh, Coonabarabran, uh,
2:39
we were kind of the Shopkeepers. So all these
2:41
astronomers used to come through, stay in the
2:43
lodge and do their research using the
2:45
telescope. So I knew a large fraction of
2:48
the astronomical population of Australia. But
2:50
that's changed, uh, because my job,
2:53
that job is no longer mine. Uh,
2:56
and so I don't see people the same way. But
2:59
it was very nice to meet a lot of new faces
3:02
and catch up with some very old faces as
3:04
well, some even older than mine. Um, and we
3:07
also discussed matters such as the future
3:10
of Australian astronomy because that's
3:12
uh, in a interesting
3:15
state at the moment. With the government
3:17
having declined, uh, to
3:20
engage in membership with the European
3:23
Southern Observatory. We are now working on
3:25
plan B. Uh, and um. Well, it looks
3:27
promising.
3:28
Andrew Dunkley: Yes, fingers crossed. A lot going on.
3:31
Okay, um, we should probably get
3:34
stuck into these storeys because there's a
3:36
lot to discuss. The first storey is a double
3:38
banger about nuclear, um, energy and
3:41
atomic weapons.
3:43
Uh, we'll start off with the storey about
3:45
SpaceX. And
3:48
um, they're looking at nuclear power
3:50
in space, nuclear powered satellites. What's
3:53
the storey here?
3:54
Professor Fred Watson: It's a test launch, really. A launch of
3:58
a cubesat basically that um,
4:01
has not a nuclear reactor inside but
4:04
um, basically a capsule of something called
4:07
tritium which is sometimes called heavy
4:09
hydrogen. It's hydrogen with two
4:11
electrons in it as well as the proton at uh,
4:14
its centre. And it's radioactive. Uh,
4:17
tritium is um, I suppose you'd call it
4:20
mildly radioactive. Um, we used to
4:22
use tritium standard lamps at the
4:25
observatory when I was working there, which
4:28
was a little capsule of tritium with some
4:30
phosphor on it. Um, and
4:33
um, basically the electrons released by the
4:36
tritium lit up the phosphor and
4:38
gave a very constant glow so we could use it
4:41
to calibrate other, other instruments.
4:44
So I've been close up and personal with um,
4:47
a little nuclear power source a bit like
4:49
that, but it was just making faint light.
4:52
This one is one that's been uh,
4:54
developed by a private company. Um,
4:57
and it's uh, basically a
5:00
company called City Labs, uh, in the United
5:03
States. Uh, they've built
5:05
um, a little, as I said, it's
5:08
effectively a cubesat which has this um,
5:11
little nuclear, not nuclear
5:14
reactor, but nuclear power source inside a
5:16
tritium, uh, source that I've just been
5:19
talking about, which doesn't actually convert
5:21
the electrons into light, it
5:24
converts them directly into electricity.
5:27
So they've got these panels on the side of it
5:30
that take the electrons that come from the
5:32
tritium and turn them straight into
5:35
um, electricity. Ah, it's
5:38
Called Bohr B O H R, uh, which is
5:40
a bit of a play on words because Niels Bohr
5:43
was one of the great founders of quantum
5:45
theory. Same spelling, um
5:48
Danish one, A uh, Danish uh
5:50
scientist, uh and it stands for
5:53
Beta Voltaic. And a
5:55
Beta Voltaic is taking the beta particles,
5:58
which are otherwise known as electrons, uh
6:01
turning them into electricity. So it's Beta
6:03
Voltaic orbital high reliability
6:06
spacecraft. That's where you get the Bohr
6:08
from and it's been launched. Uh,
6:11
so SpaceX's part in this storey is just to
6:14
provide the taxi, uh up into um, up
6:17
into orbit. It's a transporter, uh
6:19
mission, um, basically
6:22
one of uh, SpaceX's taxi rides to get stuff
6:25
up and down from uh, or up to orbit,
6:28
coming down to different storey and most of
6:30
them just burn up.
6:32
Professor Fred Watson: Yes.
6:32
Professor Fred Watson: Uh, but it is uh, probably the
6:34
first CubeSat to include a nuclear
6:37
power system. Uh and
6:40
maybe, just maybe we'll sort of illuminate
6:43
the way for a new generation of uh,
6:46
spacecraft which are equipped with uh,
6:48
these nuclear power sources.
6:50
Andrew Dunkley: I suppose they have to look at alternatives
6:53
because we've been reliant, fairly
6:55
reliant anyway on solar energy in
6:58
space, um particularly with our uh, orbiting
7:01
satellites, but also with um, the
7:04
International Space Station and others. Um,
7:07
but the time will come where we are
7:10
in places where there won't be that
7:13
much sunlight and
7:16
in some places there won't be any at all. And
7:18
solar panels are going to be useless.
7:21
Professor Fred Watson: Uh, that's correct. And we've seen already
7:23
um, the use of these UH RTGs,
7:26
radioisotope thermoelectric
7:29
generators, uh which are carried by both
7:32
the Curiosity and the uh
7:34
Perseverance rovers, uh as well as
7:37
spacecraft in deep space like uh,
7:40
Voyager 1, Voyager 2, Pioneers. I think
7:43
they've got them as well. And these are
7:45
spacecraft that are so far from the sun that
7:47
you get very little light from the sun,
7:50
uh in terms of um, you know, using it to
7:52
generate electricity. So they've, they've had
7:54
their nuclear power sources for a long time.
7:57
They are quite different though from what
7:58
we're talking about here. There are, I think
8:00
it's 13 kilogrammes if I remember rightly, is
8:02
the amount in a canister of plutonium
8:05
dioxide, uh which is
8:07
decaying all the time and getting very hot as
8:10
it does that and that heat is then used
8:13
to generate electricity, uh and
8:17
it actually dies away as time goes on. So
8:19
these nuclear uh, RTGs, the
8:22
radioisotope thermoelectric generators
8:25
gradually lose their power, um, and that's
8:28
why we hear from time to time and we usually
8:30
report this on space nuts. We hear of
8:33
uh, uh instruments on board Voyager 1
8:36
being turned off to save the power.
8:39
Andrew Dunkley: Yeah. And that happened again not so long
8:42
ago.
8:42
Professor Fred Watson: I think that's correct. Yes it did.
8:45
There was one turned off uh quite recently
8:47
but perhaps more to the point and
8:50
uh, what you've just said about there being
8:52
some places that have no sunlight whatsoever,
8:54
uh that applies to uh, those deep
8:57
craters near the moon's south pole
9:00
and that's where we're thinking of exploring.
9:03
So it may be that um, these
9:06
beta voltaic arrays
9:09
uh uh, or devices might well
9:12
be the future of power generation
9:15
near the moon's south pole because you're in
9:17
places where there's no light whatsoever from
9:20
the sun.
9:20
Andrew Dunkley: That's absolutely true. Darn cold too. It is.
9:23
Professor Fred Watson: It is always cold there. Yes, yes
9:26
indeed.
9:27
Andrew Dunkley: Uh, uh that's a really interesting storey and
9:30
we're obviously in the early phases of
9:32
finding these alternatives. Is um, tritium
9:35
safe?
9:36
Professor Fred Watson: Uh, it's probably something regarded
9:39
uh, treated carefully.
9:43
It is generally safe. I mean we never took
9:46
any real precautions with the device that we
9:48
had on the telescope. Maybe we should
9:51
have done. Although uh, most of
9:54
us are still around and in fairly good
9:56
health. But um, yes they are
9:59
releasing electrons, uh beta radiation,
10:02
uh, it's um, uh if you had a
10:05
high level though of tritium, if you had a
10:08
significant amount of it then you would have
10:10
to be careful about how you handled it and
10:12
where it was put and if it needed shielding
10:14
and things of that sort.
10:15
Andrew Dunkley: Yeah. So uh, don't sprinkle it on your
10:17
cornflakes or anything like that.
10:18
Professor Fred Watson: Yes, that's right. It's best to avoid it if
10:20
you can.
10:21
Andrew Dunkley: Yeah. Sugar's damaging enough already.
10:25
Professor Fred Watson: It is. Tell my dentist about it.
10:27
Andrew Dunkley: If you'd like to um, read up on that storey
10:30
about the uh, the launch of the cubesat with
10:32
the tritium nuclear ah power device
10:35
they're testing. Uh you can read about
10:37
it@dailygalaxy.com.
10:41
um, let's keep on this theme
10:43
Fred Watson, because that's the good news.
10:45
Uh the bad news is um,
10:49
the the problem of exploding nuclear
10:51
devices in space or firing nuclear
10:54
devices from space to targets on Earth.
10:56
That's, that's a real issue. I know.
10:59
Um, was it back in the 80s the
11:02
Star wars um
11:05
um push was uh, all the rage in the news
11:08
at the time and uh, that got shut down pretty
11:10
quickly.
11:12
Professor Fred Watson: Star wars was um, a
11:14
Reagan era initiative. Yes, I think it was, I
11:17
think it was um, uh basically
11:20
electromagnetic Radiation to zap your
11:22
satellites. It wasn't nuclear though, uh,
11:24
because nuclear weapons are in space, are
11:27
prohibited by the outer Space Treaty
11:30
1967.
11:31
Andrew Dunkley: So what's happening?
11:32
Professor Fred Watson: They're not allowed. But,
11:35
um, there may be some there
11:38
launched by powers that
11:42
stretch um, the envelope, if I can put it
11:44
that way. Governments that stretch the
11:46
envelope. And uh, we don't know. We don't
11:49
know if there are any. You know, they're
11:51
banned by the uh, Outer Space Treaty. So
11:54
there shouldn't be any nuclear weapons in
11:57
space. But that's all very well.
12:00
Professor Fred Watson: Um.
12:01
Professor Fred Watson: There's a lot of things that shouldn't happen
12:03
but do happen. And um. So it may be
12:05
that perhaps there are nuclear weapons in
12:07
space. So the question is,
12:11
um, how do you detect them if there are,
12:13
ah, these weapons? Um,
12:16
and um, that's
12:20
where this piece of research, uh, from
12:23
the Massachusetts Institute of Technology
12:26
has come from. It's um, a um, person
12:29
whose name is Areg Dana
12:31
Gulian. Sounds uh, like an Armenian name.
12:34
Does that usually I a n on the end. Armenian.
12:37
An associate professor of nuclear science and
12:39
engineering at the Massachusetts Institute of
12:42
Technology. And he has
12:45
um, essentially
12:47
thought of a neat way,
12:52
uh, of building a device that
12:55
you could fly in the vicinity
12:58
of a satellite to detect whether
13:01
it is carrying nuclear weapons.
13:04
Um, and it's all about the subatomic
13:07
particles, uh, that um, you know,
13:10
that, that nuclear um,
13:13
weapons are all about. It's all about uh,
13:16
neutrons and uh, you know, the nuclear
13:18
nuclei of atoms. That's where it all comes
13:20
from. Um, so
13:25
what he has suggested, and I might
13:27
quote, um,
13:30
I might quote from uh, Dr. Dana
13:33
Gulian's work. Uh
13:36
the risk is that
13:39
if you did explode a nuclear weapon in
13:42
low Earth orbit, then you basically wreck low
13:45
Earth orbit for everybody. It's not the
13:47
blast, it's just the subatomic particles that
13:50
do it. Uh, and so what he goes on to say
13:53
is this danger is compounded by the lack
13:56
of a verification mechanism for the Outer
13:58
Space Treaty. Um,
14:01
there's no detection methodologies that have
14:04
been proposed in the scientific literature.
14:06
So what he's saying is here's a concept and
14:09
feasibility study, um, for
14:11
verifying a satellite's compliance
14:14
to the Outer Space Treaty by observing
14:17
the neutrons induced by spallation
14:20
from the approximately
14:23
giga electron volt protons in the
14:26
Innovant Allen radiation belts, which is
14:28
a slightly complicated and technical way of
14:31
saying, uh, you've already got subatomic
14:34
particles in the radiation belts around
14:37
our planet. Um, if you can,
14:41
um, basically watch the way,
14:44
um, a satellite responds
14:47
to those protons that are in the radiation
14:50
belts. Um, if for example that uh,
14:53
bombardment of protons from the radiation
14:55
belts causes neutron neutrons to be
14:58
uh, emitted then you can
15:01
have a fair degree of
15:04
um, confidence that there might be a nuclear
15:06
weapon on board or a lot of nuclear fissile
15:08
material, heavy elements like uranium.
15:11
That's the kind of thing that this is all
15:14
about. And so um,
15:18
uh, what this is all
15:21
about is building uh, a
15:23
satellite that can detect
15:26
uh, neutrons uh, coming
15:29
from radioactive material. And
15:33
he's basically suggesting a
15:35
detector, uh, uh, uh, what
15:38
he calls an inspector satellite that flies
15:41
by, uh, the satellite that you're
15:44
interested in finding out whether it's got
15:46
nuclear weapons. And it's got these detectors
15:49
uh, which are almost like X ray detectors.
15:51
The kind of things that you see now when you
15:54
go for an X ray, a chest X ray. They're
15:56
electronic, they're not photograph they used
15:58
to be back in the day. Um, and they've got
16:01
what are called neutron sensors, uh they're
16:03
called scintillators. And uh, you
16:06
put those in a special arrangement with
16:09
other basically other detectors.
16:12
Uh, and um, if you do that then
16:15
you can apparently sort out the
16:18
neutrons from the other natural
16:21
subatomic particles that are floating around
16:23
near the radiation belts. And the neutrons
16:26
come from radioactive material and you can
16:28
also see the direct direction that they're
16:30
coming from. So you can sort of point this
16:33
thing towards your target satellite, uh, the
16:35
one that you suspect might have nuclear
16:37
weapons and it will give you the direction of
16:39
where it's coming from. Um, and
16:42
so uh, just a quote,
16:45
um again from Dr. Dana
16:48
Gulian. Um, the calculations show
16:51
that a nine unit cubesat size
16:54
detection platform, that's something the size
16:56
of, what's that, about three loaves of bread?
16:58
Something of that sort size. It's quite
17:00
small. Um, it can identify a
17:03
thermonuclear weapon from a distance of
17:06
four kilometres in approximately one
17:09
week of observation. Now that's quite a long
17:12
time but uh, apparently
17:15
if you could get it to within one kilometre
17:17
it would take you about an hour to detect a
17:20
weapon. And that's
17:23
promising. That's one flyby, that's you know,
17:26
an hour of proximity, uh, you could do that
17:29
as you go past the
17:32
suspect satell. If you got an hour in
17:35
close uh, contact with it or close uh,
17:38
proximity to it within a
17:40
kilometre, uh, then you might well
17:43
detect a nuclear weapon on board. And of
17:45
course you could improve that if you had more
17:47
than one of these inspector satellites. If
17:49
you multiplied them up, then you could get,
17:51
uh, quite significant improvements in that
17:53
performance. So it's really quite
17:56
interesting. Um, uh, one
17:58
quote that I really liked, um,
18:02
and I'm going to read, uh,
18:04
from, uh. Universe Today has a very nice
18:07
article on this. The last sentence is, right
18:09
now, nations like the USA and Russia rely on
18:12
intelligence to know what the other is doing.
18:14
And as we know from history, intelligence can
18:17
get things wrong. You can fake intelligence,
18:20
said Dr. Dana Gulian, but you can't fake
18:23
physics. I like that. Yeah, it's true. So
18:26
you could do it by physics. Yeah.
18:28
Andrew Dunkley: They do, uh, mention in this particular
18:31
article that there's one suspect satellite
18:33
that seems to have been launched by Russia.
18:35
And the bottom line is that it's
18:38
been put in an orbit that is very strange
18:42
and very hostile in terms
18:45
of its radiation, uh, in that area.
18:47
And the question is asked. Well, it says no
18:50
one puts satellites there because it's highly
18:52
radioactive. Why would you put a satellite in
18:55
that orbit? So that's one they've already.
18:58
They haven't identified as maybe carrying a
19:01
nuclear weapon, but they've certainly
19:03
identified it as suspicious.
19:05
Professor Fred Watson: Yes, that's correct. And so, um.
19:08
Yes, highlighting that, I think, you know,
19:10
puts this article in context. It
19:12
tells you that this is a real issue and, um,
19:14
we kind of need to work on how you might
19:17
detect, uh, nuclear weapons in space.
19:19
Andrew Dunkley: Of course, the other side of it is if you do
19:22
identify a satellite that's carrying a
19:24
nuclear weapon, what do you do next?
19:27
It's like trying to teach people not to
19:29
overtake emerging lanes, isn't it?
19:31
Professor Fred Watson: Uh, yes. Uh, but,
19:34
uh, it's worse than that really, because. A
19:37
little bit, yeah, you know, we have
19:39
nations that completely disregard
19:41
international law. They invade other
19:44
countries without so much as a,
19:47
you know, a sniff of the,
19:50
um, um. Of the, um.
19:53
All the international treaties, they just,
19:55
Just run amok among them and away they go.
19:58
Uh, and yes, so that's the possibility that,
20:01
uh, we might already have them.
20:02
There is a kind of
20:05
corollary of this which I was thinking of
20:07
when I read this, Storey. Um, and
20:10
that is that back in the 70s,
20:13
uh, gamma ray
20:16
satellites were launched,
20:18
satellites that detect gamma radiation. And
20:21
that was to detect any in
20:23
atmosphere nuclear tests, uh, conducted on,
20:27
uh. Because there was a test ban treaty that
20:29
was signed, uh, all the signatories
20:32
said, no, we won't test nuclear, uh, weapons
20:34
in the atmosphere. Uh, but they had to
20:37
verify it. And so the verification process
20:40
involved, uh, a number of satellites being
20:42
launched that could detect gamma rays which
20:44
would be emitted by a nuclear bomb being
20:46
detonated in the atmosphere. Uh,
20:49
now none were. But those
20:52
satellites are what detected gamma ray
20:54
bursts. These um, you know, fascinating
20:57
pulses of radiation that come from, uh, from
21:00
explosions deep in space. Yeah, of course,
21:03
man made explosions, but natural ones. Yes.
21:05
Andrew Dunkley: Because if they do start detecting nuclear,
21:08
uh, weapons in space, then the
21:11
parties involved, uh, they won't say, oh,
21:14
sorry, sorry, we'll take them all down.
21:16
They'll find ways of hiding them.
21:18
Professor Fred Watson: Probably. Yes, that's probably right.
21:21
Andrew Dunkley: Gosh, it's tough, isn't it?
21:23
Professor Fred Watson: Uh, tough world we live in.
21:24
Andrew Dunkley: Indeed. Uh, and beyond it in some
21:27
respects. Uh, you can read that
21:29
storey@universetoday.com. this
21:32
is space Nuts with Andrew Dunkley and
21:34
Professor Fred Watson Watson.
21:40
Space Nuts.
21:42
Uh, next storey, Fred Watson, uh, is
21:45
looking at, uh, all the dust on Earth
21:48
and where it might have come from. Now I was
21:50
thinking cats because
21:53
they do shed. Uh, but it's uh, a bit
21:56
more involved than that. And what
21:59
is really interesting about this storey is
22:01
they think a heck of a lot of it came from
22:04
one source.
22:07
Professor Fred Watson: That's right. And it's a mysterious one as
22:09
well. Um, so this is
22:12
quite a nice storey, uh, from publishing, uh,
22:15
Science Adventures. Um, it's
22:18
about, uh, the
22:20
micrometeorites that bombard the Earth.
22:24
And it's a bit surprising, this
22:27
stuff. Uh, you know, we think of meteorites
22:29
as big chunks of rock that come through the
22:32
atmosphere, they have a blaze of glory and
22:34
then land on the Earth somewhere. And
22:38
what we've got there is um, a
22:41
free sample of extraterrestrial
22:43
material. But there are also these
22:46
micrometeorites which rain on the Earth's
22:48
atmosphere and they're dust particles, as
22:50
you've kind of hinted. Uh,
22:53
um, and they're sort of always
22:56
falling on Earth. Uh, and that,
22:59
uh, is again, it's a free gift from space.
23:03
Um, I think. So I was sort of
23:06
vaguely involved with this stuff probably 50
23:09
years ago, back in the 70s. I think they
23:12
were then called Brownlee particles. Um.
23:14
Oh, that sounds familiar. We're talking
23:16
about. Yeah. Uh, but they're now,
23:19
I think, called cosmic spherules. Uh, I
23:21
should cheque whether Brownlee particles and
23:24
cosmic spherules are the same thing, but
23:26
basically what they are
23:29
is bits of meteor that have
23:33
melted as they come down through the
23:35
Earth's atmosphere, but
23:38
they actually survive into the inner
23:40
atmosphere and they cool down and they form a
23:43
little sphere because the um, basically the
23:46
surface tension of molten material brings
23:48
them into a sphere. Uh, and that
23:51
uh, is the storey so far
23:54
because that um, heating
23:57
that you, that they experience as
24:00
the sort of parent Body, the meteor. Meteor
24:03
or meteorite, as it comes through the
24:04
atmosphere, it, um,
24:07
kind of destroys their chemical
24:10
structure, you know, the minerals in it. It
24:12
get metamorphosed, they get changed because
24:15
they've been subject to very high
24:16
temperatures. Um, but there is
24:19
a technique, uh, that allows you
24:22
to look at, uh, some
24:25
of the characteristics of these
24:27
objects that is not destroyed by
24:30
heat. And it's the oxygen
24:33
isotope signature, uh, which we've
24:36
talked about before. We've talked about
24:38
isotopes and how they, uh, you know, how we
24:40
distinguish between heavy water and normal
24:42
water and all of that sort, sort of thing.
24:45
That's. So it's basically the. The number of,
24:47
uh, neutrons in an atom. Um,
24:51
so you've got these oxygen
24:53
signatures, uh, that,
24:56
um, essentially, uh, let you,
24:59
ah, group these cosmic
25:02
spherules, the Brownlee particles, if that's
25:05
what they are. Um, and it turns out
25:08
that so, so people do, you know, they do
25:10
population census statistics on these objects
25:13
to find out, uh, what
25:16
relationships they bear with one another.
25:19
About 10% of them of these
25:22
ferals that have been identified and
25:24
analysed collect in a group
25:27
that has got the wonderful name of Group
25:30
four, uh, which presumably means
25:33
there's another three as well. Yeah. Um,
25:36
and it's, uh, the. Again, what
25:39
makes them stand out in this group is the
25:42
oxygen isotope signature that I just
25:45
mentioned before. It's depleted in, uh, an
25:48
isotope called oxygen 16.
25:51
But here's where the storey gets very
25:54
interesting because, um,
25:57
no known meteorites have
26:00
that same oxygen isotope signature.
26:03
And you'd expect, uh, if these
26:06
things were common, that there would be
26:09
meteorites, uh, that match them in their
26:12
composition. Uh, and often with
26:15
meteorites we can get an idea where they've
26:17
come from. Uh, most of them come from the
26:19
asteroid belt from collisions between
26:21
asteroids. Uh, so, uh,
26:24
um, that is a bit mysterious
26:27
that we've got these subatomic, sorry, these
26:31
small spherules of material that have come
26:34
down through the atmosphere, uh, and got that
26:36
globular shape. Um, it's
26:40
mysterious that we don't know. We don't see
26:42
any meteorites that match their
26:45
composition.
26:46
Andrew Dunkley: Weird.
26:47
Professor Fred Watson: It is weird, yes. Uh, and so what
26:50
they're suggesting is that, um,
26:53
it's basically something that
26:55
comes from an asteroid, uh,
26:58
whose characteristics are unusual, uh,
27:01
that we have not, uh, yet, um,
27:03
identified it.
27:06
Andrew Dunkley: Wow. Okay, so we're
27:09
still looking.
27:10
Professor Fred Watson: We're still looking. There's a sort of sub
27:12
mystery as well because, um,
27:17
a detailed analysis of this, you can break
27:19
that Group 4 stuff down into other smaller
27:22
groups. And, uh, some of them
27:25
Basically show signs of having had two
27:28
different, uh, minerals in
27:31
them before they entered the Earth's
27:33
atmosphere. And, um,
27:36
one would be typical of,
27:39
uh, well known types of asteroids. And the
27:42
other, as I said, doesn't correspond to any
27:44
kind of known, um, group of, uh,
27:49
um, cosmic spherules or meteorites.
27:52
Uh, and it's really quite
27:54
remarkable that this, you know, we're being
27:57
bombarded by dust particles that come from
27:59
somewhere which we haven't identified.
28:02
Professor Fred Watson: Yeah.
28:02
Andrew Dunkley: Wow. Um, could that mean they're from
28:05
beyond our system or it's just a part of the
28:08
system that we.
28:11
Professor Fred Watson: I think it's.
28:11
Andrew Dunkley: I don't know.
28:13
Professor Fred Watson: Yeah, I think it's the other way around. Um,
28:15
because the m. The team who've done the
28:18
research on this, a very, very thorough piece
28:19
of research, they've basically,
28:23
um, as you would, you've used, uh,
28:25
simulations, computer simulations
28:28
to, to essentially work out
28:31
what conditions these things formed in when
28:33
they, um, melted coming through the Earth's
28:36
atmosphere. And it suggested that the best
28:39
fit they get to what they see, the sort of
28:42
textures that are in the material fit
28:45
with relatively low
28:47
velocities, uh, 14 to 17 kilometres
28:50
per second. Uh, which is
28:53
pretty speedy when you think of it on Earth.
28:55
But, um, uh, in space, that's a
28:58
fairly modest, uh, space speed for a
29:00
meteorite that typically will be more like 30
29:03
kilometres per second. And so that
29:05
low value, uh, suggests
29:08
that possibly those
29:11
particles originated in near
29:13
Earth asteroids, um, ones
29:16
that are, um, following a similar path
29:19
through space to the Earth. And that
29:22
might mean that we've got some sort of,
29:26
um, in the Earth's environment, some
29:28
sort of unusual asteroid
29:31
that is not, not matched by all the ones that
29:34
we know already.
29:35
Professor Fred Watson: Wow.
29:35
Andrew Dunkley: That'd be something, uh, that's probably
29:37
gonna be hard to track down though.
29:39
Professor Fred Watson: Yes, yes, that's probably right. And
29:41
especially since it might not exist anymore,
29:43
it may have collided and formed little bits
29:45
that have basically rained down on the Earth.
29:47
Andrew Dunkley: Yeah. Now, it wasn't Thea. Rusty just.
29:51
Professor Fred Watson: No, it wasn't Thea. That's right. Yeah.
29:52
Thanks, Rusty. It's not Thea.
29:55
Andrew Dunkley: Um, for the record, Brownlee particles and
29:57
cosmic spherules are closely related, but
29:59
they are not exactly the same thing.
30:01
Professor Fred Watson: Okay.
30:02
Andrew Dunkley: They represent two different ages or types
30:05
of micrometeorites.
30:07
Professor Fred Watson: There you go. Thank you for checking that.
30:10
Yes, that's all right.
30:11
Andrew Dunkley: Um, yeah, they're very close, but they're
30:13
not, not the same.
30:14
Professor Fred Watson: So I was on the right track.
30:15
Andrew Dunkley: You were, yes.
30:17
And you can read all about that at, uh,
30:20
the AstroDailyPod Galaxy website. Um, and
30:23
the article Was published where,
30:25
Fred Watson, I've lost the science advances.
30:29
That's right, yes. Want to read the whole
30:31
thing before bed so you sleep well?
30:34
Professor Fred Watson: Yep.
30:35
Professor Fred Watson: Yeah.
30:35
Andrew Dunkley: This is Space Nuts with Andrew Dunkley and
30:37
Professor Fred Watson Watson.
30:40
Professor Fred Watson: We choose to go to the moon in this decade
30:43
and do the other things, not because they are
30:46
easy, but because they are hard, these nuts.
30:50
Andrew Dunkley: Our, ah, final storey today takes us
30:53
to the edge of our galaxy. Well, it takes us
30:56
from the centre of our galaxy right out to
30:58
the edge of our galaxy because we're talking
30:59
about the whole thing lock, stock and barrel.
31:02
And it appears, Fred Watson, with some very
31:04
clever scientific brains in action,
31:07
that, uh, our galaxy stretches out further
31:10
than we thought.
31:13
Professor Fred Watson: Uh, it does. It looks as though the spiral
31:15
arms are longer than we thought they were.
31:18
And I think this is a very nice piece of
31:21
work, uh, as, uh, I hinted before,
31:24
uh, partly because it uses a technique that I
31:27
think is really extraordinary. It's a very
31:29
powerful technique, uh, using what we call
31:31
light echoes. Um,
31:35
so the storey, basically, to set this in
31:37
context, it's very hard for us to
31:40
produce a map of what our own galaxy looks
31:42
like. And that's because we're embedded in
31:45
one of the spiral arms. Uh, the
31:48
stars that we see when we look at the Milky
31:50
Way. They're stars that, uh, fellow
31:53
travellers in the spiral arms with our, uh,
31:55
sun and solar system. But they only go out to
31:57
1000 light years or so because the spiral
32:00
arms are so dusty that you can't really
32:02
penetrate much beyond that. Um,
32:05
and if you were relying only on visible
32:07
light, uh, it would be
32:10
like trying to draw a map
32:13
of the whole of Dubbo from
32:16
standing outside Dubbo jail there on, um,
32:20
uh, forgotten. Is that Macquarie Street?
32:22
Andrew Dunkley: Macquarie street, yeah.
32:23
Professor Fred Watson: Yes, yes.
32:24
Andrew Dunkley: Oh, for the record, they're putting a, um,
32:27
they've taken down the public building in
32:28
front of the old Dubbo jail.
32:30
Professor Fred Watson: Oh, there you go.
32:30
Andrew Dunkley: Now they're turning it into a public
32:33
common. Common.
32:35
Professor Fred Watson: I, uh, like that idea.
32:36
Andrew Dunkley: That's going to look very nice when it's
32:38
done.
32:39
Professor Fred Watson: So that would improve your view of the city
32:41
of Dubbo, but it still might not let you make
32:43
a map of Dubbo from just there. Uh,
32:46
and that's how we are in our galaxy. If
32:48
you're relying on visible light observations,
32:52
uh, all you're seeing when you look
32:55
is the neighbourhood of, uh, our
32:57
spiral arm, a local spiral arm. You don't get
32:59
any hint or inclination of the structure of
33:02
the galaxy, uh, beyond that. And in
33:05
particular, you know, if we see
33:08
a thousand light years or so, there's another
33:11
Hundred thousand that we're not seeing
33:12
because that's about the diameter of, ah, our
33:14
galaxy. So, um, ah, the
33:17
situation improves when you use infrared, uh,
33:20
radiation. You can sort of penetrate, uh,
33:23
through the dust and see actually the centre,
33:25
towards the centre of our galaxy. That's how
33:27
we know about the black hole in the centre of
33:30
our galaxy, because we could see stars
33:31
orbiting around it. Um, but
33:34
it improves even more on a broader scale if
33:37
you can use radio telescopes, because you can
33:39
plot, um, where the clouds of
33:42
hydrogen gas called hydrogen, uh, which
33:45
radiates in, uh, radio waves, uh, with a
33:48
wavelength of 21 centimetres, uh, that you
33:51
can plot out. But if you're going to try and
33:53
draw a map, you do need to do some modelling
33:55
with that. You've got to assume things about
33:57
the rotation of the galaxy so it doesn't just
33:59
give you a direct map, map. And that could
34:02
be wrong. We could have that little bit of it
34:04
wrong, uh, you know, uh, the stuff that comes
34:07
from the radio observations. So
34:10
what's happened now is it's a
34:13
team, uh, I think they're based in Italy,
34:16
uh, and what they've done
34:19
is used, um,
34:23
a direct method of kind of
34:26
setting up a standard ruler. Uh, because if
34:29
you've got a standard ruler and you can see
34:30
it in deep space, then you know how far away
34:32
it is because you can measure how long it
34:34
appears to be. And if you know how long it
34:37
is, which is what a standard ruler is, then
34:39
you know how far away it is. And that's
34:42
what they're doing. They have. And it goes
34:45
back to something we mentioned earlier in the
34:47
show, gamma ray bursts. These bursts of gamma
34:49
radiation, those
34:52
bursts, uh, don't just directly come to
34:55
us, they also bounce off or are
34:57
reflected by clouds of dust in our
35:00
spiral arms. And, uh, so
35:04
by timing how long,
35:07
uh, it takes for these echoes, as
35:10
they're called, light echoes, even though
35:12
it's gamma radiation, uh, to what
35:15
the delay is between a light
35:18
echo and the, uh, source itself,
35:21
which is the gamma ray burst, I should say
35:22
they probably come from collapsing
35:25
massive stars or merger of neutron
35:27
stars, uh, very energetic events
35:31
because they're bright in gamma radiation.
35:33
But if you look at a light echo from a gamma
35:36
ray burst, it gives you a scale to this,
35:39
you know, um, how far.
35:42
Basically, uh, it gives you a standard ruler,
35:44
um, because you can time it accurately, you
35:47
know that 300,000 kilometres per second is
35:50
the speed of gamma rays through space. And,
35:52
you know, if you know how far away it's gone
35:54
in that time, then that gives you a distance
35:56
measure. So you've got a standard ruler. Uh,
35:59
it's a very, very nice way of doing this.
36:01
And, um, using that, uh, these,
36:04
uh, scientists, um, as I
36:07
said, uh, at least the lead author is, uh,
36:10
certainly in Italy at ENAF in Milano,
36:13
uh, uh, they've done this work
36:16
looking at these gamma ray bursts with their
36:18
light echoes, and that allows them to
36:20
calculate basically the size of our, uh,
36:23
spiral arms without relying on any kind of
36:26
modelling. And so
36:28
they think that the new
36:31
observations indicate that, uh, our spiral
36:34
arms are something like 10%
36:37
longer than we thought they were. Wow,
36:39
that's, uh.
36:39
Professor Fred Watson: A lot.
36:40
Professor Fred Watson: Yes. That's significant, isn't it? It's
36:42
really, um. You know, this is. As I said,
36:45
this is very nice, uh, nice astronomy.
36:48
Andrew Dunkley: It is indeed. Yeah. Um, of
36:50
course, as you say, we can't really look at
36:53
our galaxy. We don't know exactly what it
36:55
looks like. Um, there's a lot of science that
36:57
they've put together to try and create
37:00
the image of it. And even in this particular
37:03
storey, uh, which is in the Universe Today
37:05
dot com, they've got an artist's impression
37:07
of what this new, uh, look is like.
37:10
Professor Fred Watson: Yes. That's all you can do.
37:11
Andrew Dunkley: Reminds me of an upside down snail.
37:15
Professor Fred Watson: It does, yes, that's right. I see what you
37:18
mean. Yes, yes.
37:22
Andrew Dunkley: Or a squid. Could be a squid.
37:24
Professor Fred Watson: Could be a squid, yeah.
37:26
Andrew Dunkley: Uh, but in real terms we just have
37:29
to. It's an edge. Very, very educated
37:32
guess, I suppose.
37:33
Professor Fred Watson: Um, yes, it is. It's a measurement.
37:37
So you're right,
37:40
it's an artist's impression. That's really
37:41
the only way we can depict the Milky Way.
37:43
Some of the depictions are very, very good
37:45
and they rely on the very best radio and
37:47
infrared observations that have been made.
37:50
But this is going to modify it a little bit
37:52
by our new knowledge of the spiral arms. And
37:55
I should say, um, this, the, um.
37:58
It's the Chandra satellite, uh, which is a,
38:01
ah, an X ray observatory, um,
38:04
by. Operated by NASA, uh,
38:07
that has been used to make the measurements.
38:10
And I do like the headline on a little, uh,
38:13
NASA video that there is Here, which is
38:15
NASA's Chandra examines Milky Way at
38:17
Arm's Length.
38:18
Andrew Dunkley: Yeah, nice. Um, very
38:21
well done.
38:22
Professor Fred Watson: Clever, clever. Yeah, they are.
38:25
There's some good people there.
38:26
Andrew Dunkley: Uh, so the articles in Universe Today, but
38:28
you can read it in a deeper form
38:31
through the NASA website or the, uh,
38:35
Astronomy and Astrophysics Journal, I think,
38:37
has published, uh, the full paper, which is.
38:40
Professor Fred Watson: Yeah, that's the European journal.
38:43
Andrew Dunkley: Lots of numbers in it. Yeah, lots and
38:45
lots of numbers. Numbers that are too big
38:48
for my brain.
38:51
All right, uh, that's where we end the show.
38:54
Fred Watson, thank you very much.
38:55
Professor Fred Watson: Much.
38:56
Professor Fred Watson: Oh, a pleasure. Uh, as you said at the
38:58
beginning, some nice storeys there.
38:59
Andrew Dunkley: Yeah. I'm very glad to be able to
39:01
Professor Fred Watson: share them with you.
39:02
Andrew Dunkley: Indeed. Uh, we'll catch you real soon. Thank
39:04
you, Fred Watson.
39:05
Professor Fred Watson: No worries. Thanks, Andrew.
39:06
Andrew Dunkley: Professor Fred Watson Watson, astronomer at
39:08
large, and, uh, as I say, between episodes,
39:10
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39:35
Huw in the studio because he didn't turn up
39:37
today. And from me, Andrew Duckling. Whoops.
39:40
Uh, thanks for your company. We'll catch you
39:42
on the next episode of Space Nuts. Bye. Bye.
39:45
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