Interstellar Comet From a Frozen Ancient World + Black Hole Mystery SOLVED

0:00 Anna: Welcome to Astronomy Daily. I'm Anna.

0:03 Avery: And I'm Avery. It is Friday

0:05 24th April, and we have got

0:08 a genuinely remarkable show lined up for you

0:10 today.

0:11 Anna: We do, and I want to kick things off with

0:13 something that had the whole team talking

0:15 this morning.

0:16 Scientists have just published the first ever

0:19 chemical analysis of water inside an

0:22 interstellar comet. And what they found is

0:25 extraordinary.

0:26 Avery: We're talking about our old friend three I

0:29 ATLs, the interstellar visitor that

0:32 swept through our solar system last year. And

0:34 the verdict from astronomers. It came from a

0:37 world that was much colder than ours.

0:40 Anna: Much colder. Like almost

0:42 incomprehensibly colder. We have that

0:45 story, plus what's been feeding the

0:47 supermassive black hole at the heart of our

0:50 galaxy. That mystery may finally be

0:53 solved.

0:53 Avery: Japan has a spacecraft sitting on a launch

0:56 pad right now ready to head to a tiny moon

0:59 of Mars and bring a piece of it back to

1:01 Earth. And tonight, Aurora watchers in

1:03 Australia and New Zealand keep your eyes on

1:06 the sky.

1:07 Anna: All that and we're asking the big question,

1:09 could aliens already know that we exist?

1:12 The answer might actually be yes.

1:15 Avery: It's a big one. Let's get into it.

1:17 Anna: Our lead story today is a world first, and

1:20 it involves the interstellar comet that

1:22 captured everyone's imagination when it

1:25 started swept through our solar system last

1:26 year.

1:27 Avery: Three I atls, the third

1:30 interstellar object ever detected passing

1:33 through our neck of the cosmic woods. And now

1:35 scientists are telling us something truly jaw

1:38 dropping about where it came from.

1:40 Anna: A team led by PhD student Louis

1:42 Salazar Manzano at the University of

1:45 Michigan, working with colleagues at the ALMA

1:47 UM telescope in Chile, has made the very

1:50 first measurement of deuterated water. What's

1:53 sometimes called sea? Semi heavy water inside

1:56 an interstellar object.

1:57 Avery: Okay, for anyone who slept through chemistry

2:00 class, what exactly is deuterated water?

2:03 Anna: Great question, though. Regular water,

2:06 H2O has hydrogen atoms with just a

2:09 proton at their core. But deuterium is a

2:11 heavier form of hydrogen that has both a

2:14 proton and a neutron. When you swap

2:17 one of those regular hydrogen atoms for a

2:19 deuterium atom, you. You get what scientists

2:21 call HDO semi heavy water,

2:24 or deuterated water.

2:26 Avery: And the key thing is the ratio of heavy

2:29 water to regular water in a comet tells you

2:32 about the temperature of the environment

2:33 where that comet originally formed.

2:36 Anna: Exactly. Cold, low radiation

2:39 environments produce more deuterium rich

2:41 water. And three I atlas it's

2:44 loaded with it. The Alma measurements show it

2:47 contains around 30 times more semi

2:49 heavy water than any comet in our own solar

2:52 system and 40 times than Earth's.

2:55 Avery: Oceans 40 times. That's

2:58 not a small difference.

2:59 Anna: It really isn't. And what that tells us is

3:02 that 3i atlas formed in an environment that

3:05 was utterly unlike the early solar system,

3:08 likely somewhere extremely cold, well

3:11 below minus 240 degrees Celsius,

3:14 in the outer reachings of some distant

3:16 planetary system, or possibly in a

3:18 primordial interstellar cloud.

3:20 Avery: And there is more intrigue here because some

3:23 researchers think, uh, three I ATLs could

3:26 be up to 10 or 12 billion years old,

3:29 which would mean it formed before our sun

3:31 even existed.

3:32 Anna: Which makes it, in the words of one of the

3:35 researchers, a preserved fragment of an

3:37 ancient planetary system. A fossil from

3:40 the early Milky Way grifting through our

3:43 neighborhood.

3:43 Avery: Harvard astronomer Avi Loeb has raised the

3:46 characteristically eyebrow raising question

3:48 about the abundance of deuterium, noting that

3:51 deuterium is actually fusion fuel and

3:54 wondering out loud whether that overabundance

3:57 might be a technological signature. Although

3:59 he admits that's highly speculative.

4:02 Anna: Very speculative, but fun to think about.

4:05 The paper is published today in the journal

4:07 Nature Astronomy. And it also marks the first

4:10 time any team has successfully performed this

4:13 kind of chemical analysis on an object that

4:15 originated beyond our solar system.

4:18 Avery: Each interstellar comet, as one of the

4:20 researchers put it, brings a little bit of

4:22 its history, its fossils, from somewhere else

4:24 in the galaxy. And with instruments like

4:27 alma, we're starting to actually read those

4:29 fossils.

4:30 Anna: A landmark result. And they say this now

4:33 opens the door to doing the same chemical

4:35 fingerprinting on future interstellar

4:37 visitors. So 3i Atlas

4:40 may have set a new template for how we study

4:43 objects from beyond.

4:44 Avery: Okay, next up, a mystery that has puzzled

4:47 astronomers for decades may finally have an

4:50 answer. And it involves the 4 millionth solar

4:52 mass black hole sitting at the very

4:54 Anna: center of our galaxy, Sagittarius A,

4:58 the sleeping giant at the heart of the Milky

5:00 Way.

5:00 Avery: For years, astronomers have been watching

5:02 strange gas clouds drift towards it along

5:05 almost identical paths. Gas clouds called

5:08 G1, G2, and the newly discovered

5:11 third cloud, informally known as G2T.

5:14 And nobody could work out where they were

5:16 coming from or why they were on such

5:18 remarkably similar orbits.

5:20 Anna: Until now. A team of researchers led

5:23 by the Max Planck Institute for

5:25 Extraterrestrial Physics, using the Very

5:28 Large Telescope in Chile, has cracked it.

5:31 And the answer is delightfully dramatic.

5:33 Avery: Go on, then.

5:34 Anna: Two massive stars locked in what the paper

5:37 describes as a violent embrace. A

5:39 binary STAR system called IRS

5:42 16SW located near the

5:45 galactic center, whose powerful stellar

5:48 winds continuously shed enormous amounts of

5:51 gas.

5:51 Avery: And as IRS 16SW orbits

5:54 Sagittarius A, each ejection of Gas

5:57 gets flung out in a slightly different orbit,

5:59 which explains why G1, G2, and

6:02 G2T are on almost identical

6:05 paths, but rotated a tiny bit relative to

6:07 each other.

6:08 Anna: Exactly. And crucially, the team's

6:10 calculations show that the infall of just one

6:13 such clump, roughly the mass of Earth

6:16 every decade, provides enough material to

6:19 sustain Sagittarius A's current level of

6:22 activity.

6:22 Avery: So it's not some exotic, mysterious process.

6:26 It's just two stars in a wild gravitational

6:28 dance, constantly shedding material that, uh,

6:31 slowly trickles down into the black hole.

6:33 Anna: It's a beautiful result because it connects

6:35 three things that astronomers study.

6:38 Stellar evolution, gas dynamics, and black

6:41 hole feeding into one consistent

6:44 picture. And it suggests that star formation

6:47 and black hole growth may be intimately

6:50 linked even in our own galaxy.

6:51 Avery: And the discovery also rules out a previous

6:54 theory that each of those gas clouds might be

6:56 hiding a star at its core. Given that G1,

6:59 G2, and G2t are all on

7:01 practically identical orbits, the odds of

7:04 three separate stars independently ending up

7:07 on those paths are essentially zero.

7:09 Anna: Right. They must share an origin. And

7:11 IRS 16 SW is the

7:14 most compelling explanation. The research is

7:17 published in the journal Astronomy and

7:19 Astrophysics.

7:20 Avery: Before we move on to our next story today,

7:22 just a quick reminder to Support our sponsor,

7:24 NordVPN and do yourself a great big money

7:26 saving favor. Get secure online for less.

7:29 With the Service we use NordVPN, I

7:32 can't recommend them enough. Check out our

7:34 special listener deal by clicking on the link

7:36 in the show Notes.

7:36 Anna: Now, a mission story that we've been keeping

7:39 an eye on for a while, and one that has a

7:41 very special connection to our part of the

7:43 world.

7:44 Avery: Japan's Martian Moons exploration mission,

7:47 mmx UM M has officially arrived at the

7:50 Tanegashima Space center and is being

7:53 prepared for launch later this year. We're

7:56 talking November or December 2026.

7:59 Anna: And the destination? Phobos, one of the

8:02 two tiny, lumpy moons of Mars.

8:05 MMX is going to fly to Phobos,

8:07 land on it, drill into it, and bring back

8:10 pieces of it to Earth.

8:12 Avery: The first ever sample return from the Mars

8:14 system. Which is pretty extraordinary when

8:16 you think about it.

8:17 Anna: It is. And this mission has had a rocky road,

8:20 no pun intended. It was originally supposed

8:23 to launch in 2024, but ran into problems

8:26 with Japan's H3 rocket. There was also

8:29 concern after a second H3 failure in

8:31 December 2025. But that issue was

8:34 isolated to a payload fairing problem, not

8:37 the rocket itself, and the path was cleared

8:39 for MMX to proceed.

8:41 Avery: So what's the mission going to actually do

8:44 once it gets there?

8:45 Anna: Ella Max will arrive in orbit around Mars in

8:48 2027 and spend time mapping both

8:51 Phobos and the smaller moon Deimos.

8:53 Then, in 2029, it will actually

8:56 land on Phobos and collect about 10 grams

8:59 of surface and subsurface material

9:02 using two different sampling systems.

9:05 Avery: 10 grams doesn't sound like much, but sample

9:07 return missions have taught us that even tiny

9:10 amounts of pristine material can be enorm

9:13 scientifically valuable. Japan's Hayabusa2

9:16 mission returned barely a teaspoon of

9:18 material from the asteroid Ryugu, and

9:20 scientists are still extracting discoveries

9:23 from it.

9:23 Anna: The big scientific question MMX hopes to

9:26 answer is how did Phobos and

9:29 Deimos actually form? Were they

9:31 asteroids captured by Mars gravity from the

9:34 outer solar system, which would mean they

9:36 should be rich in water and organics, or are

9:39 they debris from a, uh, giant impact on young

9:42 Mars, in which case the heat would have

9:44 driven off any water.

9:46 Avery: And the answer has implications for

9:48 understanding how the inner solar system

9:50 formed and possibly for the origins of life

9:52 on Earth.

9:54 Anna: Now, here's the detail that I know will

9:56 resonate with our Australian listeners, in

9:58 particular, when NMX returns to Earth in

10:01 2031 with its precious cargo.

10:04 Avery: The sample return capsule lands in Australia,

10:07 specifically the Woomera prohibited zone in

10:10 South Australia.

10:11 Anna: Though there's a direct connection for us

10:13 Phobos material delivered to Australian

10:16 soil, that's something to look forward to.

10:19 Avery: MMX also carries the IDEX rover,

10:22 built jointly by the German and French space

10:24 agencies, which will actually drive on

10:26 Phobos. Given that gravity on Phobos is

10:29 about 1800 times weaker than on Earth,

10:32 that'll be quite a drive.

10:34 Anna: An audacious mission. It's on the pad. The

10:37 clock is running.

10:38 Avery: All right, I love this next story, partly

10:41 because of the job title, Stellar

10:43 archaeologists. That's what the researchers

10:45 behind it are

10:46 Anna: calling themselves, which is a fantastic job

10:49 title. And what they found is genuinely

10:52 illuminating, not just for understanding

10:54 stars in general, but for understanding the

10:57 future of our own sun.

10:59 Avery: So what's the discovery?

11:01 Anna: Scientists at the Institute of Science and

11:03 Technology, Austria have found what they're

11:05 calling fossilized magnetism on white dwarf

11:08 stars. And they've used that to build a new

11:11 model that explains how magnetic fields

11:13 behave as a star evolves from a bloated

11:16 red giant all the way through to a cold,

11:19 dense white dwarf.

11:20 Avery: For listeners who need the refresher, a white

11:23 dwarf is what our sun will eventually become.

11:26 In about 5 billion years, the sun will

11:29 exhaust the hydrogen in its core, puff

11:32 out into a Red giant, probably swallowing

11:34 Mercury and Venus in the process, and then

11:37 shed its outer layers, leaving behind a dense

11:40 Earth sized remnant called a white dwarf.

11:43 Anna: And what this research does is connect the

11:46 magnetic field that we can detect at the core

11:48 of a red giant using a technique called

11:51 astroseismology, which is essentially

11:53 starquakes, to the magnetic field that

11:56 appears at the surface of a white dwarf

11:58 billions of years later, doesn't disappear

12:00 Avery: or reset, it's preserved. It travels with

12:03 the star through its entire evolution from

12:06 red giant to white dwarf, and then

12:08 reemerges at the surface. Hence fossil

12:11 magnetism.

12:12 Anna: And interestingly, the team found that

12:15 older white dwarfs tend to be more magnetic

12:18 than younger ones, which fits neatly with the

12:20 fossil field theory. As more of the star's

12:23 interior becomes magnetized over time,

12:26 the field gradually spreads to the surface.

12:30 Avery: So what does this mean for us, for our Sun?

12:32 Anna: Well, it deepens our understanding of how

12:35 stars like the sun evolve in their final

12:37 stages. Magnetic fields play a significant

12:41 role in how a, uh, star's interior works and

12:43 how long it lives. By understanding how

12:46 those fields persist and transform,

12:49 we get a much clearer picture of what the

12:51 Sun's twilight years will

12:53 Avery: actually look like, which is still 5 billion

12:56 years away. So, uh, I'm not immediately

12:58 worried.

12:59 Anna: Probably not your most pressing concern

13:01 today, no. But it's a beautiful piece of

13:04 science, connecting observations of different

13:06 stellar life stages across billions of years

13:09 of cosmic time. Stellar archaeology,

13:12 indeed, indeed.

13:14 Avery: And I hope this helps answer some questions

13:16 for our listeners.

13:17 We do get a lot on this

13:18 Anna: subject now, a story that I think is

13:21 going to spark some very interesting

13:23 conversations. And the premise is simple but,

13:26 uh, profound. If there are intelligent

13:28 civilizations out there looking for signs of

13:31 life in the universe, they may already have

13:34 found us.

13:35 Avery: Which is either very exciting or

13:37 mildly terrifying, depending on your point of

13:40 view.

13:40 Anna: Possibly both. The thinking goes like,

13:43 when we search for signs of intelligent life,

13:46 what do we look for? We look for

13:48 technosignatures, evidence that a, uh,

13:50 civilization has modified its environment in

13:53 detectable ways.

13:55 Avery: Radio signals, laser pulses, chemical

13:57 signatures and atmospheres. Things that

14:00 couldn't plausibly be produced by natural

14:02 processes.

14:03 Anna: And the key insight is Earth already

14:06 has a lot of those. Our planet has been

14:09 broadcasting radio waves into space for over

14:11 a century. Those signals have already reached

14:14 more than a thousand nearby stars,

14:17 including Proxima, Centauri,

14:19 Avery: Vega, uh, Barnard's Star. If there's

14:22 anyone listening around those stars, they've

14:24 potentially been receiving our broadcast for,

14:26 for decades.

14:28 Anna: And it's not just radio. Earth has

14:30 enormous human made structures that might be

14:33 visible to sufficiently Advanced telescopes,

14:36 huge solar farms covering dozens of square

14:39 kilometers. City lights visible from

14:41 orbit. The chemical fingerprint of industrial

14:44 activity in our atmosphere.

14:46 Avery: So the question flips from are we searching

14:49 for them to have they already found us?

14:53 Anna: Right. And researchers studying this angle

14:55 suggest that what we call technosignature

14:58 detection from our end, the tools we'd use

15:01 to find alien civilizations are

15:03 exactly the same tools an alien civilization

15:06 would use to find us. We're not hidden.

15:09 Avery: There's something both humbling and thrilling

15:12 about that. We've been sending out our

15:14 calling card for a hundred years. Whether

15:16 anyone's received it and decided to respond

15:19 is, of course, the great unanswered

15:22 question.

15:22 Anna: The SETI Institute is actually working on

15:25 updated protocols right now for what happens

15:27 if we do receive a confirmed signal, a

15:30 declaration of principles that would govern

15:33 how scientists announce the discovery and

15:35 how humanity responds. That's being

15:38 finalized at a major international conference

15:41 later this year.

15:42 Avery: So the scientific community is quietly,

15:45 methodically getting ready, which I find

15:47 rather reassuring.

15:49 Anna: Me, too. The universe is a big place.

15:52 The question of whether we're alone in it is

15:54 one of the oldest and most profound that

15:57 humanity has ever asked. And the answer,

15:59 one way or another, could come from someone

16:02 finding us first.

16:04 Avery: And finally today, a story for the sky

16:07 watchers among you. And if you're in

16:09 Australia or New Zealand, listen up, because

16:11 there's something potentially beautiful on

16:13 offer tonight.

16:14 Anna: A coronal mass ejection, a CME from an

16:17 eruption on the sun earlier this week is

16:20 delivering a glancing blow to Earth right

16:22 Now, today, on the 24th of April.

16:25 Avery: To give a bit of context, a few days ago, two

16:28 filaments on the sun erupted simultaneously

16:30 in opposite directions. A pretty dramatic

16:33 solar display. One of those eruptions sent a

16:36 wave of charged solar material in our

16:38 direction.

16:39 Anna: It's only a glancing blow, not a direct hit.

16:43 But combined with fast solar wind from a

16:45 coronal hole that's been rattling Earth's

16:47 magnetic field for several days now,

16:50 conditions are elevated. We could see

16:52 G1 minor geomagnetic storm

16:55 levels. That's a kp index of 5.

16:58 Avery: And, um, G1 conditions can push auroras

17:01 to lower latitudes than usual. So if you're

17:04 at a higher latitude in the southern

17:06 hemisphere, southern parts of Australia,

17:08 South Island, New Zealand, Tasmania,

17:11 and you've got clear skies tonight. It's

17:13 worth getting away from city lights and

17:15 looking south.

17:17 Anna: There are no guarantees with auroras. They're

17:20 unpredictable by nature, but the conditions

17:22 are more favorable than average. Check the

17:25 Bureau of Meteorology's Space Weather Alerts

17:28 or thespaceweather.com website for

17:31 the latest KP Index readings throughout the

17:33 evening.

17:34 Avery: And even if the aurora doesn't materialize,

17:36 there's a bonus in the southern sky right

17:39 now. Comet C

17:41 2025? S, uh, three Pan Starrs is

17:44 approaching its closest point to Earth on

17:46 April 27, just three days away.

17:49 It's estimated to reach around magnitude 7

17:52 or 8, which means binoculars or a

17:55 small telescope should show it in the evening

17:57 sky in early May for Southern Hemisphere

18:00 observers.

18:01 Anna: So eyes to the south tonight. Aurora

18:03 conditions and a, uh, comment on approach.

18:06 Not a bad Friday evening, all things

18:08 considered.

18:09 Avery: Not bad at all.

18:10 Anna: And that brings us to the end of today's

18:12 astronomy Daily Season 5, Episode

18:15 92.

18:17 Avery: What a show. An interstellar

18:19 comet carrying water from a billion year old

18:22 frozen world. The secret of what's feeding

18:25 the Milky Way's most famous black hole,

18:28 Japan's audacious mission to Mars

18:31 Moon with the return

18:32 Anna: capsule landing in Australia,

18:35 stellar archaeologists decoding the future of

18:38 our sun, the sobering and exciting

18:41 possibility that aliens already know we

18:43 exist, and a, uh, solar storm making a run

18:46 at our magnetosphere as we speak.

18:48 Avery: If you enjoyed the episode, please leave us a

18:51 review wherever you listen. It makes a huge

18:53 difference for an independent show like ours.

18:56 Anna: Find us on X, Facebook, TikTok,

18:59 YouTubeMusic Rumble and Instagram

19:02 Strodaily Podcast and visit

19:04 astronomydaily.IO for show notes,

19:07 transcripts and links to all the research we

19:09 covered today from me, Avery and from me

19:12 Anna. Clear skies, Curious

19:15 minds.

19:29 Avery: Sam

19:37 mhm.