Stellar Breakthroughs: The Discovery of Deuterated Methanol and the First Green Star

0:00 Anna: Hello everyone. Welcome to Astronomy AstroDailyPod. A molecule nobody had ever found in space, sitting around a star that hasn't finished being born. Avery: A dead star that would glow green if only you could get close enough to look at it. And six pulsars that were hiding in old Australian radio data the whole time. Anna: Plus a supernova caught just days after it went off when the universe was barely more than a billion years old. And an update on Hera's big breaking burn. Avery: It's Friday 16th October 2026, and this is Astronomy AstroDailyPod series five, episode 206.

0:40 I'm, um, Avery. Anna: And I'm Anna. Let's get into it. Avery: Ready when you are. Why don't you lead things off, Anna? Anna: Our lead story today is about chemistry, and it comes from the Atacama Large Millimetre Submillimeter Array on Alma, high on the Chognator Plateau in northern Chile. A large international programme called compass, which stands for Complex Organic Molecules in Protostars with ALMA Spectral Surveys, has published its first results this month as uh, seven papers in the journal Astronomy and Astrophysics.

1:17 Avery: And the headline is A molecule that has never been detected in space Before. Anna: That's right, but let's set the scene first, because the survey itself is the reason the discovery was possible. Compus pointed Alma at 11 nearby protostars. These are young sun like stars that are still wrapped in the cloud of gas and dust they're forming from. The programme took more than a hundred hours of telescope time. Avery: And instead of looking for one molecule at a time, they recorded white slices of the spectrum all at once.

1:50 Anna: Exactly. Every molecule in space emits at its own set of radio frequencies, a kind of barcode. A broadband spectral survey records thousands of those lines simultaneously. And then the work is untangling which lines belong to which molecule. The programme is led by Jes Jorgensen at the Niels Bohr Institute in Copenhagen, with co leads in the United States, France, Switzerland and South Korea. Jorgensen describes the results as completely new insight into the chemistry around the very youngest stars.

2:22 Avery: Let's take the two big results in turn. The first one is about methanol masers. Anna: Methanol is the simplest alcohol. It's one carbon, one oxygen and four hydrogens. And in space it matters because it is a stepping stone to bigger organic molecules. A maser is the microwave cousin of a laser. Under the right conditions, the molecules amplify radiation at one very specific frequency and you get an intensely bright narrow signal. Avery: And um, methanol masers are well known around massive stars.

2:59 Anna: They are what a Study led by Jaeheng Jiang, a graduate student at Seoul National University, found is that methanol maser emission shows up in more than half of the low mass protostars in the sample. That was not expected for stars on the way to being something like rsut. The team also identified a new maser transition of methanol and found it associated with another organic molecule, acetaldehyde. Avery: So it may be common and we simply weren't looking hard enough. Anna: That's the team's reading that this emission may be a normal part of the earliest stages and only shows up once the observations are sensitive enough.

3:43 Avery: Now the result in the headline this Anna: one is led by Arno Balas at the Max Planck Institute for Radio Astronomy. The target is a protostar called IRAS4A2 in the Perseus molecular cloud about 1000 light years away and around it, the team made the first interstellar detection of fully deuterated methanol. Its formula is CD3OD. Avery: Explain deuterium for us. Anna: Deuterium is heavy hydrogen. A normal hydrogen nucleus is a single proton. Deuterium has a proton and a neutron. Chemically, it behaves almost the same, so it can take hydrogen's place in a molecule.

4:26 Ordinary methanol has four hydrogen atoms. Fully deuterated methanol has all four, replaced by deuterium. The paper notes it's the first molecule with four deuterium atoms ever identified in the interstellar medium. Avery: And deuterium is rare, very rare. Anna: Across the cosmos, there are only about two deuterium atoms for every 100,000 hydrogen atoms. If molecules simply picked up deuterium at that ratio, you would essentially never see one with four of them. So the fact that this molecule exists at all in enough quantity for ALMA to detect tells you something has been concentrating deuterium very strongly.

5:07 Avery: How do you prove you found a molecule in a spectrum that crowded with Anna: many lines, not one? A single spectral line could be a coincidence, because a protostar like this has thousands of lines from dozens of molecules overlapping. So the test is whether every line that the lab says this molecule should produce appears at the right frequency with sensible relative strengths and with nothing better explaining it. The paper reports 10 lines of fully deuterated methanol clearly detected under those criteria.

5:42 Avery: And this has been a long hunt. Anna: It has Methanol with a single deuterium was first found in space in 1988 toward Orion. Versions with two and three deuterium atoms followed in the early 2000s around another young protostar, IRAS16.293. The forward deuterium version is the last step on that ladder, and until now, there had been no robust identification of it anywhere in the interstellar medium. Avery: And this is where it becomes a clock rather than a curiosity. Anna: Right before a star switches on, the cloud core it forms from is extraordinarily cold, around 10 degrees above absolute zero.

6:25 In those conditions, carbon monoxide freezes onto dust grains and the chemistry in the gas tilts in favour of handing deuterium to whatever forms next. Methanol forms on the icy grains by adding hydrogen atoms one at a time, to frozen carbon monoxide. The colder and older the core, the more of those added atoms are deuterium. Avery: So the amount of deuterium in the methanol reflects when and in what conditions it formed? Anna: That's the idea the paper sets out. The deuterium fraction can reflect the time when a molecule formed.

7:01 Then the protostar switches on and warms its surroundings. The ice evaporates, the methanol comes off the grains into the gas and ALMA can see it. What we're reading in that gas is an effect of fossil record of the cold phase before the star existed. Avery: There's a nice callback here for regular listeners. Anna: There is. In episode 200, we covered the deuterium to hydrogen ratio in the water of the interstellar comet 3I Atlas. And before that, in episode 194, molecular nitrogen used as a thermometer for where that comet formed.

7:38 Same principle, isotopes and ices as thermometers and clocks for places we can never visit. Avery: Now, caveats, because there are some important ones. Anna: Yes. First, the deuterium pattern itself is a puzzle. The team detected every form of methanol with lab data available, and the apparent deuterium fraction rises as you go from 1 deuterium to 2, 3 and 4. That's a pattern seen in other young stars too. But the current chemical models of cold cores don't reproduce it. And the new detection makes the mismatch worse, not better.

8:15 Avery: So it's a result that breaks the models rather than confirming them. Anna: It is. Second, the authors themselves suspect their measurement of ordinary methanol is too low, possibly because the emission is clumpy and that would shift the ratios. Third, this is one protostar. And fourth, the obvious one. Organic molecules are chemistry, not biology. Jorgensen frames the bigger question as how these ingredients might shape conditions on planets that form later. That's a question, not a finding.

8:48 Avery: And, um, these are the first papers. The full data set is still being analysed. Anna: Seoul National University's Jung Unlee, one of the CO leads, says they're just beginning to tap the richness of the data. A key goal is working out whether differences between young stars come from where they were born or develop as they grow up. Avery: And the southern angle, two of them, Anna: honestly labelled Alma itself, sits at 5,000 metres in the Chilean Andes. And three of the seven papers focus on another protostar called BHR71, a dark globule deep in the southern sky from Sydney.

9:27 It is circumpolar and climbs to almost 60 degrees. It never rises for our listeners in Los Angeles, New York or London. Perseus, where the heavy methanol was found, is the opposite. Low for us, almost overhead for California. Avery: Both hemispheres in one survey. Lovely. Anna: Right, on to our next story from Avery: chemistry around a star being born to the colours of stars that have died. Astronomers at the University of Warwick have published the study this week in RAS Techniques and Instruments, with a lovely title, any colour you like and a claim Anna: nobody has made before.

10:07 Avery: The first star that would genuinely look green. Here's a setup. For most stars, colour is just temperature. Cooler stars look orange. Stars, like the sun, look white. The hottest look pale blue. Physicists call that a perfect radiator, like iron glowing in a blacksmith's forge. Anna: And white dwarfs, the dense cores left behind by sun like stars, were assumed to follow the same rule. Avery: They were. But the team led by Mark Hollins points out that the coolest white dwarf atmospheres are astonishingly dense, around 1 gramme per cubic centimetre, about the density of water, and millions of times denser than the sun's visible surface.

10:51 Trace elements in that dense helium absorb light across much wider bands than they normally would, and that pushes the colour off the usual track. Anna: So how do you see the colour of a star nobody can get close to? Avery: You don't. And this is the key caveat. No white dwarf is close enough for its colour to be seen directly. The team took spectra astronomers already have, and ran them through a model of human colour vision to calculate what colour the light would look like to your eye. And the green one, it's called WDJ1336435.

11:28 It's around 4,000 degrees Celsius and it has swallowed rocky material from its own old planetary system that has loaded its atmosphere with calcium, lithium and sodium. Sodium in that dense atmosphere absorbs the orange part of the spectrum and what's left comes out chartreuse green. Hollins invites you to imagine standing on a planet and looking up at a green star. Anna: Which connects to the polluted white dwarf we covered in episode 201. Avery: Exactly the same family dead stars eating the remains of their planets.

12:02 At the other extreme, WD J1011 2845 just 48 light years away, has dredged carbon up uh, from its core. Carbon molecules squeeze almost all of its light beyond 600 nanometers and it uh, may be the reddest star ever recorded. A ah, deep salmon pink. Anna: But the average white dwarf is white, Avery: which is a nice correction. The team looked at the 151 white dwarfs within 20 parsecs about 65 light years. Five had unusual colours, two yellow and three pink. So roughly one in 30. For the rest the median colour temperature is about 6,800 Kelvin, which reads as white.

12:46 Astronomers have tended to think of white dwarfs as blue only because the hot blue ones are brighter. So they dominate surveys that pick stars by brightness. Anna: That's a selection effect we've talked about before. Catalogues are detection limits, not censuses. Avery: And one honest audience note. The green star sits in the far northern sky, circumpolar from London and New York and it never rises from Sydney. It's far too faint to see the colour in any telescope anywhere, so nobody's missing out.

13:20 Anna: Our next story is built on old data. Two new preprints, both posted to the archive on 8 October report Pulsars found by going back through archived Observations from Meiriang CSIRO's Parkes Radio Telescope in New South Wales. Avery: And they're not in our galaxy. Anna: They're in the Magellanic Clouds, the two satellite galaxies of the Milky Way, around 160 to 200,000 light years away. Only just over 1% of all known radio pulsars live there because at that distance they're faint and hard to catch.

13:58 Avery: Remind us what a pulsar is. Anna: A neutron star, the collapsed core of a uh, massive star spinning and sweeping a beam of radio waves across us like a lighthouse. We see a pulse each time the beam goes past. The faint ones are buried in noise and you find them by folding the data, stacking it at a trial spin period until the pulses add up. Avery: So what did they do differently? Anna: The first paper is led by Rahul Sangar with co authors including Matthew Bales of Swinburne University of Technology.

14:35 They reprocessed the original Parkes multibeam surveys of the Magellanic Clouds with search techniques tuned for faint pulsars with very narrow pulses folding candidates right down near the noise floor. They found six new pulsars five are in the Large Magellanic Cloud, and one of those spins once every 3.8 seconds, the slowest pulsar known in either cloud, and the sixth seen toward the Small Magellanic Cloud. But it turns out to be in our own galaxy in the foreground. The new finds bring the count of radio pulsars known in the Large magellanic Cloud to 49.

15:12 The team also finds that as a population, the Magellanic Cloud pulsars look consistent with ordinary pulsars in the Milky Way. Avery: And, um, the second paper. Anna: That's Weiyu Wing and Rahul Sengar. They went back through archival Park's pointings at supernova remnants in the Small Magellanic Cloud and found a Pulsar now called PSR J010372. It spins once every 1.33 seconds, which makes it the slowest radio pulsar known in the small cloud. Its dispersion measure, a measure of how much ionised gas the signal has passed through, is the second highest of any pulsar there.

15:45 And it was missed by earlier searches of exactly the same data. Avery: Caveats. Anna: Both are preprints. The pulsars don't yet have precise timing positions, so the locations are approximate in one case, uncertain by several arcminutes. The authors say plainly that the next step is follow up and the bigger lesson they draw is about method. A faint signal that sits just under a threshold in one search can be recovered by a better one. There's a, uh. Avery: Both hemispheres twist here too. Anna: There is a separate paper Posted on the 12th reprocesses the green Bank Telescope's Northern Sky Survey with the same kind of approach and reports 51 new pulsars.

16:30 And. And it cites the Magellanic Cloud work as part of its motivation. But the clouds themselves are a southern story from Sydney. Both are circumpolar and they never rise from Los Angeles, New York or London. Avery: Asking an old question of archive data. We keep coming back to that one, Anna: proving yet again that old data can be good data when looked at through fresh eyes. Avery: Next, a star that exploded when the Universe was about 1.2 billion years old and was caught by the James Webb Space Telescope within days of going off.

17:08 Anna: This one's a preprint, so let's flag that up front. Avery: Yes, it was posted on 29th September by Ming Yang, Zhang Yui Shen and colleagues from the Nexus programme, a web survey that keeps returning to the same patch of sky near the North Ecliptic Pole, coming back to the same field over and over is what lets you spot something new appearing. Anna: And something did. Avery: On 7 August this year, a new point of light appeared in a star forming galaxy at a redshift of 5.017. It's catalogued as at 2026ABCK.

17:44 It's faint, around magnitude 27.5, and the team estimates it was seen roughly four to 10 days after the explosion in the star's own time. Anna: That phrase in the star's own time matters. Avery: Here it does. At a redshift of about five, time itself appears stretched by a factor of six. So four to ten days at uh, the explosion shows up to us as, uh, somewhere around a month to two months. That stretching is actually helpful because it slows the early fast changing phase down enough to catch. Anna: And what does it look like?

18:22 Avery: Hot and bright for its age. The team says it's hotter and more luminous than normal type 2 supernovae at comparable early phases. Those are the explosions of massive stars whose cores collapse. Its position off centre between two parts of its host galaxy also fits a massive star rather than a black hole flaring in the core. The authors call it the first robustly detected transient at a redshift around 5 or beyond in a field without gravitational lensing. Anna: That's a distinction from SN EOS earlier this year.

18:59 Avery: Right. SN EOS at a slightly higher redshift was magnified by a gravitational lens and confirmed with a spectrum. This one was found in an ordinary blank field, which says that regular high cadence web surveys can catch these young explosions directly. Anna: And the caveat with this one, there Avery: is no spectrum of the transient. Without one, its classification stays uncertain. And the authors say it could also be a super luminous supernova caught on the way up. So a strong candidate, a good demonstration of the method and, um, not M yet a confirmed type.

19:40 Anna: Time for some quick hits. First, ESA's Hera, its first braking manoeuvre, BRM1 was scheduled for early Thursday morning, European time. Three thrusters firing together for 93 minutes to shed a few hundred metres per second relative to the asteroid pair Didymos and Dimorphos at the time of recording. ESA hasn't yet published confirmation, so we'll bring you the result as soon as it's out. Avery: And ESA was going to check it through New Norcia in Western Australia. Anna: That's right. The second shorter burn, around 31 minutes, is set for Thursday the 22nd.

20:17 Then three small manoeuvres late in the month before arrival in November. Meanwhile, at the space station SpaceX's CRS 35 cargo Dragon docked on Thursday about 27 minutes past 10 in the morning US Eastern Time. That's 27 past 1 on Friday morning in Sydney. It brought more than 6,300 pounds of supplies, including the last two rollout solar arrays which are due to be installed on spacewalks. NASA will preview on Tuesday with Anil Menon and Canada's Joshua Kutryk. Avery: And um, Monday. Anna: Monday is the eve of Japan's Martian Moons exploration mission.

20:57 MMX is set to launch on an H3 rocket from Tanegashima at 4:41 minutes past 4 on Tuesday morning Japan time. That's 6:41 on Tuesday morning in Sydney and Monday afternoon in the Americas. It's going to Phobos to bring back a sample which is due to land in Australia in 2031. Full preview on Monday. Avery: Let's look up now. The moon is a waxing crescent this evening and it reaches first quarter on Sunday the 18th at 12 minutes past 4 in the afternoon universal time. That's 3:12 on Monday morning in Sydney, around midday on Sunday in New York and Sunday morning in Los Angeles and full moon Monday the 26th at uh, 11 minutes past 4 universal time.

21:49 That's the afternoon of the 26th in Sydney, just after midnight on the 26th in New York and the evening of the 25th in in Los Angeles. A reminder for UK listeners that your clocks go back on Sunday the 25th while North America changes on the 1st of November. Anna: The big event this week is a meteor shower. Avery: The Orionids, made of dust shed by Hallie's comet peak on the night of the 21st into the 22nd. They're a modest shower, but the good news this year is that the gibbous moon sets before dawn in all four of our cities at about 2:50 in London, 10 past three in New York, 20 past three in Los Angeles, and just after half past three in Sydney.

22:36 The window between moonset and dawn is the one to use. Anna: And this one works for both hemispheres. Avery: It does because the radiant near Orion's raised club sits close to the celestial equator. At nautical Dawn on the 22nd, it's about 40 degrees up from Sydney, 52 from London, 62 from New York and 68 from Los Angeles. Northern skies have the edge, but Sydney's very much in the game. Anna: What about the evening? Avery: This one favours the south. Mercury is a lovely evening object for us tonight.

23:12 Half an hour after sunset, it's about 19 degrees up in the west from Sydney at about magnitude 0, and it doesn't set until after 9. From Los Angeles, it's only 5 degrees up. From New York 3. And from London, it's already below the horizon at that point. Anna: And Venus is leaving. Avery: Venus is heading for inferior conjunction, passing between us and the sun around the 24th. From Sydney tonight, it's only about 7 degrees up at civil dusk and dropping fast in the north. It's already gone. It comes back as a morning star next month.

23:49 Anna: Saturn's still around. Avery: Saturn, just past opposition, is in the east after dark and climbs all evening at, uh, dusk Tonight it's about 19 degrees up from Sydney and lower further north. But give it an hour or two wherever you are. The moon passes about 6 degrees from Saturn on the 24th, and the mornings Anna: belong to the north. Avery: They do. Mars and Jupiter keep closing in the predawn sky. They're about 10 degrees apart on the 22nd, and they'll be just over a degree apart on the 16th of November.

24:24 At nautical dawn on the 22nd, Jupiter is about 50 degrees up and Mars nearly 60. From New York and Los Angeles from Sydney, both are only around 20 to 25 degrees up. And our stories today, a nicely balanced week. The Magellanic Clouds, home of those new pulsars, and the Southern Protostar BHR 71, are circumpolar from Sydney and never rise from the north. The green white dwarf and the Perseus Cloud are northern targets. Neither the pulsars nor the green star is anything you'd see by eye. So the sky's best offer this week is the Orionids together.

25:07 Anna: And our standing reminder, never look at Avery: the sun directly or through binoculars, a telescope or a camera. Without a proper solar filter certified to the ISO 123122 standard. Sunglasses are not enough and eye damage can happen without any pain. Anna: That's the episode. Heavy methanol around a newborn star. The first green star. Six pulsars recovered from the Parkes archive and another from the small cloud. And a supernova caught days old at redshift 5. Avery: Plus HERA's braking burns, a new delivery at the space station.

25:45 And the Orionids to look forward to. Anna: If you've got a question about any of today's stories, send it through the contact form at. Ah. Astronomydaily.IO listener questions have shaped segments before and we'd love more. You'll find us as astrodaily Pod on social media. Avery: We're back tomorrow with the weekend wrap and on Monday with the MMX launch eve. Until then, clear skies. Anna: I'm Anna. Avery: And I'm Avery. This has been Astronomy AstroDailyPod part of the bytes.com podcast network.

26:17 Clear skies, everyone. Astronomy Day Stories we told.

26:30 The stories.

26:39 Were told.