The Youngest Planet Ever Found

0:00 Anna: Every planet you have ever heard of was already finished when we found it. Grown up, settled into its orbit. The disc of gas and dust it was built from long gone. Avery: Not this one. Astronomers have found a planet that is still being built, less than a million years old, sitting in the gap it is carving through its own birth cloud. Anna: Also today, a brand new crater on the Moon, a Victorian train delay that turns out to be a solar storm, and a dead star that has got six times hotter in 30 years.

0:36 Avery: I'm Avery. Anna: And I'm Anna. This is Astronomy AstroDailyPod. Here is a number that should stop you. Every previously confirmed young planet, every single one held up as an example of a world caught in the act of forming, was at least 5 million years old. 5 million years sounds young. It is young. Our own solar system is about four and a half billion. But five million years is also long enough that the most interesting part is already over. The gas is mostly gone. The building is done. You are looking at the result, not the process.

1:09 Yesterday in the Astrophysical Journal Letters, a team led from Chile published the confirmation of a planet that is less than 1 million years old, not 5, less than 1. It is called Elias 224B. And the most remarkable thing about it is that we are watching it being made. Avery: And this is one of those results where the storey of how we got there is as good as the result itself. Because the first hint of this planet is 9 years old, it is. Anna: Let me take you back to 2017. A team including Lucas Sieza, who is an author on today's paper as well, pointed Alma, the Big Millimetre array up on the Chagnantor Plateau in northern Chile at a young star in the Ophiuchus molecular cloud.

1:54 Ophiuchus is one of the closest active star forming regions to us, about 450 light years away. And from here in the southern hemisphere, it rides high across the winter sky. The star is catalogued as Elias224. It is a K type star, roughly the mass of the sun, but much cooler and much puffier because it has not finished contracting yet. What Alma saw was a disc of dust around that star with gaps in it. Dark rings, clean circular lanes swept through the dust. And the standard interpretation of a gap like that is simple and beautiful.

2:30 Something massive is orbiting in there and its gravity is hurting the dust out of its path. The gap is the wake, a footprint Avery: rather than a foot. Anna: Exactly that. And footprints are frustrating because a gap can be made by other things. Ice lines, where a particular molecule freezes out and changes how the dust sticks together. Magnetic effects in the disc turbulence. For nine years, Elias224 has been a beautiful set of rings and an unproven assumption. What Andrea Bernardi at Universidad Diego Portales in Santiago did was go looking for the foot and the data had been sitting in an archive the whole time.

3:08 Avery: This is the part I love. Anna: The W.M. keck Observatory on Mauna Kea observed this system in 2018 and again in 2020 using a coronagraph on the NIRC 2 infrared camera. A, uh, coronagraph is a mask that blocks the light of the star itself so you can see the much fainter things next to it. The same basic trick the Roman Space Telescope's coronagraph is being commissioned to do right now, which we talked about on Wednesday. Those Keck observations were taken, archived and not fully mined. Bernardi's team went back into them, reprocessed them and found a point of infrared light sitting inside one of the gaps.

3:49 And here is Bernardi's line, which is the whole paper in one. The planets should be found within the gaps since they are carving them. And that's exactly where we found Elias224B, end quote. Avery: So the prediction and the detection line up. Anna: They line up and then the confirmation needed a third instrument. ESO's Very Large Telescope at Paranal in the Atacama had also caught a faint point of light in that gap. Put the three together. ALMA showing you the gap in millimetre dust. The the VLT and KECK both showing you an infrared source sitting in it at two separate epochs, two years apart.

4:28 So you can cheque it is moving with the star rather than being a background object and you have a planet. Avery: Bernardi made a point of that in the release. Something like we usually hear about telescopes working separately. But this confirmation was only possible by using multiple telescopes together, which is worth sitting with for a second because it is also a storey about hemispheres. ALMA and the VLT are both in Chile. Keck is in Hawaii. Ophiuchus sits at about 24 degrees south, so it is a target both hemispheres can reach.

5:02 And it took all three facilities on both sides of the equator to nail this down. The southern telescopes found the gap and the northern telescope had the planet sitting in its archive. Now the physics and this is where it gets genuinely awkward for the textbooks. Elias224B is roughly the mass of Jupiter and it is orbiting about 55 times further from its star than Earth is from the Sun. 55 astronomical units for scale. Neptune is at 30, Pluto averages about 39. So this is a Jupiter mass planet out past where our own Kuiper Belt starts.

5:42 And it got there in under a million years. And the standard way we build giant planets does not go that fast, that far out. Anna: It does not core accretion. The mainstream model says you assemble a solid core first by sticking pebbles together. And once that core is heavy enough, it starts pulling gas down onto itself and runs away into a gas giant. The trouble is that the further out you go, the thinner the disc is and the slower everything orbits. So there is less material and fewer collisions per orbit.

6:16 Building a Jupiter at 55 au by core accretion is slow. Estimates run to many millions of years. This planet did not have many millions of years. It had at the outside one. Lucas Sieza put it plainly, our planet formation models already struggled to explain the previous record holders. Elias224B shows us that even our best models are still missing some important processes. End quote. Avery: There is an alternative, isn't there? The disc fragmenting directly. Anna: There is gravitational instability.

6:51 Instead of building a planet from the bottom up, you let a patch of the disc become dense enough that it collapses under its own gravity all at once and makes a giant planet more or less the way a star forms. That is fast, and it works better at large distances where discs are cooler and more prone to collapse. A planet like this one, this young, this far out, is exactly the sort of object people point to when they argue that gravitational instability has to be part of the picture rather than a, uh, curiosity.

7:21 But I want to be careful here. And this is the caveat that does not come out of the script. Go on directly Imaged protoplanets have a history. Candidates around the stars Lkca 15 and AB Orige were both announced as planets in the making, and both ended up disputed. In some cases, what looked like a planet turned out to be a bright knot of disc material or an artefact of how the starlight was subtracted. The system PDS 70 is the one everybody agrees on, and that took years of independent confirmation.

7:54 So Elias 224B is a strong detection with three telescopes behind it. And it is also a detection that will get tested hard over the next few years, as it should be. And the mass number deserves the same care. At an age under a million years, you cannot weigh a planet directly. You measure how bright it is in the infrared, and you convert that to, uh, a mass using models of how a young giant planet cools. Those models disagree with each other most severely at exactly this age, because they depend on how much heat the planet held onto from its formation.

8:25 And some of the light you are seeing may not be the planet's surface at all, but gas falling onto it and glowing as it lands. So when we say Jupiter mass, read that as Jupiter ish, with real room on either side. An earlier kinematic estimate for whatever is carving that gap put it as high as five Jupiter masses. Avery: None of which changes the headline. Anna: None of which changes the headline. Something with the mass of a giant planet is sitting in that gap and the star it orbits is younger than our species.

8:58 We have around 6,000 confirmed exoplanets now and almost every one of them is a finished product. This is a building site with the scaffolding still up and it is going to be observed to death, which is the correct fate for a result like this one. Avery: Moving on to storey two, sometime between 11 April and 22 May 2024, something the size of a three to six storey building hit the moon. Nobody saw it happen. We found the hole 18 months later and the papers describing it were published yesterday in Science Advances.

9:36 Anna: How big a hole? Avery: 222 metres across and about 43 metres deep. That is roughly two football pitches wide and a 14 storey building deep. And here is the part that makes it news rather than trivia. It is about three times wider than the largest new crater found in the entire 17 years the lunar Reconnaissance Orbiter has been watching. The team put an impact this size at something like one in a hundred and thirty years. It is on the near side at about 1.4 degrees north, 67 degrees east, out on the outer ring of the crisium basin, roughly 20 kilometres east of Mare Speumens, right on the boundary where the bright highlands meet the dark Mare plains.

10:21 It is being referred to informally by the name of its neighbourhood, Magecheon, after Thomas Magn, who once directed the Lunar and Planetary Institute. Formal naming is the IAU's business and that is a separate process. Anna: And nobody was looking at that patch of the moon at the time. Avery: Nobody was. It was found by Robert Wagner, an image processing specialist at Intuitive Machines, working with the orbiter's camera team. In October last year, doing routine data quality cheques, he was running software that compares before and after maps of the whole moon and flags.

10:59 What has changed? His description of the moment is my favourite thing. In the release I just stopped, dropped everything and started looking into what that spot was. What stood out was a bright splash of fresh ejecta. And the ejecta is the science. The continuous blanket of thrown out rock reaches a median of about 258 metres from the centre. Bright disturbance shows up 15 kilometres out. Fainter, darker disturbance runs beyond a hundred kilometres. The biggest boulder they measured is 13 metres by 9 by 3 from a hole 200 metres wide.

11:39 The surface is measurably rearranged over an area the size of a small country, Anna: which is a lot of energy, about Avery: 65 trillion joules on assumptions of a rocky impactor at 15 kilometres a second. And the second paper is the one I would not have predicted. A team led by Powell went to Diviner, the orbiter's thermal instrument and found a cold spot about seven kilometres across, centred on the crater eight or nine Kelvin, cooler than its surroundings. That is the signature of fluffed up soil.

12:12 The impact did not just dig a hole, it loosened the top layer of regolith across seven kilometres. And loose soil holds heat differently from packed soil. Mark Robinson, the camera's chief scientist, framed it as gardening impacts, as the process that turns the lunar soil over, churning buried material up and fresh material down. And he drew the conclusion people always want drawn on that turnover rate. The Apollo footprints will, in his words, definitely be long gone in about 80,000 Anna: years, which is not soon.

12:47 But it is not forever either. Avery: That is the thing to take away. We talk about the moon as the dead unchanging one, the place where nothing happens. It is not unchanging. It is changing slowly and it changed in a big way two years ago. And the only reason we know is that there is a spacecraft up there photographing the same ground over and over. Take the watcher away and this simply would not be a, ah, known event. Anna: Okay, now on to our next storey. This one is a detective storey and it has an Australian fingerprint on it for 178 years.

13:23 The textbook answer to when did space weather first disrupt human Technology has been 18 October 1841 in Devon, in the southwest of England. A train leaving Exeter at 5 past 10 at night was held for 16 minutes because the railway telegraph between Exeter and the village of Starcross had stopped working and the signalman could not confirm the line ahead was clear. Avery: Sixteen minutes. Hardly a catastrophe. Anna: Hardly a catastrophe. And that is precisely why it is famous. It is the first time we can point at a piece of critical infrastructure and say the sun did that.

14:03 Trains stopped because of something happening 93 million miles away and the people involved had no idea. It is quoted in review papers, in government resilience reports, in lectures. 1841 is the date everyone uses yesterday in the Journal Space Weather. A team led by Jim Wild at Lancaster University, with Brett Carter at RMIT in Melbourne, Mike Hapgood at RAL Space and colleagues at the British Geological Survey, Natural Resources Canada and Baylor published the correction. It did not happen in 1841.

14:39 It happened on the 18th of October Avery: 1848, seven years out. How does a date like that survive a century and a half? Anna: Because nobody went back to the source. The original account is an anonymous article in the journal nature, published in 1871, 30 years after the fact. And the giveaway, once you look, is almost embarrassing. The railway line between Exeter and Star Cross did not open until 1846. The event could not have happened on the line in 1841, because in 1841 there was no line. Avery: So it is a typo.

15:16 Anna: It looks like a typo. 1848 misprinted as 1841, probably by the anonymous author, who the team think was most likely Nathaniel John Holmes, a telegraph engineer of the period. But proving that took real archival work and this is the part I enjoyed. They went through old railway timetables to find when a five past ten evening service from Exeter actually existed, which narrowed it to a four month window. They pulled the magnetic observatory records from Greenwich. They read the sunspot drawings.

15:48 They went through newspaper archives and 18 October 1848 lights up Greenwich recorded powerful magnetic disturbance from about 20 past 9 in the evening Universal Time. There were aurora sightings right across the United Kingdom. And there was a large sunspot group on the disc recorded from Durham. The timetable, the magnetometer, the aurora reports and the sunspot all agree on one night. Avery: Mike Hapgood had a line about that he did quote. Anna: Our research has a hint of a Detective Storey piecing together a wide range of archived records to better understand a historically severe space weather event.

16:28 End quote. And there is a reason this matters beyond tidying up. A footnote. 1848 is 11 years before the Carrington event of 1859, which is the storm everyone uses as the worst case. Redating this one does not just move a date, it puts a severe infrastructure affecting storm into the record in a decade where we thought we had one. How often the really big storms happen is a question we answer by counting them in the historical record. And the historical record is only as good as the record keeping, which is Avery: the same trap we keep running into with catalogues.

17:03 Anna: It is exactly the same trap moved from telescopes to archives and it sits squarely in a thread we have been pulling all month. The superflare potential work back On Saturday the 12th, the cosmic radiation at aviation altitudes. On Monday the 14th, same dial. Jim Wilde's closing thought is the one to keep Space weather is not a new threat, but a long standing natural hazard. Society has been experiencing the effects of space weather on technology for almost as long as electrical technologies have existed.

17:35 End quote. The Victorians were not protected from the sun. They just had less to lose. Avery: In February 1996, a Japanese amateur astronomer named Yukio Sakurai found a new star in Sagittarius. It was announced through the usual channel, an IAU circular on 23 February. At first everyone assumed it was a nova. Anna: It wasn't. Avery: No, it certainly wasn't. What Sakurai had found was one of the rarest events in stellar astrophysics. A star that had already died coming back to life. It is catalogued as V4334 Sagittarius and everybody calls it Sakurai's object.

18:19 Yesterday, a team led by Albert Zylstra at the Jodrell Bank Centre for Astrophysics in Manchester, with Peter Van Hoof at the Royal Observatory of Belgium and colleagues at the Valongo Observatory in Rio de Janeiro published new measurements of it in monthly notices of the Royal Astronomical Society. And the number is. In 30 years, the the star has become about six times hotter. Its surface was sun like when Sakurai found it. It is now somewhere between 27,000 and 36,000 kelvin. That is among the fastest heating rates ever measured on any star.

18:59 Anna: Take us through what actually happened to it. Avery: So this star had finished. It had been a sun like star. It had run through its fuel, blown off its outer layers and and settled down to be a white dwarf, an inert cooling cinder that is meant to be the end. But there was still a thin layer of helium sitting on top of the carbon and oxygen core. And that layer reignited one last shell flash after the star had already become a white dwarf. The technical term is a very late thermal pulse and the effect is dramatic.

19:34 The star puffs back up into a giant in years rather than millennia. It ends up hydrogen poor and enriched in helium and carbon because the flash has dragged process material up from deep inside. Astronomers call these born again stars and we know of only a handful. Anna: And then it vanished. Avery: Didn't, did. And that is the frustrating part of the storey. By late 1998 the Star had manufactured so much carbon dust that that it wrapped itself in an opaque shell and by 1999 it had disappeared from optical telescopes entirely.

20:13 Imagine watching the one event you have been waiting a career for and the object pulls a curtain across itself. What this team has done is get back in. They used ESO's Very Large Telescope in Chile for spectroscopy. They used ALMA, and they compared what they saw against models built for Wolf Rayet stars, the hot stripped, fiercely windy stars that show strong carbon and helium signatures. And that is what Sakurai's object now looks like. The paper's title says the emergence of a WC star in Sakurai's object.

20:49 Astronomers write it in square brackets, which is the notation for the low mass version. It has the spectrum of a Wolf Rayet star without being a massive star at all. Anna: So the curtain is thinning. Avery: You could say that. And the star underneath is a different star from the one that went behind it. And the headline result is a disagreement with theory, which is the useful kind of result. Zelstra's team find it is reheating more gradually than some of the newer models predicted. That is a direct constraint on how convection and mixing work inside a star during a shell flash, a process we normally can only model because it takes longer than a civilization.

21:32 Here it takes about as long as a career. One honest caveat. The distance to this object is genuinely poorly known. Published estimates run from under 2 kiloparsecs to more than 5, which is a factor of nearly 3. And distance feeds into luminosity. The temperature measurement does not depend on it. That comes from the spectrum. But be wary of any brightness figure quoted to more precision than that spread allows. Anna: And where is it headed? Avery: Back where it came from. It will keep heating, blow away what is left and settle down to being a white dwarf again.

22:12 The same fate reached twice. Peter van Hoof's summary is the one to end on. Sakurai's object offers something far rarer. It is one of the very few stars known to have changed dramatically within just a few decades, end quote. Most of stellar evolution is a slideshow. We get one frame of this one is a film. Anna: A quick update on a storey we left deliberately unfinished Back On Monday the 14th we told you Crew 13 had been stood down, that the cause was an oxidizer leak found in Dragon's propulsion system during pre launch processing.

22:52 That the Canadian Space Agency had said late September and that NASA had published no specific date. We said on air that the absence of a date was itself the news. Avery: And now there is one. Anna: Now there is a window. NASA's station blog updated yesterday says the oxidizer valve has been replaced and that NASA and SpaceX are targeting quote as soon as early October end quote for the launch. The extra time is for pre launch activities. Readiness reviews and coordinating with station operations.

23:24 So still not a calendar date, but a valve that has been fixed rather than a leak being investigated and a month you can plan around. The crew is unchanged. Jessica Watkins commanding, Luke Delaney as pilot, Joshua Kutryk for the Canadian Space agency and Sergey to Teriatnikov for Roscosmos on a Falcon 9 from Space Launch Complex 40. Avery: And the station is not going hungry in the meantime, it is not. Anna: Progress 96 launched yesterday morning US time with nearly three tonnes of food, fuel and cargo for the Expedition 75 crew.

24:00 And it docks to the POISK module on Saturday. Avery: Right, what to actually go outside and look at. And there is a genuine event on the calendar for tomorrow night. Friday the 18th Venus reaches greatest brilliancy. That is the single brightest Venus gets in this entire evening apparition at about magnitude -4.8. And tonight it is already within a whisker of it. So do not wait for permission. The reason the peak falls now rather than when Venus is closest or when Venus is fullest, is worth 30 seconds because it is a lovely bit of geometry.

24:40 Anna: It is a trade off. Avery: It is exactly a trade off. Brightness is lit fraction times disc size. As Venus swings round toward us, it gets bigger. The disc is now about 39 arc seconds across, which is enormous, roughly three times the size it was at the start of the apparition. But as it comes toward us, we also see less of its lit face. It is only about 26% illuminated. A big thin crescent beats a small full disc. And tomorrow night the two curves cross. Put a pair of binoculars on it, steadied against a fence or a door frame, and the crescent shape is obvious.

25:21 That is not a subtle target. One note on the date. Some listings give 22 September for greatest brilliancy. On a slightly different definition, we are using the 18th. The difference is a definition, not a disagreement about Venus. And either way, this week and next are spectacular. Now, where you are standing decides how good a night you have. And the gap is enormous. Right now. From Sydney, the Sun sets at 11 minutes to 6 and Venus is 39 degrees above the western horizon at that moment, most of the way from the horizon to overhead.

26:00 It does not set until three minutes past nine. That is three and a quarter hours of Venus after sunset. Melbourne, Brisbane, Perth, Auckland, Cape Town, Santiago, same storey. Anna: And for our, uh, North American listeners, who are the biggest part of this audience, considerably tougher. Avery: And I am not going to pretend otherwise. From Los angeles, Venus is 14 degrees up at sunset and sets an hour and 20 minutes later from New York, 10 degrees and an hour and five from London, three degrees and half an hour.

26:39 Genuinely difficult. This is the ecliptic tilt again and it is at its most extreme in the weeks around the equinox. The line the planets follow stands almost vertically up from the western horizon at dusk from the southern hemisphere and, and lies almost flat along it from the northern. Same planet, same evening, radically different altitude. Anna: So what is the practical advice up north? Avery: Find a clear western horizon, the sea, a lake, a ridge with nothing on it. And look 20 to 45 minutes after sunset.

27:14 Venus is bright enough to punch through twilight and you will not mistake it for anything else. It is worth the effort. You just cannot be casual about it the way we can down here. Mercury is the harder version of the same lesson. From Sydney, it is 15 degrees up, uh, at sunset, a genuinely good apparition. And it sets an hour and a quarter after the Sun. From Los angeles, it is 8 degrees. From New York, six from London, three Southern. Listeners, this is your Mercury. It sits below and to the right of Venus, about 24 degrees away then the Moon.

27:55 And this is where both hemispheres get the same present. It is a fat Crescent tonight, about 37% lit, going to 47% tomorrow. And first quarter falls on Friday the 18th at 43 minutes past 8 in the evening, universal time, which is quarter to 7 on Saturday morning here in Sydney. And that timing is not an accident because Saturday the 19th is international. Observe the Moon night, which is deliberately Anna: scheduled for this phase. Avery: Deliberately and for the right reason. A full moon is a flat, glaring, shadowless disc and it is the worst night of the month to look at it.

28:36 At first quarter, the terminator, the line between lunar day and lunar night, runs straight down the middle. The sunlight comes in almost sideways and every crater, rim and mountain throws a long shadow. Through even the smallest telescope. The Moon stops being a picture and becomes a landscape. And in the light of our second storey, have a look at Mare Chrisium, the dark oval near the eastern limb. It is obvious in binoculars. Somewhere out on its outer ring, 20 kilometres east of Mare Spumans, is the crater that was not there before the middle of 2024.

29:15 You will not see it. 200 metres is far below anything Earth based equipment can resolve. And at this phase that region is fully lit and flat, rather than sitting on the terminator. But you will be looking at the right patch of ground and knowing it is there changes what you are looking at. Before dawn, the balance flips and this one belongs to the North Jupiter Is the prize at the start of nautical Twilight. Jupiter is 26 degrees up from Los Angeles, 24 from New York, 21 from London and only 8 1/2 degrees from Sydney.

29:52 Still fighting the horizon murk. Mars is even more lopsided, 48 degrees up from Los Angeles, 46 from New York, 40 from London against uh, 20 from Sydney. Mars is faint at the moment, magnitude 1.2, an unremarkable orange dot, but the two are 23 degrees apart and closing. They will be about 12 degrees apart by mid October and about 2 degrees apart by mid November. Start watching that gap now and the shrinking is the whole point. Saturn is well placed for everybody before dawn around 23 to 28 degrees up wherever you are and it is worth getting familiar with because opposition is on the 4th of October rings about 7 degrees open disc a uh touch under 20 arc seconds.

30:44 One note for the southern zodiacal light hunters, not this week. The evening sky is moonlit from here through full moon on the 26th. That false dusk in the west. The faint cone of sunlight scattered off interplanetary dust which is an evening object from the southern hemisphere and a pre dawn object from the northern at this time of year comes back into play in the first week of October and the equinox Wednesday the 23rd at five minutes past midnight Universal time which is the evening of Tuesday the 22nd across the Americas and mid morning on Wednesday here in Australia.

31:24 It is an instant, not a day, so the date depends on where you are standing. Finally, and we say this every single episode for a reason, our space weather storey mentioned a big sunspot group visible in 1848 and every time we mention sunspots someone quite reasonably wants to go and look. Do not point any telescope, any binoculars or any camera at the sun without a purpose built solar filter fitted over the front of the optics. If you are using eclipse glasses or a handheld solar viewer they must meet the ISO 123122 international safety standard cheque for that marking and cheque the filter for scratches or pinholes before every single use.

32:10 Sunglasses are not a solar filter. Exposed film, smoked glass and welding glass below shade 14 are not solar filters. Eye damage from the sun is painless and permanent and it does not announce itself until it is done. Anna: That is Astronomy AstroDailyPod for Thursday 17th September. A planet under a million years old caught in the gap. It is carving a 200 metre hole in the moon that nobody saw arrive. A Victorian train delay recovered from the wrong decade and a dead star getting hotter by the year.

32:47 Avery: Show notes Sources and links for everything we have covered are at astronomydaily IO and there is a contact form there. Listener questions have started whole segments on this show, so use it. Anna: We are on x, Facebook, Instagram, TikTok and Tumblr. AstroDaily Pod Astronomy AstroDailyPod is part of the Bitesz.com podcast network produced in Sydney. Avery: I'm Avery. Anna: And I'm Anna. Clear Skies.

33:18 Mhm.