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00:00:01 --> 00:00:03 Anna: Sometime tomorrow morning, a piece of a
00:00:03 --> 00:00:06 rocket that has been lost in space for a year
00:00:06 --> 00:00:09 and a half is going to hit the moon and dig
00:00:09 --> 00:00:11 a brand new crater into a world that has kept
00:00:11 --> 00:00:13 its scars for 4 billion years.
00:00:14 --> 00:00:17 Avery: No one planned it, no one can stop it. And a
00:00:17 --> 00:00:19 small army of astronomers have set their
00:00:19 --> 00:00:21 alarms to watch and good
00:00:21 --> 00:00:23 Anna: day and welcome to Astronomy Daily. I'm
00:00:23 --> 00:00:24 Anna.
00:00:24 --> 00:00:27 Avery: And I'm Avery. Today is all about impacts.
00:00:27 --> 00:00:29 The ones we make and the ones the universe
00:00:29 --> 00:00:30 made long before us.
00:00:30 --> 00:00:33 Anna: A dead Falcon nine about to punch the moon.
00:00:33 --> 00:00:36 The asteroid that may have charbroiled the
00:00:36 --> 00:00:39 dinosaurs. Within hours, the ancient smash
00:00:39 --> 00:00:41 up that shattered Neptune's moons. And then
00:00:41 --> 00:00:44 to zoom right out, a new map that just
00:00:44 --> 00:00:45 doubled the X ray sky.
00:00:46 --> 00:00:48 Avery: Plus a uh, both hemisphere skywatch with a
00:00:48 --> 00:00:51 genuinely special comet in it. Let's get into
00:00:51 --> 00:00:51 it.
00:00:52 --> 00:00:54 Anna: So let's start with the story everyone will
00:00:54 --> 00:00:57 be talking about tomorrow. Early on Wednesday
00:00:57 --> 00:01:00 5 August, at about 06:35
00:01:00 --> 00:01:03 Universal Time, a spent upper stage of a
00:01:03 --> 00:01:05 SpaceX Falcon 9 is going to slam into
00:01:05 --> 00:01:08 the far western edge of the Moon's near side,
00:01:09 --> 00:01:11 close to a feature called Einstein Crater.
00:01:11 --> 00:01:14 Avery: And um, this isn't a controlled landing gone
00:01:14 --> 00:01:17 wrong. This is a genuinely derelict object.
00:01:17 --> 00:01:19 Space junk finally running out of road.
00:01:20 --> 00:01:23 Anna: Exactly. Let's rewind back.
00:01:23 --> 00:01:25 In January 2025 a Falcon
00:01:25 --> 00:01:28 9 launched from Kennedy Space center carrying
00:01:28 --> 00:01:31 two moon bound Firefly's
00:01:31 --> 00:01:34 Blee Ghost which went on to land beautifully,
00:01:34 --> 00:01:36 and Ispace's resilience which
00:01:36 --> 00:01:39 sadly didn't survive its own touchdown.
00:01:39 --> 00:01:42 The landers separated and went on their way.
00:01:42 --> 00:01:45 But the rocket's upper stage, the big
00:01:45 --> 00:01:47 second stage tube that does the final push,
00:01:48 --> 00:01:50 was left stranded, too high to
00:01:50 --> 00:01:52 Avery: fall straight back to Earth, too slow to
00:01:52 --> 00:01:55 escape cleanly. So it just wandered
00:01:55 --> 00:01:56 for about 18
00:01:56 --> 00:01:59 Anna: months in a long chaotic loop shaped
00:01:59 --> 00:02:02 by the tug of the Earth, the Moon, the sun
00:02:02 --> 00:02:05 and even the faint pressure of sunlight
00:02:05 --> 00:02:08 itself. It's cataloged unglamorously
00:02:08 --> 00:02:10 as 2025010
00:02:11 --> 00:02:13 D. And an independent astronomer named
00:02:13 --> 00:02:16 Bill Gray, who runs the tracking project
00:02:16 --> 00:02:18 Project Pluto, has been following it the
00:02:18 --> 00:02:19 whole way.
00:02:19 --> 00:02:21 Avery: This is the same Bill Gray who called the
00:02:21 --> 00:02:22 last one, isn't it?
00:02:22 --> 00:02:25 Anna: It is. A few years back he identified
00:02:25 --> 00:02:28 another derelict stage on a lunar collision
00:02:28 --> 00:02:30 course. This is his second and around
00:02:30 --> 00:02:33 March, watching the numbers tighten, he
00:02:33 --> 00:02:35 realized this one wasn't going to be a near
00:02:35 --> 00:02:37 miss. It was going to connect.
00:02:38 --> 00:02:40 Avery: So give us the ballistics. How hard does a
00:02:40 --> 00:02:41 thing like this hit?
00:02:41 --> 00:02:44 Anna: It's roughly a four ton object, about
00:02:44 --> 00:02:47 a 12 meter metal tube arriving at
00:02:47 --> 00:02:49 something like two and a half kilometers a
00:02:49 --> 00:02:52 second. That's about 5
00:02:52 --> 00:02:55 miles an hour, comfortably faster than a
00:02:55 --> 00:02:57 rifle bullet. The energy release is on the
00:02:57 --> 00:03:00 order of three tons of tnt.
00:03:00 --> 00:03:01 Avery: And um, what does that carve out?
00:03:02 --> 00:03:04 Anna: Best estimates put the new crater somewhere
00:03:04 --> 00:03:07 between about 17 and 27
00:03:07 --> 00:03:10 meters across and a few meters deep,
00:03:10 --> 00:03:13 small on a lunar scale. But here's the thing
00:03:13 --> 00:03:15 that has scientists genuinely excited.
00:03:16 --> 00:03:18 We will know almost to the second and to
00:03:18 --> 00:03:21 within a few kilometers exactly when
00:03:21 --> 00:03:24 and where a known object of known mass
00:03:24 --> 00:03:27 and known speed hit. That's an
00:03:27 --> 00:03:30 extraordinarily rare natural experiment
00:03:30 --> 00:03:30 because
00:03:30 --> 00:03:33 Avery: normally a fresh moon crater just appears.
00:03:33 --> 00:03:34 And you're working backwards.
00:03:35 --> 00:03:37 Anna: Right here we get to work forwards.
00:03:37 --> 00:03:40 NASA's Lunar Reconnaissance Orbiter can
00:03:40 --> 00:03:43 photograph the site before and after. And
00:03:43 --> 00:03:45 because Bill Gray can hand the orbiter team a
00:03:45 --> 00:03:48 pinpoint, they'll know precisely where to
00:03:48 --> 00:03:51 look for the new scar. That before and after
00:03:51 --> 00:03:53 pair is gold for understanding how
00:03:53 --> 00:03:56 craters actually form and how the lunar
00:03:56 --> 00:03:58 surface throws material around.
00:03:58 --> 00:04:00 Avery: And um, there's a whole observing campaign
00:04:00 --> 00:04:01 around it too.
00:04:01 --> 00:04:03 Anna: I gather there is a paper with
00:04:03 --> 00:04:06 something like two dozen authors is
00:04:06 --> 00:04:08 coordinating professional and amateur
00:04:08 --> 00:04:10 observers to try and catch the ejecta
00:04:10 --> 00:04:13 plume, the spray of debris thrown up at the
00:04:13 --> 00:04:16 moment of impact. Now I want to be careful
00:04:16 --> 00:04:18 here because this feeds straight into our
00:04:18 --> 00:04:21 sky. Watch later. You are not going to see a
00:04:21 --> 00:04:24 flash with your eyes. The impact is on sunlit
00:04:24 --> 00:04:26 ground near the day night line on the Moon's
00:04:26 --> 00:04:29 western limb. The plume is a long shot even
00:04:29 --> 00:04:31 for advanced amateurs with serious
00:04:31 --> 00:04:32 instruments.
00:04:32 --> 00:04:35 Avery: But timing wise, who's best placed?
00:04:35 --> 00:04:38 Anna: Americas north and south? For North
00:04:38 --> 00:04:41 American listeners, it's about 2:35 in the
00:04:41 --> 00:04:44 morning. Eastern pre dawn moon well up in the
00:04:44 --> 00:04:46 west will give Southern hemisphere viewers
00:04:46 --> 00:04:49 the honest picture in the skywatch, because
00:04:49 --> 00:04:51 from here in Sydney, the Moon is actually
00:04:51 --> 00:04:53 below the horizon at impact.
00:04:53 --> 00:04:55 Avery: Ana, uh, can we talk about the uncomfortable
00:04:55 --> 00:04:58 part of this? Because a rocket hitting the
00:04:58 --> 00:05:01 Moon by accident is a great story, but it's
00:05:01 --> 00:05:02 also a warning, isn't it?
00:05:02 --> 00:05:05 Anna: It really is, and I'm glad you raised it.
00:05:05 --> 00:05:07 This is only the second time we've ever
00:05:07 --> 00:05:10 documented an uncontrolled rocket body
00:05:10 --> 00:05:12 hitting the Moon. The first left a pair of
00:05:12 --> 00:05:15 craters on the far side back in 2022.
00:05:15 --> 00:05:18 Two in a few years. And as commercial
00:05:18 --> 00:05:21 lunar traffic ramps up toward permanent Moon
00:05:21 --> 00:05:23 based plans later this decade, the amount of
00:05:23 --> 00:05:26 hardware drifting around in cislunar space,
00:05:26 --> 00:05:29 the region between Earth and the Moon is only
00:05:29 --> 00:05:30 going up.
00:05:30 --> 00:05:33 Avery: And unlike low Earth orbit, there's really no
00:05:33 --> 00:05:35 rulebook out there that's the crux.
00:05:35 --> 00:05:38 Anna: In low Earth orbit, we at least have debris
00:05:38 --> 00:05:41 coordination guidelines for CIS lunar space.
00:05:41 --> 00:05:44 There is no equ international framework,
00:05:44 --> 00:05:47 no agreed way to track, catalog or safely
00:05:47 --> 00:05:50 dispose of these stages. Longtime
00:05:50 --> 00:05:52 listeners will remember we covered a study
00:05:52 --> 00:05:54 just last week on debris in distant
00:05:54 --> 00:05:57 retrograde orbits around the moon and how it
00:05:57 --> 00:06:00 becomes a hazard as traffic grows. This
00:06:00 --> 00:06:03 impact is that abstract worry made
00:06:03 --> 00:06:05 suddenly, literally concrete.
00:06:05 --> 00:06:07 Avery: Interestingly, the industry does seem to be
00:06:07 --> 00:06:10 learning. I read that a more recent SpaceX
00:06:10 --> 00:06:12 upper stage was deliberately parked in a long
00:06:12 --> 00:06:15 term solar orbit rather than left wander.
00:06:15 --> 00:06:18 Anna: That's right. A commercial choice, though not
00:06:18 --> 00:06:21 a regulation. Which is rather the point.
00:06:21 --> 00:06:24 So tomorrow morning, when a lost rocket
00:06:24 --> 00:06:26 finally comes home to the moon, it's worth
00:06:26 --> 00:06:29 holding two thoughts at once. It's a rare
00:06:29 --> 00:06:32 and valuable science opportunity. And it's
00:06:32 --> 00:06:35 a small, bright flag planted on a problem we
00:06:35 --> 00:06:36 haven't solved yet.
00:06:36 --> 00:06:39 Avery: One crater, two lessons. Beautifully put.
00:06:40 --> 00:06:42 Speaking of ancient scars, shall we go and
00:06:42 --> 00:06:44 look at some far older wreckage?
00:06:44 --> 00:06:47 Anna: Let's over to you go out to
00:06:47 --> 00:06:48 Avery: the cold edge of the solar system, to
00:06:48 --> 00:06:51 Neptune, and you find a little family of
00:06:51 --> 00:06:53 small inner moons huddled just outside the
00:06:53 --> 00:06:56 planet's rings. Voyager 2 spotted most of
00:06:56 --> 00:06:58 them on its one and only Flyby back in
00:06:58 --> 00:07:01 1989. And ever since they've been too small
00:07:01 --> 00:07:04 and too far to really study. Until the James
00:07:04 --> 00:07:06 Webb Space Telescope turned its spectrograph
00:07:06 --> 00:07:07 on them.
00:07:07 --> 00:07:10 Anna: And this is a Caltech team, Mike Brown's
00:07:10 --> 00:07:12 group, the Pluto Killer, himself. Led by
00:07:12 --> 00:07:13 Riley Davis?
00:07:14 --> 00:07:17 Avery: The very same. And what they found genuinely
00:07:17 --> 00:07:19 startled them in the light from three of
00:07:19 --> 00:07:22 those moons, Larissa, Galatea and Proteus.
00:07:22 --> 00:07:24 And in the rings, they detected clay
00:07:24 --> 00:07:27 minerals, specifically magnesium rich
00:07:27 --> 00:07:28 phyllosilicates.
00:07:28 --> 00:07:31 Anna: Clay in the outer solar system? Why is
00:07:31 --> 00:07:32 that such a shock?
00:07:33 --> 00:07:35 Avery: Because phyllosilicates had never been seen
00:07:35 --> 00:07:37 anywhere out there beyond Jupiter. And
00:07:37 --> 00:07:40 crucially, clays only form in the presence of
00:07:40 --> 00:07:43 liquid water, as Davis put it. It was
00:07:43 --> 00:07:45 simply not on their list of things to look
00:07:45 --> 00:07:48 for. It hit them in the face. You don't make
00:07:48 --> 00:07:51 these minerals on a tiny cold moonlet. You
00:07:51 --> 00:07:53 make them deep inside a much larger world
00:07:53 --> 00:07:55 with liquid water in its guts.
00:07:55 --> 00:07:57 Anna: Though, uh, the material is telling you it
00:07:57 --> 00:08:00 came from somewhere bigger, somewhere that no
00:08:00 --> 00:08:01 longer exists.
00:08:01 --> 00:08:04 Avery: That's the whole story in one sentence. The
00:08:04 --> 00:08:07 leading explanation is dramatic. Neptune
00:08:07 --> 00:08:09 once had its own orderly system of moons,
00:08:09 --> 00:08:12 much like Uranus does today. And then
00:08:12 --> 00:08:14 Triton arrived.
00:08:14 --> 00:08:17 Anna: Triton being Neptune's giant backwards
00:08:17 --> 00:08:17 orbiting moon.
00:08:18 --> 00:08:20 Avery: Right. And the smoking gun is that
00:08:20 --> 00:08:23 backwards orbit Triton almost certainly
00:08:23 --> 00:08:25 didn't form At Neptune. It's a captured
00:08:25 --> 00:08:28 Kuiper Belt object, a big icy world
00:08:28 --> 00:08:31 that wandered in from further out and got
00:08:31 --> 00:08:34 gravitationally snared. And the process
00:08:34 --> 00:08:36 of capturing something that large would have
00:08:36 --> 00:08:38 been catastrophic for whatever moons were
00:08:38 --> 00:08:40 already there. It would have scattered and
00:08:40 --> 00:08:42 shattered the original family.
00:08:42 --> 00:08:45 Anna: And these little inner moons are the
00:08:45 --> 00:08:48 Avery: reassembled shrapnel rubble from the
00:08:48 --> 00:08:50 interiors of those destroyed worlds
00:08:50 --> 00:08:53 exposed by the smashup. Some of it drifting
00:08:53 --> 00:08:55 back together into the moonlets we see now.
00:08:56 --> 00:08:59 Davis called it, seeing the fingerprints left
00:08:59 --> 00:09:01 behind by that process. There's even a neat
00:09:01 --> 00:09:04 consistency check. The largest of the three,
00:09:04 --> 00:09:07 Proteus, doesn't show the clays. And the
00:09:07 --> 00:09:08 team think it's because it's big enough to
00:09:08 --> 00:09:11 have reheated and reprocess itself after
00:09:11 --> 00:09:14 reforming, hiding its past better than its
00:09:14 --> 00:09:15 smaller siblings.
00:09:15 --> 00:09:18 Anna: That's a lovely detail. The biggest one is
00:09:18 --> 00:09:20 the best at, uh, covering its tracks. And it
00:09:20 --> 00:09:22 ties us right back to the top of the show,
00:09:22 --> 00:09:25 doesn't it? A crater tomorrow, a demolished
00:09:25 --> 00:09:27 moon system billions of years ago. Same
00:09:27 --> 00:09:29 violence, wildly different scale.
00:09:29 --> 00:09:32 Avery: The solar system builds by breaking things.
00:09:33 --> 00:09:35 And it means the next spacecraft we sent out
00:09:35 --> 00:09:37 there and an ice giant mission is a top
00:09:37 --> 00:09:40 priority whenever it happens would be flying
00:09:40 --> 00:09:42 to a, uh, genuine crime scene.
00:09:42 --> 00:09:44 Anna: Now to the most famous impact of them all.
00:09:44 --> 00:09:47 And a new twist on how it actually did its
00:09:47 --> 00:09:50 killing. 66 million years ago, a
00:09:50 --> 00:09:52 roughly 10 kilometer asteroid struck what's
00:09:52 --> 00:09:55 now the Yucatan Peninsula. And the age of the
00:09:55 --> 00:09:57 dinosaurs ended. The long standing picture is
00:09:57 --> 00:10:00 a slow death. Dust and soot blot out the sun.
00:10:00 --> 00:10:03 An impact. Winter sets in, food webs
00:10:03 --> 00:10:05 collapse over months and years.
00:10:05 --> 00:10:08 Avery: The years of darkness story, which is grim
00:10:08 --> 00:10:09 but slow.
00:10:09 --> 00:10:11 Anna: Right? But this new study out of Purdue,
00:10:12 --> 00:10:14 Brandon Johnson and colleagues in the Journal
00:10:14 --> 00:10:16 of Geophysical Research argues the very
00:10:16 --> 00:10:19 first few hours may have been far more brutal
00:10:19 --> 00:10:21 than we thought. Their headline essentially
00:10:21 --> 00:10:24 is that exposed animals could have been
00:10:24 --> 00:10:25 charbroiled within hours.
00:10:26 --> 00:10:28 Avery: Charbroiled being the technical term.
00:10:28 --> 00:10:31 Anna: Fair enough. Here's the mechanism. The
00:10:31 --> 00:10:34 impact vaporized an enormous amount of rock
00:10:34 --> 00:10:36 and flung it skyward. Some of that cooled
00:10:36 --> 00:10:39 into tiny glassy beads, spherules,
00:10:39 --> 00:10:41 which rained back down. And the friction of
00:10:41 --> 00:10:43 all that debris re entering the atmosphere
00:10:43 --> 00:10:46 creates, uh, a global heat pulse. That part
00:10:46 --> 00:10:48 we knew. But earlier models suggested the
00:10:48 --> 00:10:51 heat pulse, while nasty, might not be enough
00:10:51 --> 00:10:53 to set the whole planet alight.
00:10:53 --> 00:10:55 Avery: So what did this team add?
00:10:55 --> 00:10:58 Anna: Dust. Not the beads, the ultra fine
00:10:58 --> 00:11:01 stuff. A huge quantity of rock vapor never
00:11:01 --> 00:11:03 condensed into spherules. It stayed as
00:11:03 --> 00:11:06 microscopic dust high in the atmosphere. And
00:11:06 --> 00:11:08 when they put that dust layer into their
00:11:08 --> 00:11:11 simulations. It acted like an insulating
00:11:11 --> 00:11:13 blanket, trapping the heat from all those
00:11:13 --> 00:11:15 falling particles and radiating it down.
00:11:16 --> 00:11:18 Their number is striking surface heating
00:11:18 --> 00:11:20 about three and a half times more intense
00:11:20 --> 00:11:21 than the beads alone.
00:11:22 --> 00:11:22 Avery: Enough to.
00:11:23 --> 00:11:26 Anna: Enough, they argue, to ignite spontaneous
00:11:26 --> 00:11:28 wildfires around the world and kill
00:11:28 --> 00:11:31 exposed thin skinned animals within the first
00:11:31 --> 00:11:34 hour or two. Johnson's line was that you're
00:11:34 --> 00:11:36 essentially in the realm of killing off
00:11:36 --> 00:11:38 almost everything in that first window.
00:11:38 --> 00:11:40 Avery: So who survived that?
00:11:40 --> 00:11:43 Anna: Uh, exactly the ones you'd guess. Anything
00:11:43 --> 00:11:45 sheltering underground or underwater had a
00:11:45 --> 00:11:48 fighting chance. Which starts to explain the
00:11:48 --> 00:11:50 winners and losers pattern of that
00:11:50 --> 00:11:53 extinction. And then this is the elegant
00:11:53 --> 00:11:56 part. The same dust that cooked the surface
00:11:56 --> 00:11:58 in hour one goes on to block sunlight
00:11:58 --> 00:12:01 for years afterward. So it doesn't replace
00:12:01 --> 00:12:04 the impact winter idea. It bolts a
00:12:04 --> 00:12:06 ferocious opening act onto the front of it.
00:12:07 --> 00:12:09 Avery: I do want to flag the honest caveat though,
00:12:09 --> 00:12:10 please.
00:12:10 --> 00:12:12 Anna: And it's an important one. The clearest
00:12:12 --> 00:12:15 physical evidence for these global wildfires
00:12:15 --> 00:12:18 so far is really only found in North American
00:12:18 --> 00:12:21 rocks. A researcher not involved in the
00:12:21 --> 00:12:23 study, Alfio Chiarenza at University College
00:12:23 --> 00:12:26 London, made the fair point that we may
00:12:26 --> 00:12:29 eventually find a truly global fire record,
00:12:29 --> 00:12:31 but we just don't have it yet. So a
00:12:31 --> 00:12:34 compelling model, strong regional evidence,
00:12:34 --> 00:12:37 and a, uh, genuinely open question about how
00:12:37 --> 00:12:40 planet wide those first hour fires really
00:12:40 --> 00:12:40 were.
00:12:40 --> 00:12:43 Avery: And the Throughline Today show writes itself
00:12:43 --> 00:12:45 the same basic physics that'll carve a modest
00:12:45 --> 00:12:48 hole in the moon tomorrow. Scaled up is what
00:12:48 --> 00:12:49 reset life on Earth.
00:12:50 --> 00:12:53 Okay, moving on. Let's pull all the way back
00:12:53 --> 00:12:55 now from one new crater to nearly 2 million
00:12:56 --> 00:12:58 cosmic objects. The Erocita X ray
00:12:58 --> 00:13:00 telescope on the Spectrum Ringen Gamma
00:13:00 --> 00:13:03 mission has just put out its second big
00:13:03 --> 00:13:05 public data release, Dr. 2 and it is
00:13:05 --> 00:13:08 a genuine landmark for the high energy sky X
00:13:08 --> 00:13:11 Anna: rays, meaning the violent universe.
00:13:11 --> 00:13:13 Avery: The hot stuff, the hot, the violent,
00:13:13 --> 00:13:16 the extreme. Growing black holes,
00:13:16 --> 00:13:19 exploded stars, million degree gas between
00:13:19 --> 00:13:21 galaxies. Erocita scans the entire
00:13:21 --> 00:13:24 sky every six months and this release stacks
00:13:24 --> 00:13:26 the first three of those all sky scans
00:13:26 --> 00:13:29 together. The result, around 1.9
00:13:29 --> 00:13:32 million point like sources, things like stars
00:13:32 --> 00:13:34 and supermassive black holes, plus about
00:13:34 --> 00:13:37 64 extended sources, which are things
00:13:37 --> 00:13:39 like galaxy clusters and supernova remnants.
00:13:40 --> 00:13:42 Anna: Put that number in perspective for me.
00:13:42 --> 00:13:45 Avery: Happily. The previous great all sky X ray
00:13:45 --> 00:13:48 survey was ROSAT. Back in the early 1990s,
00:13:48 --> 00:13:51 it cataloged around 130 sources
00:13:51 --> 00:13:53 and that was the field's benchmark for 30
00:13:53 --> 00:13:56 years. Hirosita's first release already
00:13:56 --> 00:13:59 blew past it. Dr. 2 roughly doubles that
00:13:59 --> 00:14:02 again as the lead author, Miriam Ramos
00:14:02 --> 00:14:04 Ceja at the Max Planck Institute put it Every
00:14:04 --> 00:14:07 extra scan drags fainter sources up out of
00:14:07 --> 00:14:08 the noise.
00:14:08 --> 00:14:11 Anna: And there's a specific old mystery. This
00:14:11 --> 00:14:12 cracks, isn't there?
00:14:12 --> 00:14:15 Avery: There is and I love this one. For about 30
00:14:15 --> 00:14:17 decades we've known the flat disk of our own
00:14:17 --> 00:14:20 galaxy glows faintly in X rays. The
00:14:20 --> 00:14:23 galactic ridge, X ray emission. Without being
00:14:23 --> 00:14:25 able to prove source by source what's
00:14:25 --> 00:14:28 producing it, Dr. 2 delivers the first
00:14:28 --> 00:14:31 direct census of a population of cataclysmic
00:14:31 --> 00:14:33 variables, close binary stars where a dense
00:14:33 --> 00:14:36 white dwarf is pulling material off a
00:14:36 --> 00:14:38 companion. And it turns out there are enough
00:14:38 --> 00:14:40 of them to account for that mysterious glow.
00:14:41 --> 00:14:43 A 30 year puzzle resolved by sheer
00:14:43 --> 00:14:44 completeness.
00:14:44 --> 00:14:47 Anna: Though it's not one headline discovery, it's
00:14:47 --> 00:14:49 ah, a map good enough to answer questions we
00:14:49 --> 00:14:51 couldn't even properly ask before.
00:14:52 --> 00:14:55 Avery: That's exactly it. And it lands alongside a
00:14:55 --> 00:14:57 huge Sloan Digital Sky Survey data release.
00:14:57 --> 00:14:59 So a couple of hundred thousand of these X
00:14:59 --> 00:15:02 ray sources now have optical fingerprints and
00:15:02 --> 00:15:05 distances, which lets astronomers map growing
00:15:05 --> 00:15:07 black holes in three dimensions across cosmic
00:15:07 --> 00:15:10 time. Its infrastructure for a decade of
00:15:10 --> 00:15:10 discovery.
00:15:11 --> 00:15:14 Anna: From a single rooftop sized crater to
00:15:14 --> 00:15:17 a three dimensional map of the hot universe.
00:15:17 --> 00:15:19 Not a bad range for one episode.
00:15:19 --> 00:15:22 Avery: Let's move on to today's skywatch. Both
00:15:22 --> 00:15:23 hemispheres.
00:15:23 --> 00:15:26 Anna: Right? Let's take all this upward and outward
00:15:26 --> 00:15:29 and bring it to your own sky. And we start
00:15:29 --> 00:15:31 of course with tomorrow's morning's impact.
00:15:32 --> 00:15:34 Avery: The honest expectations version.
00:15:34 --> 00:15:37 Anna: The honest version. To be clear, this is
00:15:37 --> 00:15:40 not a naked eye event. There's no flash to
00:15:40 --> 00:15:42 see if you're a serious amateur in the
00:15:42 --> 00:15:45 Americas with a large telescope and a lot of
00:15:45 --> 00:15:48 patience. The ejectiplume is a long
00:15:48 --> 00:15:51 shot target near the Moon's western limb
00:15:51 --> 00:15:54 around 6:35 universal time.
00:15:54 --> 00:15:57 That's about 2:35 eastern for north
00:15:57 --> 00:15:59 America, Moon high in the west for
00:15:59 --> 00:16:02 everyone else. The real payoff comes later
00:16:02 --> 00:16:05 when the Lunar Reconnaissance Orbiter returns
00:16:05 --> 00:16:08 before an after images of the fresh crater.
00:16:09 --> 00:16:11 And from here in the southern hemisphere in
00:16:11 --> 00:16:13 Sydney, the Moon is below the horizon at
00:16:13 --> 00:16:16 impact time. So this one's an after the fact
00:16:16 --> 00:16:19 story for us. Watch for those orbiter
00:16:19 --> 00:16:20 images now.
00:16:20 --> 00:16:23 Avery: The one I'm genuinely excited about, the
00:16:23 --> 00:16:25 Anna: comet, Comet 10P Tempel 2.
00:16:26 --> 00:16:29 It rounded the sun on the 2nd of August and
00:16:29 --> 00:16:31 made its closest pass by Earth on the 3rd.
00:16:32 --> 00:16:34 About 0.41 astronomical
00:16:34 --> 00:16:37 units, roughly 62 million
00:16:37 --> 00:16:40 kilometers. So right now it's near its best,
00:16:40 --> 00:16:43 around 8th to 9th magnitude. That's
00:16:43 --> 00:16:46 not naked eye. Think large binoculars
00:16:46 --> 00:16:49 or a small telescope from A dark site, a
00:16:49 --> 00:16:51 small fuzzy patch near the globular cluster
00:16:52 --> 00:16:54 M M30 in Capricornus. But here's why
00:16:54 --> 00:16:57 it matters. This is expected to be Tempel
00:16:57 --> 00:17:00 2's finest return for the rest of the
00:17:00 --> 00:17:00 century.
00:17:01 --> 00:17:03 Avery: And this one actually favors us in the south.
00:17:03 --> 00:17:06 Anna: It does a nice one for our Southern
00:17:06 --> 00:17:08 Hemisphere listeners, where the comet climbs
00:17:08 --> 00:17:10 higher and sits up for much of the night.
00:17:11 --> 00:17:13 Northern Hemisphere friends you can catch it
00:17:13 --> 00:17:16 too. But it stays low over your southern
00:17:16 --> 00:17:19 horizon, so you'll want a clear flat sky
00:17:19 --> 00:17:22 in that direction. Your darkest window opens
00:17:22 --> 00:17:24 on the nights around the seventh and eighth,
00:17:24 --> 00:17:26 once the waning moon is out of the way.
00:17:27 --> 00:17:29 Avery: Anything for the early evening crowd who
00:17:29 --> 00:17:31 don't fancy a midnight comet hunt?
00:17:31 --> 00:17:34 Anna: Yes, look west after sunset tonight
00:17:34 --> 00:17:36 and you'll find brilliant Venus threaded
00:17:36 --> 00:17:39 neatly between two bright stars,
00:17:39 --> 00:17:41 Regulus, the heart of Leo and Spica,
00:17:41 --> 00:17:44 uh, in Virgo, a lovely easy
00:17:44 --> 00:17:46 lineup for both hemispheres. No equipment
00:17:46 --> 00:17:49 needed and if you're an early riser.
00:17:49 --> 00:17:52 Mercury reached its best morning showing on
00:17:52 --> 00:17:55 the second and is still hanging low in the
00:17:55 --> 00:17:58 pre dawn east. Catch it before the twilight
00:17:58 --> 00:17:58 drowns it out.
00:17:58 --> 00:18:01 Avery: And then the big one. Mark the calendar.
00:18:01 --> 00:18:03 Anna: The 12th of August, an enormous
00:18:03 --> 00:18:06 day. A total solar eclipse sweeps
00:18:06 --> 00:18:09 across Greenland, Iceland and Spain,
00:18:09 --> 00:18:12 Earth's first totality in more than two
00:18:12 --> 00:18:15 years. And on the very same day, the
00:18:15 --> 00:18:17 Perseid meteor shower peaks under a new
00:18:17 --> 00:18:20 moon sky, which is about as good as the
00:18:20 --> 00:18:23 perseids ever get. Plus a 6
00:18:23 --> 00:18:25 planet alignment. We'll build up to all of it
00:18:25 --> 00:18:28 over the coming episodes. And the essential
00:18:28 --> 00:18:30 safety note, which we will repeat every
00:18:30 --> 00:18:33 single time. A total solar eclipse is
00:18:33 --> 00:18:36 only safe to watch with your unaided eyes
00:18:36 --> 00:18:39 during the brief moments of totality itself.
00:18:39 --> 00:18:42 Any other time and everywhere outside the
00:18:42 --> 00:18:45 narrow path of totality, you must use
00:18:45 --> 00:18:47 certified ISO
00:18:47 --> 00:18:50
00:18:50 --> 00:18:53 eclipse. Uh, glasses or a, ah, proper solar
00:18:53 --> 00:18:55 filter. Ordinary sunglasses will not
00:18:55 --> 00:18:58 protect your eyes. Please look after them.
00:18:58 --> 00:19:01 Avery: Couldn't agree more. A spectacular sky ahead.
00:19:01 --> 00:19:04 Watched safely. And that's our lot for today.
00:19:04 --> 00:19:07 Impacts large, small, ancient and brand new.
00:19:07 --> 00:19:10 Anna: If today's show sparked something, come and
00:19:10 --> 00:19:13 find us at astronomydaily IO
00:19:13 --> 00:19:16 you can stream every back episode. Follow
00:19:16 --> 00:19:19 our continually updating Space News feed,
00:19:19 --> 00:19:22 Leave us a review, drop us a note and sign up
00:19:22 --> 00:19:24 for the daily newsletter. So the cosmos lands
00:19:24 --> 00:19:25 in your inbox
00:19:25 --> 00:19:27 Avery: each morning, Find us on social
00:19:27 --> 00:19:30 astrodaily pod and tell a
00:19:30 --> 00:19:32 stargazing friend. Word of mouth is how this
00:19:32 --> 00:19:33 little show grows.
00:19:33 --> 00:19:35 Anna: We are back tomorrow and if you're in the
00:19:35 --> 00:19:38 Americas with a big scope and an early alarm
00:19:38 --> 00:19:41 best of luck chasing that plume. Until then,
00:19:41 --> 00:19:44 From Anna and M. Avery, clear skies.