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This episode includes AI-generated content.
00:00:00 --> 00:00:01 Anna: Hello and welcome back.
00:00:02 --> 00:00:05 22 years ago this month NASA launched
00:00:05 --> 00:00:07 a satellite designed to last two years.
00:00:08 --> 00:00:10 Right now it is skimming the top of the
00:00:10 --> 00:00:13 atmosphere, falling a little lower on every
00:00:13 --> 00:00:16 orbit and by the time some of you hear this
00:00:17 --> 00:00:18 it may already be gone.
00:00:18 --> 00:00:21 Avery: Today, Swift's last orbit.
00:00:22 --> 00:00:24 What it found, where it could come down
00:00:25 --> 00:00:27 and why Northern Australia sits inside the
00:00:27 --> 00:00:30 zone. Then a uh, burst
00:00:30 --> 00:00:33 with caught back in 2016 that looks like
00:00:33 --> 00:00:35 two explosions of two completely different
00:00:35 --> 00:00:38 kinds four minutes apart. And
00:00:39 --> 00:00:41 Webb finds the interstellar comet 3I
00:00:41 --> 00:00:44 Atlas was built from 30 year ice than our
00:00:44 --> 00:00:45 own comets.
00:00:45 --> 00:00:46 Anna: I'm Anna.
00:00:46 --> 00:00:49 Avery: And I'm Avery. This is astronomy
00:00:49 --> 00:00:51 AstroDailyPod Series 5 Episode
00:00:51 --> 00:00:54 221 let's get into it
00:00:55 --> 00:00:57 Anna: so where are we up to with Swift?
00:00:57 --> 00:01:00 Avery: Let's start with where things stand. On
00:01:00 --> 00:01:02 Monday NASA said its Neil Garrell Swift
00:01:02 --> 00:01:05 Observatory is expected to re enter Earth's
00:01:05 --> 00:01:08 atmosphere on Wednesday 4 November.
00:01:08 --> 00:01:11 The US Space Force prediction as of Monday
00:01:11 --> 00:01:14 puts that at about 3:30 in the morning US
00:01:14 --> 00:01:16 Eastern Time, plus or minus 11 hours.
00:01:17 --> 00:01:20 That's half past eight Ah UTC. Half past
00:01:20 --> 00:01:23 seven on Wednesday evening in Sydney, half
00:01:23 --> 00:01:25 past eight on Wednesday morning in London and
00:01:25 --> 00:01:27 half past midnight on the US West Coast.
00:01:28 --> 00:01:31 Anna: Plus or uh, minus 11 hours is
00:01:31 --> 00:01:32 a big window.
00:01:32 --> 00:01:35 Avery: It's normal for an uncontrolled re entry.
00:01:35 --> 00:01:37 The spacecraft is skimming the top of the
00:01:37 --> 00:01:40 atmosphere at nearly 8 kilometres a second
00:01:40 --> 00:01:43 and how quickly it slows depends on how
00:01:43 --> 00:01:45 puffed up that atmosphere is, which depends
00:01:45 --> 00:01:48 on the sun. Other forecasters have published
00:01:48 --> 00:01:50 times several hours either side of NASA's.
00:01:51 --> 00:01:54 So the honest version is Wednesday, give
00:01:54 --> 00:01:56 or take and we'll know when it has happened.
00:01:56 --> 00:01:59 Anna: And this is the end of a story a
00:01:59 --> 00:02:01 lot of you have followed with us.
00:02:01 --> 00:02:04 Avery: It is Swift, launched on
00:02:04 --> 00:02:07 20 November 2004 into
00:02:07 --> 00:02:09 an orbit about 600 kilometres up.
00:02:10 --> 00:02:12 Over the last couple of years the rising
00:02:12 --> 00:02:15 solar cycle heated and expanded Earth's upper
00:02:15 --> 00:02:17 atmosphere and the extra drag pulled Swift
00:02:17 --> 00:02:20 down far faster than anyone planned.
00:02:21 --> 00:02:24 NASA paid Catalyst space $30 million
00:02:24 --> 00:02:27 for a robotic rescue. That was the Link
00:02:27 --> 00:02:30 spacecraft launched on the 3rd of July. Many
00:02:30 --> 00:02:31 of you wrote in through the contact form, um,
00:02:31 --> 00:02:34 asking what Link was doing and we've followed
00:02:34 --> 00:02:37 it ever since. Link ran into attitude control
00:02:37 --> 00:02:40 trouble close to within about 15 kilometres
00:02:40 --> 00:02:42 of swift. And in August NASA called off the
00:02:42 --> 00:02:45 capture. Swift went back to doing science for
00:02:45 --> 00:02:48 a final few weeks, made its last observation
00:02:48 --> 00:02:51 on 20 October and NASA announced the end of
00:02:51 --> 00:02:52 the mission on the 23rd.
00:02:52 --> 00:02:55 Anna: So what made Swift special?
00:02:55 --> 00:02:58 They are much bigger telescopes
00:02:58 --> 00:03:01 Avery: speed. Swift was built for
00:03:01 --> 00:03:03 gamma ray bursts, the most powerful
00:03:03 --> 00:03:06 explosions known, they're flashes that can
00:03:06 --> 00:03:09 last a fraction of a second and fade within
00:03:09 --> 00:03:11 minutes before Swift.
00:03:12 --> 00:03:14 By the time anyone knew where a burst had
00:03:14 --> 00:03:16 been, the trail had gone cold.
00:03:17 --> 00:03:19 Swift's Wide Field burst alert telescope
00:03:19 --> 00:03:22 spotted the flash, worked out where it was,
00:03:22 --> 00:03:24 sent the position to observatories on the
00:03:24 --> 00:03:26 ground, and then swung the whole spacecraft
00:03:26 --> 00:03:29 around to point its X ray and ultraviolet
00:03:29 --> 00:03:32 optical telescopes at the spot. The
00:03:32 --> 00:03:34 mission's principal investigator, Brad Senko
00:03:34 --> 00:03:36 at NASA Goddard, says that typically took
00:03:36 --> 00:03:39 about a minute with no human in
00:03:39 --> 00:03:40 the loop.
00:03:40 --> 00:03:43 Anna: A minute for a spacecraft about the
00:03:43 --> 00:03:45 size of a minibus.
00:03:46 --> 00:03:49 How do you even point a gamma ray telescope?
00:03:49 --> 00:03:52 You can't focus gamma rays with a mirror.
00:03:52 --> 00:03:55 Avery: You can't. So Swift used a trick
00:03:55 --> 00:03:58 called a coated mask. In front of the
00:03:58 --> 00:04:00 detector sits a plate covered in about
00:04:00 --> 00:04:02 52 small lead tiles
00:04:03 --> 00:04:06 laid out in a random looking pattern. Uh, a
00:04:06 --> 00:04:08 burst casts a shadow of that pattern onto the
00:04:08 --> 00:04:10 detector, and the way the shadow is shifted
00:04:10 --> 00:04:12 tells you which direction the light came
00:04:12 --> 00:04:15 from. Work that out on board in a few seconds
00:04:15 --> 00:04:18 and you know where to turn. Then the X
00:04:18 --> 00:04:20 ray telescope narrows the position down to a
00:04:20 --> 00:04:23 few arcseconds, and the ultraviolet optical
00:04:23 --> 00:04:26 telescope often finds the fading visible
00:04:26 --> 00:04:28 counterpart close enough for big ground based
00:04:28 --> 00:04:30 telescopes to take a spectrum while the
00:04:30 --> 00:04:31 afterglow is still bright.
00:04:32 --> 00:04:34 Anna: And that's the whole game, isn't it?
00:04:34 --> 00:04:36 Afterglows fade fast,
00:04:36 --> 00:04:39 Avery: very fast. An afterglow can drop by
00:04:39 --> 00:04:42 a factor of 100 in its first hour.
00:04:42 --> 00:04:45 Every minute you save is light you get to
00:04:45 --> 00:04:45 keep.
00:04:46 --> 00:04:48 Anna: And that minute settled one of the biggest
00:04:48 --> 00:04:50 arguments in high energy astronomy.
00:04:51 --> 00:04:53 Gamma ray bursts come in two broad
00:04:54 --> 00:04:57 long ones lasting more than about 2 seconds
00:04:57 --> 00:05:00 and short ones under 2 seconds. The
00:05:00 --> 00:05:02 long ones had been tied to the collapse of
00:05:02 --> 00:05:05 massive stars. The short ones nobody could
00:05:05 --> 00:05:08 pin down because they were over before anyone
00:05:08 --> 00:05:10 could look. In 2005,
00:05:10 --> 00:05:13 Swift caught a short burst lasting about
00:05:13 --> 00:05:16 three hundredths of a second and swung around
00:05:16 --> 00:05:18 fast enough to collect 11x ray photons from
00:05:18 --> 00:05:19 its afterglow.
00:05:20 --> 00:05:21 Avery: 11 photons.
00:05:22 --> 00:05:25 Anna: 11. It was the first afterglow
00:05:25 --> 00:05:28 ever seen from a short burst. And it opened
00:05:28 --> 00:05:29 the road to the picture we now take for
00:05:29 --> 00:05:32 granted. Short bursts come from merging
00:05:32 --> 00:05:33 neutron stars.
00:05:34 --> 00:05:36 Avery: What else is on the highlight reel?
00:05:36 --> 00:05:39 Anna: In 2009, Swift caught GRB
00:05:39 --> 00:05:42 090423, a burst
00:05:42 --> 00:05:44 whose light left home when the universe was
00:05:44 --> 00:05:47 only about 630 million years old.
00:05:48 --> 00:05:50 For a while, that was the most distant object
00:05:50 --> 00:05:53 known. In October 2022,
00:05:53 --> 00:05:56 together with NASA's Fermi telescope, it
00:05:56 --> 00:05:58 caught GRB 2210,
00:05:59 --> 00:06:02 nicknamed the boat the brightest of all time,
00:06:03 --> 00:06:05 about 2.4 billion light years away.
00:06:06 --> 00:06:09 And along the way, Swift stopped being just a
00:06:09 --> 00:06:12 burst hunter because m it could repoint so
00:06:12 --> 00:06:14 quickly and take requests from anyone. It
00:06:14 --> 00:06:17 became astronomy's rapid response multi tool
00:06:18 --> 00:06:20 supernovae, comets flaring
00:06:20 --> 00:06:23 stars, novae and stars being torn
00:06:23 --> 00:06:26 apart by black holes. In 2011,
00:06:26 --> 00:06:28 it caught a star being shredded by a distant
00:06:28 --> 00:06:31 black hole that launched a jet pointed almost
00:06:31 --> 00:06:33 straight at us, one of the first events of
00:06:33 --> 00:06:36 its kind ever seen. And in August 2017,
00:06:37 --> 00:06:39 when gravitational waves announced two
00:06:39 --> 00:06:42 neutron stars colliding, Swift was among the
00:06:42 --> 00:06:44 telescopes that turned to the kilonova and
00:06:44 --> 00:06:46 caught its early ultraviolet glow.
00:06:47 --> 00:06:49 Avery: So Swift was there for the first neutron star
00:06:49 --> 00:06:51 merger we ever heard.
00:06:51 --> 00:06:52 As well as saw
00:06:53 --> 00:06:55 Anna: it was. Swift had spent 12 years building
00:06:55 --> 00:06:58 the case that short bursts come from neutron
00:06:58 --> 00:07:01 star mergers. And in 2017, it got
00:07:01 --> 00:07:03 to see one with gravitational waves attached.
00:07:03 --> 00:07:06 Give us the scoreboard. By
00:07:06 --> 00:07:09 NASA's count, more than 2000
00:07:09 --> 00:07:12 gamma ray bursts, more than 1400
00:07:12 --> 00:07:15 supernovae, one and a half
00:07:15 --> 00:07:17 million images from the Ultraviolet Optical
00:07:18 --> 00:07:21 Telescope, and about 12 terabytes of data.
00:07:21 --> 00:07:24 That data sits behind roughly 7
00:07:24 --> 00:07:27 published papers, which works out at nearly
00:07:27 --> 00:07:29 one a day for 22 years.
00:07:30 --> 00:07:32 The archive is public, and it stays public.
00:07:33 --> 00:07:36 Swift will keep producing science after it's
00:07:36 --> 00:07:39 gone, and you'll hear exactly that in our
00:07:39 --> 00:07:39 next story.
00:07:40 --> 00:07:43 Avery: Now, the bit everyone is asking about, where
00:07:43 --> 00:07:44 does it come down?
00:07:45 --> 00:07:48 Anna: Nobody can say yet. And, uh, anyone who names
00:07:48 --> 00:07:50 you a town is guessing. What we do
00:07:50 --> 00:07:53 know comes from the orbit. Swift's
00:07:53 --> 00:07:56 orbit is tilted only about 20 and a half
00:07:56 --> 00:07:58 degrees to the equator, so it never flies
00:07:59 --> 00:08:01 further north or south than that.
00:08:01 --> 00:08:04 NASA says any surviving fragments are limited
00:08:04 --> 00:08:06 to between 20.6 degrees south
00:08:07 --> 00:08:09 and 20.6 degrees north.
00:08:10 --> 00:08:13 That band is mostly ocean, but it also
00:08:13 --> 00:08:16 covers parts of Central and South America,
00:08:16 --> 00:08:19 Africa, India, Southeast Asia
00:08:19 --> 00:08:20 and northern Australia.
00:08:22 --> 00:08:24 Roughly the southern edge runs at, uh, about
00:08:24 --> 00:08:27 the latitude of Mackay, Tennant Creek
00:08:27 --> 00:08:28 and Marble Bar.
00:08:28 --> 00:08:30 Avery: Should people up there be worried?
00:08:31 --> 00:08:33 Anna: No. NASA expects most of the
00:08:33 --> 00:08:36 spacecraft, about one and a half tons, to
00:08:36 --> 00:08:39 burn up. Some dense parts may survive.
00:08:40 --> 00:08:42 Sanko has pointed to tungsten components and
00:08:42 --> 00:08:45 some mirror parts. NASA puts
00:08:45 --> 00:08:48 the chance of anyone anywhere on Earth being
00:08:48 --> 00:08:50 harmed at roughly 1 in
00:08:50 --> 00:08:53 2100. That's for the whole
00:08:53 --> 00:08:56 planet, not for you personally. And most of
00:08:56 --> 00:08:58 the band is open sea. If you're in the
00:08:58 --> 00:09:00 tropics and the timing falls at night, you
00:09:00 --> 00:09:03 might, just might, see a fireball.
00:09:04 --> 00:09:06 So what does astronomy actually lose?
00:09:07 --> 00:09:10 The thing Swift did, catching a, uh,
00:09:10 --> 00:09:12 fleeting event and telling everyone else
00:09:12 --> 00:09:15 exactly where to look within a minute or so.
00:09:15 --> 00:09:18 NASA's Fermi still detects several bursts a
00:09:18 --> 00:09:21 week, but its positions are much coarser.
00:09:21 --> 00:09:23 Newer missions like the Chinese French
00:09:23 --> 00:09:26 SVOM and China's Einstein probe,
00:09:26 --> 00:09:29 both launched in 2024, now carry part
00:09:29 --> 00:09:30 of that load.
00:09:31 --> 00:09:33 But NASA has no dedicated Swift replacement
00:09:33 --> 00:09:34 waiting in the wings,
00:09:35 --> 00:09:38 Avery: 22 years from a AH2 year design
00:09:38 --> 00:09:38 life
00:09:39 --> 00:09:41 Anna: more than 10 times what it was built for.
00:09:42 --> 00:09:45 In 2018, NASA renamed the observatory
00:09:45 --> 00:09:48 for Neil Garrels, its principal investigator,
00:09:48 --> 00:09:49 who died the year before.
00:09:51 --> 00:09:54 Sometime around Wednesday, somewhere over
00:09:54 --> 00:09:56 the tropics, his observatory finishes its
00:09:56 --> 00:09:57 last orbit.
00:09:58 --> 00:10:01 Avery: Here's the Swift data point I promised on
00:10:01 --> 00:10:03 25 April 2016, Swift's
00:10:03 --> 00:10:06 Burst Alert Telescope triggered on a gamma
00:10:06 --> 00:10:08 ray burst far down in the southern sky.
00:10:08 --> 00:10:09 It's called
00:10:09 --> 00:10:12 GRB160425A.
00:10:12 --> 00:10:15 A new analysis published in Nature Astronomy
00:10:15 --> 00:10:17 last month argues it is two different
00:10:18 --> 00:10:20 kinds of explosion from one place
00:10:20 --> 00:10:21 four minutes apart.
00:10:22 --> 00:10:23 Anna: Two kinds of
00:10:23 --> 00:10:26 Avery: here's the light curve. First a sharp
00:10:26 --> 00:10:29 spike lasting about 1.7 seconds,
00:10:30 --> 00:10:32 then nothing at all for about
00:10:32 --> 00:10:33 256 seconds.
00:10:34 --> 00:10:37 Then a broad smooth burst lasting
00:10:37 --> 00:10:39 about 51 seconds.
00:10:40 --> 00:10:43 Swift panned both to the same spot on the sky
00:10:43 --> 00:10:46 and both are tied to the same afterglow and
00:10:46 --> 00:10:48 the same host galaxy at a redshift of
00:10:48 --> 00:10:50 0.
00:10:51 --> 00:10:53 That's light that set out more than 5 billion
00:10:53 --> 00:10:54 years ago.
00:10:55 --> 00:10:58 Anna: Couldn't that just be one burst
00:10:58 --> 00:10:59 with a pause in it?
00:11:00 --> 00:11:03 Avery: That's the question. The team led by Liang Li
00:11:03 --> 00:11:05 at Ningbo University and Yu Wang at Italy's
00:11:05 --> 00:11:08 inaf, with Bing Zong and Rung
00:11:08 --> 00:11:11 Jingkai among the co authors set out to test.
00:11:11 --> 00:11:14 They ran every standard classification test
00:11:14 --> 00:11:17 on each piece separately. Hardness,
00:11:17 --> 00:11:20 the shortest flicker time, the delay between
00:11:20 --> 00:11:23 high and low energy photons, and the well
00:11:23 --> 00:11:25 known energy relations. The first
00:11:25 --> 00:11:28 spike flickers on an 18 millisecond
00:11:28 --> 00:11:30 timescale with essentially no delay between
00:11:30 --> 00:11:32 energies, and comes out short type every
00:11:32 --> 00:11:35 time. The merger family. The
00:11:35 --> 00:11:38 second piece flickers on a timescale of about
00:11:38 --> 00:11:40 half a second with a delay of more than a
00:11:40 --> 00:11:43 second, and comes out long type every time.
00:11:43 --> 00:11:45 The collapsing star family
00:11:45 --> 00:11:48 Anna: and uh, the obvious alternatives?
00:11:48 --> 00:11:51 Avery: They looked at those too. Two unrelated
00:11:51 --> 00:11:53 bursts lining up in time and position by
00:11:53 --> 00:11:56 chance comes out at roughly two in a
00:11:56 --> 00:11:59 trillion. A short burst followed by
00:11:59 --> 00:12:02 a so called extended emission tail has
00:12:02 --> 00:12:04 never shown a four minute gap or a tail this
00:12:04 --> 00:12:07 bright. A long burst with a small
00:12:07 --> 00:12:09 precursor doesn't fit either because the
00:12:09 --> 00:12:11 first spike actually has the higher peak.
00:12:12 --> 00:12:15 The Authors say no existing model predicted
00:12:15 --> 00:12:15 this.
00:12:16 --> 00:12:19 Anna: So what's holding it back from being settled?
00:12:19 --> 00:12:22 Avery: Three things. It's one event, the
00:12:22 --> 00:12:24 telltale sign of a collapsing star. A
00:12:24 --> 00:12:26 supernova a couple of weeks later was
00:12:26 --> 00:12:28 searched for and not clearly found.
00:12:29 --> 00:12:32 So any supernova was fainter than the classic
00:12:32 --> 00:12:35 SN 1998BW. And no
00:12:35 --> 00:12:37 kilonova was confirmed either. To be fair to
00:12:37 --> 00:12:39 the timeline as well, the paper first
00:12:39 --> 00:12:42 appeared as a preprint in March, so this is
00:12:42 --> 00:12:44 published last month rather than brand new.
00:12:45 --> 00:12:47 Interestingly, the host looks like a pair of
00:12:47 --> 00:12:50 interacting galaxies and NASA's Fermi was on
00:12:50 --> 00:12:52 the far side of the Earth at the time, so
00:12:52 --> 00:12:55 Swift was the only gamma ray eye on it.
00:12:55 --> 00:12:58 Anna: And uh, the southern angle is real. Here
00:12:58 --> 00:12:59 Avery: it is.
00:12:59 --> 00:13:02 The redshift came from the VLT's X
00:13:02 --> 00:13:05 shooter at Paranol, with follow up from
00:13:05 --> 00:13:08 grand at La Silla and the SMART telescope
00:13:08 --> 00:13:10 at Cerro Tololo. The burst
00:13:10 --> 00:13:13 sits at a declination of about
00:13:13 --> 00:13:16 -54 from Sydney. That patch
00:13:16 --> 00:13:18 of sky climbs to about 70 degrees
00:13:19 --> 00:13:22 from New York and London. It never rises
00:13:22 --> 00:13:24 at all. A 10 year old Swift
00:13:24 --> 00:13:27 burst. Rewriting the rulebook in the very
00:13:27 --> 00:13:28 week Swift comes home
00:13:29 --> 00:13:31 Anna: to our third visitor from another star.
00:13:32 --> 00:13:35 Last week marked a year since interstellar
00:13:35 --> 00:13:37 comet 3I ATLAS made its closest
00:13:37 --> 00:13:40 approach to the Sun. And a new paper in the
00:13:40 --> 00:13:43 Astrophysical Journal Letters published on
00:13:43 --> 00:13:46 26 October looks at what its ice
00:13:46 --> 00:13:47 is actually made of.
00:13:48 --> 00:13:50 Avery: This is the comet discovered from Chile
00:13:51 --> 00:13:53 Anna: by the ATLAS survey telescope at
00:13:53 --> 00:13:56 Riojuto. Yes. The study
00:13:56 --> 00:13:58 is led by Sylvia Protopapa at the
00:13:58 --> 00:14:01 Southwest Research Institute, with NASA
00:14:01 --> 00:14:03 Goddard's Martin Cordner among the co authors
00:14:03 --> 00:14:05 who leads Webb's Interstellar Object
00:14:05 --> 00:14:08 Programme. They used Webb's near
00:14:08 --> 00:14:10 infrared spectrograph
00:14:11 --> 00:14:13 three times in August 2025,
00:14:14 --> 00:14:16 December 2025 and April
00:14:17 --> 00:14:20 2026, spanning the comet's swing past the
00:14:20 --> 00:14:20 Sun.
00:14:20 --> 00:14:22 Avery: What were they looking for?
00:14:22 --> 00:14:25 Anna: Water ice has a fingerprint in
00:14:25 --> 00:14:28 infrared light, a deep absorption band
00:14:28 --> 00:14:30 at 3 microns and 2 weaker ones at
00:14:30 --> 00:14:33 uh 1.5 and 2 microns.
00:14:34 --> 00:14:36 In ordinary comets of our own, you see all
00:14:36 --> 00:14:39 three in 3i Atlas,
00:14:39 --> 00:14:41 the 3 micron band was strong.
00:14:42 --> 00:14:44 It cut the reflected light by about
00:14:44 --> 00:14:47 77% at its deepest in August
00:14:47 --> 00:14:49 and by 94% in April.
00:14:50 --> 00:14:53 But the two shorter bands were very weak
00:14:53 --> 00:14:54 or missing altogether.
00:14:55 --> 00:14:57 Avery: So the ice is there but
00:14:58 --> 00:14:59 behaving oddly.
00:15:00 --> 00:15:03 Anna: Exactly. The team modelled how light scatters
00:15:03 --> 00:15:05 off grains of different sizes and
00:15:05 --> 00:15:08 compositions. The best fit is
00:15:08 --> 00:15:10 grains about a micron or smaller made
00:15:10 --> 00:15:13 of water ice mixed with A lot of dark
00:15:13 --> 00:15:16 rocky dust in grains like that
00:15:16 --> 00:15:18 light crosses very little ice before it
00:15:18 --> 00:15:21 scatters back out. So the weak bands
00:15:21 --> 00:15:24 vanish and only the strong one survives.
00:15:25 --> 00:15:27 Protopapa's point is that the grains are
00:15:27 --> 00:15:29 about the same size as those in our own
00:15:29 --> 00:15:32 comets. What sets 3i Atlas
00:15:32 --> 00:15:34 apart is how much dust is mixed into the
00:15:34 --> 00:15:37 ice. Comet Hartley 2 sheds nearly
00:15:37 --> 00:15:40 pure ice. 3 I Atlas sits at the
00:15:40 --> 00:15:41 dusty end.
00:15:42 --> 00:15:44 Avery: And um, the comparison with our own outer
00:15:44 --> 00:15:45 solar system,
00:15:45 --> 00:15:48 Anna: that's the striking part. When the team
00:15:48 --> 00:15:51 put three I Atlas alongside Webb
00:15:51 --> 00:15:54 spectra of Trans Neptunian objects, the
00:15:54 --> 00:15:57 icy bodies beyond Neptune, it no longer
00:15:57 --> 00:16:00 looked out of place. Some of them also lack
00:16:00 --> 00:16:02 the shorter water ice bands. The
00:16:02 --> 00:16:05 resemblance is in the water ice, not the
00:16:05 --> 00:16:08 carbon dioxide. The suggestion is that
00:16:08 --> 00:16:10 ice in planet forming discs here and
00:16:10 --> 00:16:13 around other stars may start out as tiny
00:16:13 --> 00:16:16 grains spanning a continuum from clean to
00:16:16 --> 00:16:19 dusty. And by the final observation in
00:16:19 --> 00:16:22 April, Webb picked up a second population of
00:16:22 --> 00:16:25 larger ice rich grains, possibly
00:16:25 --> 00:16:26 fresher material from deeper down.
00:16:27 --> 00:16:28 Avery: Caveats
00:16:28 --> 00:16:31 Anna: 2 that matter. It's one interstellar
00:16:31 --> 00:16:34 comet seen three times, so we don't know if
00:16:34 --> 00:16:37 it's typical. And this comes from modelling
00:16:37 --> 00:16:39 spectra, not from imaging individual grains.
00:16:40 --> 00:16:43 The December spectrum was messier with strong
00:16:43 --> 00:16:45 gas emission, so the detailed fits lean on
00:16:45 --> 00:16:48 August and April. The paper first went up as
00:16:48 --> 00:16:50 a preprint in late September,
00:16:51 --> 00:16:53 Avery: so it carries on our thread from September.
00:16:54 --> 00:16:57 Anna: It does. We've heard it's nitrogen
00:16:57 --> 00:17:00 which pointed to a frigid birthplace and
00:17:00 --> 00:17:02 its heavy water which pointed to an old one.
00:17:03 --> 00:17:06 Now its ice says it was built from the same
00:17:06 --> 00:17:08 kinds of grains as the far edge of our own
00:17:08 --> 00:17:08 solar system.
00:17:09 --> 00:17:10 Just dirtier.
00:17:10 --> 00:17:13 Avery: A few quick hits. Starship first
00:17:14 --> 00:17:16 flight 15 is targeted for no earlier than
00:17:16 --> 00:17:19 Thursday 12 November US time, according to
00:17:19 --> 00:17:22 the FAA's listing pending regulatory
00:17:22 --> 00:17:25 approval. SpaceX itself hasn't
00:17:25 --> 00:17:27 confirmed a date. Booster 22 and ship
00:17:28 --> 00:17:30 42 have both completed static fires and the
00:17:30 --> 00:17:32 plan is to catch both stages with the tower
00:17:32 --> 00:17:34 arms on one flight, which would be the first
00:17:34 --> 00:17:37 attempt to catch a ship. So that's Targeted.
00:17:37 --> 00:17:38 Not scheduled.
00:17:39 --> 00:17:40 Anna: BepiColombo
00:17:41 --> 00:17:43 Avery: Two and a half weeks out, the
00:17:43 --> 00:17:46 European Japanese spacecraft is due to be
00:17:46 --> 00:17:48 captured into orbit around Mercury on the
00:17:48 --> 00:17:51 21st of November. We'll have a proper curtain
00:17:51 --> 00:17:52 raiser closer to the day
00:17:52 --> 00:17:53 Anna: and Voyager
00:17:54 --> 00:17:57 Avery: around 18 November. Voyager
00:17:57 --> 00:18:00 1 is expected to reach one light day from
00:18:00 --> 00:18:03 Earth. That means a radio command takes uh,
00:18:03 --> 00:18:05 a full 24 hours to arrive. And
00:18:06 --> 00:18:08 the reply another 24 to come back.
00:18:09 --> 00:18:12 49 years after launch, it's still
00:18:12 --> 00:18:12 talking
00:18:13 --> 00:18:16 Anna: Time to look up. US Clocks fell
00:18:16 --> 00:18:19 back last weekend, so this week's times are
00:18:19 --> 00:18:21 in standard time in North America. Daylight
00:18:22 --> 00:18:24 in Sydney and GMT in London
00:18:25 --> 00:18:27 Avery: start before dawn, low in the east.
00:18:27 --> 00:18:30 Venus is back as a morning star, rising more
00:18:30 --> 00:18:33 than an hour before the Sun. Wednesday
00:18:33 --> 00:18:35 morning, it sits about 2 degrees from Spica,
00:18:35 --> 00:18:38 uh, the brightest star in Virgo. By Saturday
00:18:38 --> 00:18:41 the 7th, the gap closes to about one and
00:18:41 --> 00:18:43 a third degrees. And on Saturday,
00:18:44 --> 00:18:46 a very thin crescent moon, about 5%
00:18:46 --> 00:18:48 lit, joins them.
00:18:48 --> 00:18:50 Anna: How close does the Moon get?
00:18:50 --> 00:18:53 Avery: It depends where you are. About half
00:18:53 --> 00:18:56 an hour before sunrise on Saturday, the moon
00:18:56 --> 00:18:59 is about 1 1/2 degrees from Venus from
00:18:59 --> 00:19:01 New York, 2 degrees from London
00:19:02 --> 00:19:04 and nearly 3 from Los Angeles.
00:19:05 --> 00:19:07 From Sydney they're further apart, about
00:19:07 --> 00:19:10 8 1/2 degrees from the far
00:19:10 --> 00:19:13 south of South America. The Moon actually
00:19:13 --> 00:19:15 passes in front of Venus.
00:19:16 --> 00:19:19 Everywhere they'll be low. Venus is only
00:19:19 --> 00:19:21 about 8 to 13 degrees up, uh, half an hour
00:19:21 --> 00:19:24 before sunrise. So you need a clear eastern
00:19:24 --> 00:19:25 horizon.
00:19:26 --> 00:19:28 Anna: And with Venus that close to sunrise,
00:19:29 --> 00:19:30 the safety line matters.
00:19:31 --> 00:19:33 Avery: It does if you're scanning with binoculars.
00:19:33 --> 00:19:35 Put them away before the sun comes up.
00:19:36 --> 00:19:38 Never look at the sun with the naked eye,
00:19:38 --> 00:19:40 binoculars or a telescope, unless you're
00:19:40 --> 00:19:42 using eclipse glasses or a solar filter
00:19:42 --> 00:19:45 certified to the international standard ISO
00:19:45 --> 00:19:47 123122.
00:19:48 --> 00:19:50 Anna: Higher up before dawn, Mars
00:19:50 --> 00:19:51 and Jupiter.
00:19:52 --> 00:19:55 Avery: This is one for the north. On
00:19:55 --> 00:19:56 Wednesday, they're about four and a half
00:19:56 --> 00:19:59 degrees apart. Jupiter blazing at magnitude
00:19:59 --> 00:20:02 -2, and Mars, a much fainter
00:20:02 --> 00:20:05 orange 0.7. They closed
00:20:05 --> 00:20:08 the gap all fortnight, reaching about 1.2
00:20:08 --> 00:20:10 degrees on the morning of Monday the 16th
00:20:11 --> 00:20:13 from Los Angeles and New York. At the start
00:20:13 --> 00:20:15 of nautical dawn, they stand more than 60
00:20:15 --> 00:20:18 degrees up, around 50 from London.
00:20:18 --> 00:20:21 From Sydney, a, uh, more modest 27 to 30.
00:20:22 --> 00:20:24 Still an easy pairing. Just lower in the
00:20:24 --> 00:20:25 northeast,
00:20:25 --> 00:20:26 Anna: erm, um, the evening
00:20:27 --> 00:20:29 Avery: Saturn at the end of evening twilight. On
00:20:29 --> 00:20:32 Wednesday, it's about 38 degrees up from
00:20:32 --> 00:20:34 Sydney, 20 to 23 from the US
00:20:35 --> 00:20:38 and only about 13 from London. So the
00:20:38 --> 00:20:40 evening is the South's half of the week. A
00:20:40 --> 00:20:42 small telescope shows the rings, though
00:20:42 --> 00:20:44 they're still fairly narrow
00:20:44 --> 00:20:45 Anna: moon phases.
00:20:46 --> 00:20:48 Avery: New moon falls on Monday the 9th at
00:20:48 --> 00:20:51 0202 UTC. That's six
00:20:51 --> 00:20:54 in the evening Monday in Sydney and two in
00:20:54 --> 00:20:56 the morning Monday on the US East Coast.
00:20:57 --> 00:20:59 So the coming week is a good dark sky
00:20:59 --> 00:21:02 stretch. And the Taurid meteors are still
00:21:02 --> 00:21:05 trickling along. They're slow and they
00:21:05 --> 00:21:08 occasionally throw a bright fireball. Then
00:21:08 --> 00:21:10 the Leonids peak on the night of the 17th
00:21:10 --> 00:21:13 into the 18th first quarter is on the
00:21:13 --> 00:21:16 17th, so the moon sets around midnight and
00:21:16 --> 00:21:19 leaves the morning hours dark, which is when
00:21:19 --> 00:21:20 the Leonids are best.
00:21:20 --> 00:21:23 Anna: And a, uh, southern bonus from today's show,
00:21:23 --> 00:21:26 Avery: that burst from Our second story sits at
00:21:26 --> 00:21:29 declination minus 54. There's nothing to see
00:21:29 --> 00:21:31 there now, of course, but it's a reminder
00:21:31 --> 00:21:33 that a good share of swift sky lay in
00:21:33 --> 00:21:34 southern constellations.
00:21:34 --> 00:21:36 Most of our north Northern listeners never
00:21:36 --> 00:21:37 get to see
00:21:37 --> 00:21:38 Anna: Clear skies, everyone.
00:21:39 --> 00:21:42 Avery: That's the show. Swift's last orbit around
00:21:42 --> 00:21:44 Wednesday, with debris possible anywhere from
00:21:44 --> 00:21:47 20.6 degrees north to 20.6 south,
00:21:48 --> 00:21:50 a Swift burst that looks like two different
00:21:50 --> 00:21:53 explosions four minutes apart and Webb
00:21:53 --> 00:21:55 finding interstellar comet 3I
00:21:56 --> 00:21:58 ATLS made of dusty ice.
00:21:58 --> 00:22:01 Anna: If you followed the Swift link story with us
00:22:01 --> 00:22:04 because you asked about it, thank you. That's
00:22:04 --> 00:22:06 exactly how the contact form @astronomydaily
00:22:07 --> 00:22:10 IO is meant to work. Peep, the question's
00:22:10 --> 00:22:10 coming.
00:22:10 --> 00:22:13 Avery: You'll find us @astronomydaily IO
00:22:13 --> 00:22:16 and astrodaily pod on social media,
00:22:16 --> 00:22:18 part of the bytes.com podcast network.
00:22:19 --> 00:22:19 I'm Avery.
00:22:20 --> 00:22:23 Anna: And I'm Anna. Keep looking up
00:22:23 --> 00:22:24
00:22:26 --> 00:22:27 stories we told.