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This episode includes AI-generated content.
00:00:00 --> 00:00:03 Anna: Seven and a half light years away, there's a
00:00:03 --> 00:00:05 world with no sun, um, colder than a
00:00:05 --> 00:00:08 Sydney winter's night. And this week,
00:00:08 --> 00:00:10 we watched its clouds change.
00:00:11 --> 00:00:14 Avery: Not a picture, a single point of light
00:00:14 --> 00:00:17 measured every 15 minutes for 11 hours by
00:00:17 --> 00:00:19 the James Webb Space Telescope. Getting a
00:00:19 --> 00:00:22 little brighter and a little dimmer as the
00:00:22 --> 00:00:22 weather moved.
00:00:23 --> 00:00:25 Anna: Also today, a small star
00:00:25 --> 00:00:28 slowly eating a brown dwarf in an orbit that
00:00:28 --> 00:00:29 would fit inside the sun.
00:00:30 --> 00:00:33 10 minutes of X rays from a collision that
00:00:33 --> 00:00:35 should have been over in half a second. And
00:00:35 --> 00:00:38 a dead Soviet satellite that came apart over
00:00:38 --> 00:00:39 Western Australia.
00:00:40 --> 00:00:42 Avery: Plus, NASA goes caving on the Moon. And
00:00:42 --> 00:00:45 Mercury puts on its best evening show of the
00:00:45 --> 00:00:46 year for the Southern Hemisphere.
00:00:46 --> 00:00:47 Anna: I'm Anna.
00:00:48 --> 00:00:50 Avery: And I'm Avery. This is
00:00:50 --> 00:00:51 Astronomy AstroDailyPod.
00:00:52 --> 00:00:55 Anna: Let's start with the object itself, because
00:00:55 --> 00:00:57 it's a strange one. WISE
00:00:57 --> 00:01:00 0855 was found in 2014 by
00:01:00 --> 00:01:02 Kevin Lumen at Penn State in data from NASA's
00:01:02 --> 00:01:05 WISE infrared survey. It sits about
00:01:05 --> 00:01:08 seven and a half light years away, which
00:01:08 --> 00:01:10 makes it the fourth closest system to the sun
00:01:10 --> 00:01:13 after Alpha Centauri, Barnard Star, and the
00:01:13 --> 00:01:16 brown dwarf pair Luhman 16. And it's
00:01:16 --> 00:01:19 the coldest brown dwarf we know of, roughly
00:01:19 --> 00:01:21 265 kelvin. That's about minus 8
00:01:21 --> 00:01:22 Celsius.
00:01:22 --> 00:01:25 Avery: A brown dwarf is an object that formed the
00:01:25 --> 00:01:28 way a star does, collapsing out of a gas
00:01:28 --> 00:01:30 cloud, but never gathered enough mass to fuse
00:01:30 --> 00:01:33 hydrogen. So it just slowly
00:01:33 --> 00:01:35 cools. Wise
00:01:35 --> 00:01:37 0855 has been cooling for billions of
00:01:37 --> 00:01:40 years, and it drifts through space on its
00:01:40 --> 00:01:42 own. No parent star, no
00:01:42 --> 00:01:45 sunlight. Every bit of light we get from it
00:01:45 --> 00:01:47 is its own leftover heat.
00:01:48 --> 00:01:49 Anna: How heavy is it?
00:01:49 --> 00:01:52 Avery: Somewhere between a few and about 10
00:01:52 --> 00:01:54 times Jupiter's mass, depending on whose
00:01:54 --> 00:01:57 models you use. The universities really says
00:01:57 --> 00:01:59 about twice Jupiter. It's about Jupiter's
00:01:59 --> 00:02:02 size either way, which is why astronomers
00:02:02 --> 00:02:05 have wanted it so badly. It's the closest
00:02:05 --> 00:02:06 thing we have to a Jupiter we can study
00:02:06 --> 00:02:09 without a star blinding the view. But
00:02:09 --> 00:02:11 here's the part I didn't know until I read
00:02:11 --> 00:02:14 this. On Jupiter, the water clouds are there,
00:02:14 --> 00:02:16 but you can't see them because there's a deck
00:02:16 --> 00:02:19 of ammonia clouds sitting on top of right.
00:02:19 --> 00:02:22 Anna: At wise 0855's temperature,
00:02:22 --> 00:02:25 ammonia doesn't condense into clouds, so the
00:02:25 --> 00:02:28 water clouds are the top layer. That means if
00:02:28 --> 00:02:30 you could watch this object closely enough,
00:02:30 --> 00:02:32 you'd be looking straight at water weather.
00:02:33 --> 00:02:35 Avery: And, um, this isn't the first time someone
00:02:35 --> 00:02:37 has said water clouds about wise
00:02:37 --> 00:02:39 0855.
00:02:39 --> 00:02:41 Anna: No. And we should be careful because a lot of
00:02:41 --> 00:02:44 Headlines this week said first water clouds
00:02:44 --> 00:02:47 outside the solar system. That claim was made
00:02:47 --> 00:02:50 for this exact object in 2014 from a
00:02:50 --> 00:02:53 ground based detection and again in 2016 when
00:02:53 --> 00:02:55 the first spectrum showed water vapour and
00:02:55 --> 00:02:56 the signature of clouds.
00:02:57 --> 00:03:00 What's new is the word variable. This is
00:03:00 --> 00:03:02 the first time anyone has watched water
00:03:02 --> 00:03:04 clouds outside our solar system change.
00:03:04 --> 00:03:07 Avery: And that 2014 detection has an Australian
00:03:07 --> 00:03:07 name on it.
00:03:08 --> 00:03:10 Anna: It does. The 2014 paper
00:03:10 --> 00:03:13 that first saw Y0855 from the
00:03:13 --> 00:03:16 ground, led by Jacqueline Verity and using
00:03:16 --> 00:03:18 the Magellan telescope at Las Campanas in
00:03:18 --> 00:03:21 Chile, had Chris Tinney from UNSW
00:03:21 --> 00:03:22 as a co author.
00:03:22 --> 00:03:25 Verity's on this new paper too. So it's
00:03:25 --> 00:03:28 a 12 year thread and it began in the south.
00:03:29 --> 00:03:31 Avery: So what did the new study actually do?
00:03:31 --> 00:03:34 Anna: The team was led by Brittany Miles at the
00:03:34 --> 00:03:36 University of Arizona's Steward Observatory.
00:03:36 --> 00:03:39 With more than 25 CO authors.
00:03:39 --> 00:03:41 They pointed Webb's Nurse Spec Instrument at
00:03:41 --> 00:03:44 WISE 0855 for 11 hours
00:03:44 --> 00:03:47 and took a Spectru 15 minutes.
00:03:47 --> 00:03:49 That's about 44 snapshots of its light.
00:03:50 --> 00:03:52 Each one split into hundreds of infrared
00:03:52 --> 00:03:54 wavelengths from about 3 to 5
00:03:54 --> 00:03:55 micrometres.
00:03:56 --> 00:03:58 Avery: And wise 0855 is just a
00:03:58 --> 00:04:01 point. You can't see a cloud on it.
00:04:01 --> 00:04:04 Anna: Exactly. You can't resolve it into a
00:04:04 --> 00:04:07 disc. You get one dot of light
00:04:07 --> 00:04:09 and you watch how that light changes over
00:04:09 --> 00:04:11 time, wavelength by wavelength.
00:04:11 --> 00:04:14 Different molecules absorb at different
00:04:14 --> 00:04:16 wavelengths. Clouds dim things in a different
00:04:16 --> 00:04:19 pattern. So if the brightness at a
00:04:19 --> 00:04:22 carbon monoxide wavelength wobbles while the
00:04:22 --> 00:04:24 water wavelengths hold steady, that tells you
00:04:24 --> 00:04:26 which part of the atmosphere is changing.
00:04:27 --> 00:04:30 Avery: Which sounds like the Simp 0136
00:04:30 --> 00:04:32 story we did back in episode 197.
00:04:33 --> 00:04:35 Anna: It's the same tool that team used
00:04:35 --> 00:04:38 Principal Component Analysis to reduce a
00:04:38 --> 00:04:41 brown dwarf's weather to two underlying
00:04:41 --> 00:04:44 patterns. Miles and colleagues used
00:04:44 --> 00:04:46 the same technique here, sorting the changes
00:04:46 --> 00:04:49 into a few patterns that move together so the
00:04:49 --> 00:04:51 signal isn't drowned by the sheer number of
00:04:51 --> 00:04:54 wavelengths. So what
00:04:54 --> 00:04:57 moved two things at two different
00:04:57 --> 00:04:58 heights.
00:04:58 --> 00:05:00 The biggest swing was carbon monoxide
00:05:00 --> 00:05:03 changing by up to about 10% at some
00:05:03 --> 00:05:06 wavelengths. And phosphine moved in step
00:05:06 --> 00:05:08 with it. The two rise and fall together.
00:05:09 --> 00:05:12 Avery: Phosphine. That's the molecule from the Venus
00:05:12 --> 00:05:13 argument a few years back.
00:05:13 --> 00:05:15 Anna: Same molecule, completely different story
00:05:16 --> 00:05:19 here. Phosphine is a tracer. Neither carbon
00:05:19 --> 00:05:21 monoxide nor phosphine should survive in this
00:05:21 --> 00:05:24 cold upper atmosphere for long. They're made
00:05:24 --> 00:05:27 deep down, where it's hot and dense and
00:05:27 --> 00:05:29 carried up by convection faster than
00:05:29 --> 00:05:31 chemistry can destroy them. Jupiter does the
00:05:31 --> 00:05:33 same thing that's where Jupiter's phosphine
00:05:33 --> 00:05:34 comes from.
00:05:35 --> 00:05:37 So when both gases brighten and dim together,
00:05:37 --> 00:05:40 you're seeing deep air welling up.
00:05:40 --> 00:05:43 Avery: Wasn't phosphine supposed to be missing on
00:05:43 --> 00:05:44 this object?
00:05:44 --> 00:05:47 Anna: It was a genuine puzzle. A 2018
00:05:47 --> 00:05:50 ground based study which Miles was also part
00:05:50 --> 00:05:52 of found no sign of phosphine at all in
00:05:52 --> 00:05:55 Ys 0855 spectrum. Even though
00:05:55 --> 00:05:57 Jupiter style chemistry says it should be
00:05:57 --> 00:06:00 there now with Webb, it isn't just
00:06:00 --> 00:06:03 present, it's, it's moving with the carbon
00:06:03 --> 00:06:03 monoxide.
00:06:04 --> 00:06:07 That's a reminder that a non detection is
00:06:07 --> 00:06:09 often a statement about the instrument, not
00:06:09 --> 00:06:12 the object. The observing time itself came
00:06:12 --> 00:06:15 from a web cycle one programme led by Andrew
00:06:15 --> 00:06:17 Schemer at UC Santa Cruz who also led that
00:06:17 --> 00:06:20 2016 spectrum. Same team
00:06:20 --> 00:06:23 10 years on, finally with the telescope to
00:06:23 --> 00:06:24 answer its own question
00:06:25 --> 00:06:27 Avery: and the water higher up.
00:06:29 --> 00:06:32 Anna: Comparing the data to models, the team
00:06:32 --> 00:06:34 found that the overall shape of the spectrum
00:06:34 --> 00:06:37 needs water clouds and that the clouds are
00:06:37 --> 00:06:39 patchy and getting thicker and thinner.
00:06:40 --> 00:06:43 Biles own line was that they can watch the
00:06:43 --> 00:06:46 water clouds thicken and thin and the deep
00:06:46 --> 00:06:48 gases rise and fall as it happens.
00:06:49 --> 00:06:51 Two layers of weather stacked on top of each
00:06:51 --> 00:06:53 other and both visible at once.
00:06:55 --> 00:06:57 Avery: There's a nice quote from Mark Marley, one of
00:06:57 --> 00:06:58 the co authors.
00:06:58 --> 00:07:01 Anna: He compared the atmosphere to a screen
00:07:01 --> 00:07:04 door. The light from deep inside has to
00:07:04 --> 00:07:04 pass through it.
00:07:05 --> 00:07:07 So you can't understand what's behind the
00:07:07 --> 00:07:09 screen until you understand the screen.
00:07:10 --> 00:07:13 That's really the point of this work. Clouds
00:07:13 --> 00:07:15 are the screen on almost every cold planet
00:07:15 --> 00:07:16 we'll ever study.
00:07:17 --> 00:07:18 Avery: So what are the caveats?
00:07:18 --> 00:07:19 Anna: 3.
00:07:20 --> 00:07:22 First, we don't actually know how long a day
00:07:22 --> 00:07:25 is on Y0855. Its
00:07:25 --> 00:07:28 rotation period hasn't been pinned down so we
00:07:28 --> 00:07:31 can't yet say whether 11 hours caught a full
00:07:31 --> 00:07:33 turn, half a turn or more.
00:07:34 --> 00:07:37 The teen's next step is more web time to
00:07:37 --> 00:07:39 measure the rotation and map the weather in
00:07:39 --> 00:07:42 three dimensions. Second, um,
00:07:42 --> 00:07:45 it's one object the physics probably
00:07:45 --> 00:07:48 carries over to cold gas giant exoplanets
00:07:48 --> 00:07:50 and that's the hope. But. But that's a
00:07:50 --> 00:07:52 suggestion from the authors, not a
00:07:52 --> 00:07:54 demonstrated result. And third,
00:07:55 --> 00:07:57 everything here depends on atmosphere models.
00:07:58 --> 00:08:00 Marley's screen door cuts both ways. The
00:08:00 --> 00:08:03 clouds are the finding and the clouds are
00:08:03 --> 00:08:05 also the hardest part to model.
00:08:05 --> 00:08:07 Avery: And where was this published?
00:08:07 --> 00:08:08 I've seen two answers.
00:08:09 --> 00:08:12 Anna: So have we. The preprint went up in mid
00:08:12 --> 00:08:14 September and says the paper is accepted to
00:08:14 --> 00:08:17 the Astronomical Journal, while the
00:08:17 --> 00:08:19 university's release says the Astrophysical
00:08:19 --> 00:08:22 Journal. Both are American Astronomical
00:08:22 --> 00:08:25 Society journals. So we'll just say it's out
00:08:25 --> 00:08:27 this month in an AAS journal.
00:08:27 --> 00:08:30 Avery: Bring it home for me. Why does a cloudy
00:08:30 --> 00:08:31 brown dwarf matter?
00:08:32 --> 00:08:35 Anna: Because it's the bridge. We know Jupiter
00:08:35 --> 00:08:38 in detail, but only one Jupiter.
00:08:38 --> 00:08:41 The cold exoplanets that future telescopes
00:08:41 --> 00:08:44 will image directly will mostly be faint
00:08:44 --> 00:08:46 dots orbiting bright stars.
00:08:47 --> 00:08:49 Wise 0855 is a faint dot
00:08:49 --> 00:08:52 with no star in the way. Cold enough to have
00:08:52 --> 00:08:55 water. Weather close enough that Webb can
00:08:55 --> 00:08:58 take a spectrum every 15 minutes. If we can
00:08:58 --> 00:09:00 learn to read weather from one point of light
00:09:00 --> 00:09:02 here, that's the method we'll use for every
00:09:02 --> 00:09:04 cold giant planet after it.
00:09:04 --> 00:09:07 Avery: A rehearsal for exoplanet weather
00:09:07 --> 00:09:08 forecasting.
00:09:08 --> 00:09:11 Anna: And the forecast for wise 0855
00:09:12 --> 00:09:15 as far as anyone can tell, is minus
00:09:15 --> 00:09:17 8 Cloudy with patchy water
00:09:17 --> 00:09:20 clouds and a chance of phosphine.
00:09:20 --> 00:09:23 Avery: From one brown dwarf to another and this one
00:09:23 --> 00:09:26 is being eaten. The system is called
00:09:26 --> 00:09:28 ZTFJ0440
00:09:28 --> 00:09:31 2325, about 300
00:09:31 --> 00:09:34 light years away in Taurus. It's a small red
00:09:34 --> 00:09:37 dwarf star about 85 times Jupiter's mass
00:09:37 --> 00:09:40 with a brown dwarf of about 25 Jupiter
00:09:40 --> 00:09:42 masses orbiting it every 87 minutes.
00:09:43 --> 00:09:46 Anna: 87 minutes, that's a full year and
00:09:46 --> 00:09:48 under an hour and a half and
00:09:48 --> 00:09:51 Avery: the whole orbit would fit inside the Sun.
00:09:52 --> 00:09:54 At that range the star's gravity pulls gas
00:09:54 --> 00:09:56 off the brown dwarf in a steady stream.
00:09:57 --> 00:10:00 The paper led by MIT graduate student Aaron
00:10:00 --> 00:10:03 Householder with Kevin Burge came out in
00:10:03 --> 00:10:05 nature astronomy on the 5th of October.
00:10:06 --> 00:10:08 Housekeeping first. The preprint went up in
00:10:08 --> 00:10:10 March, so this is a seven month old result
00:10:11 --> 00:10:12 that's now been through peer review.
00:10:14 --> 00:10:14 Anna: How did they find?
00:10:15 --> 00:10:18 Avery: Started as a puzzle. Burge was going through
00:10:18 --> 00:10:20 data from the Zwicky Transient Facility at
00:10:20 --> 00:10:23 Palomar, which photographs the northern sky
00:10:23 --> 00:10:25 over and over, looking for things that
00:10:25 --> 00:10:28 change. One source traced a uh, triangle
00:10:28 --> 00:10:31 shaped light curve rising and falling in
00:10:31 --> 00:10:34 straight lines. His reaction roughly
00:10:34 --> 00:10:36 was that stars don't do that.
00:10:37 --> 00:10:39 Anna: So what does make a triangle?
00:10:39 --> 00:10:42 Avery: A hotspot. Because the star is much
00:10:42 --> 00:10:44 bigger than the stream, the gas doesn't form
00:10:44 --> 00:10:47 a disc. It slams straight into the star's
00:10:47 --> 00:10:50 surface at high speed. Birch compared it to
00:10:50 --> 00:10:53 an asteroid hitting the moon that heats one
00:10:53 --> 00:10:55 patch of the star. And as the pair orbits,
00:10:55 --> 00:10:58 the hot patch swings into view and out again.
00:10:59 --> 00:11:01 Anna: And the obvious alternative was a black
00:11:01 --> 00:11:03 widow, right?
00:11:03 --> 00:11:06 Avery: A pulsar slowly eroding a uh, light
00:11:06 --> 00:11:08 companion. But a pulsar is
00:11:08 --> 00:11:11 heavy and it would make the visible star
00:11:11 --> 00:11:14 wobble a lot. Householder measured the wobble
00:11:14 --> 00:11:16 with follow of spectroscopy and it was far
00:11:16 --> 00:11:17 too small.
00:11:17 --> 00:11:20 A red dwarf and a brown dwarf was the only
00:11:20 --> 00:11:21 thing that fit.
00:11:22 --> 00:11:24 Anna: And why is a slow um, meal surprising?
00:11:25 --> 00:11:28 Avery: Because the usual expectation is that when
00:11:28 --> 00:11:30 a star and a substellar companion get too
00:11:30 --> 00:11:33 close, it ends quickly. The
00:11:33 --> 00:11:36 orbit decays or the star swells
00:11:36 --> 00:11:38 and the companion is swallowed.
00:11:39 --> 00:11:41 Here the lighter object is the one giving up
00:11:41 --> 00:11:44 mass. And when the lighter partner is the
00:11:44 --> 00:11:47 donor, the orbit tends to respond by
00:11:47 --> 00:11:49 widening slightly, which keeps the flow
00:11:49 --> 00:11:52 gentle rather than runaway. The team
00:11:52 --> 00:11:55 estimates the brown dwarf loses roughly a
00:11:55 --> 00:11:57 hundred thousandth of an Earth mass each
00:11:57 --> 00:12:00 year. Burge's line was that the star can
00:12:00 --> 00:12:01 gradually eat it for billions of years.
00:12:02 --> 00:12:03 Anna: Is it the only one?
00:12:04 --> 00:12:07 Avery: It's the first confirmed case of stable
00:12:07 --> 00:12:09 mass transfer from a substellar object
00:12:09 --> 00:12:11 onto a normal star.
00:12:12 --> 00:12:13 They also present a strong
00:12:14 --> 00:12:16 ZTF J1444
00:12:16 --> 00:12:19 4820, a 67
00:12:19 --> 00:12:22 minute pair sitting inside a triple system.
00:12:23 --> 00:12:25 No Australian team on this one. And Taurus
00:12:25 --> 00:12:28 sits low in the north from here. So this is
00:12:28 --> 00:12:31 an honestly northern discovery. But it
00:12:31 --> 00:12:33 suggests that some of the brown dwarfs we
00:12:33 --> 00:12:35 count as missing close to their stars, may
00:12:35 --> 00:12:37 not have been swallowed.
00:12:37 --> 00:12:39 They may just be getting slowly eaten.
00:12:39 --> 00:12:41 Anna: Next, on 4 July
00:12:42 --> 00:12:44 2025, two gamma ray instruments,
00:12:44 --> 00:12:47 the Chinese French SVOM mission and
00:12:47 --> 00:12:49 China's Insight HXMT
00:12:50 --> 00:12:52 recorded a short Gamma Ray Burst.
00:12:53 --> 00:12:55 GRB2507 04B
00:12:56 --> 00:12:58 lasted about 0.37 seconds.
00:12:59 --> 00:13:01 Avery: Short bursts are the ones we associate with
00:13:01 --> 00:13:03 neutron star collisions.
00:13:03 --> 00:13:04 Anna: Usually yes.
00:13:04 --> 00:13:07 A quick spike of gamma rays, then a fading
00:13:07 --> 00:13:10 afterglow. But China's Einstein probe,
00:13:10 --> 00:13:13 which has a wide field soft X ray camera,
00:13:13 --> 00:13:16 was watching the same patch of sky and the X
00:13:16 --> 00:13:19 rays didn't stop. They kept coming in
00:13:19 --> 00:13:22 bursts for about 560 seconds.
00:13:22 --> 00:13:25 Nearly 10 minutes after a half second flash.
00:13:25 --> 00:13:28 Avery: That's the longest prompt X ray flash ever
00:13:28 --> 00:13:29 seen from a merger like this.
00:13:30 --> 00:13:33 Anna: That's the team's claim. The paper is in
00:13:33 --> 00:13:35 Science Bulletin with the release at the
00:13:35 --> 00:13:37 start of this month for disclosure. The
00:13:37 --> 00:13:40 preprint dates back to January and the event
00:13:40 --> 00:13:42 itself is from July last year.
00:13:42 --> 00:13:44 Avery: How sure are they about what made it
00:13:45 --> 00:13:45 graduate?
00:13:45 --> 00:13:48 Anna: Uh, student Nikolo Pasaleva led
00:13:48 --> 00:13:50 follow up with the X shooter spectrograph on
00:13:50 --> 00:13:53 ESO's Very Large Telescope at
00:13:53 --> 00:13:55 Paranal in Chile. That pinned the
00:13:55 --> 00:13:58 redshift at 0. So the
00:13:58 --> 00:14:00 light has been travelling for more than 6
00:14:00 --> 00:14:03 billion years. Then they looked for a
00:14:03 --> 00:14:05 supernova because the collapse of a massive
00:14:05 --> 00:14:08 star could also produce long lasting X rays.
00:14:08 --> 00:14:09 There wasn't one.
00:14:10 --> 00:14:13 Avery: So a short burst A known distance
00:14:13 --> 00:14:14 and no supernova.
00:14:15 --> 00:14:18 Anna: All of which points to two compact objects
00:14:18 --> 00:14:21 merging. The paper's own wording is a
00:14:21 --> 00:14:24 compact object merger and we'll keep
00:14:24 --> 00:14:26 that. Two neutron stars is the favoured
00:14:26 --> 00:14:29 reading, but a neutron star meeting a black
00:14:29 --> 00:14:31 hole fits that description too.
00:14:31 --> 00:14:34 Avery: And what was powering 10
00:14:34 --> 00:14:35 minutes of X rays?
00:14:36 --> 00:14:38 Anna: The team favours a magnetar.
00:14:38 --> 00:14:41 If two neutron stars merge and the combined
00:14:41 --> 00:14:43 object doesn't immediately collapse into a
00:14:43 --> 00:14:46 black hole, you can get a very rapidly
00:14:46 --> 00:14:48 spinning neutron star with an enormous
00:14:48 --> 00:14:51 magnetic field. Its spin energy
00:14:51 --> 00:14:54 drives a magnetised wind that keeps radiating
00:14:55 --> 00:14:57 the rapid flickering. The change in the
00:14:57 --> 00:15:00 spectrum and a later kick of energy into the
00:15:00 --> 00:15:01 debris all fit.
00:15:02 --> 00:15:05 Avery: Which connects to episode 191. The paper
00:15:05 --> 00:15:07 suggesting magnetars could be about half of
00:15:07 --> 00:15:08 all neutron stars.
00:15:09 --> 00:15:11 Anna: It does, but this is indirect
00:15:11 --> 00:15:14 evidence. Nobody saw the magnetar
00:15:15 --> 00:15:17 at this distance. No gravitational wave
00:15:17 --> 00:15:20 detector could have heard the merger and any
00:15:20 --> 00:15:22 kilonova would have been too faint to catch.
00:15:23 --> 00:15:24 Avery: So why does it matter?
00:15:25 --> 00:15:28 Anna: Because it suggests long X ray tails may
00:15:28 --> 00:15:30 be common and we've been missing them
00:15:31 --> 00:15:31 since.
00:15:31 --> 00:15:34 Gamma ray instruments only see the first
00:15:34 --> 00:15:36 second. If that's right, then the next
00:15:36 --> 00:15:39 time Ligo, Virgo and Kagra hear a nearby
00:15:39 --> 00:15:42 merger, a soft X ray camera like
00:15:42 --> 00:15:44 Einstein probes may be the thing that finds
00:15:44 --> 00:15:47 it in the sky. And that matters more with
00:15:47 --> 00:15:49 Swift, the old workhorse of burst
00:15:49 --> 00:15:52 astronomy, expected to re enter the
00:15:52 --> 00:15:53 atmosphere early next month.
00:15:54 --> 00:15:57 Avery: Lets move to some news. A satellite that
00:15:57 --> 00:15:59 stopped working decades ago has broken into
00:15:59 --> 00:16:00 pieces.
00:16:00 --> 00:16:03 Meteor 27 was a Soviet weather
00:16:03 --> 00:16:06 satellite launched in May 1981 to
00:16:06 --> 00:16:09 photograph clouds. On 5
00:16:09 --> 00:16:11 October it fragmented in low
00:16:11 --> 00:16:14 Anna: Earth orbit and it was caught from
00:16:14 --> 00:16:14 Australia.
00:16:15 --> 00:16:17 Avery: It was. The tracking company
00:16:17 --> 00:16:20 LeoLabs picked up several new objects next
00:16:20 --> 00:16:22 to the satellite as it passed over its radar
00:16:22 --> 00:16:24 site in Western Australia.
00:16:25 --> 00:16:27 And other radars confirm the debris
00:16:27 --> 00:16:29 generating event. The orbital
00:16:29 --> 00:16:32 debris analyst Jim Shell has narrowed the
00:16:32 --> 00:16:34 timing to about 9:45
00:16:35 --> 00:16:37 UTC, give or take 10 minutes.
00:16:37 --> 00:16:39 That's quarter to nine on the evening of the
00:16:39 --> 00:16:41 fifth Sydney time?
00:16:41 --> 00:16:42 Anna: Hell higher.
00:16:43 --> 00:16:46 Avery: Roughly 850 kilometres in a
00:16:46 --> 00:16:48 steep polar orbit inclined about 81
00:16:48 --> 00:16:49 degrees.
00:16:49 --> 00:16:51 And it came apart near the top of that orbit,
00:16:52 --> 00:16:55 where it reaches its highest latitude. That's
00:16:55 --> 00:16:57 a crowded part of the sky for debris because
00:16:57 --> 00:17:00 so many polar orbits cross there. The
00:17:00 --> 00:17:02 reports so far say tens of new trackable
00:17:02 --> 00:17:03 fragments.
00:17:03 --> 00:17:05 Anna: Do we know what caused it?
00:17:05 --> 00:17:08 Avery: No. There are two broad options.
00:17:08 --> 00:17:11 Something inside let go, like an old
00:17:11 --> 00:17:14 battery or leftover propellant after 45
00:17:14 --> 00:17:17 years of heating and cooling. Or
00:17:17 --> 00:17:19 it was hit by a piece of debris too small to
00:17:19 --> 00:17:22 track. Chao leans towards a collision,
00:17:22 --> 00:17:24 but he's also said we'll likely never know
00:17:25 --> 00:17:27 because a, uh, dead satellite sends no data.
00:17:28 --> 00:17:31 Anna: And this isn't a one off, it isn't.
00:17:31 --> 00:17:34 Avery: LeoLabs calls it the latest in a series it
00:17:34 --> 00:17:36 has detected over the past six months. A
00:17:36 --> 00:17:39 Starlink satellite in March that SpaceX put
00:17:39 --> 00:17:42 down to an internal energy source. A Chinese
00:17:42 --> 00:17:44 Long March rocket body in August. And
00:17:44 --> 00:17:47 Space.com reports the Cold War era US
00:17:47 --> 00:17:50 satellite USA 32 broke up in
00:17:50 --> 00:17:52 September. The point about altitude is the
00:17:52 --> 00:17:53 important one.
00:17:53 --> 00:17:56 At around 850 kilometres, the air is so
00:17:56 --> 00:17:59 thin that debris can stay up for decades or
00:17:59 --> 00:18:00 even centuries.
00:18:01 --> 00:18:04 Anna: And for astronomers, every
00:18:04 --> 00:18:05 fragment is another
00:18:05 --> 00:18:08 Avery: thing for operational satellites to dodge. In
00:18:08 --> 00:18:11 an FCC filing earlier this year, SpaceX said
00:18:11 --> 00:18:13 each Starlink satellite averaged more than 40
00:18:13 --> 00:18:16 avoidance manoeuvres a year. And
00:18:16 --> 00:18:18 every bright fragment is another possible
00:18:18 --> 00:18:20 streak across a telescope image.
00:18:21 --> 00:18:23 One breakup doesn't close off space.
00:18:24 --> 00:18:27 The worry is the trend and the fact that
00:18:27 --> 00:18:29 nobody owns the job of cleaning up after a
00:18:29 --> 00:18:31 satellite launched in 1980. One.
00:18:31 --> 00:18:34 Anna: Quick one before the sky. NASA
00:18:34 --> 00:18:37 has chosen three new science payloads for its
00:18:37 --> 00:18:39 M Moon Base programme, announced on 30th
00:18:39 --> 00:18:40 September.
00:18:40 --> 00:18:42 They'll fly to the surface on commercial
00:18:42 --> 00:18:45 landers through the CLPS programme. And the
00:18:45 --> 00:18:47 one with the best story is called Gimli,
00:18:48 --> 00:18:49 like the dwarf from
00:18:49 --> 00:18:51 Avery: the Lord of the Rings who would definitely
00:18:51 --> 00:18:52 approve of going underground.
00:18:53 --> 00:18:55 Anna: Bewud it stands for Geophysical
00:18:55 --> 00:18:58 Instruments for Marius Lunar Pit
00:18:58 --> 00:19:00 Investigation led by Nathaniel Putzig at
00:19:00 --> 00:19:03 the Planetary Science Institute. The target
00:19:03 --> 00:19:06 is the Marius Hills pit, a hole about
00:19:06 --> 00:19:09 34 metres deep found by Japan's Kaguya
00:19:09 --> 00:19:10 orbiter in 2009.
00:19:11 --> 00:19:14 The idea is that it's a skylight, a spot
00:19:14 --> 00:19:16 where the roof of an old lava tube collapsed.
00:19:16 --> 00:19:19 Gimli will use ground penetrating radar,
00:19:19 --> 00:19:22 seismic sensors and gravity measurements to
00:19:22 --> 00:19:24 see whether a tunnel actually runs away from
00:19:24 --> 00:19:24 the
00:19:24 --> 00:19:27 Avery: pit, which would be a natural shelter from
00:19:27 --> 00:19:29 radiation and temperature swings.
00:19:29 --> 00:19:32 Anna: If it's there, nobody has yet
00:19:32 --> 00:19:34 confirmed a lava tube on the moon from the
00:19:34 --> 00:19:37 surface. The other two picks are a
00:19:37 --> 00:19:39 long term monitoring station for the South
00:19:39 --> 00:19:42 Pole from Medi Bena at UMBC
00:19:42 --> 00:19:45 and Disko from NASA Ames, which
00:19:45 --> 00:19:48 will look for ice in tiny cold traps and
00:19:48 --> 00:19:50 measure how rocket exhaust disturbs the
00:19:50 --> 00:19:51 ground.
00:19:52 --> 00:19:54 No launch dates yet and no dollar fifth
00:19:54 --> 00:19:57 year's in the announcement to the sky.
00:19:57 --> 00:20:00 Avery: And um, this week the Southern hemisphere
00:20:00 --> 00:20:02 gets the best of it in the evening with a,
00:20:02 --> 00:20:04 uh, fair trade for the north before dawn.
00:20:05 --> 00:20:08 Quick note for Australian listeners, daylight
00:20:08 --> 00:20:10 saving started on the 4th, so the Sydney
00:20:10 --> 00:20:11 Times are AEDT.
00:20:12 --> 00:20:15 Anna: Mercury reached greatest eastern elongation
00:20:15 --> 00:20:17 on Monday evening, about 25 degrees from
00:20:17 --> 00:20:20 the sun. That's as far from the sun as it
00:20:20 --> 00:20:21 gets on this path.
00:20:21 --> 00:20:22 So this is the week to find
00:20:22 --> 00:20:25 Avery: it and the geometry is wildly
00:20:25 --> 00:20:28 unequal. Our calculations for Tuesday
00:20:28 --> 00:20:31 evening. From Sydney, the sun sets
00:20:31 --> 00:20:34 at 7:06pm and mercury is still
00:20:34 --> 00:20:37 24 degrees up, setting a little over
00:20:37 --> 00:20:40 two hours after the sun. From Los
00:20:40 --> 00:20:42 Angeles, it's about 10 degrees up at sunset
00:20:42 --> 00:20:44 and gone within an hour.
00:20:44 --> 00:20:47 From New York, seven and a half degrees, gone
00:20:47 --> 00:20:50 in under 50 minutes. And, uh, from London,
00:20:50 --> 00:20:51 just three degrees.
00:20:52 --> 00:20:55 Anna: This is the same steep spring ecliptic
00:20:55 --> 00:20:57 we talked about at the equinox. From the
00:20:57 --> 00:21:00 south, the planets stack almost straight up
00:21:00 --> 00:21:02 from the western horizon after sunset.
00:21:02 --> 00:21:05 Avery: So for Southern Hemisphere listeners, it's
00:21:05 --> 00:21:07 the easiest Mercury of the year.
00:21:07 --> 00:21:10 Look west about 40 minutes after sunset for
00:21:10 --> 00:21:13 a steady pinkish point of light well clear of
00:21:13 --> 00:21:16 the horizon. Northern listeners, you need a
00:21:16 --> 00:21:19 flat western horizon and good timing about
00:21:19 --> 00:21:22 20 to 30 minutes after sunset and
00:21:22 --> 00:21:23 binoculars help.
00:21:23 --> 00:21:26 Anna: Venus is the brilliant object lower down
00:21:26 --> 00:21:28 and to the left of Mercury from the south,
00:21:29 --> 00:21:31 but it's sinking fast. It heads into
00:21:31 --> 00:21:34 inferior conjunction on the 24th, passing
00:21:34 --> 00:21:37 between us and the Sun. From Sydney, it's
00:21:37 --> 00:21:39 still about 17 degrees up at sunset this week
00:21:39 --> 00:21:42 and sets around an hour and a half after the
00:21:42 --> 00:21:42 Sun.
00:21:43 --> 00:21:45 From North America, it's already lost in
00:21:45 --> 00:21:48 Avery: the glare and the Moon joins them.
00:21:48 --> 00:21:51 The thin Crescent was about 3 degrees from
00:21:51 --> 00:21:53 Venus on Monday evening. On, um, Tuesday,
00:21:54 --> 00:21:57 it's climbed to about 6 degrees from mercury,
00:21:57 --> 00:22:00 8% lit with earthshine on the dark
00:22:00 --> 00:22:02 part. If your sky is clear, that's a lovely
00:22:02 --> 00:22:04 pairing from Australia, New Zealand and South
00:22:04 --> 00:22:05 America.
00:22:06 --> 00:22:09 Anna: Now the trade before dawn, the Northern
00:22:09 --> 00:22:12 hemisphere has Mars and Jupiter at
00:22:12 --> 00:22:15 nautical dawn on Wednesday. Mars is about 58
00:22:15 --> 00:22:18 degrees up from Los Angeles and 56 from New
00:22:18 --> 00:22:20 York, with Jupiter in the mid-40s.
00:22:21 --> 00:22:23 From Sydney, they're only about 23 and
00:22:23 --> 00:22:24 18 degrees.
00:22:25 --> 00:22:27 Avery: And Mars has been doing something lovely. It
00:22:27 --> 00:22:30 passed right through the Beehive cluster M44
00:22:30 --> 00:22:32 in cancer over the weekend, coming within
00:22:32 --> 00:22:35 about a tenth of a degree of the cluster
00:22:35 --> 00:22:36 centre on Saturday UTC.
00:22:37 --> 00:22:39 It's still close enough this week for a
00:22:39 --> 00:22:39 binocular view.
00:22:41 --> 00:22:43 Anna: And Mars and Jupiter are closing in about
00:22:43 --> 00:22:46 13 degrees apart now two and a half by the
00:22:46 --> 00:22:49 10th of November and about one and a quarter
00:22:49 --> 00:22:52 degrees by the 15th. That conjunction
00:22:52 --> 00:22:54 is worth a full sky watch closer to the date.
00:22:55 --> 00:22:57 Avery: And coming up, the Orionids.
00:22:58 --> 00:23:00 The meteor shower made of dust from Holly's
00:23:00 --> 00:23:03 comet peak on the night of the 21st into the
00:23:03 --> 00:23:06 22nd, the moon will be about
00:23:06 --> 00:23:09 78% lit, but it sets around
00:23:09 --> 00:23:10 three in the morning in all four of our
00:23:10 --> 00:23:13 cities Sydney, Los Angeles, New York and
00:23:13 --> 00:23:14 London.
00:23:14 --> 00:23:17 So the dark hour or two before dawn is your
00:23:17 --> 00:23:20 window from either hemisphere. And
00:23:20 --> 00:23:23 Saturn, just past opposition, is up
00:23:23 --> 00:23:24 all evening. For anyone with a small
00:23:24 --> 00:23:26 telescope, one
00:23:26 --> 00:23:29 Anna: safety point, and it matters, especially this
00:23:29 --> 00:23:31 week. Mercury and Venus are close to the
00:23:31 --> 00:23:34 sun, so wait until the sun has fully
00:23:34 --> 00:23:37 set before you sweep binoculars or a
00:23:37 --> 00:23:39 telescope anywhere near the western horizon.
00:23:40 --> 00:23:43 Never look at the sun through any optics. If
00:23:43 --> 00:23:45 you ever do want to look at the sun, use only
00:23:45 --> 00:23:48 a certified solar filter or eclipse glasses
00:23:48 --> 00:23:49 that meet the ISO
00:23:49 --> 00:23:52 1123122 international
00:23:52 --> 00:23:54 standard. Fitted properly over the front of
00:23:54 --> 00:23:57 the instrument, sunglasses are not safe.
00:23:58 --> 00:24:00 Avery: That's the show today. Water
00:24:00 --> 00:24:03 clouds changing on the coldest brown dwarf we
00:24:03 --> 00:24:04 know.
00:24:04 --> 00:24:07 A star patiently eating a Brown Dwarf
00:24:07 --> 00:24:10 every 87 minutes. 10 minutes of
00:24:10 --> 00:24:12 X rays after a half second burst,
00:24:13 --> 00:24:15 a dead Soviet satellite falling to pieces
00:24:15 --> 00:24:18 over Western Australia and NASA going
00:24:18 --> 00:24:20 looking for caves on the moon.
00:24:20 --> 00:24:23 Anna: If you've got a question about anything we
00:24:23 --> 00:24:25 covered or something you'd like us to follow,
00:24:25 --> 00:24:28 the contact form at astronomydailyio
00:24:28 --> 00:24:31 comes straight to the team and a lot of what
00:24:31 --> 00:24:34 we chase starts there. You'll also find show
00:24:34 --> 00:24:36 notes, the newsletter and the full back
00:24:36 --> 00:24:38 catalogue on the site. And we're
00:24:38 --> 00:24:40 astrodaily pod on social.
00:24:40 --> 00:24:43 Avery: And if you're in the south, go and find
00:24:43 --> 00:24:46 Mercury this week. It won't be this easy
00:24:46 --> 00:24:46 again for a while.
00:24:47 --> 00:24:48 Anna: I'm Anna.
00:24:48 --> 00:24:49 Avery: And I'm Avery.
00:24:50 --> 00:24:51 Anna: Clear skies, everyone.