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00:00:01 --> 00:00:04 Anna: Welcome to Astronomy Daily. I'm Anna.
00:00:04 --> 00:00:07 Avery: And I'm avery. It's Monday, the 27th
00:00:07 --> 00:00:10 of July, 2026, and tonight,
00:00:10 --> 00:00:12 the smallest headliner we've had in a while
00:00:12 --> 00:00:13 gets top billing.
00:00:14 --> 00:00:16 Anna: That's right. Our lead is a world you
00:00:16 --> 00:00:19 cannot see without a decent telescope,
00:00:19 --> 00:00:21 one that half of the astronomy community will
00:00:21 --> 00:00:24 tell you isn't even a planet. And today is
00:00:24 --> 00:00:27 its brightest night of the year. Pluto
00:00:27 --> 00:00:30 reaches opposition. We're going to spend some
00:00:30 --> 00:00:32 proper time there. The discovery, the
00:00:32 --> 00:00:35 demotion that people are still arguing about,
00:00:35 --> 00:00:38 and the frozen world New Horizons actually
00:00:38 --> 00:00:39 found waiting for us.
00:00:40 --> 00:00:43 Avery: Then, um, three quick stops. A crew comes
00:00:43 --> 00:00:46 home after 241 days in orbit.
00:00:46 --> 00:00:48 New modeling suggests the most common planet
00:00:48 --> 00:00:51 in the galaxy may be hiding oceans of molten
00:00:51 --> 00:00:54 rock. And astronomers have taken the famous
00:00:54 --> 00:00:56 first ever black hole image and pulled a
00:00:56 --> 00:00:58 whole new layer of physics out of it.
00:00:58 --> 00:01:01 Anna: And we'll close where we always do, under the
00:01:01 --> 00:01:03 sky north and south, with a M meteor
00:01:03 --> 00:01:06 shower that's putting on its best show for
00:01:06 --> 00:01:09 our Southern Hemisphere listeners. Let's get
00:01:09 --> 00:01:09 into it.
00:01:09 --> 00:01:12 So, Avery set the scene for me. If someone
00:01:12 --> 00:01:15 walks out tonight and looks up, are they
00:01:15 --> 00:01:16 going to see Pluto?
00:01:17 --> 00:01:19 Avery: Honestly, no. Not with their eyes and not
00:01:19 --> 00:01:22 with a pair of binoculars. Tonight, Pluto
00:01:22 --> 00:01:24 sits directly opposite the sun in our sky,
00:01:24 --> 00:01:27 over in the constellation Capricornus. That's
00:01:27 --> 00:01:29 what opposition means. Earth is passing
00:01:29 --> 00:01:32 between Pluto and the Sun. So Pluto rises
00:01:32 --> 00:01:35 at sunset, sits highest around midnight,
00:01:35 --> 00:01:37 and it's fully lit and as close to us as it
00:01:37 --> 00:01:40 gets all year. A, uh, touch under 35
00:01:40 --> 00:01:43 astronomical units. So roughly 35
00:01:43 --> 00:01:44 times the Earth's sun
00:01:44 --> 00:01:46 Anna: distance, and that's as good as it gets.
00:01:46 --> 00:01:49 Avery: And it's still faint, painfully
00:01:49 --> 00:01:52 faint. We're talking about magnitude 15,
00:01:52 --> 00:01:55 to put that in human terms. It's millions of
00:01:55 --> 00:01:57 times dimmer than the faintest star you can
00:01:57 --> 00:01:59 pick out on a dark night. You realistically
00:01:59 --> 00:02:02 need an 8 inch telescope and a good star
00:02:02 --> 00:02:04 chart. And even then, Pluto looks like
00:02:04 --> 00:02:07 a star, a dot that only gives itself away
00:02:07 --> 00:02:09 because it shifts position over a
00:02:09 --> 00:02:12 Anna: couple of nights, which is exactly how it was
00:02:12 --> 00:02:14 found in the first place. Let's rewind.
00:02:14 --> 00:02:17 Because the Pluto story is one of the great
00:02:17 --> 00:02:19 underdog tales in astronomy.
00:02:19 --> 00:02:22 1894, Percival Lowell, the same
00:02:22 --> 00:02:25 wealthy Bostonian who convinced himself
00:02:25 --> 00:02:27 Mars was covered in canals, sets up an
00:02:27 --> 00:02:30 observatory in Flagstaff, Arizona, and
00:02:30 --> 00:02:33 becomes obsessed, um, with a planet X he
00:02:33 --> 00:02:36 was sure was tugging on the orbits of Uranus
00:02:36 --> 00:02:36 and Neptune.
00:02:37 --> 00:02:40 Avery: And, um, he never found it. He died in 1916,
00:02:40 --> 00:02:41 still hunting.
00:02:41 --> 00:02:44 Anna: He did the search, went cold, then
00:02:44 --> 00:02:46 restarting. And in 1929 the
00:02:46 --> 00:02:49 job landed on a 23 year old Kansas farm
00:02:49 --> 00:02:52 boy with no colonies college degree named
00:02:52 --> 00:02:55 Clyde Tombaugh. His method was brutal,
00:02:55 --> 00:02:58 painstaking work. Photograph the same patch
00:02:58 --> 00:03:00 of sky on different nights. Then flick
00:03:00 --> 00:03:02 between the two plates in a machine called a
00:03:02 --> 00:03:05 blink comparator, looking for the one dot
00:03:05 --> 00:03:07 out of hundreds of thousands that moved.
00:03:08 --> 00:03:10 Avery: That is the definition of patience.
00:03:10 --> 00:03:13 Anna: On the 18th of February 1930 he
00:03:13 --> 00:03:16 found it. And here's a detail I love. The
00:03:16 --> 00:03:18 name didn't come from an astronomer. It came
00:03:18 --> 00:03:21 from an 11 year old English schoolgirl,
00:03:21 --> 00:03:23 Venetia Burney. Over breakfast she
00:03:23 --> 00:03:25 suggested Pluto, the Roman God of the
00:03:25 --> 00:03:28 underworld, fitting for a cold, dark,
00:03:28 --> 00:03:31 distant world. And the first two letters, P
00:03:31 --> 00:03:33 and L also happen to honor Percival
00:03:33 --> 00:03:35 Lowell. It stuck.
00:03:35 --> 00:03:38 Avery: So for 76 years, Pluto is the ninth
00:03:38 --> 00:03:41 planet. It's on every classroom wall, um,
00:03:41 --> 00:03:43 every lunchbox, every mobile over a
00:03:43 --> 00:03:46 cottage. Then 2006 happens.
00:03:46 --> 00:03:49 Anna: Then 2006 happens. And this is
00:03:49 --> 00:03:52 the part people still get heated about. So
00:03:52 --> 00:03:55 let me try to be fair to both sides because
00:03:55 --> 00:03:57 there genuinely are two good sides.
00:03:57 --> 00:04:00 The trouble started in the years before when
00:04:00 --> 00:04:03 astronomers began finding other icy
00:04:03 --> 00:04:06 bodies out past Neptune in a region called
00:04:06 --> 00:04:08 the Kuiper belt. And in 2005
00:04:08 --> 00:04:11 a team found Eris, which at the time
00:04:11 --> 00:04:13 looked to be bigger than Pluto.
00:04:14 --> 00:04:16 Avery: And that's the crunch. If Pluto's a planet,
00:04:16 --> 00:04:19 is eris planet number 10? What about the
00:04:19 --> 00:04:20 next 20 objects we
00:04:20 --> 00:04:23 Anna: find out there exactly the corner they were
00:04:23 --> 00:04:25 backed into. So in August
00:04:25 --> 00:04:28 2006, the International Astronomical
00:04:28 --> 00:04:31 Union voted on a formal definition of planet
00:04:31 --> 00:04:33 for the first time. Three rules. It has to
00:04:33 --> 00:04:36 orbit the Sun. It has to be roundish under
00:04:36 --> 00:04:39 its own gravity and the killer it, it
00:04:39 --> 00:04:41 has to, uh, have cleared its neighborhood of
00:04:41 --> 00:04:44 other debris. Pluto passes the first two
00:04:44 --> 00:04:46 easily, but it shares its zone with all that
00:04:46 --> 00:04:49 Kuiper Belt material. So it fails the third
00:04:49 --> 00:04:52 reclassified as a dwarf planet. It
00:04:52 --> 00:04:54 even got a minor planet catalog
00:04:54 --> 00:04:57 Avery: number 134340,
00:04:57 --> 00:05:00 a demotion with a filing number.
00:05:00 --> 00:05:02 Ouch. Not everyone accepted it,
00:05:03 --> 00:05:03 not at all.
00:05:03 --> 00:05:06 Anna: And this is the bit I want listeners to sit
00:05:06 --> 00:05:08 with because it's not settled science. It's a
00:05:08 --> 00:05:11 definition. And definitions are choices.
00:05:11 --> 00:05:14 The loudest objection comes from planetary
00:05:14 --> 00:05:16 scientists and Alan Stern, who leads the New
00:05:16 --> 00:05:19 Horizons mission, is the most prominent.
00:05:19 --> 00:05:21 Their argument is roughly clearing the
00:05:21 --> 00:05:24 neighborhood is a strange test because it
00:05:24 --> 00:05:26 depends on where an object is, not what it
00:05:26 --> 00:05:29 is. Put Earth out at Pluto's distance and
00:05:29 --> 00:05:32 Earth wouldn't clear that huge orbit either.
00:05:32 --> 00:05:35 They prefer a geophysical definition if
00:05:35 --> 00:05:37 it's big enough for gravity to pull it round.
00:05:37 --> 00:05:40 And it's not a star, it's a planet, full
00:05:40 --> 00:05:43 stop. By that logic, Pluto is a planet, and
00:05:43 --> 00:05:45 so are, uh, a dozen other round worlds.
00:05:46 --> 00:05:48 Avery: And the counterargument, the dynamical
00:05:48 --> 00:05:49 camp.
00:05:49 --> 00:05:51 Anna: The folks who wrote the IAU rule say a
00:05:51 --> 00:05:54 definition has to be useful. And anything
00:05:54 --> 00:05:56 round gives you potentially hundreds of
00:05:56 --> 00:05:58 planets, which tells you nothing about how
00:05:58 --> 00:06:01 the solar system is actually organized.
00:06:01 --> 00:06:03 Clearing your orbit captures something real.
00:06:03 --> 00:06:06 The eight major planets are gravitationally
00:06:06 --> 00:06:09 dominant and the Kuiper bell objects simply
00:06:09 --> 00:06:12 aren't. So it's genuinely a values question.
00:06:12 --> 00:06:15 Do you classify by the object itself or by
00:06:15 --> 00:06:17 the role it plays in the system? Reasonable
00:06:17 --> 00:06:19 people land differently.
00:06:19 --> 00:06:22 Avery: And then, as if the universe wanted to make
00:06:22 --> 00:06:24 everyone regret the timing, New
00:06:24 --> 00:06:27 Anna: horizon shows up the best twist in the
00:06:27 --> 00:06:29 whole saga. The probe launched in January
00:06:29 --> 00:06:32 2006, seven months before the vote.
00:06:32 --> 00:06:34 So it left Earth as a mission to the ninth
00:06:34 --> 00:06:37 planet and arrived in July 2015
00:06:37 --> 00:06:40 at a dwarf planet. And what it sent back
00:06:40 --> 00:06:43 demolished the idea that small and far means
00:06:43 --> 00:06:44 dull and dead.
00:06:44 --> 00:06:47 Avery: This is my favorite part. Because we expected
00:06:47 --> 00:06:48 a cratered frozen billiard
00:06:48 --> 00:06:51 Anna: ball, we got a stunningly complex
00:06:51 --> 00:06:54 active world. There's a vast bright plain of
00:06:54 --> 00:06:57 frozen nitrogen sputnik plantina that
00:06:57 --> 00:06:59 sits inside a uh, giant heart shaped feature
00:06:59 --> 00:07:02 the whole Internet fell for. And that heart
00:07:02 --> 00:07:05 isn't static. The nitrogen ice is slowly
00:07:05 --> 00:07:08 churning, convecting like a lava lamp in
00:07:08 --> 00:07:10 ultra slow motion. Which is why it has almost
00:07:10 --> 00:07:12 no crater. The surface is being
00:07:12 --> 00:07:15 resurfaced. There's mountains of water ice
00:07:15 --> 00:07:18 as tall as the rockies. Because at Pluto's
00:07:18 --> 00:07:21 temperatures, water ice is hard as rock. A
00:07:21 --> 00:07:23 thin blue tinged nitrogen atmosphere with
00:07:23 --> 00:07:26 layers of haze and a real possibility of a
00:07:26 --> 00:07:29 liquid water ocean sloshing beneath the
00:07:29 --> 00:07:29 crust.
00:07:30 --> 00:07:32 Avery: A subsurface ocean on um, a world people were
00:07:32 --> 00:07:34 arguing wasn't important enough to be a
00:07:34 --> 00:07:35 planet.
00:07:35 --> 00:07:37 Anna: Which is the poetry of it, isn't it? The
00:07:37 --> 00:07:40 label we hang on Pluto changed nothing about
00:07:40 --> 00:07:43 Pluto. It's exactly as fascinating as the day
00:07:43 --> 00:07:45 before the vote. And it's not alone out
00:07:45 --> 00:07:48 there. It has five moons of its own. The big
00:07:48 --> 00:07:51 one, Charon, so large that the two of them
00:07:51 --> 00:07:53 orbit a point in empty space between them
00:07:53 --> 00:07:55 Like a slow cosmic waltz.
00:07:55 --> 00:07:58 Avery: So tonight, when it's at its brightest and
00:07:58 --> 00:08:00 best place for the year, that faint 15th
00:08:00 --> 00:08:03 magnitude.in Capricornus is a churning, hazy,
00:08:04 --> 00:08:06 possibly ocean bearing world with a heart on
00:08:06 --> 00:08:06 its face.
00:08:07 --> 00:08:09 Anna: That's the one and whatever you want to call
00:08:09 --> 00:08:12 it, planet, dwarf planet, Kuiper belt object.
00:08:12 --> 00:08:15 Tonight is Pluto's night. We'll tell you
00:08:15 --> 00:08:17 exactly where to point a scope in the sky.
00:08:17 --> 00:08:19 Watch. Clyde Tombaugh, by the way, passed
00:08:19 --> 00:08:22 away in 1997. And new horizons
00:08:22 --> 00:08:25 carried a small portion of his ashes on that
00:08:25 --> 00:08:27 flyby. He got to visit the world he found.
00:08:28 --> 00:08:30 Avery: Okay, I'm not crying. You're crying.
00:08:31 --> 00:08:33 Lets bring it back to Earth literally.
00:08:34 --> 00:08:36 Speaking of coming home, three people did
00:08:36 --> 00:08:39 exactly that yesterday on, um, Sunday, a
00:08:39 --> 00:08:42 Soyuz MS.28 capsule parachuted down
00:08:42 --> 00:08:45 onto the steppe of Kazakhstan, bringing NASA
00:08:45 --> 00:08:47 astronaut Chris Williams and Roscosmos
00:08:47 --> 00:08:50 cosmonauts Sergey Kut Sverchkov and Sergey
00:08:50 --> 00:08:53 Mikhayev back after 241 days
00:08:53 --> 00:08:55 aboard the International Space Station.
00:08:55 --> 00:08:58 Anna: 241 days put a number on what
00:08:58 --> 00:08:59 that actually is.
00:09:00 --> 00:09:02 Avery: Nearly eight months, around
00:09:02 --> 00:09:05 3 laps of the
00:09:05 --> 00:09:08 Earth and more than 102 million miles
00:09:08 --> 00:09:10 traveled, all while effectively standing
00:09:10 --> 00:09:13 still in orbit. They launched back on the
00:09:13 --> 00:09:16 27th of November, American Thanksgiving. So
00:09:16 --> 00:09:18 they've missed an entire summer and winter
00:09:18 --> 00:09:19 depending on your hemisphere.
00:09:20 --> 00:09:22 Anna: And it was a first flight for two of them.
00:09:22 --> 00:09:24 Avery: It was first mission for Williams and for
00:09:24 --> 00:09:27 Mikhayv. Gutsverchkov's the veteran. He's
00:09:27 --> 00:09:30 now passed 425 days in space
00:09:30 --> 00:09:33 across two flights. And I want to flag the
00:09:33 --> 00:09:35 quiet significance here. A, uh, NASA
00:09:35 --> 00:09:38 astronaut and two Russian cosmonauts riding
00:09:38 --> 00:09:40 home together in a Russian capsule. Whatever
00:09:40 --> 00:09:43 the politics on the ground, the crude side of
00:09:43 --> 00:09:45 this partnership just keeps functioning, seat
00:09:45 --> 00:09:46 swaps and all.
00:09:46 --> 00:09:48 Anna: What was Williams actually doing up there?
00:09:48 --> 00:09:51 It's easy to forget these are working science
00:09:51 --> 00:09:52 missions, not just endurance feats.
00:09:53 --> 00:09:55 Avery: Right. And his work is genuinely down to
00:09:55 --> 00:09:58 Earth in its aims. He supported research into
00:09:58 --> 00:10:00 novel cancer therapies which benefit from the
00:10:00 --> 00:10:03 way proteins and cells behave in microgravity
00:10:03 --> 00:10:05 and into manufacturing high performance
00:10:05 --> 00:10:07 materials, the kind used in advanced
00:10:07 --> 00:10:10 electronics and computing that you can make
00:10:10 --> 00:10:12 more plainly without gravity pulling
00:10:12 --> 00:10:14 everything around. The pair of cosmonauts
00:10:14 --> 00:10:17 also did a spacewalk back in May to install a
00:10:17 --> 00:10:19 solar radiation instrument on the station's
00:10:19 --> 00:10:20 exterior.
00:10:20 --> 00:10:22 Anna: And the handover keeps the station rolling
00:10:22 --> 00:10:23 seamlessly.
00:10:24 --> 00:10:26 Avery: Command passed to NASA's Jessica Meyer as
00:10:26 --> 00:10:29 Expedition 74 became 75 and
00:10:29 --> 00:10:31 a fresh crew. Anil, uh Menin and two
00:10:31 --> 00:10:34 cosmonauts arrived earlier this month to keep
00:10:34 --> 00:10:36 the lab staffed. The hard part now,
00:10:36 --> 00:10:39 ironically, is gravity. After eight months,
00:10:39 --> 00:10:42 just holding your own head up is exhausting.
00:10:42 --> 00:10:44 The readjustment takes weeks.
00:10:44 --> 00:10:47 Anna: Welcome home to the three of them now from
00:10:47 --> 00:10:49 people orbiting one planet to the most common
00:10:49 --> 00:10:51 kind of planet in the entire galaxy.
00:10:52 --> 00:10:55 Avery: Moving on to story three, sub Neptune's
00:10:55 --> 00:10:58 clouds of Rock, oceans of magma. What's this
00:10:58 --> 00:10:58 all about?
00:10:58 --> 00:11:01 Anna: Here's a fact that still catches me out. The
00:11:01 --> 00:11:03 most common type of planet in the Milky Way
00:11:03 --> 00:11:06 is a type we don't have. It's the sub
00:11:06 --> 00:11:08 Neptune. Bigger than Earth, smaller than
00:11:08 --> 00:11:10 Neptune. There's nothing like it in our solar
00:11:10 --> 00:11:13 system, yet they turn up everywhere else. Out
00:11:13 --> 00:11:16 of more than 6 confirmed exoplanets, well
00:11:16 --> 00:11:18 over 2 are, uh, sub Neptunes.
00:11:18 --> 00:11:20 Avery: And we barely understand what they're made
00:11:20 --> 00:11:20 of.
00:11:21 --> 00:11:23 Anna: That's the frustration. They could be small,
00:11:23 --> 00:11:25 rocky cores wrapped in thick hydrogen
00:11:25 --> 00:11:28 atmospheres, or they could be water worlds,
00:11:28 --> 00:11:30 volatile, rich, drowning in water and carbon
00:11:30 --> 00:11:33 molecules. And we can't easily tell because
00:11:33 --> 00:11:36 even the James Webb telescope can only read
00:11:36 --> 00:11:38 the very top of the atmosphere. And these
00:11:38 --> 00:11:41 atmospheres are deep and hazy. New
00:11:41 --> 00:11:43 modeling from a team at Arizona State,
00:11:43 --> 00:11:46 recently published, offers a clever way
00:11:46 --> 00:11:48 through. And it puts clouds at the center of
00:11:48 --> 00:11:48 the story.
00:11:49 --> 00:11:52 Avery: Clouds on a planet where weather must
00:11:52 --> 00:11:53 mean something wild.
00:11:53 --> 00:11:56 Anna: Wild is the word deep down, where the
00:11:56 --> 00:11:59 pressure is crushing. The team modeled clouds
00:11:59 --> 00:12:02 made of vaporized rock and salt. Think
00:12:02 --> 00:12:04 aluminum oxide, iron silicates,
00:12:04 --> 00:12:07 potassium chloride. Actual mineral
00:12:07 --> 00:12:10 clouds. And here's the key finding those
00:12:10 --> 00:12:13 clouds act like a blanket. They trap heat
00:12:13 --> 00:12:15 trying to escape from the interior, which
00:12:15 --> 00:12:17 pushes the boundary between the atmosphere
00:12:17 --> 00:12:19 and the solid body to temperatures high
00:12:19 --> 00:12:20 enough to melt rock.
00:12:21 --> 00:12:23 Avery: So beneath the clouds, you might have an
00:12:23 --> 00:12:26 ocean of magma, a global magma
00:12:26 --> 00:12:28 Anna: ocean in the cloudy scenario. In the cloud
00:12:28 --> 00:12:31 free version, that boundary is cooler and
00:12:31 --> 00:12:33 might stay solid. Same planet from the
00:12:33 --> 00:12:36 outside, two completely different interiors,
00:12:36 --> 00:12:38 depending on the clouds. And that matters for
00:12:38 --> 00:12:41 us for a very practical reason. It changes
00:12:41 --> 00:12:44 how we interpret what Webb sees, and it feeds
00:12:44 --> 00:12:47 directly into which of these worlds we bother
00:12:47 --> 00:12:48 calling potentially habitable.
00:12:48 --> 00:12:51 Avery: To be fair, this is modeling, not a direct
00:12:51 --> 00:12:53 observation, completely fair.
00:12:53 --> 00:12:55 Anna: This is simulation work, pointing observers
00:12:55 --> 00:12:58 at what to look for. Not a photograph of
00:12:58 --> 00:13:01 magma, but it reframes clouds from being just
00:13:01 --> 00:13:04 an annoying smudge that ruins our data into
00:13:04 --> 00:13:06 an active ingredient, shaping the whole
00:13:06 --> 00:13:09 planet. For the galaxy's most common world,
00:13:09 --> 00:13:09 that's
00:13:09 --> 00:13:12 Avery: a meaningful shift from world we're modeling
00:13:12 --> 00:13:14 to a monster we've actually photographed.
00:13:14 --> 00:13:16 Let's go to M M87.
00:13:16 --> 00:13:19 Anna: Next up, story four, a sharper look at M
00:13:19 --> 00:13:20 M87's black hole.
00:13:21 --> 00:13:24 Avery: Cast your mind back to 2019, that
00:13:24 --> 00:13:27 first ever image of a black hole, the orange
00:13:27 --> 00:13:29 donut. That was M M87,
00:13:29 --> 00:13:32 the supermassive black hole at the heart of
00:13:32 --> 00:13:35 a giant galaxy in Virgo, about
00:13:35 --> 00:13:38 55 million light years away. Weighing
00:13:38 --> 00:13:40 in at around six and a half billion
00:13:40 --> 00:13:43 suns. That Single image was one of the
00:13:43 --> 00:13:46 defining science pictures of the decade.
00:13:46 --> 00:13:48 Anna: And now a team has gone back to the data and
00:13:48 --> 00:13:50 done something new with it.
00:13:50 --> 00:13:53 Avery: They have. Researchers led by the Shanghai
00:13:53 --> 00:13:55 Astronomical Observatory with international
00:13:55 --> 00:13:57 collaborators have produced the first
00:13:57 --> 00:14:00 spatially resolved dual frequency spectral
00:14:00 --> 00:14:03 map of M M87. And I know that's a mouthful,
00:14:03 --> 00:14:05 so let me unpack it because it's clever.
00:14:05 --> 00:14:08 Anna: Please. Dual frequency spectral map needs a
00:14:08 --> 00:14:08 translation.
00:14:09 --> 00:14:12 Avery: Think of it like this. The 2019 picture was
00:14:12 --> 00:14:14 a single color photo of the ring. What this
00:14:14 --> 00:14:17 team did was image the black hole at two
00:14:17 --> 00:14:19 different radio wavelengths, 1.3
00:14:19 --> 00:14:22 millimeters and 3.5 millimeters, using the
00:14:22 --> 00:14:25 Event Horizon Telescope and a partner network
00:14:25 --> 00:14:27 called the GMVA from observations back in
00:14:27 --> 00:14:30 2018. Then they compared them point
00:14:30 --> 00:14:33 by point to see how the color of the glow
00:14:33 --> 00:14:35 changes as you move outward from the center.
00:14:35 --> 00:14:38 That comparison is the spectral index, and
00:14:38 --> 00:14:40 mapping it across the ring had never been
00:14:40 --> 00:14:41 done before.
00:14:41 --> 00:14:42 Anna: And what did the map show?
00:14:43 --> 00:14:45 Avery: A, uh, clear structure. The signal is one
00:14:45 --> 00:14:47 character inside the bright ring, and it
00:14:47 --> 00:14:50 steepens, changes flavor as you move outward,
00:14:50 --> 00:14:53 with the transition landing right at the ring
00:14:53 --> 00:14:55 itself, about 30 micro arcseconds out.
00:14:56 --> 00:14:58 And that's the headline. It tells us the ring
00:14:58 --> 00:15:01 we photographed in 2019 isn't just a trick of
00:15:01 --> 00:15:03 where the light happens to glow. It's tied to
00:15:03 --> 00:15:06 a real physical change in the plasma right
00:15:06 --> 00:15:07 around the event horizon.
00:15:07 --> 00:15:10 Anna: So why does that matter beyond. Nice. A, uh,
00:15:10 --> 00:15:11 sharper map.
00:15:11 --> 00:15:14 Avery: Because reading a black hole means untangling
00:15:14 --> 00:15:16 two things that are mixed together. The pure
00:15:16 --> 00:15:19 warping of space by gravity and the messy
00:15:19 --> 00:15:21 physics of superheated plasma spiraling in.
00:15:22 --> 00:15:24 The researchers say looking at multiple
00:15:24 --> 00:15:26 wavelengths lets them start to separate those
00:15:26 --> 00:15:28 two. That's the path to understanding how
00:15:28 --> 00:15:31 these monsters feed, how they fire off those
00:15:31 --> 00:15:33 enormous jets, and eventually to a cleaner
00:15:33 --> 00:15:36 test of Einstein's general relativity. It's
00:15:36 --> 00:15:38 the difference between having a portrait and
00:15:38 --> 00:15:39 starting to read the biography.
00:15:40 --> 00:15:42 Anna: A portrait to a biography. I'll take that.
00:15:42 --> 00:15:45 And on that note, let's step outside,
00:15:45 --> 00:15:48 because it's skywatch time. And as always,
00:15:48 --> 00:15:50 wherever you are on the planet, we've got
00:15:50 --> 00:15:52 you. Avery, you take the south, I'll take the
00:15:52 --> 00:15:54 north, and we'll meet in the middle at Pluto.
00:15:55 --> 00:15:57 Avery: Deal. Southern hemisphere first. And friends
00:15:57 --> 00:16:00 down south. This is your week. The Southern
00:16:00 --> 00:16:03 Delta Aquarids are peaking. This is a shower
00:16:03 --> 00:16:05 that genuinely favors the south. The radiant
00:16:05 --> 00:16:07 in Aquarius climbs high after midnight for
00:16:07 --> 00:16:10 you. And under a dark sky, you could see
00:16:10 --> 00:16:13 something like 20 to 25 meteors an hour.
00:16:13 --> 00:16:16 No equipment, just a reclining chair, a wide
00:16:16 --> 00:16:18 Open view and some patience while your eyes
00:16:18 --> 00:16:18 adapt.
00:16:18 --> 00:16:20 Anna: And there's a comet. For the early risers,
00:16:21 --> 00:16:22 There is Comet
00:16:22 --> 00:16:25 Avery: 10P Tempel 1 low in the pre
00:16:25 --> 00:16:27 dawn sky. It's uh, a binocular or small
00:16:27 --> 00:16:30 telescope object rather than a naked eye
00:16:30 --> 00:16:33 showpiece. But here's a southern bonus. It's
00:16:33 --> 00:16:35 diving southward through August, so our
00:16:35 --> 00:16:37 Southern Hemisphere listeners get the better
00:16:37 --> 00:16:40 and improving view. Northern folks, catch it
00:16:40 --> 00:16:40 now before it
00:16:40 --> 00:16:43 Anna: drops away from you Northern Hemisphere. Your
00:16:43 --> 00:16:46 headline is a star with a wonderful name.
00:16:46 --> 00:16:47 Look high toward the north for the
00:16:47 --> 00:16:50 constellation Cepheus. It looks like a
00:16:50 --> 00:16:52 child's drawing of a house. And near the
00:16:52 --> 00:16:54 bottom of that house sits Mu Cepheii,
00:16:55 --> 00:16:57 better known as Herschel's Garnet Star. It's
00:16:57 --> 00:16:59 one of the reddest stars you can see with the
00:16:59 --> 00:17:02 naked eye. A, uh, bloated red supergiant so
00:17:02 --> 00:17:05 vast that if you dropped it where the sun is,
00:17:05 --> 00:17:07 its surface would swallow Jupiter.
00:17:07 --> 00:17:10 Binoculars really bring out that deep ember
00:17:10 --> 00:17:12 color. And you northern observers get the
00:17:12 --> 00:17:15 Delta Aquariids too, just lower down toward
00:17:15 --> 00:17:16 your southern horizon.
00:17:16 --> 00:17:19 Avery: And now the meeting point, the one we teased
00:17:19 --> 00:17:21 at the top, Pluto.
00:17:21 --> 00:17:23 Anna: Pluto's at opposition tonight over in
00:17:23 --> 00:17:26 Capricornus, which is beautifully placed for
00:17:26 --> 00:17:29 the Southern Hemisphere high overhead and
00:17:29 --> 00:17:31 perfectly workable low to mid northern skies
00:17:31 --> 00:17:34 too. Now the honest part. At
00:17:34 --> 00:17:36 magnitude 15, this is a genuine
00:17:36 --> 00:17:39 challenge. You'll want at least an 8 inch
00:17:39 --> 00:17:41 telescope, a detailed finder chart, and the
00:17:41 --> 00:17:44 trick is patience. Sketch or photograph
00:17:44 --> 00:17:47 the star field two or three nights running
00:17:47 --> 00:17:50 and watch for the one star that moves. That
00:17:50 --> 00:17:52 mover is Pluto. It is the ultimate
00:17:52 --> 00:17:54 bragging rights target.
00:17:54 --> 00:17:56 Avery: And, um, there's a catch tonight for
00:17:56 --> 00:17:56 everyone.
00:17:57 --> 00:17:59 Anna: There is a big bright moon, about
00:17:59 --> 00:18:02 95% full, washing out the sky
00:18:02 --> 00:18:05 all week. That won't bother the Garnet star
00:18:05 --> 00:18:07 or the brighter meteors much, but it makes
00:18:07 --> 00:18:10 faint Pluto even harder. If chasing
00:18:10 --> 00:18:12 Pluto is your goal, wait for it to clear the
00:18:12 --> 00:18:15 worst of the moonlight or give it a week. Oh,
00:18:15 --> 00:18:18 and Saturn is rising after midnight over in
00:18:18 --> 00:18:21 Pisces for both hemispheres, rings and all.
00:18:21 --> 00:18:23 A lovely consolation prize in any scope,
00:18:24 --> 00:18:25 north or south.
00:18:25 --> 00:18:26 Avery: There's something up there for you tonight.
00:18:27 --> 00:18:30 Anna: And that's Astronomy daily for Monday
00:18:30 --> 00:18:32 27th July. A faint little
00:18:32 --> 00:18:35 world having its big night, A crew safely
00:18:35 --> 00:18:38 home, magma oceans on the galaxy's
00:18:38 --> 00:18:41 commonest planet, and a, uh, sharper look at
00:18:41 --> 00:18:43 the first black hole we ever photographed.
00:18:43 --> 00:18:46 Avery: You can find show notes, links, and every
00:18:46 --> 00:18:49 past episode@astronomydaily.IO
00:18:49 --> 00:18:51 and the observant amongst you will notice
00:18:51 --> 00:18:53 that we have a brand new website today, so
00:18:53 --> 00:18:55 make sure you check it out. And we're
00:18:55 --> 00:18:58 AstroDaily Pod Across Social. If
00:18:58 --> 00:19:00 tonight's Pluto story settled or restarted,
00:19:00 --> 00:19:02 an argument in your house, we'd love to hear
00:19:02 --> 00:19:03 it.
00:19:03 --> 00:19:06 Anna: For Avery, I'm Anna. Whatever you decide to
00:19:06 --> 00:19:08 call Pluto, clear skies.
00:19:19 --> 00:19:20 The stories.
00:19:22 --> 00:19:22 Mhm.
00:19:27 --> 00:19:28 Avery: We told.