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In today's Astronomy Daily, Anna and Avery cover six major stories: Ireland becomes the 65th nation to sign the Artemis Accords; the Artemis III rocket core stage arrives at Kennedy Space Center; NASA's nuclear-electric SR-1 Freedom Mars mission ramps up toward a 2028 launch; the Eta Aquariid meteor shower peaks overnight May 5-6; NASA releases spectacular dual panoramas from Curiosity and Perseverance rovers; and new research makes a compelling case that the Large Magellanic Cloud is on its first-ever pass by the Milky Way. Story Summaries & Key Facts 1. Ireland Signs the Artemis Accords • Ireland signed as the 65th Artemis Accords signatory on May 4, 2026 at NASA HQ, Washington DC • Hosted by NASA Administrator Jared Isaacman alongside Irish Ambassador Geraldine Byrne Nason and Minister Peter Burke • Three new signatories in two weeks: Latvia (#62), Morocco (#64), Ireland (#65) • Accords established in 2020, covering peaceful exploration, transparency, data sharing, and heritage preservation 2. Artemis III SLS Core Stage Arrives at KSC • The top four-fifths of the 212-foot SLS core stage arrived at Kennedy on April 27, 2026 via the Pegasus barge • Traveled 900 miles from Michoud Assembly Facility in New Orleans • Now inside the Vehicle Assembly Building, being mated to the engine section • Artemis III (targeted late 2027) will test Orion docking with commercial landers in low Earth orbit — not a lunar landing • Artemis IV (2028) will land astronauts on the Moon's south pole 3. NASA SR-1 Freedom Nuclear Mars Mission • SR-1 Freedom will be the first nuclear-electric powered interplanetary spacecraft, launching December 2028 • Uses Nuclear Electric Propulsion (NEP): fission reactor generates 20kW of electricity to power ion thrusters • Hardware repurposed from the Gateway Power and Propulsion Element (PPE) • Will deploy the 'Skyfall' payload: three Ingenuity-class helicopters to scout for subsurface water ice • Could pave the way for megawatt-class reactors cutting human Mars transit time to two months 4. Eta Aquariid Meteor Shower Peak • Peak: overnight May 5-6, 2026, with pre-dawn hours on May 6 as prime window • Source: debris trail of Halley's Comet — Earth passes through it each May • Meteor speed: ~66 km/s — fast, with persistent glowing trails • Southern Hemisphere: up to 50 meteors/hour under ideal conditions — best shower for southern sky • Moon challenge: 84% waning gibbous — block the Moon behind a tree or building for best results • Active through May 28 — more opportunities if clouds intervene tonight 5. Curiosity & Perseverance Mars Panoramas • NASA released dual 360-degree panoramas from both active Mars rovers — 3,775 km apart on the planet • Curiosity: 1,031-image panorama of 'boxwork' formations in Gale Crater — fossil records of ancient groundwater • Perseverance: 980-image panorama near Jezero Crater rim showing some of the oldest rocks in the solar system • The two rovers are 'time-travelling in opposite directions' — Curiosity into younger terrain, Perseverance into older • Perseverance carries 23 rock core samples in sealed tubes, awaiting future Earth-return mission 6. Large Magellanic Cloud — First-Time Visitor • New pre-print paper claims definitive evidence the LMC is on its first-ever pass by the Milky Way • LMC mass: roughly 10-20% of the Milky Way — large enough to send gravitational ripples through our galaxy • Key evidence: LMC's gas corona is still largely intact — a previous close Milky Way pass would have stripped it away • Also explains why the SMC and companion satellites haven't been tidally disrupted • Rewrites the origin of the Magellanic Stream — now attributed to LMC-SMC interactions rather than Milky Way tidal forces
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This episode includes AI-generated content.
00:00:00 --> 00:00:02 Anna: Hello and welcome to Astronomy Daily.
00:00:03 --> 00:00:03 I'm Anna.
00:00:04 --> 00:00:06 Avery: And I'm, um, avery. It's Monday, May 4,
00:00:06 --> 00:00:09 2026. And yes, may the 4th be with
00:00:09 --> 00:00:10 you.
00:00:10 --> 00:00:13 Anna: But while you're looking up for X wings and
00:00:13 --> 00:00:15 TIE fighters, keep your eyes peeled for
00:00:15 --> 00:00:18 something very real shooting across the skies
00:00:18 --> 00:00:21 tonight because Halley's Comet has left us
00:00:21 --> 00:00:22 a little gift.
00:00:22 --> 00:00:25 Avery: That's right, the Eta Equinarians meteor
00:00:25 --> 00:00:27 shower is peaking this week. And for our
00:00:27 --> 00:00:28 Southern Hemisphere listeners in Australia,
00:00:29 --> 00:00:31 New Zealand and beyond, it could be spectac.
00:00:32 --> 00:00:34 Anna: We have that story and five more today,
00:00:34 --> 00:00:37 including Ireland joining the Global Space
00:00:37 --> 00:00:40 Coalition, the next moon rocket's backbone
00:00:40 --> 00:00:43 arriving at Kennedy, and a, uh, nuclear
00:00:43 --> 00:00:45 powered mission to Mars that sounds like
00:00:45 --> 00:00:47 science fiction, but is very much science
00:00:47 --> 00:00:48 fact.
00:00:48 --> 00:00:50 Avery: And we'll visit two rovers having very
00:00:50 --> 00:00:52 different days on the Red planet and meet a
00:00:52 --> 00:00:54 galaxy that turns out to be a first time
00:00:54 --> 00:00:57 visitor to our cosmic neighborhood. Let's get
00:00:57 --> 00:00:57 into it.
00:00:57 --> 00:01:00 Anna: We start today with a historic signing
00:01:00 --> 00:01:03 happening right now as we record Ireland
00:01:03 --> 00:01:06 is joining the Artemis accords, becoming the
00:01:06 --> 00:01:09 65th nation to commit to responsible and
00:01:09 --> 00:01:10 peaceful space exploration.
00:01:11 --> 00:01:12 Avery: The ceremony is taking place at NASA
00:01:12 --> 00:01:14 headquarters in Washington, D.C. today,
00:01:14 --> 00:01:17 Monday, May 4, hosted by NASA
00:01:17 --> 00:01:19 Administrator Jared Isaacman, alongside
00:01:19 --> 00:01:21 Ireland's Ambassador to the US Geraldine
00:01:21 --> 00:01:24 Byrne Nason and Minister for Enterprise Peter
00:01:24 --> 00:01:25 Burke.
00:01:25 --> 00:01:27 Anna: Now, for listeners who may be new to the
00:01:27 --> 00:01:30 show, the Artemis Accords are a set of
00:01:30 --> 00:01:32 principles established back in 2020
00:01:32 --> 00:01:35 during the first Trump administration, and
00:01:35 --> 00:01:37 they've grown steadily since. They cover
00:01:37 --> 00:01:40 everything from peaceful exploration and
00:01:40 --> 00:01:43 transparency to protecting historically
00:01:43 --> 00:01:45 significant sites in space and ensuring
00:01:45 --> 00:01:48 scientific data is shared openly.
00:01:48 --> 00:01:50 Avery: What's notable here is the pace at which
00:01:50 --> 00:01:52 nations are joining. Just two weeks ago,
00:01:52 --> 00:01:55 Latvia signed as a 62nd signatory.
00:01:55 --> 00:01:58 Then Morocco joined as the 64th last week,
00:01:58 --> 00:02:01 and now Ireland makes 65. That's
00:02:01 --> 00:02:02 three new nations in a fortnight.
00:02:02 --> 00:02:05 Anna: Ireland actually has a, uh, growing space
00:02:05 --> 00:02:07 sector. It's home to the European Space
00:02:07 --> 00:02:10 Agency's European Space Astronomy center
00:02:10 --> 00:02:13 operations and has been part of ESA for
00:02:13 --> 00:02:16 decades. Joining the Accords formalizes
00:02:16 --> 00:02:18 its commitment to the broader international
00:02:18 --> 00:02:20 framework for lunar and deep space
00:02:20 --> 00:02:21 activities.
00:02:22 --> 00:02:24 Avery: With 65 nations now on board, the Artemis
00:02:24 --> 00:02:26 Accords represent the most extensive
00:02:26 --> 00:02:29 multilateral framework for space exploration
00:02:29 --> 00:02:31 ever assembled. And the list keeps growing.
00:02:31 --> 00:02:34 As NASA says all countries are welcome,
00:02:34 --> 00:02:35 whether or not they have their own space
00:02:35 --> 00:02:36 program.
00:02:36 --> 00:02:39 Anna: A lovely milestone to mark on May 4th of
00:02:39 --> 00:02:39 all days.
00:02:40 --> 00:02:42 Avery: Well, Ireland did pick a memorable date,
00:02:43 --> 00:02:43 dory2.
00:02:43 --> 00:02:46 Anna: And we are staying firmly in the Artemis
00:02:46 --> 00:02:49 universe. The ink is barely dry on the
00:02:49 --> 00:02:51 Artemis 2 mission. Reid Wiseman, Victor
00:02:51 --> 00:02:54 Glover, Christina Koch and Jeremy Hansen
00:02:54 --> 00:02:57 splashed down just three weeks ago, and
00:02:57 --> 00:02:59 NASA is already pressing ahead at pace.
00:03:00 --> 00:03:02 Avery: The massive core stage of the Space Launch
00:03:02 --> 00:03:04 Systems rocket for Artemis 3 arrived at
00:03:04 --> 00:03:07 Kennedy Space center in Florida last week on
00:03:07 --> 00:03:10 April 27, completing a 900 mile
00:03:10 --> 00:03:12 journey by barge from NASA's Michaud Assembly
00:03:12 --> 00:03:14 Facility in New Orleans.
00:03:14 --> 00:03:17 Anna: And when we say massive, we mean it.
00:03:17 --> 00:03:19 The SLS core stage is
00:03:19 --> 00:03:22 212ft tall. When fully
00:03:22 --> 00:03:25 assembled, it houses two propellant tanks
00:03:25 --> 00:03:27 that together hold over
00:03:27 --> 00:03:30 733 gallons
00:03:30 --> 00:03:33 of super chilled liquid propellant to feed
00:03:33 --> 00:03:36 four RS25 engines. It's the
00:03:36 --> 00:03:38 heart of the most powerful rocket currently
00:03:38 --> 00:03:38 flying.
00:03:39 --> 00:03:41 Avery: The core stage is now inside the vehicle
00:03:41 --> 00:03:44 assembly bab, the vab, where it will be mated
00:03:44 --> 00:03:46 to its engine section. And NASA has been
00:03:46 --> 00:03:49 running everything in parallel. Solid rocket
00:03:49 --> 00:03:51 booster segments have already arrived by rail
00:03:51 --> 00:03:53 from Utah. And the mobile launcher was
00:03:53 --> 00:03:56 returned to the VAB even before the barge
00:03:56 --> 00:03:56 docked.
00:03:57 --> 00:03:59 Anna: Now here's where Artemis 3 gets interesting.
00:04:00 --> 00:04:02 Because this mission is not going to the
00:04:02 --> 00:04:05 moon's surface, its job is to test the
00:04:05 --> 00:04:07 rendezvous and docking capabilities between
00:04:07 --> 00:04:10 the Orion spacecraft and the commercial
00:04:10 --> 00:04:13 landers, SpaceX's Starship and Blue
00:04:13 --> 00:04:16 Origin's blue moon in low Earth orbit.
00:04:16 --> 00:04:19 Think Apollo 9, which did the same kind of
00:04:19 --> 00:04:21 dress rehearsal in 1969.
00:04:21 --> 00:04:23 Avery: That groundwork is critical because it's
00:04:23 --> 00:04:26 Artemis 4 that will actually put astronauts
00:04:26 --> 00:04:28 back on the lunar surface targeted for
00:04:28 --> 00:04:31 2028. So Artemis 3,
00:04:31 --> 00:04:34 likely launching in late 2027, is
00:04:34 --> 00:04:35 the essential bridge.
00:04:36 --> 00:04:38 Anna: There's something exhilarating about seeing
00:04:38 --> 00:04:41 hardware arrive. It's real, it's
00:04:41 --> 00:04:44 tangible, it's happening. Artemis,
00:04:44 --> 00:04:47 as one NASA official put it last week, is
00:04:47 --> 00:04:48 full steam ahead.
00:04:49 --> 00:04:51 Avery: Story three, and we're venturing a little
00:04:51 --> 00:04:54 further out to Mars and the most audacious
00:04:54 --> 00:04:57 propulsion experiment in decades. NASA
00:04:57 --> 00:05:00 is pressing ahead with plans to launch the
00:05:00 --> 00:05:02 world's first nuclear electric powered
00:05:02 --> 00:05:04 interplanetary spacecraft in December
00:05:05 --> 00:05:05 2028.
00:05:06 --> 00:05:09 Anna: It's called Space Reactor One Freedom
00:05:09 --> 00:05:12 SR One Freedom for short. And if it
00:05:12 --> 00:05:14 launches on schedule, it will be the first
00:05:14 --> 00:05:16 spacecraft to use nuclear fission for
00:05:16 --> 00:05:19 propulsion since the 1960s.
00:05:19 --> 00:05:21 Over 60 years in the making,
00:05:22 --> 00:05:22 the
00:05:22 --> 00:05:24 Avery: concept is called Nuclear Electric
00:05:24 --> 00:05:26 propulsion, or nep.
00:05:27 --> 00:05:29 Unlike nuclear thermal propulsion, which
00:05:29 --> 00:05:32 heats propellant directly, NEP uses
00:05:32 --> 00:05:35 a fission reactor to generate electricity,
00:05:35 --> 00:05:37 which then powers highly efficient ion
00:05:37 --> 00:05:40 thrusters. The spacecraft accelerates slowly
00:05:40 --> 00:05:43 at first, but continuously building up
00:05:43 --> 00:05:45 extraordinary speed over weeks.
00:05:45 --> 00:05:48 Anna: The reactor itself will produce 20
00:05:48 --> 00:05:50 kilowatts of electrical power using high
00:05:50 --> 00:05:53 assay low enriched uranium. And in
00:05:53 --> 00:05:56 a clever piece of engineering pragmatism,
00:05:56 --> 00:05:59 NASA is repurposing hardware that was already
00:05:59 --> 00:06:01 built for the now paused lunar gateway
00:06:01 --> 00:06:04 program, the power and propulsion element
00:06:04 --> 00:06:06 as the spacecraft bus.
00:06:07 --> 00:06:10 Avery: Once SR1 Freedom reaches Mars roughly a
00:06:10 --> 00:06:12 year after launch, it will deploy a payload
00:06:12 --> 00:06:15 called Skyfall three Ingenuity class
00:06:15 --> 00:06:17 helicopters that will scout the martian
00:06:17 --> 00:06:20 surface for subsurface water ice and
00:06:20 --> 00:06:22 survey potential future human landing sites.
00:06:23 --> 00:06:25 Anna: Ingenuity, you'll recall, was only supposed
00:06:25 --> 00:06:28 to fly five times. On the Perseverance
00:06:28 --> 00:06:30 mission, it flew 72. So
00:06:30 --> 00:06:33 NASA knows these little rotorcraft can punch
00:06:33 --> 00:06:34 well above their weight.
00:06:35 --> 00:06:37 Avery: NASA Administrator Isaacman announced the
00:06:37 --> 00:06:40 mission back in March at what they called the
00:06:40 --> 00:06:43 ignition event, and he was emphatic this
00:06:43 --> 00:06:45 isn't a concept study. Hardware development
00:06:45 --> 00:06:48 is ramping up now with assembly and testing
00:06:48 --> 00:06:51 scheduled from early 2028. The December
00:06:51 --> 00:06:54 2028 Mars launch window is the deadline, and
00:06:54 --> 00:06:55 the scope bends around it.
00:06:56 --> 00:06:59 Anna: If successful, SR1 freedom does
00:06:59 --> 00:07:02 far more than test a propulsion system. It
00:07:02 --> 00:07:04 establishes the regulatory and launch
00:07:04 --> 00:07:06 precedents for nuclear hardware in space,
00:07:07 --> 00:07:10 activates the industrial base, and opens the
00:07:10 --> 00:07:13 door to megalot class reactors that could one
00:07:13 --> 00:07:15 day cut a human journey to Mars to just
00:07:15 --> 00:07:16 two months.
00:07:16 --> 00:07:19 The stakes couldn't be higher now for
00:07:19 --> 00:07:21 Avery: something you can actually go outside and
00:07:21 --> 00:07:24 experience yourself because the ADA
00:07:24 --> 00:07:27 Aquarids meteor shower is peaking right now
00:07:27 --> 00:07:29 with the best viewing on the mornings of May
00:07:29 --> 00:07:30 5th and 6th.
00:07:31 --> 00:07:33 Anna: And we know we've touched on this in recent
00:07:33 --> 00:07:36 episodes, but the peak is literally upon us.
00:07:36 --> 00:07:38 So here's your final briefing and viewing
00:07:38 --> 00:07:39 guide.
00:07:39 --> 00:07:42 Avery: The ETA Aquarids are one of the most famous
00:07:42 --> 00:07:44 annual meteor showers, and they come from a
00:07:44 --> 00:07:47 truly iconic source, the debris trail of
00:07:47 --> 00:07:50 Halley's Comet. Earth passes through
00:07:50 --> 00:07:52 Halley's dusty wake each May. Those
00:07:52 --> 00:07:55 particles, some as small as a grain of sand,
00:07:55 --> 00:07:58 slam into our atmosphere at around 66
00:07:58 --> 00:08:00 km per second and vaporize in
00:08:00 --> 00:08:02 brilliant streaks of light.
00:08:03 --> 00:08:05 Anna: Halley's Comet last visited the inner solar
00:08:05 --> 00:08:08 system in 1986 and won't return
00:08:08 --> 00:08:11 until 2061. So these annual
00:08:11 --> 00:08:14 showers are our way of staying connected to
00:08:14 --> 00:08:16 one of the most celebrated objects in
00:08:16 --> 00:08:17 astronomical history.
00:08:18 --> 00:08:20 Avery: Now, the great news for our Southern
00:08:20 --> 00:08:23 Hemisphere listeners, and that's a lot of you
00:08:23 --> 00:08:25 in Australia, New Zealand, and South Africa,
00:08:26 --> 00:08:28 is that this shower strongly favors your
00:08:28 --> 00:08:31 skies. The radiant point in Aquarius
00:08:31 --> 00:08:34 climbs much higher before dawn in the
00:08:34 --> 00:08:36 southern latitudes, giving you potential
00:08:36 --> 00:08:39 rates of around 50 meteors per hour under
00:08:39 --> 00:08:40 ideal dark sky conditions.
00:08:41 --> 00:08:44 Anna: The challenge this year is the moon. On the
00:08:44 --> 00:08:46 peak night, we have a waning gibbous moon
00:08:46 --> 00:08:49 that's about 84% illuminated, which will wash
00:08:49 --> 00:08:51 out the fainter meteors. The best strategy is
00:08:51 --> 00:08:54 to find a dark location and physically block
00:08:54 --> 00:08:57 the moon behind a treeline, building or hill,
00:08:57 --> 00:08:59 your eyes will adjust and you'll catch the
00:08:59 --> 00:09:01 brighter, faster meteors.
00:09:01 --> 00:09:04 Avery: Even so, the pre dawn hours are, uh, the
00:09:04 --> 00:09:07 prime window. Watch from around 2am
00:09:07 --> 00:09:10 onwards as the radiant climbs highest. These
00:09:10 --> 00:09:12 are fast meteors that often leave glowing,
00:09:12 --> 00:09:15 persistent trails. Set up a reclining
00:09:15 --> 00:09:18 chair, wrap up warm, yes, even in
00:09:18 --> 00:09:20 autumn for you southern listeners and let the
00:09:20 --> 00:09:21 skies do the rest.
00:09:21 --> 00:09:24 Anna: The shower remains active through May 28,
00:09:25 --> 00:09:27 so there are more opportunities ahead, even
00:09:27 --> 00:09:30 if clouds interrupt tonight. But the peak is
00:09:30 --> 00:09:31 now. Get out there.
00:09:31 --> 00:09:34 Avery: Story five takes us to the Red Planet, where
00:09:34 --> 00:09:37 two remarkable robots are currently writing
00:09:37 --> 00:09:40 history from opposite ends of geological
00:09:40 --> 00:09:42 time. NASA has released sweeping
00:09:42 --> 00:09:45 360 degree panoramas from both Curiosity
00:09:45 --> 00:09:48 and Perseverance. And together they tell
00:09:48 --> 00:09:50 one of the most compelling stories in
00:09:50 --> 00:09:51 planetary science.
00:09:52 --> 00:09:54 Anna: Here's the beautiful paradox of what's
00:09:54 --> 00:09:57 happening. Curiosity, now approaching 15
00:09:57 --> 00:10:00 years on Mars, is climbing Mount Sharp
00:10:00 --> 00:10:02 and exploring progressively younger terrain.
00:10:03 --> 00:10:06 Perseverance, just five years in, is heading
00:10:06 --> 00:10:08 into some of the oldest landscapes in the
00:10:08 --> 00:10:10 entire solar system. They're time traveling
00:10:10 --> 00:10:12 in opposite directions.
00:10:12 --> 00:10:15 Avery: Curiosity's new panorama is assembled from
00:10:15 --> 00:10:17 over a thousand images captured between
00:10:17 --> 00:10:20 November and December last year. It reveals
00:10:20 --> 00:10:23 a vast network of what scientists call
00:10:23 --> 00:10:26 boxwork formations, low ridges that
00:10:26 --> 00:10:29 from orbit look like giant spiderwebs etched
00:10:29 --> 00:10:31 across the landscape. These ridges formed
00:10:31 --> 00:10:34 billions of years ago when groundwater flowed
00:10:34 --> 00:10:36 through fractures in the bedrock, depositing
00:10:36 --> 00:10:39 minerals that hardened everything around them
00:10:39 --> 00:10:42 eroded away. What's left is essentially
00:10:42 --> 00:10:44 a fossil of ancient water activity.
00:10:45 --> 00:10:47 Anna: Perseverance is panorama focuses on a region
00:10:47 --> 00:10:50 near the rim of Jezero Crater, a place
00:10:50 --> 00:10:53 nicknamed Lac des Charmes. Assembled from
00:10:53 --> 00:10:56 nearly 980 images taken over
00:10:56 --> 00:10:59 several weeks in late 2025 and early
00:10:59 --> 00:11:01 2026. The crater held a lake
00:11:02 --> 00:11:04 billions of years ago, fed by a river system.
00:11:05 --> 00:11:07 The sediments that filled that lakebed could
00:11:07 --> 00:11:10 have preserved signs of microbial life. In
00:11:10 --> 00:11:13 2024, Perseverance found a rock called
00:11:13 --> 00:11:16 Chayava Falls, covered with what scientists
00:11:16 --> 00:11:19 call leopard spots caused by chemical
00:11:19 --> 00:11:21 reactions that microbes are known to
00:11:22 --> 00:11:22 Earth.
00:11:22 --> 00:11:25 Avery: And Perseverance is carrying 23
00:11:25 --> 00:11:27 intact rock cores in sealed tubes,
00:11:28 --> 00:11:30 waiting for a future sample return mission to
00:11:30 --> 00:11:33 bring them to Earth labs. The science
00:11:33 --> 00:11:35 locked inside those tubes could quite
00:11:35 --> 00:11:38 literally answer the question of whether life
00:11:38 --> 00:11:40 ever existed beyond our planet.
00:11:41 --> 00:11:43 Anna: These panoramas aren't just beautiful,
00:11:43 --> 00:11:46 although they absolutely are. At over a
00:11:46 --> 00:11:49 billion pixels, curiosities alone is one
00:11:49 --> 00:11:51 of the largest it's ever taken. There's
00:11:51 --> 00:11:54 scientific archives, time capsules,
00:11:54 --> 00:11:57 two snapshots of a world that was once warm
00:11:57 --> 00:11:59 Wet and possibly alive.
00:12:00 --> 00:12:00 Avery: Two rovers,
00:12:01 --> 00:12:04 3km
00:12:04 --> 00:12:06 apart, filling in the missing chapters of
00:12:06 --> 00:12:09 Mars's extraordinary biography.
00:12:09 --> 00:12:11 What a time to be alive.
00:12:11 --> 00:12:14 Anna: And our final story today is one for anyone
00:12:14 --> 00:12:17 who's looked south on a clear night and seen
00:12:17 --> 00:12:19 those two glowing smudges in the sky, the
00:12:19 --> 00:12:22 Large and Small Magellanic Clouds. If you're
00:12:22 --> 00:12:25 in Australia or New Zealand, they're part of
00:12:25 --> 00:12:27 your night sky heritage. But new research
00:12:27 --> 00:12:30 suggests their history is far stranger than
00:12:30 --> 00:12:31 we ever imagined.
00:12:32 --> 00:12:35 Avery: The Large Magellanic Cloud, the LMC
00:12:35 --> 00:12:38 is our galaxy's most massive satellite.
00:12:38 --> 00:12:40 For decades, astronomers assumed it had been
00:12:40 --> 00:12:43 orbiting the Milky Way for billions of years,
00:12:43 --> 00:12:46 making multiple passes. A competing theory
00:12:46 --> 00:12:48 said it's actually on its first approach.
00:12:49 --> 00:12:51 Now a new preprint paper claims to provide
00:12:51 --> 00:12:54 what the authors call definitive evidence
00:12:54 --> 00:12:57 that the LMC is a first time visitor.
00:12:57 --> 00:12:59 Anna: The paper comes from researchers including
00:12:59 --> 00:13:01 Scott Luccini and colleagues, and it
00:13:01 --> 00:13:04 addresses a fierce ongoing debate in
00:13:04 --> 00:13:06 astrophysics. The stakes are high because the
00:13:06 --> 00:13:09 LMC is genuinely massive. It's roughly
00:13:09 --> 00:13:12 one tenth to one fifth the mass of the Milky
00:13:12 --> 00:13:14 Way itself. A galaxy that big, swinging
00:13:14 --> 00:13:17 through our neighborhood sends gravitational
00:13:17 --> 00:13:19 shock waves through everything around us.
00:13:19 --> 00:13:22 Avery: The evidence lies in the LMC's corona, a, uh,
00:13:22 --> 00:13:25 diffuse halo of warm gas surrounding it. If
00:13:25 --> 00:13:28 the LMC had made a previous close pass by the
00:13:28 --> 00:13:30 Milky Way, that corona should have been
00:13:30 --> 00:13:32 stripped away by our galaxy's gravity. The
00:13:32 --> 00:13:35 fact that it's still there, relatively
00:13:35 --> 00:13:37 intact, strongly supports the first infall
00:13:37 --> 00:13:40 scenario. It also explains why the Small
00:13:40 --> 00:13:42 Magellanic Cloud and other satellites, ah,
00:13:42 --> 00:13:45 that travel with the LMC haven't been tidally
00:13:45 --> 00:13:48 torn apart. They simply haven't had enough
00:13:48 --> 00:13:50 close encounters with the Milky Way to be
00:13:50 --> 00:13:50 disrupted.
00:13:51 --> 00:13:53 Anna: There's something almost poetic about this.
00:13:53 --> 00:13:55 That gorgeous smudge of light you can see
00:13:55 --> 00:13:58 from a southern dark sky visible to the naked
00:13:58 --> 00:14:01 eye, named after Magellan, is essentially a
00:14:01 --> 00:14:04 first time visitor. It fell toward us for the
00:14:04 --> 00:14:06 first time in cosmic history, passed its
00:14:06 --> 00:14:09 closest point recently in astronomical terms,
00:14:09 --> 00:14:11 and now is swing back out. We're
00:14:11 --> 00:14:14 witnessing something that has never happened
00:14:14 --> 00:14:15 before in our galaxy's history.
00:14:16 --> 00:14:18 Avery: It also rewrites our understanding of the
00:14:18 --> 00:14:20 Magellanic Stream, that vast trail of
00:14:20 --> 00:14:23 hydrogen gas stretching across the southern
00:14:23 --> 00:14:25 sky behind the clouds. That stream was
00:14:25 --> 00:14:28 thought to have been shaped by multiple Milky
00:14:28 --> 00:14:30 Way interactions. Now researchers have to
00:14:30 --> 00:14:33 explain it through LMC SMC interactions
00:14:33 --> 00:14:36 alone. More work ahead. But what a puzzle to
00:14:36 --> 00:14:37 have for
00:14:37 --> 00:14:39 Anna: our Southern Hemisphere listeners. Next time
00:14:39 --> 00:14:41 you step outside on a clear night and spot
00:14:41 --> 00:14:44 the Magellanic Clouds, take a moment. You're
00:14:44 --> 00:14:46 watching a, uh, first encounter between
00:14:46 --> 00:14:48 galaxies unfolding in slow motion
00:14:48 --> 00:14:50 across the cosmos.
00:14:50 --> 00:14:52 Avery: And that's your Astronomy daily for Monday,
00:14:52 --> 00:14:55 May 4. Six stories from Ireland
00:14:55 --> 00:14:58 joining the Space Coalition to a galaxy
00:14:58 --> 00:15:00 making its first visit in cosmic history.
00:15:01 --> 00:15:02 What a day to be an astronomy.
00:15:02 --> 00:15:04 Anna: Enthusiastic if you're heading out to watch
00:15:04 --> 00:15:07 the IDA Aquarids tonight or tomorrow morning,
00:15:07 --> 00:15:09 we'd love to hear how you got on. Find us at
00:15:09 --> 00:15:12 astronomydaily IO or reach out on
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00:15:15 --> 00:15:17 Tumblr astrodaily pod.
00:15:17 --> 00:15:19 Avery: And if the show brings you joy, please leave
00:15:19 --> 00:15:21 us a review. Wherever you listen, it
00:15:21 --> 00:15:23 genuinely makes a difference and helps more
00:15:23 --> 00:15:24 people find us.
00:15:25 --> 00:15:27 Anna: This has been Astronomy Daily, part of the
00:15:27 --> 00:15:30 bytes.com podcast network. I'm Anna
00:15:30 --> 00:15:32 and just before I go, a quick reminder to
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00:15:45 --> 00:15:48 Avery: notes and I'm Avery. Keep looking up.
00:15:48 --> 00:15:50 The universe has never been more alive.
00:15:51 --> 00:15:52 We'll see you tomorrow.
00:15:55 --> 00:15:55 Anna: Mhm.
00:16:03 --> 00:16:04 The story.