Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomy podcast. Each episode offers a
Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
Speaker 1: unwinding after a long day. Let's travel through the mysteries
Speaker 1: of the universe as you drift off into a peaceful
Speaker 1: slumber under the night sky.
Speaker 2: Okay, So for our look into the sources today, we're
Speaker 2: zooming out, way out, way out, Yeah, past the edge
Speaker 2: of our own galaxy, the Milky Way.
Speaker 3: And we're focusing on our two closest and probably most
Speaker 3: famous galactic neighbors.
Speaker 2: Right if you're in the southern hemisphere, you just can't
Speaker 2: miss them, the large and small Magellantic Cloud.
Speaker 3: There's so much more than just these beautiful patches of
Speaker 3: light in the sky though. I mean, for centuries they
Speaker 3: were guides for sailors and inspiration.
Speaker 2: For poets, sure, but for astronomers they represent something else entirely.
Speaker 3: Oh absolutely, for astronomers, these irregular dwarf galaxies are home
Speaker 3: to some of the most profound and honestly most frustrating
Speaker 3: mysteries in all of galaxy evolution.
Speaker 2: And that's why we're looking at this today because this
Speaker 2: isn't just about another observation. We're talking about it massive
Speaker 2: dedicated research.
Speaker 3: Program monumental is the word, a five year program focused
Speaker 3: entirely on these two galaxies.
Speaker 2: The whole mission here is to take what look like
Speaker 2: these these abstract clouds of stars and gas and turn
Speaker 2: them into a detailed, meticulous cosmic history.
Speaker 3: And that's exactly what we're going to unpack. We are
Speaker 3: looking at the sources that detail this new astronomical campaign,
Speaker 3: try to figure out what makes these two galaxies the
Speaker 3: ultimate cosmic.
Speaker 2: Lab, and what are the core scientific puzzles that this
Speaker 2: huge data collection is really designed to solve.
Speaker 3: Exactly, We want to give you the shortcut to understanding
Speaker 3: the secrets that are locked away inside the Magellanic clouds.
Speaker 2: So the starting point, the ultimate takeaway, really begins with
Speaker 2: just geography, or I guess cosmic geography. Proximity.
Speaker 3: Proximity is everything in galactic terms. They are practically on
Speaker 3: our doorstep.
Speaker 2: How close are we talking.
Speaker 3: The LMC, the large one is about one hundred and
Speaker 3: sixty three thousand light years away. The SMC is a
Speaker 3: little bit further, around two hundred and six thousand.
Speaker 2: And just to give you some perspective on that the
Speaker 2: next big galaxy, Andromeda is what over two and a
Speaker 2: half million light.
Speaker 3: Years away, right, So this sheer closeness is what makes
Speaker 3: them so scientifically valuable.
Speaker 2: Invaluable because they give us a perspective we just can't
Speaker 2: get from inside our own galaxy.
Speaker 3: Precisely, we can resolve individual stars with incredible clarity. Because
Speaker 3: they're so close, we can map out their entire structure,
Speaker 3: their stellar populations, the internal dynamics without.
Speaker 2: All the clutter of the Milky Way getting in.
Speaker 3: The way exactly. The sources call them excellent natural laboratories
Speaker 3: for studying things like galaxy evolution and star formation, and
Speaker 3: those are processes that are either completely hidden by dust
Speaker 3: in our own galaxy or just impossible to see coherently
Speaker 3: from where we sit inside the galactic disc.
Speaker 2: Okay, so we have the perfect subjects. Now, we need
Speaker 2: the team and the tools, and this is a huge
Speaker 2: international project, but there's one institution really spear hitting it.
Speaker 3: That's right. This whole push is being led by a
Speaker 3: new research group at the Libniz Institute for Astrophysics, Potsdam,
Speaker 3: the AIP, and.
Speaker 2: A key person here is doctor Laura Colinane, yes.
Speaker 3: A postdoc at AIP, and her focus is really on
Speaker 3: the nitty gritty details, the chemistry the motion of individual
Speaker 3: stars within that bigger galactic picture.
Speaker 2: And the project itself has this wonderfully grand name one
Speaker 2: thousand and one Magellanic.
Speaker 3: Fields, mercifully shortened to one thousand and one MC.
Speaker 2: It does have a nice ring to it.
Speaker 3: It sounds like an adventure, and honestly the scale fits.
Speaker 3: The main goal here for doctor Colinane and her colleagues
Speaker 3: is to resolve individual stars. We're not talking about just
Speaker 3: blurry smudges of light.
Speaker 2: No, this is getting down to the component parts exactly.
Speaker 3: The idea is that if you can understand the detailed
Speaker 3: chemistry and the movement of say half million single stars,
Speaker 3: you can piece together the whole.
Speaker 2: Life story, the bigger picture, how these galaxies formed, how
Speaker 2: they've interacted with each other, how they've changed over billions
Speaker 2: of years.
Speaker 3: It's like collecting billions of tiny stellar history books to
Speaker 3: write the complete biography of the clouds themselves.
Speaker 2: You're turning an abstract cloud into a detailed family tree.
Speaker 2: That's the mission.
Speaker 3: We're moving from just observing the symptoms of galactic evolution
Speaker 3: to actually understanding the mechanics behind it.
Speaker 2: So let's get a bit deeper into this idea of
Speaker 2: than being a superior laboratory. I mean, why is it
Speaker 2: so much better than just studying in the Milky Way?
Speaker 3: Well, you know that analogy we sometimes use, the one.
Speaker 2: About being stuck in a foggy valley.
Speaker 3: Exactly that one trying to map our own galaxy from
Speaker 3: the inside is it's like that you've got dust, You've
Speaker 3: got clutter everywhere.
Speaker 2: Extinction right, just blocks the view completely.
Speaker 3: But with the Magellanic clouds we get this this holistic view.
Speaker 3: We see the whole thing top to bottom. We can
Speaker 3: map their entire stellar populations without that heavy interference.
Speaker 2: It's more than just the view, right, Their actual physical characteristics.
Speaker 3: Are oh, very different, and that's what makes them such
Speaker 3: perfect test beds. It's really about their gas content and
Speaker 3: you could say their maturity.
Speaker 2: And the contrast with the Milky Way is pretty stark.
Speaker 3: Absolutely, two main things define them. First, they are way
Speaker 3: more gas rich than.
Speaker 2: We are, meaning a much higher fraction of their mass
Speaker 2: is just raw hydrogen and helium.
Speaker 3: The pristine fuel for making new stars exactly, so they have.
Speaker 2: A lot of gas left in the tank waiting to
Speaker 2: be used.
Speaker 3: They do. And second, and this is probably even more
Speaker 3: critical for testing our big cosmological models, they have a
Speaker 3: much lower metallicity.
Speaker 2: Okay, so when astronomers say metallicity, we're talking about all
Speaker 2: the elements heavier than hydrogen and helium. Why is it
Speaker 2: so important that they have less of that stuff?
Speaker 3: Well, low metallicity means the LMC and SMC have had
Speaker 3: less chemical enrichment over their lifetimes. Heavy elements are forged
Speaker 3: inside stars and then blasted out into the galaxy see
Speaker 3: when those stars die, usually in supernovae.
Speaker 2: So lower metallicity means a less mature or maybe a
Speaker 2: less efficient star making system compared to our own.
Speaker 3: Galaxy precisely, and that's what helps us test our models
Speaker 3: of galaxy formation. How So, our big cosmological simulations have
Speaker 3: always kind of struggled with dwarf galaxies. A key problem
Speaker 3: is figuring out how chemical enrichment that build up of
Speaker 3: heavy elements actually happens in these small, low mass systems, because.
Speaker 2: They don't have enough gravity to hang onto all the
Speaker 2: gas that gets blown out by supernovae exactly.
Speaker 3: So, the LMC and SMC being both metal poor and
Speaker 3: actively forming stars. They let us see star formation happening
Speaker 3: in the exact conditions that our theories predict dominated the
Speaker 3: early universe.
Speaker 2: So we can watch how stars form when the environment
Speaker 2: is still relatively pristine, something we just can't do in
Speaker 2: the Milky Way's mature, metal rich disc.
Speaker 3: They're like living fossils of early galaxy formation. It's an
Speaker 3: incredible opportunity.
Speaker 2: That context is invaluable. And within these metal poor games
Speaker 2: as clouds, there are some specific spots that are just
Speaker 2: they're astronomical showstoppers.
Speaker 3: They really are cosmic extremes. In the large Magellanic cloud
Speaker 3: you've got the tarantulin Nebula was not as thirty durraatus,
Speaker 3: and our sources describe it as an extremely active star
Speaker 3: forming region, which is frankly an understatement.
Speaker 2: It's the most active region of massive star formation in
Speaker 2: our entire local group of galaxies, isn't it? It is?
Speaker 3: It is an absolute engine room of stellar creation. It
Speaker 3: has some of the biggest, most luminous, most massive stars
Speaker 3: we know of, Some are dozens of times the mass
Speaker 3: of our Sun.
Speaker 2: And the fact that a relatively small low metallis city
Speaker 2: galaxy like the LMC can host such a monster star
Speaker 2: forming region is a puzzle in itself.
Speaker 3: It is the radiation and wanes from those newborn giant
Speaker 3: stars are just constantly sculpting the gas around them. Studying
Speaker 3: them helps us understand the absolute upper limits of star
Speaker 3: formation physics.
Speaker 2: In the small Magellanic Cloud it has its own version
Speaker 2: of those.
Speaker 3: It does three six. It's an open star cluster and
Speaker 3: nebula that's also actively forming a lot of high mass stars.
Speaker 2: So it's another real time test bed.
Speaker 3: But crucially it's doing it in the even lower metallicity
Speaker 3: environment of the SMC, so we get to observe the
Speaker 3: same physics but under slightly different, more primitive chemical conditions.
Speaker 3: It's a perfect comparative study.
Speaker 2: And beyond these crazy star forming regions, the clouds also
Speaker 2: contain objects that are well, they're fundamental to how we
Speaker 2: map the entire universe.
Speaker 3: You're talking about their huge population of variable stars. Exactly
Speaker 3: these stars, specifically the Cepheide variables, are absolutely vital. There
Speaker 3: are standard candles for the cosmic distance ladder.
Speaker 2: Because the relationship between how fast they pulse and how
Speaker 2: bright they truly are is very well.
Speaker 3: Understood, extremely well understood, so you can compare their true
Speaker 3: brightness to how bright they appear from Earth, and from
Speaker 3: that you can calculate their distance with incredible accuracy.
Speaker 2: And by extension, the distance to the galaxy they live
Speaker 2: in precisely.
Speaker 3: And because the Magellanic clouds are so close, we can
Speaker 3: make hyper accurate foundational distance measurements to their cepheides. Those
Speaker 3: distances then calibrate the entire cosmic distance scale.
Speaker 2: The yardstick we use to measure the whole universe, all
Speaker 2: the way up to calculate in the Hubble constant and
Speaker 2: the expansion rate.
Speaker 3: Right, So, detailed data on the variable stars in the
Speaker 3: LMC and SMC is bedrock science for the whole field.
Speaker 2: It sounds like they're just constantly churning out stars and
Speaker 2: lighting up the cosmos. But you mentioned there's a kind
Speaker 2: of inconsistency to their activity levels, not a smooth process.
Speaker 3: And this is maybe the most fundamental question about their
Speaker 3: internal life that this one thousand and one MC survey
Speaker 3: wants to answer. The sources show that even though the
Speaker 3: clouds have stars of all ages from very young to
Speaker 3: very old, the rate of star formation hasn't been constant.
Speaker 2: It seems to happen in what they call episodic bursts.
Speaker 3: Exactly episodic brusts, which suggests long periods of relative quiet
Speaker 3: punctuated by these intense, spectacular fire displays of starbirth.
Speaker 2: But what's pushing the on switch for those fireworks?
Speaker 3: That is the core puzzle why the bursts. Is the
Speaker 3: gas compression that you need to trigger mass star formation
Speaker 3: coming from something internal like complex gas dynamics within the
Speaker 3: galaxy itself?
Speaker 2: Or is the trigger external?
Speaker 3: Right? Is it the gravitational or physical interaction with the
Speaker 3: Milky Way, or even just the frequent close passes between
Speaker 3: the LMAC and the SMC themselves.
Speaker 2: And the source suggests that if the bursts line up
Speaker 2: with the times of close gravitational encounters, that would point
Speaker 2: very strongly to an external trigger.
Speaker 3: Absolutely, a gravitational shockwave from a close pass can compress
Speaker 3: gas and kick off a huge wave of star formation.
Speaker 3: But to know that for sure, we need hard data.
Speaker 3: We need the precise ages and the motions of the
Speaker 3: stars that were born in those bursts.
Speaker 2: To verify that connection, we need to figure out who's
Speaker 2: pushing the nitro button that accelerates everything.
Speaker 3: And that leads us perfectly into the instruments that are
Speaker 3: designed to find out.
Speaker 2: Okay, So if the clouds of the perfect lab. You
Speaker 2: need the perfect tools, and the instruments for this are well,
Speaker 2: they're pretty incredible. Right down at the Paranol Observatory in Chile, Oh.
Speaker 3: The hardware is state of the art. It all centers
Speaker 3: on the Vista Telescope.
Speaker 2: VISTA. That's the visible and infrared survey telescope for astronomy.
Speaker 3: Right, but it's just been given this massive upgrade a
Speaker 3: new instrument called Foremost.
Speaker 2: Four meter multi object spectrograph telescope, So it's spectrograph.
Speaker 3: Exactly, which is attached to Vista. Let's start with Visit
Speaker 3: itself though. It's got a huge four point one meter
Speaker 3: primary mirror.
Speaker 2: But its real specialty is its vision. It sees in
Speaker 2: the near infrared.
Speaker 3: And that near infrared or NR capability is just crucial.
Speaker 3: Vista is the largest telescope in the world dedicated to
Speaker 3: wide field surveys in the NIR.
Speaker 2: Why is NR so important for this.
Speaker 3: Because it lets you see through the dust Galactic dust
Speaker 3: particles that block visible light are well, they're basically transparent
Speaker 3: to the longer wavelengths of near infrared light, so.
Speaker 2: You're not just seeing the bright stars on the surface
Speaker 2: of the clouds. You're actually peering right into the heart
Speaker 2: of those star forming regions, like deep inside the transil
Speaker 2: and neibula precisely.
Speaker 3: It lets them do an accurate census of stars that
Speaker 3: would be completely invisible in a normal optical light survey.
Speaker 3: It's essential for getting a complete, unbiased sample.
Speaker 2: And the camera on this thing is it's a monster,
Speaker 2: a three ton sixty seven megapixel camera.
Speaker 3: It's stunning technology. But Foremost is the new brain of
Speaker 3: the operation. That's the upgrade that takes all that light
Speaker 3: gathering power and turns it into historical evidence.
Speaker 2: A multi object spectrograph what does that actually mean.
Speaker 3: It's a fiber fed spectroscopic survey instrument, and the multi
Speaker 3: object part is the real game changer.
Speaker 2: Instead of looking at one start a time.
Speaker 3: Right, instead of pointing at a single star to get
Speaker 3: its spectrum, Foremost has this complex robotic positioner that moves
Speaker 3: thousands of tiny little optical fibers across the focal plane.
Speaker 2: How many targets could I hit at once?
Speaker 3: It can collect light from up to twenty four hundred
Speaker 3: different objects simultaneously in a single observation twenty four hundre
Speaker 3: so it's basically doing twenty four hundred separate spectroscopic measurements
Speaker 3: in the time it would have taken older instruments to
Speaker 3: do maybe one or two. It's the only way you
Speaker 3: could hope to get a sample size of half a
Speaker 3: million stars in a reasonable time.
Speaker 2: That just completely changes the logistics of a survey like this.
Speaker 2: So what's the timeline.
Speaker 3: This is all happening right now. Foremost achieved first light
Speaker 3: back in October twenty twenty five. It's in its commissioning
Speaker 3: phase as we speak, getting everything calibrated.
Speaker 2: And science operations are scheduled to start.
Speaker 3: Soon second quarter of twenty twenty six. And here's the kicker,
Speaker 3: the thing that shows you how important this mission is.
Speaker 3: For a stripped five year period, this to and Foremost
Speaker 3: are completely dedicated to this program. It excludes all other observations.
Speaker 2: Wow, a five year block on a world class telescope.
Speaker 2: That's an enormous commitment of astronomical resources.
Speaker 3: It is which brings us to the mission itself, one
Speaker 3: thousand and one.
Speaker 2: MC, the one thousand and one Magellanic Fields co led
Speaker 2: by doctor Colinade.
Speaker 3: The ambition is just staggering. The goal is to get
Speaker 3: the spec of about half a million stars across the
Speaker 3: main bodies of the clouds and just as importantly, way
Speaker 3: out into their faint, outlying regions.
Speaker 2: Half a million individual stellar life stories. So for someone listening,
Speaker 2: what's the really crucial data that the spectrograph gives you
Speaker 2: that you can't get from just a picture.
Speaker 3: It gives you two revolutionary types of data. First, high
Speaker 3: precision elemental abundances.
Speaker 2: The star's chemical fingerprint, it's Perth certificate exactly.
Speaker 3: And second, extremely accurate kinematics.
Speaker 2: Which is its detailed motion, its travel history, it's velocity
Speaker 2: toward us or away from us.
Speaker 3: Let's drill down on those abundances for a second. When
Speaker 3: you say chemical fingerprint, which elements tell you the most
Speaker 3: about the history?
Speaker 2: I assume things like iron are important.
Speaker 3: Iron is key, yes, for overall metallicity, but also what
Speaker 3: are called the alpha elements, things like magnesium and titanium.
Speaker 3: The ratio of iron to these alpha elements is super
Speaker 3: sensitive to the history of star formation. No so, because slow,
Speaker 3: steady rate of star formation produces a different chemical ratio
Speaker 3: than a rapid, intense burst, does it tells you about
Speaker 3: the rate of enrichment, not just the amount.
Speaker 2: And the kinematics. How does the spectrograph measure motion?
Speaker 3: It all comes down to the Doppler effect. Light from
Speaker 3: a star moving toward use gets slightly blue.
Speaker 2: Shifted, its wavelengths get compressed right.
Speaker 3: And light from a star moving away gets red shifted,
Speaker 3: its wavelengths get stretched, And you need a high resolution
Speaker 3: spectrograph to measure those tiny shifts with enough precision to
Speaker 3: get the star's velocity down to say a kilometer per second.
Speaker 2: So you get the star's life history from its chemistry
Speaker 2: and its current path from its motion and Doctor Colony
Speaker 2: and specifically mentioned measuring this data in the outskirts.
Speaker 3: Why is that so important, Because the outskirts the halos
Speaker 3: of these galaxies are where the tug of war is
Speaker 3: most obvious. If the Milky Way is tidally pulling material
Speaker 3: off the clouds, it's going to strip the stars and
Speaker 3: gas from the edges first.
Speaker 2: Those are the regions that are most weakly held on
Speaker 2: by the clouds side.
Speaker 3: Gravity exactly, and they're very faint, which is why you
Speaker 3: need Vista's wide field and niur sensitivity and foremost ability
Speaker 3: to target faint stars so efficiently.
Speaker 2: Her quote really sums it all up, doesn't it. She said.
Speaker 2: The goal is to trace the effects of interactions between
Speaker 2: the clouds by analyzing the kinematics and abundances of their
Speaker 2: stellar populations, particularly in the outskirts.
Speaker 3: That's it in a nutshell. The focus is on finding
Speaker 3: the physical scars left by these massive gravitational fights.
Speaker 2: So this incredible new data set is really designed to
Speaker 2: test some of the biggest, most revolutionary ideas happening in
Speaker 2: galactic dynamics right now. For decades, we had a pretty
Speaker 2: comfortable story about how the Milky Way and the clouds
Speaker 2: were interacting.
Speaker 3: We did. The old paradigm was that the clouds were
Speaker 3: ancient satellites. They had been orbiting the Milky Way for
Speaker 3: maybe ten billion years. They'd completed lots of passes.
Speaker 2: Which implied a long slow history of co evolution, a very.
Speaker 3: Long slow dance. But the sources are clear that this
Speaker 3: law held idea has just been completely challenged, and that's
Speaker 3: what created the urgency for one thousand and one MC.
Speaker 2: What was it that shifted the foundation of that theory.
Speaker 3: The shift came from the ESA's Gaya Mission Ayah, which.
Speaker 2: Is just mapping everything with insane precision.
Speaker 3: Insane precision. Its strength is mapping the positions and the
Speaker 3: proper motions. That's the sideways movement of billions of stars,
Speaker 3: and that data, when you combine it with some older
Speaker 3: Hubble observations, it suggests something well, something revolutionary, which is
Speaker 3: that the clouds might be on their very first passage
Speaker 3: by the Milky Way.
Speaker 2: Hold on their first pass not ancient satellites that have
Speaker 2: been orbiting for billions.
Speaker 3: Of years exactly. They might just be newcomers, just arriving
Speaker 3: in our cosmic neighborhood for the first time.
Speaker 2: That's a massive revision of their history. If they're new,
Speaker 2: it means all the dramatic effects we see, the star formation,
Speaker 2: the gas streams, all of that has to be the
Speaker 2: result of a fresh, violent, rapid encounter, not.
Speaker 3: A slow, billions of years long orbital decay. That's the
Speaker 3: profound implication. If they're on a first pass, their relationship
Speaker 3: with the Milky Way has only just begun.
Speaker 2: And that has to have huge implications for understanding our
Speaker 2: own galaxy too.
Speaker 3: Oh massive. It changes our estimates for the total mass
Speaker 3: of the Milky Way, because if the clouds are moving
Speaker 3: fast enough to just be passing through, our galaxy has
Speaker 3: to be heavy enough to have captured them only temporarily,
Speaker 3: or to be pulling them into orbit.
Speaker 2: Right now, not having held onto them for eons. It
Speaker 2: affects our understanding of our own dark matter halo absolutely.
Speaker 3: And the most dramatic piece of evidence for this interaction,
Speaker 3: whether it's old or new, is the huge stream of
Speaker 3: material we see being ripped away from the clouds right now,
Speaker 3: the Magelanic stream, the Magelanic stream, this enormous ribbon of
Speaker 3: gas that trails hundreds of thousands of light years behind
Speaker 3: the clouds, stretching down toward the Milky Way's south pole.
Speaker 3: And there's also the leading arm, which is material fling
Speaker 3: out ahead of them.
Speaker 2: These things are just immense physical scars that shows something
Speaker 2: dramatic is happening.
Speaker 3: And their very existence immediately raises three competing ideas about
Speaker 3: how they were created, which is what one thousand and
Speaker 3: one MC is perfectly designed to test.
Speaker 2: We need to figure out which force is responsible because
Speaker 2: each one leaves a different kind of signature.
Speaker 3: That's the challenge. Is it hypothesis one, two, or three
Speaker 3: or a mix of all of them? And the key
Speaker 3: to figuring it out is in the kinematic and chemical
Speaker 3: data from one thousand and one MC.
Speaker 2: Okay, let's take the first one RAM pressure stripping.
Speaker 3: Ram pressure stripping is what happens when the clouds plow
Speaker 3: through the thin hot gas that makes up the Milky
Speaker 3: Way's extended halo. It's like a cosmic headwind, a perfect analogy.
Speaker 3: The pressure of that headwind just pushes the gas right
Speaker 3: out of the dwarf galaxies, stripping it away. But crucially,
Speaker 3: this mechanism mostly strips away gas, not.
Speaker 2: Stars, because the stars are much more tightly bound by gravity.
Speaker 3: Exactly, So if the Magellanic string was purely from ram pressure,
Speaker 3: you wouldn't expect to find many stars in.
Speaker 2: It, Okay. But then there's the second hypothesis title stripping.
Speaker 3: That's the purely gravitational pull of the Milky Way.
Speaker 2: The galaxy's gravity just yank's material off the edges of
Speaker 2: the clouds.
Speaker 3: Yes, And because it's purely gravitational, it affects both the
Speaker 3: gas and the stars, especially those in the outer regions
Speaker 3: where the cloud's own gravity is weakest.
Speaker 2: So if a one thousand and one MC finds a
Speaker 2: lot of stars in the Magellanic stream and their motions
Speaker 2: show they're on these wide, high velocity paths that follow
Speaker 2: the stream, that would be strong evidence for tidle stripping.
Speaker 3: That is, the core methodology, the kinematics of the stars
Speaker 3: act as the filter tidle. Stripping leaves a very specific
Speaker 3: kinematic signature. RAM pressure predicts fewer strip stars and their
Speaker 3: motion would be more irregular.
Speaker 2: And then there's the third hypothesis, which kind of complicates everything.
Speaker 2: The interactions between the LMC and the SMC themselves.
Speaker 3: They're close enough that their own gravity is causing problems
Speaker 3: for each other. The LMC is much bigger than the SMC,
Speaker 3: and it's actively distorting its smaller companion. Some models even
Speaker 3: suggest the stream was created mainly by the LMC ripping
Speaker 3: material off SMC.
Speaker 2: That seems like the hardest one to untangle. How does
Speaker 2: one thousand and one MC solve that?
Speaker 3: This is where the chemical abundance data becomes.
Speaker 2: Your second filter chemical tagging.
Speaker 3: Right, if you find a star in the stream that
Speaker 3: has the low metallicity chemical fingerprint of the SMC, you
Speaker 3: know it came from the SMC. Then you look at
Speaker 3: its motion. If its path suggests it was flung out
Speaker 3: during a close pass with the LMC, you know that
Speaker 3: interaction was dominant.
Speaker 2: But if a star with an LMC fingerprint is on
Speaker 2: a path that clearly follows the Milky Way's tidal forces,
Speaker 2: then the Milky Ways the main culprit.
Speaker 3: It's an astronomical forensics investigation, and you need the chemical
Speaker 3: tags from half a million stars to get enough data
Speaker 3: points to separate these different effects.
Speaker 2: And this all ties back to that question of the
Speaker 2: episodic star formation. Yeah, what triggers the bursts exactly?
Speaker 3: The survey gives us the tools to finally connect those
Speaker 3: two phenomena. We can figure out the age of a
Speaker 3: group of stars from their chemistry and life cycle stage,
Speaker 3: and we can correlate that age with the history of interactions.
Speaker 2: So you can ask did a burst of star formation
Speaker 2: happen and right when the clouds were making a close
Speaker 2: pass to the Milky Way, or when the LMC and
Speaker 2: SMC were closest to each other.
Speaker 3: That's the key. If the star is born in that burst,
Speaker 3: are kinematically linked to material that was just compressed or
Speaker 3: flung out by shockwave, that's a strong argument for an
Speaker 3: external trigger.
Speaker 2: And if they're just randomly distributed, it points to internal processes.
Speaker 3: Right. And finally, all this ties into understanding the chemical
Speaker 3: evolution and what are called metallicity gradients across the clouds.
Speaker 2: The abundance data doesn't just tell you if a star
Speaker 2: is metal poor, it tells you how those elements are distributed.
Speaker 3: A metallicity gradient just tracks how the concentration of heavy
Speaker 3: elements changes as you move from the center of a
Speaker 3: galaxy out to its edge.
Speaker 2: And typically you'd expect it to be highest in the
Speaker 2: center and then drop off.
Speaker 3: Generally, yes, and the steepness of that gradient tells you
Speaker 3: about the history of gas flow and mixing. If galaxy
Speaker 3: has been constantly stirred up by interactions, the gradient will
Speaker 3: be shallower the elements get spread out. If the gas
Speaker 3: days put, the gradient will be steep.
Speaker 2: So the chemistry of the stars actually reveals the plumbing
Speaker 2: system and the mixing efficiency of the galaxy's gas.
Speaker 3: That's a huge leap, a massive leap in our understanding.
Speaker 2: So someone listening might be thinking, Okay, but we've known
Speaker 2: about these clouds forever. We've pointed huge telescopes at them
Speaker 2: for decades. Why is this survey the one that's going
Speaker 2: to crack it.
Speaker 3: That's a really good question, and the answer comes down
Speaker 3: to one word spectroscopy.
Speaker 2: Because all those other big surveys, you know, VMC, STEP, smash,
Speaker 2: ogl E, they were mostly doing photometry overwhelmingly.
Speaker 3: And photometry is great. You know. It gives you brightness,
Speaker 3: it gives you color, It can track changes in brightness
Speaker 3: over time.
Speaker 2: It gives you a beautiful detailed map.
Speaker 3: A beautiful but kind of flat map. It tells you
Speaker 3: what a star looks like and where it is. It
Speaker 3: does not tell you two absolutely vital things what.
Speaker 2: It's made of and how fast it's moving toward or
Speaker 2: away from you exactly.
Speaker 3: And the official European Southern Observatory documentation for Foremost says
Speaker 3: it directly. It points out that there is a pronounced
Speaker 3: lack of spectroscopic observations across the range of stellar populations
Speaker 3: and substructures of the Magellanic clouds. That lack of spectral
Speaker 3: data is the scientific bottleneck.
Speaker 2: So why does spectroscopy breaking the light down into its
Speaker 2: component wavelengths. Why does that change the game so much
Speaker 2: for these specific questions.
Speaker 3: Because it's the only way to measure the tiny Dopplar
Speaker 3: shift you need for kinematics, and the only way to
Speaker 3: see the absorption lines that tell you the elemental composition,
Speaker 3: and the quality has to be extremely high.
Speaker 2: You can't just do low resolution spectroscopy.
Speaker 3: No, Because that might give you a rough idea of
Speaker 3: total metallicity, but it's not good enough for the technique
Speaker 3: they're relying on, which is chemical tagging.
Speaker 2: Chemical tagging it sounds like a forensic technique.
Speaker 3: It is entirely forensic. Stars are born from huge clouds
Speaker 3: of gas, and that gas cloud, at the moment it
Speaker 3: collapses to form stars, it has a unique uniform chemical signature.
Speaker 2: Its specific blend of iron, oxygen and sol right.
Speaker 3: Which depends on which supernovae enriched it right before it collapsed.
Speaker 3: So every single star born from that cloud is a
Speaker 3: chemical sibling. They share an identical chemical fingerprint.
Speaker 2: And they keep that fingerprint for their entire life.
Speaker 3: Yes, so even if those siblings get thrown to opposite
Speaker 3: ends of the galaxy by gravitational forces over billions of years,
Speaker 3: their elemental abundance ratios stay the same.
Speaker 2: So by analyzing their chemical fingerprints with high resolution spectroscopy,
Speaker 2: you can prove that two stars that are now thousands
Speaker 2: of light years apart were actually born together.
Speaker 3: That is the profound part. You can reconstruct the original
Speaker 3: birthplace of populations that were scattered by the Milky Way's influence.
Speaker 2: And previous spectroscopic surveys just didn't have the power to
Speaker 2: do this.
Speaker 3: They lacked the sheer volume of targets and the high
Speaker 3: resolution needed for this kind of detailed chemical analysis across
Speaker 3: such a huge population. They could tell us the clouds
Speaker 3: were metal poor, but they couldn't reliably do this tagging
Speaker 3: to trace where stars came from.
Speaker 2: So the advantage of the one thousand and one mc
Speaker 2: is really three five. The sheer number of stars, the
Speaker 2: wide area covers including the outskirts, and the high resolution
Speaker 2: of the data.
Speaker 3: That combination is what makes it revolutionary. The ESO documents
Speaker 3: describe it as allowing for a comprehensive study of the
Speaker 3: kinematics and chemistry of a large number of stars at
Speaker 3: different evolutionary phases and with a wide spatial distribution.
Speaker 2: So getting the depth of chemistry and the bredth of
Speaker 2: kinematics across the entire system for the first time exactly.
Speaker 2: So what does this mean for that GAYA data? Can
Speaker 2: one thousand and one mc actually confirm or deny the
Speaker 2: first pass idea?
Speaker 3: It can provide the final critical piece of confirmation. GAYA
Speaker 3: measures the proper motion right the sideways movement across the sky.
Speaker 2: But to know if something is truly bound to the
Speaker 2: Milky Way just flying by. You need its full three
Speaker 2: D velocity.
Speaker 3: You do, and you're missing the radial velocity how fast
Speaker 3: it's moving toward or away from us. Foremost high precision
Speaker 3: kinematic measurements provide exactly that missing piece.
Speaker 2: And once you combine those two velocity components, you get
Speaker 2: the true three D space.
Speaker 3: Velocity, which is the ultimate test. It tells you their
Speaker 3: orbital energy and whether they're gravitationally bound to the Milky
Speaker 3: Way or if they really are just newcomers passing through,
Speaker 3: which brings.
Speaker 2: Us back to the ultimate goal. This isn't really just
Speaker 2: about the LMC and SMC, not at all.
Speaker 3: It's about refining our knowledge of how all galaxies evolve.
Speaker 3: The Magellanic Clouds are our best, and maybe our only
Speaker 3: opportunity in the local universe to study the life cycles
Speaker 3: of these gas rich dwarf galaxies in such detail.
Speaker 2: To see how they form stars in metal poor environments,
Speaker 2: how they move gas around, how they interact, and how
Speaker 2: they evolve under these huge external forces.
Speaker 3: This data set, when it's complete, is going to be
Speaker 3: the bedrock for modeling dwarf galaxy evolution and for testing
Speaker 3: our big cosmological simulations for decades.
Speaker 2: It promises to finally resolve these decades long arguments over
Speaker 2: their history and the powerful forces that are shaping those
Speaker 2: incredible Magellanic streams.
Speaker 3: It's an amazing project.
Speaker 2: Wow. Okay, so this is this is a genuinely monument
Speaker 2: mental project.
Speaker 3: It really is.
Speaker 2: So just to sort of wrap up the main points here,
Speaker 2: we're talking about a five year dedicated.
Speaker 3: Program using the foremost spectrograph on the Vista telescope.
Speaker 2: To get the spectra of half a million stars, which.
Speaker 3: Gives us their chemistry and their motion, the two things
Speaker 3: we were missing.
Speaker 2: And this spectroscopic power is what's going to let researchers
Speaker 2: finally test these huge new ideas, like confirming or denying
Speaker 2: the Gaya data that suggests the clouds might be on
Speaker 2: their very first pass by the Milky Way.
Speaker 3: And crucially using that chemical, tacking and motion data to
Speaker 3: finally figure out what created the Magellanic stream, whether it
Speaker 3: was title stripping, ram pressure or the clouds fighting with
Speaker 3: each other.
Speaker 2: So by the time this is all done, astronomers will
Speaker 2: have the most comprehensive, detailed, high resolution spectroscopic data set
Speaker 2: ever put together for dwarf galaxies.
Speaker 3: And that data is essential for finding real answers about
Speaker 3: gas mixing, star formation bursts, and rewriting the history of
Speaker 3: our closest galactic neighbors.
Speaker 2: Okay, so for our final thought for you to ponder,
Speaker 2: we spend a lot of time on this revolutionary idea
Speaker 2: that the Magellanic clouds might be on their very first pass.
Speaker 3: Meaning their gravitational interaction with the Milky Way is only
Speaker 3: just beginning.
Speaker 2: So if that first pass hypothesis turns out to be true,
Speaker 2: if the clouds have only recently encountered the Milky Way's
Speaker 2: massive gravitational and gaseous halo, what does the already vast
Speaker 2: and dramatic appearance of the Magellan extreme tell us.
Speaker 3: It implies that the forces of gravity and ram pressure
Speaker 3: are so incredibly potent that they don't need billions of
Speaker 3: years of slow, gradual work. They can rip material off
Speaker 3: a galaxy and stretch it across hundreds of thousands of
Speaker 3: light years in what is cosmically speaking, a brief moment.
Speaker 2: The streams aren't the result of a slow bleed over eons.
Speaker 3: No, they are the evidence of an unbelievably powerful, almost
Speaker 3: instantaneous cosmic collision and the one thousand and one MC
Speaker 3: spectra will be what tells us just how violent that
Speaker 3: first encounter truly is. Stas