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: If you look up at the Andromeda galaxy tonight, you're
Speaker 2: actually looking at a completely incomplete map.
Speaker 3: Yeah, totally incomplete. We miss so much of what's.
Speaker 2: Actually there, right because just recently on March thirtieth, twenty
Speaker 2: twenty six, astronomers announced this incredible update to our cosmic backyard.
Speaker 3: It's honestly one of the most fascinating finds in recent years.
Speaker 2: It really is. They found an entirely new galaxy hiding
Speaker 2: right there, orbiting Andromeda, not you know, billions of light
Speaker 2: years away at the edge of the universe, but literally
Speaker 2: right next door.
Speaker 3: And the kicker is are billion dollars supercomputers and all
Speaker 3: those advanced algorithms they entirely missed it.
Speaker 2: Which is wild. But before we get into that, I mean,
Speaker 2: new galaxy is a phrase we need to handle carefully, right.
Speaker 3: Oh absolutely. When people hear new galaxy, it immediately brings
Speaker 3: to mind like sweeping spiral arms, glowing pink nebulas, supermassive.
Speaker 2: Black holes, like the classic Hubble desktop backgrounds exactly.
Speaker 3: But this newly discovered object, officially designated Andromeda X six
Speaker 3: six or nxx six for short, is the absolute antithesis
Speaker 3: of that majestic imagery.
Speaker 2: So what are we actually looking at here?
Speaker 3: Well, we classify it as an ultra faint dwarf galaxy
Speaker 3: a UFD. It's a tiny, incredibly elusive and just profoundly
Speaker 3: ancient system.
Speaker 1: Right.
Speaker 2: It's less of a shiny metropolis and more of a
Speaker 2: cosmic ghost wandering through Andromeda's halo.
Speaker 3: A ghost is the perfect way to describe it. And
Speaker 3: we aren't just going to list off coordinates for a
Speaker 3: new speck in this guy.
Speaker 2: Today, no, because the reason this faint little ghost matters
Speaker 2: to you listening right now is that it's essentially a
Speaker 2: cosmic time machine.
Speaker 3: Yeah. It operates as this pristine, untouched laboratory for the
Speaker 3: universe's most mysterious substance, which is dark.
Speaker 2: Matter, and understanding how it was found requires looking at
Speaker 2: the sheer power of the human eye, even in an
Speaker 2: era totally dominated by artificial intelligence.
Speaker 3: What makes an object so small capable of answering the
Speaker 3: biggest questions in physics is it's extreme nature. It's a
Speaker 3: tiny size and profound faintness. Hold the real.
Speaker 2: Secrets, because massive galaxies are just too chaotic exactly.
Speaker 3: They're noisy, but tiny dead systems like this one offer
Speaker 3: a completely clean environment to observe fundamental physics at work.
Speaker 2: Okay, so let's figure out what it actually means to
Speaker 2: be an ultra faint dwarf galaxy. Just how small and
Speaker 2: how dim does a collection of stars have to be
Speaker 2: to get that classification?
Speaker 3: Well, geographically speaking, and sits about two point five to
Speaker 3: three million light years away from.
Speaker 2: Earth, which puts it squarely in the local group our neighborhood, right, But.
Speaker 3: The really vital measurement is its distance from the center
Speaker 3: of the Andromeda galaxy itself, which clocks in at roughly
Speaker 3: three hundred and eighty eight thousand light years.
Speaker 2: That sounds like a massive distance. I mean, that's farther
Speaker 2: than the Moon is from the Earth. If you scale
Speaker 2: it up to glact.
Speaker 3: Proportions, it does sound distant, but in galactic physics it
Speaker 3: sits deep within Andromeda's gravitational grip. Atrophysicists use this metric
Speaker 3: called the virial.
Speaker 2: Radius, the virial radio. Okay, break that down for us.
Speaker 3: You can think of the virial radius as the ultimate
Speaker 3: boundary line of a galaxy's gravitational dominance.
Speaker 2: So it's like the city limits of its gravity.
Speaker 3: Yeah, exactly. It's the sphere of influence where the larger
Speaker 3: galaxies gravity dictates the motion of everything inside it, rather
Speaker 3: than the expansion of the universe pulling things apart.
Speaker 2: And what's the virial radius for a giant spiral like Andromeda?
Speaker 3: For Andromeda, that radius extends outward to roughly eight hundred
Speaker 3: and fifty thousand light years.
Speaker 2: Oh wow, So at three hundred and eighty eight thousand
Speaker 2: light years, and XXI six is well within the city.
Speaker 3: Limits, firmly within the suburbs. Yeah, it is securely and
Speaker 3: permanently a gravitationally bound satellite of Andromeda.
Speaker 2: It's just orbiting the larger galaxy, locked in this cosmic bands,
Speaker 2: governed entirely by Andromeda's immense mass, exactly.
Speaker 3: So it's locked in. But the sheer compactness of this
Speaker 3: object is what really dons.
Speaker 2: The mind Yeah, the measurements show it has a half
Speaker 2: light radius of just two hundred and eight light years.
Speaker 3: Which is incredibly tiny.
Speaker 2: I mean, our Milky Way is roughly one hundred thousand
Speaker 2: light years across. This entire new galaxy is just a
Speaker 2: couple of hundred light.
Speaker 3: Years wide, barely a blip.
Speaker 2: I do need to stop right there, though, because half
Speaker 2: light radius is sort of a weird term. Why don't
Speaker 2: astronomers just measure from the center to the edge.
Speaker 3: Well, because galaxies do not have hard, sharp edges like
Speaker 3: a planet or a table.
Speaker 2: Right, they kind of just fade out.
Speaker 3: Yeah, there are diffuse clouds of stars. They gradually thin
Speaker 3: out into nothingness. Yeah, if you try to measure to
Speaker 3: the absolute outermost star, you get wildly inconsistent results.
Speaker 2: Because it just depends on how sensitive your telescope is.
Speaker 3: Very sisely, Instead, astronomers use the half light radius. It's
Speaker 3: the distance from the core, within which exactly fifty percent
Speaker 3: of the galaxy's total light is emitted.
Speaker 2: Got it. So it provides a robust, mathematically consistent way
Speaker 2: to define the bulk of this fuzzy edgeless object exactly.
Speaker 3: So the core, the main glowing heart of this thing,
Speaker 3: is only two hundred and eight light years across. That's
Speaker 3: about sixty four parsex.
Speaker 2: And I was reading that its structure is unusually uniform too.
Speaker 3: It is. We measure the shape of these objects using ellipticity.
Speaker 3: A perfect circle has an ellipticity.
Speaker 2: Of zero, and a highly stretched like cigar like oval
Speaker 2: would be closer to one.
Speaker 3: Right, and XXC six has an ellipticity of abouto points
Speaker 3: zero one.
Speaker 2: Five, So it's virtually a perfect sphere.
Speaker 3: It is remarkably spherical. It makes it potentially the second
Speaker 3: most compact ultra faint dwarf satellite ever found orbiting Andromeda.
Speaker 2: Wow. And then we get to the brightness, or I
Speaker 2: guess the complete lack of brightness.
Speaker 3: Yeah, it's staggeringly dim.
Speaker 2: The data gives it an absolute visual magnitude of roughly
Speaker 2: negative six point zero, and the astronomical magnitude scale is
Speaker 2: notoriously counterintuitive.
Speaker 3: Oh, it's totally backwards.
Speaker 2: The lower or more negative the number, the brighter the object. Right,
Speaker 2: our sun sits at around negative twenty six, and.
Speaker 3: The full moon is around negative thirteen.
Speaker 2: So a whole galaxy sitting at negative six is just
Speaker 2: profoundly dim. It's like a single dimly lit neighborhood out
Speaker 2: in the countryside trying to be seen next to the
Speaker 2: glaring neon lights of a megacity, and.
Speaker 3: That megacity being Andromeda. That visual illustrates the detection problem perfectly, honestly.
Speaker 2: Because its intrinsic light is just entirely washed out by
Speaker 2: the larger galaxy, washed.
Speaker 3: Out by the glare, and the vast distance is involved,
Speaker 3: it barely registers against the background static of the cosmos.
Speaker 2: Well wait, if it is so incredibly small, just two
Speaker 2: hundred something light years across and unfathomably dim, why are
Speaker 2: we even classifying this as a galaxy?
Speaker 3: That's a great question, because.
Speaker 2: There are globular clusters out there, these tight spheres of
Speaker 2: thousands of stars that are way brighter and denser than this.
Speaker 2: Why does an X six six get the prestigious title
Speaker 2: of galaxy instead of just being a random rogue star cluster.
Speaker 3: The distinction between a star cluster and a dwarf galaxy
Speaker 3: is one of the most crucial concepts in modern astronomy,
Speaker 3: and it actually has nothing to do with size or
Speaker 3: star count.
Speaker 2: Oh really, what does it come down to?
Speaker 3: Then it comes down to invisible mass. A globular cluster
Speaker 3: is a collection of stars, gas, and dust held together
Speaker 3: exclusively by their own mutual gravity.
Speaker 2: So what you see is what you get exactly.
Speaker 3: If you add up the mass of all the glowing
Speaker 3: stars in a globular cluster, it perfectly accounts for the
Speaker 3: gravitational glue holding the whole structure together.
Speaker 2: No hidden variables, none at all.
Speaker 3: But a galaxy, even an ultra fane dwarf like six,
Speaker 3: is fundamentally dark matter dominated.
Speaker 2: Okay, So it's essentially a massive invisible halo of dark
Speaker 2: matter that just happens to have a few stars sprinkled
Speaker 2: in the very center of it.
Speaker 3: That's exactly it. The stars are merely the glowing paint
Speaker 3: on a much larger invisible structural foundation.
Speaker 2: That's wild. So when astronomers analyze the dynamics of these objects,
Speaker 2: the visible matter is basically negligible.
Speaker 3: Completely negligible. Without a massive dark matter halo, the galaxy
Speaker 3: would simply fly apart. That halo is the defining signature.
Speaker 3: If it has a halo, it's a galaxy.
Speaker 2: So its dimness isn't a sign that it failed at
Speaker 2: being a galaxy. It's not like a star cluster that
Speaker 2: just gave up.
Speaker 3: No, not at all. The dimness is an artifact of
Speaker 3: extreme age, which really brings us to the origins of
Speaker 3: this object, right, because.
Speaker 2: We aren't looking at a dynamic evolving system here, we
Speaker 2: are looking at.
Speaker 3: A fossil, a literal cosmic fossil. The estimated age of
Speaker 3: the stars in EXI six and Exiscitos is roughly twelve
Speaker 3: point five billion years.
Speaker 2: The universe itself is only thirteen point eight billion years old,
Speaker 2: so the star is in this tiny smudge formed shortly
Speaker 2: after the Big Bang itself.
Speaker 3: They were among the very first generations of stars to
Speaker 3: light up the cosmos.
Speaker 2: So what happened to it? Why did it stop growing?
Speaker 3: Systems of this nature are referred to as reionization fossils.
Speaker 3: To grasp the mechanics of that, you have to picture
Speaker 3: the universe during its infancy.
Speaker 2: Okay, setting the scene for several hundred.
Speaker 3: Million years following the Big Bang, the universe was filled
Speaker 3: with this thick, obscuring fog of neutral hydrogen.
Speaker 2: Gas, like a literal fog.
Speaker 3: Essentially, yeah, light could not travel freely. The cosmos was opaque.
Speaker 3: Astronomers call this period the Dark Ages.
Speaker 2: It was just a giant soup of hydrogen waiting for
Speaker 2: something to happen.
Speaker 3: Then the first stars and the first primitive galaxies ignited.
Speaker 3: And these early stars were monstrously massive, incredibly hot, and.
Speaker 2: They must have pumped out staggering amounts of radiation.
Speaker 3: Huge amounts of ultraviolet radiation. This intense UV radiation literally
Speaker 3: tore the electrons away from the neutral hydrogen atoms in
Speaker 3: the surrounding space.
Speaker 2: And that process is what we call reionization.
Speaker 3: Exactly, it burned away the fog, making the universe transparent.
Speaker 3: But this epoch was exceptionally violent.
Speaker 2: Violent. How like, if I'm this little forming bwarf galaxy
Speaker 2: gathering my own hydrogen to make my own stars, what
Speaker 2: does that uvwave actually do to me?
Speaker 3: A delicate system with a weak gravitational welt like in
Speaker 3: XX sixty six, that wave of intense radiation was absolutely.
Speaker 2: Devastating because it heated up the gas.
Speaker 3: Right. The intense UV light heated the gas inside these
Speaker 3: small dark matter halos, And when a gas heats up,
Speaker 3: its particles move faster.
Speaker 2: Oh I see, So the thermal kinetic energy of the
Speaker 2: gas rapidly exceeded the escape velocity of the tiny galaxies gravity.
Speaker 3: Exactly, the gas expanded and literally boiled away into deep space.
Speaker 2: It just got blasted dry by the bigger galaxies turning
Speaker 2: their lights on. And without cold dense gas, a galaxy
Speaker 2: cannot form new stars.
Speaker 3: The factory gets permanently shut down. The initial burst of
Speaker 3: star formation is abruptly quenched. Wow.
Speaker 2: And we can verify this quenching by looking at the
Speaker 2: galaxy's chemical signature, right.
Speaker 3: We can, specifically, we look at its metallicity. The spectroscopic
Speaker 3: data for XXS shows a metallicity of roughly negative two
Speaker 3: point five.
Speaker 2: I actually need to translate an astronomical quirk for everyone
Speaker 2: listening here, because metallicity in astronomy doesn't mean what it
Speaker 2: means in chemistry class.
Speaker 3: No, it definitely doesn't.
Speaker 2: To an astronomer, anything heavier than hydrogen and helium is
Speaker 2: considered a metal, like oxygen, carbon, nitrogen. Those are all
Speaker 2: metals in this context.
Speaker 3: It's a funny historical artifact in the terminology, but the
Speaker 3: physics it describes tells a vital story about the universe.
Speaker 2: Because the Big Bang essentially produced only hydrogen, helium, and
Speaker 2: a microscopic trace of lithium right right.
Speaker 3: All the heavier elements these astronomical metals were forged much later.
Speaker 2: They were crushed together inside the extreme heat and pressure.
Speaker 3: Of stellar cores, and then distributed across the universe when
Speaker 3: those stars died in supernova explosions.
Speaker 2: So the very first stars to ever exist in the
Speaker 2: universe were made of pure hydrogen and helium. They had
Speaker 2: a metallicity of basically zero.
Speaker 3: Correct. When those first generation stars exploded, they seeded the
Speaker 3: surrounding gas clouds with the newly forged heavier.
Speaker 2: Elements, So the second generation of stars formed from that
Speaker 2: slightly polluted gas, making their metallicity slightly higher.
Speaker 3: Exactly, the more generations of stars a galaxy produces, the
Speaker 3: more metal rich its gas becomes.
Speaker 2: I mean, our Sun is a relatively modern star, forming
Speaker 2: only about four point six billion years ago, so.
Speaker 3: It has a high metallicity because it formed from gas
Speaker 3: enriched by countless generations of dead stars over billions of years.
Speaker 2: An xpite has an incredibly low metallicity of negative two
Speaker 2: point five. It's chemically pristine.
Speaker 3: It barely has any heavy elements at all. It is
Speaker 3: absolute chemical conformation that there has been no recent star
Speaker 3: formation there.
Speaker 2: It is a completely unevolved system totally.
Speaker 3: It birthed its initial crop of stars roughly twelve point
Speaker 3: five billion years ago, the process of realization boiled away
Speaker 3: the rest of its fuel, and then it simply stopped.
Speaker 2: It's really like finding a perfectly preserved Roman ruin.
Speaker 3: That's a great analogy.
Speaker 2: Imagine uncovering a massive ancient city, but it was suddenly
Speaker 2: abandoned just a few decades after it was built, and
Speaker 2: nobody ever came back. It was never built over.
Speaker 3: You can see the original stones exactly as they.
Speaker 2: Right, whereas massive galaxies like our Milky Way or Andromeda
Speaker 2: are like modern, sprawling cities. They are built on top
Speaker 2: of countless layers of demolition and new construction.
Speaker 3: Paving over the old, mixing all the materials together. You
Speaker 3: can't easily see the ancient history because there's a skyscraper
Speaker 3: on top of it.
Speaker 2: But the undisturbed nature of X six sixty six is
Speaker 2: what makes it so incredibly valuable.
Speaker 3: Yes, because it lost its original gas, perhaps from that
Speaker 3: early universe reionization, or potentially due to brutal tidal interactions
Speaker 3: with Andromeda itself.
Speaker 2: Oh like Andromeda's immense gravity physically stripping the gas away
Speaker 2: as the dwarf galaxy orbits.
Speaker 3: Exactly Regardless of the exact mechanism of gas loss, its
Speaker 3: development was just frozen in time, and because.
Speaker 2: It lost its gas so early, it never formed enough
Speaker 2: stars to be bright, which brings us to the profound
Speaker 2: dimness and the story of how we actually found it,
Speaker 2: which is just ridiculous.
Speaker 3: It's an amazing story.
Speaker 2: We have this phenomenally dim, incredibly tiny, twelve point five
Speaker 2: billion year old ghost floating in the massive glare of Andromeda,
Speaker 2: barely emitting any light at all. How do you even
Speaker 2: find that?
Speaker 3: The discovery process highlights this fascinating intersection between massive astronomical
Speaker 3: survey data and pure human intuition.
Speaker 2: So where did the initial data come from?
Speaker 3: The foundational data came from the Panandromeda Archaeological Survey or PANDAAS.
Speaker 3: This was a sweeping deep imaging campaign utilizing the Canada, France,
Speaker 3: Hawaii telescope right.
Speaker 2: And the goal there was to map the extended halo
Speaker 2: of Andromeda, essentially looking deep into the galactic suburbs.
Speaker 3: Deep imaging surveys like pandas operate by taking incredibly long
Speaker 3: exposure photographs of the exact same patches of sky, just
Speaker 3: staring at the dark yes, and then stacking those images
Speaker 3: to capture the absolute faintest possible photons they generate an
Speaker 3: incomprehensible amount of data.
Speaker 2: Terabytes and terabytes of wide field images capturing millions of
Speaker 2: faint points of light. It's a digital Haystag of cosmic proportions.
Speaker 3: And this is where the story gets w wonderfully human
Speaker 3: because the person who found this wasn't an algorithm, and
Speaker 3: it wasn't a team of postdocs in a supercomputing lab.
Speaker 2: It was an amateur astronomer, right, Giuseppe Donaciello.
Speaker 3: Yes, despite all our advanced technology, Donaicello found this galaxy
Speaker 3: through systematic visual inspection of the PANDAS footprint.
Speaker 2: He literally just sat there, looked closely at the images
Speaker 2: and spotted an incredibly subtle overdensity of stars.
Speaker 3: Donnacila has a famously keen eye for spotting these structures. Actually,
Speaker 3: he has contributed to several previous Dwarf galaxy discoveries.
Speaker 2: Out in the outskirts of Andromeda and other nearby groups.
Speaker 3: Right, yeah, he possesses this unique visual acuity for identifying faint,
Speaker 3: diffuse stellar associations that just blend into the background for
Speaker 3: anyone else.
Speaker 2: But of course science requires verification and amateur spotting. A
Speaker 2: smudge on a monitor is the spark, but the professionals
Speaker 2: have to move in to prove it's actually a galaxy definitely.
Speaker 3: The professional follow up was spearheaded by Joanna di Sakowska
Speaker 3: from the Insane of Astrophysics of Andalusia.
Speaker 2: And they need an immense light gathering power to prove
Speaker 2: this wasn't an optical artifact or just a random clustering
Speaker 2: of four ground Milky Way stars.
Speaker 3: So they utilized the Osiris Plus instrument, which is mounted
Speaker 3: on the Grand Telescope you of Canarius in La Palma.
Speaker 2: That's a ten point four meter telescope that is serious
Speaker 2: heavy artillery.
Speaker 3: It is one of the premiere optical and infrared telescopes
Speaker 3: on the planet. Its massive mirror was absolutely necessary to
Speaker 3: capture enough light to resolve the individual stars within this
Speaker 3: faint smudge.
Speaker 2: So they aren't just looking at a blurry blob anymore.
Speaker 2: They are separating the blob into its constituent individual suns.
Speaker 3: Exactly, and by doing so they constructed a color magnitude
Speaker 3: diagram or CMD.
Speaker 2: I really want to break down what a color magnitude
Speaker 2: diagram actually is because this sounds intimidating, but it is
Speaker 2: one of the coolest diagnostic tools in.
Speaker 3: Astronomy, it's foundational to our understanding of stars.
Speaker 2: Imagine taking every individual star that the ten point four
Speaker 2: meter telescope resolved in that small ud and plotting it
Speaker 2: on a graph. The vertical axis is its magnitude, or
Speaker 2: how bright it.
Speaker 3: Is, and the horizontal axis is its color, which tells
Speaker 3: you its temperature.
Speaker 2: Right, Blue stars are brutally hot, red stars are cooler, and.
Speaker 3: Stars do not scatter randomly on this graph. Because the
Speaker 3: laws of stellar physics govern exactly how stars burn hydrogen,
Speaker 3: a group of stars born at the same time will
Speaker 3: align along very specific predictable curves.
Speaker 2: Right because they all form from the same cloud of
Speaker 2: gas exactly.
Speaker 3: The most massive blue hot stars burn through their fuel
Speaker 3: incredibly fast and die young.
Speaker 2: Will the smaller, cooler red stars burn their fuel slowly
Speaker 2: over hundreds of billions of years.
Speaker 3: So by looking at which stars are still burning and
Speaker 3: which are missing from that curve, you can tell exactly
Speaker 3: how old the whole group is.
Speaker 2: That is such a brilliant mechanism.
Speaker 3: It is by plotting the resolve stars from the Grand
Speaker 3: Telescopio Canarias, the team identified the unmistakable shape of an
Speaker 3: ancient metal poor stellar population.
Speaker 2: They found the main sequence turnoff point.
Speaker 3: Yes, the exact spot on the graph where stars of
Speaker 3: a certain mass are currently exhausting their hydrogen cores.
Speaker 2: And that turnoff point acts like a cosmic clock, providing
Speaker 2: that twelve point five billion year age estimate we talked
Speaker 2: about exactly.
Speaker 3: The stacked images also revealed a clear over density of
Speaker 3: these specific ancient stars, perfectly nestled between two incredibly bright
Speaker 3: four ground stars.
Speaker 2: Oh, those four grand stars are in our own Milky Way,
Speaker 2: right physically in the way, just photo bombing the image
Speaker 2: of the distant dwarf galaxy.
Speaker 3: They really are, But the data is definitive. This was
Speaker 3: a distinct galactic structure.
Speaker 2: But wait, let's be real here. It is twenty twenty six.
Speaker 2: We live in an era of massive computing power and
Speaker 2: highly advanced machine learning. We do Why on earth are
Speaker 2: we relying on a guy looking at a computer monitor
Speaker 2: to find this. Shouldn't a train algorithm have flagged this
Speaker 2: instant anomaly the millisecond the PANDEES data was uploaded.
Speaker 3: You'd think so, But the limits of our automated detection
Speaker 3: systems are really exposed in these extreme low surface brightness regimes.
Speaker 3: How so well machine learning algorithms are phenomenally powerful at
Speaker 3: recognizing patterns they have been explicitly trained to detect, and
Speaker 3: they are ruthlessly efficient at filtering out noise.
Speaker 2: But an ultra faint dwarf galaxy like an XXS operates
Speaker 2: right at the absolute threshold of detectability.
Speaker 3: The signal to noise ratio is just terrible. It is
Speaker 3: almost entirely.
Speaker 2: Noise, So to an algorithm, it just looks like junk data.
Speaker 3: Basically, to a machine learning algorithm searching for statistically significant clusters,
Speaker 3: a few dozen faint, spread out stars scattered among tens
Speaker 3: of thousands of bright foreground stars registers as a minor
Speaker 3: random fluctuation.
Speaker 2: Just background static, so the algorithm smooths it out or
Speaker 2: ignores it entirely exactly.
Speaker 3: And if you tune the algorithms to be sensitive enough
Speaker 3: to flag and xxygiscs automatically, they would also generate tens
Speaker 3: of thousands of false positives.
Speaker 2: Oh I see, every random clump of three stars would
Speaker 2: trigger an alert. The algorithm is too rigid. It lacks
Speaker 2: that subjective gut feeling of human intuition.
Speaker 3: Right, the human visual cortex evolved as an exquisite pattern
Speaker 3: recognition engine. We are biologically tuned to notice subtle anomalies
Speaker 3: in texture and.
Speaker 2: Structure, even when the data is incredibly messy.
Speaker 3: Exactly, human insight remains highly complementary to machine learning. The
Speaker 3: algorithm dismisses the faint whisper of a galaxy as an
Speaker 3: artifact or pixel noise.
Speaker 2: But a dedicated human observer like Doniciello looks at the
Speaker 2: exact same pixels and recognizes a cohesive shape.
Speaker 3: The machines gather the light from two point five million
Speaker 3: light years away, but it takes a human mind to
Speaker 3: actually recognize the ghost hidden inside the data.
Speaker 2: That's incredible, and cataloging these ghosts is critical because finding
Speaker 2: themselves one of the most frustrating, glaring mysteries in modern astrophysics.
Speaker 3: Right, oh, absolutely, It directly addresses the missing satellite problem.
Speaker 2: The missing satellite problem. Let's scale this up from one
Speaker 2: tiny galaxy to the architecture of the entire universe.
Speaker 3: It's a problem that has been a thorn in the
Speaker 3: side of theoretical astrophysics for decades. It fundamentally challenges our
Speaker 3: standard cosmological model.
Speaker 2: So our current understanding of the universe relies on a
Speaker 2: framework called cold dark matter.
Speaker 3: Right and when astrophysicists run massive complex supercomputer simulations known
Speaker 3: as n body simulations, they model how the universe.
Speaker 2: Evolved, going from a relatively smooth state shortly after the
Speaker 2: Big Bang into the massive cosmic web of galaxies we
Speaker 2: see today.
Speaker 3: And in these simulations, dark matter acts as the gravitational scaffolding.
Speaker 2: The dark matter clumps together first, because it only interacts
Speaker 2: via gravity. It doesn't bounce off itself or emit light.
Speaker 2: It just gathers into these massive, invisible blobs.
Speaker 3: We call those blobs dark matter halos. Once a massive
Speaker 3: halo forms, its immense gravity pulls in the ordinary matter,
Speaker 3: the hydrogen and helium gas.
Speaker 2: And that gas falls into the center of the dark
Speaker 2: matter well, compresses and ignites into a galaxy.
Speaker 3: It's exactly, but the high resolution supercomputer simulations reveal a
Speaker 3: critical detail. A massive dark matter halo like the ones
Speaker 3: surrounding the Milky Way or Andromeda shouldn't be a single
Speaker 3: smooth sphere.
Speaker 2: It should be highly substructured.
Speaker 3: Right, Yes, it should be swarming with thousands of smaller
Speaker 3: independent dark matter subhelos orbiting within and around it.
Speaker 2: And if the math says those thousands of dark matter
Speaker 2: sub halos exist, they should have pulled in their own
Speaker 2: gas to form thousands of small dwarf galaxies.
Speaker 3: That's the logical conclusion. The Milky Way and Andromeda should
Speaker 3: look like massive glowing cities surrounded by thousands of smaller
Speaker 3: satellite towns.
Speaker 2: But when astronomers actually pointed their telescopes at the sky,
Speaker 2: they didn't see thousands of satellite galaxies.
Speaker 3: Not even close. For a long time, we only saw
Speaker 3: a few dozen around the Milky Way, and even fewer
Speaker 3: around Andromeda.
Speaker 2: That is a massive glaring discrepancy. The computer simulations predict
Speaker 2: thousands of satellites and the actual observations show a mere.
Speaker 3: Handful, and that is the missing satellite problem.
Speaker 2: It sounds like a crisis in the making. I mean,
Speaker 2: if the math says there should be thousands and the
Speaker 2: telescopes only c twenty, either the math is wrong or
Speaker 2: the telescopes are blind.
Speaker 3: Exactly, it suggested that either our fundamental theories of cold
Speaker 3: dark matter were completely flawed, or there was a physical
Speaker 3: mechanism preventing us from detecting the vast majority of these galaxies.
Speaker 2: And the discovery of Benic six, along with a recent
Speaker 2: surge of similar discoveries, proves that the latter is true.
Speaker 3: By pushing the limits of our observational thresholds to find
Speaker 3: extremely faint, diffuse objects, we are slowly closing the gap
Speaker 3: between simulation and reality.
Speaker 2: We are finding the missing satellites. They weren't missing, They
Speaker 2: were just incredibly dark right.
Speaker 3: Andromeda is now estimated to host nearly one hundred dwarf satellites,
Speaker 3: with roughly half of them firmly confirmed through follow up.
Speaker 2: Observations discoveries like an XX six, along with other recent
Speaker 2: finds like an XXV and PEGASUSV also known as an
Speaker 2: xx four.
Speaker 3: They are populating the extreme faint end of the luminosity function.
Speaker 3: We are proving that these smaller dark matter subhills do exist,
Speaker 3: and they do contain stellar populations.
Speaker 2: They are simply operating at the very edge of what
Speaker 2: our current technology can perceive exactly.
Speaker 3: But what gets really interesting is comparing the satellite galaxies
Speaker 3: around Andromeda to the ones orbiting our own Milky Way.
Speaker 2: You'd think they would be identical, Honestly, two massive spiral
Speaker 2: galaxies should have similar cosmic suburbs.
Speaker 3: You would think so, but they actually exhibit fascinating differences.
Speaker 3: When we compare the ultra faint dwarf populations. Andromeda's UFDs
Speaker 3: frequently exhibit much more extended star formation histories, really yeah,
Speaker 3: and a wider spread of metallicity than their Milky Way counterparts,
Speaker 3: even when comparing galaxies of identical total mass.
Speaker 2: What is the mechanism behind that? Why would a dwarf
Speaker 2: galaxy around Andromeda keep making stars longer than a dwarf
Speaker 2: galaxy around the Milky Way.
Speaker 3: It points toward the different accretion histories and environmental factors
Speaker 3: of the two host.
Speaker 2: Galaxies, Because the Milky Way and Andromeda built up their
Speaker 2: massive bulk over billions of years by cannibalizing smaller galaxies.
Speaker 3: Right, it is possible that the specific orbital dynamics or
Speaker 3: the density of the circumngalactic medium around Andromeda allowed some
Speaker 3: of these incoming dwarfs to hold onto their cold gas
Speaker 3: reservoirs slightly longer.
Speaker 2: Ah so before the ram pressure or tidal force is
Speaker 2: totally stripped away, they got a little extra time exactly.
Speaker 3: Holding onto that gas for an extra few hundred million
Speaker 3: years allows for multiple subsequent generations of star formation.
Speaker 2: Which enriches the gas and creates that wider metallicity spread
Speaker 2: we observe. That's amazing.
Speaker 3: It provides subtle clues about the divergent evolutionary paths of
Speaker 3: these two giant spirals.
Speaker 2: We are literally slowly flushing out this invisible dark matter map.
Speaker 2: But a nexus sexist six offers us something uniquely.
Speaker 3: Powerful because it's so compact.
Speaker 2: Right just two hundred and eight light years across. It
Speaker 2: sits in one of the absolute smallest dark matter halos
Speaker 2: mathematically capable of holding onto enough gas to form star.
Speaker 3: It is the extreme lower limit of galaxy formation. It
Speaker 3: represents the absolute threshold.
Speaker 2: Meaning any dark matter halo smaller than x six six
Speaker 2: simply doesn't have the gravitational depth to capture gas. The
Speaker 2: gas just drifts right past it.
Speaker 3: Therefore, studying in next six of work is studying the
Speaker 3: smallest possible unit of galactic dark matter.
Speaker 2: But I need to challenge this whole concept for a second.
Speaker 2: We constantly talk about dark matter as this invisible theoretical substance.
Speaker 3: It's tricky to conceptualize.
Speaker 2: It doesn't emit light, it doesn't reflect light, it doesn't
Speaker 2: block light, it doesn't interact with electromagnetism whatsoever. So how
Speaker 2: can looking at a couple hundred incredibly slow ancient faint
Speaker 2: stars in XX six actually allow an astrophysicist to measure
Speaker 2: something that is fundamentally invisible.
Speaker 3: Consider this analogy. It's like watching a handful of autumn
Speaker 3: leaves caught in an invisible tornado.
Speaker 2: Okay, I like that. You absolutely cannot see the wind.
Speaker 2: The wind is completely transparent.
Speaker 3: But if you watch the leaves and you measure exactly
Speaker 3: how fast they are swirling around, the speed of those
Speaker 3: leaves tells you exactly how much force the invisible wind
Speaker 3: must be exerting.
Speaker 2: Oh, that makes perfect sense. The physics translates perfectly.
Speaker 3: The leaves are the ancient visible stars in X sixty six,
Speaker 3: and the invisible tornado is the massive gravitational well of
Speaker 3: the dark matter halo.
Speaker 2: So astrophysicists measure the invisible wind through a technique called
Speaker 2: stellar kinematics.
Speaker 3: Specifically calculating the internal velocity dispersion of the stars.
Speaker 2: You literally measure how fast the stars are buzzing around
Speaker 2: inside the galaxy.
Speaker 3: Even though the dwarf galaxy appears static and frozen in
Speaker 3: a photograph, those individual stars are moving rapidly. By employing
Speaker 3: high resolution spectroscopy, astronomers analyze the light from individual stars.
Speaker 2: They're looking for minute Doppler shifts in the absorption lines
Speaker 2: of the stars spectrum right.
Speaker 3: Exactly, if a star is moving slightly toward our telescope,
Speaker 3: the light waves are compressed and the spectrum shifts slightly
Speaker 3: toward the blue end.
Speaker 2: And if the star is moving away from us in
Speaker 2: its orbit, the light waves are stretched and the spectrum
Speaker 2: shifts towards the red end.
Speaker 3: Perfect So by measuring those red and blue shifts you
Speaker 3: get the precise speed of the star relative to us.
Speaker 3: We map the speeds of dozens of stars within the
Speaker 3: dwarf galaxy.
Speaker 2: Now, if sx six was only held together by the
Speaker 2: weak gravity of its sparse visible stars, those stars would
Speaker 2: have to be moving very slowly, wouldn't.
Speaker 3: They extremely slowly? If they moved fast, the weak gravity
Speaker 3: of the visible matter wouldn't be strong enough.
Speaker 2: To hold them, and they would simply fly off into
Speaker 2: deep space, totally dissipating the cluster.
Speaker 3: However, what observational data consistently reveals with these ultra faint
Speaker 3: dwarfs is that the stars are moving much much faster
Speaker 3: than the visible mass allows.
Speaker 2: The leaves are swirling at hurricane.
Speaker 3: Speeds, yes, which proves there is a massive invisible wind
Speaker 3: a huge source of unseen gravity holding them locked in
Speaker 3: that tight little two hundred light year sphere.
Speaker 2: So the velocity dispersion, the statistical spread of all those
Speaker 2: varying stellar speeds, provides a direct mathematical measurement of the
Speaker 2: total gravitational mass present.
Speaker 3: You subtract the visible mass of the stars, and the
Speaker 3: remainder is the mass of the dark matter halo.
Speaker 2: And because x tex six is so tiny and incredibly compact,
Speaker 2: that immense amount of dark matter is packed into a
Speaker 2: very small dense volume.
Speaker 3: This is where we get to actually put competing models
Speaker 3: of theoretical physics to the test, because not all dark
Speaker 3: matter theories are identical.
Speaker 2: Right. The standard cosmological model relies on cold dark matter,
Speaker 2: and in this context, cold means the theoretical dark matter
Speaker 2: particles move sluggishly compared to the speed.
Speaker 3: Of light exactly, and because they move slowly, they easily
Speaker 3: clump together into very tight, dense small structures.
Speaker 2: Like the halo hosting and xixty six.
Speaker 3: But there are competing models attempting to solve other cosmic anomalies.
Speaker 3: There's warm dark matter, where the theoretical particles move much faster.
Speaker 2: The higher kinetic energy of warm dark matter would smooth
Speaker 2: out small scale gravitational structures, making it incredibly difficult to
Speaker 2: form tiny dense halos.
Speaker 3: Right, so, if dark matter was warm and X six
Speaker 3: physically couldn't.
Speaker 2: Exist because the fast moving dark matter particles would never
Speaker 2: clump tightly enough to pull in the gas to make
Speaker 2: those first stars.
Speaker 3: Precisely why finding these extreme micro galaxies is so absolutely vital.
Speaker 2: Are there any other theories?
Speaker 3: There is also the theory of self interacting dark matter,
Speaker 3: which proposes that dark matter particles don't just pass through
Speaker 3: each other like ghosts, but they.
Speaker 2: Actually bounce off one another in the dense centers of halos.
Speaker 3: Yes, this scattering effect would fundamentally alter the density profile
Speaker 3: of the halo, making the core less dense than standard coal.
Speaker 3: Dark matter predicts WOW.
Speaker 2: So by measuring the exact speed of the leaves in
Speaker 2: this one specific tiny tornado, astrophysicists can reverse engineer the
Speaker 2: fundamental particle physics of the invisible wind.
Speaker 3: It's all connected. If the dark matter is cold and clumpy,
Speaker 3: the stars will orbit with a specific velocity profile, and.
Speaker 2: If the dark matter particles are bouncing off each other,
Speaker 2: the internal gravity changes and the stars will move differently.
Speaker 3: Exactly. This tiny faint smudge spotted by guy looking at
Speaker 3: a computer screen provides the exact raw data that theoretical
Speaker 3: physicists need.
Speaker 2: They need it to either validate or completely rewrite our
Speaker 2: fundamental understanding of the universe's most abundant substance.
Speaker 3: It illustrates the profound interconnectedness of modern astrophysics. You cannot
Speaker 3: decipher the microscopic quantum nature of a dark matter particle
Speaker 3: without observing the macroscopic gravitational dynamics of the faintest, oldest
Speaker 3: galaxies in the universe.
Speaker 2: The sub atomic and the cosmic scales are inexorably linked.
Speaker 3: They really are.
Speaker 2: We started by looking up at Andromeda, this familiar mapped
Speaker 2: out neighbor in the night sky, but hidden within the
Speaker 2: immense glare of its billions of stars. We found Andromeda
Speaker 2: xxy six stix.
Speaker 3: A twelve point five billion year old collection of chemically
Speaker 3: pristine stars.
Speaker 2: A pristine Roman ruin of a galaxy whose ability to grow, evolve,
Speaker 2: and shine was brutally quenched by the ferocious stripping radiation
Speaker 2: of the early universe's first light.
Speaker 3: A structure so faint and so diffuse that the most
Speaker 3: advanced automated supercomputers and machine learning algorithms swept right.
Speaker 2: Past it mathematically dismissing it as background noise. It required
Speaker 2: the dedication, patience, and exquisite biological pattern recognition of a
Speaker 2: human being to pull its signal out of the shatters.
Speaker 3: And from that human discovery confirmed by aiming a ten
Speaker 3: point four meters mirror at the sky to dissect its
Speaker 3: individual suns, we are granted a profound new laborator.
Speaker 2: A tiny two hundred and eight light year wide bubble
Speaker 2: of intense dark matter that helps solve the missing satellite problem.
Speaker 3: It proves the math of the universe right while providing
Speaker 3: the exact kind of extreme high density environment physicists need
Speaker 3: to test the fundamental laws of reality.
Speaker 2: It is a staggering caspade of scientific knowledge generated from
Speaker 2: a single barely perceptible smudge.
Speaker 3: And as we push our observational capabilities further, we are
Speaker 3: going to find many more of them.
Speaker 2: Especially as deeper imaging surveys come online.
Speaker 3: Oh absolutely, as we continually utilize the phenomenal resolving power
Speaker 3: of instruments like the James Webb Space Telescope and Hubble,
Speaker 3: we will peel back more layers of this cosmic ecosystem.
Speaker 2: We will inevitably map dozens, perhaps hundreds more of these
Speaker 2: ultra faint satellites hidden in the halos of both Andromeda
Speaker 2: and the Milky Way.
Speaker 3: We are mapping the true, underlying, invisible architecture of the
Speaker 3: local group. These tiny systems aren't just anomalies or astronomical curiosities.
Speaker 2: They are the fundamental building blocks of cosmic structure. The massive,
Speaker 2: majestic spiral galaxies we see today were literally constructed by
Speaker 2: cannibalizing and merging thousands of these tiny, ancient systems over
Speaker 2: billions of years.
Speaker 3: Objects like NSXT sixty six are the rare survivors.
Speaker 2: They are the few that managed to avoid being entirely consumed,
Speaker 2: left to orbit in the dark suburbs for over twelve
Speaker 2: billion years, preserving the chemical and physical conditions of the
Speaker 2: universe's dawn.
Speaker 3: It fundamentally changes how you perceive the universe.
Speaker 2: It really does. I want to leave you with a
Speaker 2: final thought, something to maul over. The next time you
Speaker 2: step outside on a clear night, When you look up,
Speaker 2: your eyes are naturally inevitably drawn to the bright things.
Speaker 3: The shining stars, the glowing planets.
Speaker 2: The sweeping arm of the Milky Way itself. We are
Speaker 2: biologically and culturally conditioned to think that the light is
Speaker 2: where the action is, that the glowing points are where
Speaker 2: the universe happens.
Speaker 3: But the story of Andromeda xxty six suggests something far
Speaker 3: more profound.
Speaker 2: It suggests that the empty, seemingly black spaces between those
Speaker 2: bright stars aren't empty at all. They are secretly teeming
Speaker 2: with ancient invisible ghosts, vast dark matter dominated relics holding
Speaker 2: the pristine secrets of the universe's very first billion years.
Speaker 2: They are out there right now, quietly guarding the history
Speaker 2: of the cosmos in the dark, just waiting for someone
Speaker 2: patient enough to look closely.