Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomie 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: Every single star you see when you look up at
Speaker 2: the night sky is well, it's essentially a survivor.
Speaker 3: Oh absolutely, that is a great way to put.
Speaker 2: It right, because it is the glowing, burning byproduct of
Speaker 2: this completely violent, chaotic and just incredibly destructive factory that
Speaker 2: likely blew itself to pieces millions of years ago.
Speaker 3: Yeah, I think people really lose sight of that.
Speaker 2: I want you to just imagine stepping outside your house tonight,
Speaker 2: or you know, just standing outside on a perfectly clear, crisp,
Speaker 2: moonless night.
Speaker 3: Away from all the city lights, hopefully exactly.
Speaker 2: You look up and the canopy is just scattered with
Speaker 2: these brilliant points of light, and it feels quiet.
Speaker 3: It feels very stable.
Speaker 2: Yeah right, it feels serene. But that stability is a
Speaker 2: profound optical illusion.
Speaker 3: It really is the visible universe is effectively just the
Speaker 3: exhaust of the system.
Speaker 2: The exhaust. I love that.
Speaker 3: I mean, it's true. The glowing stars the things that
Speaker 3: have captivated human attention for millennia. They represent the absolute
Speaker 3: final stage of a vastly longer, darker, and infinitely more
Speaker 3: turbulent process.
Speaker 2: So if you only look at the stars.
Speaker 3: You're entirely missing the actual story of how the universe
Speaker 3: builds itself, which.
Speaker 2: Is exactly why we are completely shifting our perspective today.
Speaker 2: We are going to plunge into the absolute coldest, darkest,
Speaker 2: and literally the most massive structures that exist in the cosmos.
Speaker 3: The giant molecular clouds or GMCs.
Speaker 2: GMCs. Yeah, our goal here is to figure out the
Speaker 2: actual mechanics, how does the universe take a vast region
Speaker 2: of cold, dead, seemingly empty gas and somehow crush it
Speaker 2: down until it ignites into a burning fusion engine.
Speaker 3: And to really understand that we can't just poke around
Speaker 3: our own local neighborhood.
Speaker 2: Right, We're going big. We're going to look fifty to
Speaker 2: sixty million light years away at an entire galaxy is
Speaker 2: worth of these factories, just to see the actual blueprints of.
Speaker 3: Creation, because it is the only way to really understand
Speaker 3: the fundamental life cycle of a galaxy. I mean, a
Speaker 3: giant molecular cloud isn't just the birthplace of a single.
Speaker 2: Star or even a single cluster of stars, right exactly.
Speaker 3: The sheer, scale, the mass, the mechanics of these structures.
Speaker 3: They dictate everything about a galaxy. They determine how it
Speaker 3: changes shape over billions of years, how it breathe, and.
Speaker 2: Ultimately what kinds of chemical elements are even available to
Speaker 2: forge planets.
Speaker 3: Yes, and by extension biology itself.
Speaker 2: But the scale, the scale is the part that I
Speaker 2: think breaks the human brain first, because we use the
Speaker 2: word cloud in everyday life.
Speaker 3: Right, you look out the window on a cloudy day, exactly.
Speaker 2: You see these fluffy white collections of water vapor suspended
Speaker 2: a few miles above your head. But when astrophysicists use
Speaker 2: the term giant molecular cloud.
Speaker 3: They are talking about something so immensely huge that our
Speaker 3: entire solar system wouldn't even register as a single speck
Speaker 3: of dust inside it.
Speaker 2: A speck of dust. Yeah, So before we even get
Speaker 2: to the specific galaxy we are mapping out, we need
Speaker 2: to understand the anatomy of the beast what actually is
Speaker 2: a GMC.
Speaker 3: Well, to define a giant molecular cloud, you have to
Speaker 3: first look at the baseline environment of space. Okay, the
Speaker 3: interstellar medium, right, the space between the stars is not
Speaker 3: an absolute perfect vacuum. It is filled with a highly
Speaker 3: diffuse mixture of gas and dust.
Speaker 2: But out in the open that gas is relatively warm.
Speaker 3: Right, Yeah, it's ionized by starlight and it's spread incredibly thin.
Speaker 3: But a giant molecular cloud forms when, through a variety
Speaker 3: of different galactic processes, vast amounts of that gas just
Speaker 3: gets swept up together.
Speaker 2: It starts to clup up exactly.
Speaker 3: Its density increases dramatically, and the sheer volume of it
Speaker 3: shields is the inside from the radiation of the rest
Speaker 3: of the galaxy.
Speaker 2: Like it's building its own shade.
Speaker 3: That's a good way to look at it. And because
Speaker 3: it is shielded, it can finally cool down. And when
Speaker 3: I say cool down, I mean it reaches temperatures just
Speaker 3: barely hovering above absolute zero.
Speaker 2: Okay, Wait, let's put a hard number on that for
Speaker 2: anyone listening in their car or at the gym right now.
Speaker 2: Because cold is relative, how cold is this.
Speaker 3: Environment we are talking about internal temperatures of around ten
Speaker 3: to twenty.
Speaker 2: Kelvin, which in fahrenheit is what in.
Speaker 3: Fahrenheit that is roughly minus four hundred and forty degrees.
Speaker 2: Minus four hundred and forty degrees. Wow.
Speaker 3: Yeah, And to give you some context for that, the
Speaker 3: ambient background temperature of the entire universe, the leftover heat
Speaker 3: from the Big Bang itself, is about two point seven kelvin.
Speaker 2: So these clouds are just a tiny, tiny fraction of
Speaker 2: a degree warmer than the fundamental floor.
Speaker 3: Of physics, exactly, just barely warmer than the background of
Speaker 3: the universe.
Speaker 2: At minus four hundred and forty degrees. Matter has to
Speaker 2: behave completely differently, right, I mean everything just stops.
Speaker 3: The atomic behavior changes fundamentally. Yes. In the warmer and
Speaker 3: more diffuse interstellar medium, hydrogen exists mostly as single unbound
Speaker 3: atoms just bouncing.
Speaker 2: Around because they have too much kinetic energy to stick together, right.
Speaker 3: They just ricochet off each other. But inside these dark,
Speaker 3: incredibly cold clouds, the hydrogen atoms lose that kinetic energy.
Speaker 3: They slow down, they get sluggish, they get very sluggish.
Speaker 3: They meet and they bond together to form molecular hydrogen,
Speaker 3: which is H two two hydrogen atoms sharing their electrons.
Speaker 2: And that chemical transition is the defining characteristic of these structures. Right,
Speaker 2: That's why we specifically call them molecular clouds.
Speaker 3: Precisely, It's all about the molecules.
Speaker 2: Okay, so we have this freezing dark pocket of paired
Speaker 2: up hydrogen. But let's talk size. We throw around astronomical
Speaker 2: terms a lot, but I really want to ground this.
Speaker 2: How big is a typical GMC?
Speaker 3: A standard giant molecular cloud will span anywhere from tens
Speaker 3: to hundreds of light years across or in the units
Speaker 3: astronomers actually prefer to use tends to hundreds of parsecs.
Speaker 2: Okay, let's quickly define the parsec because it's one of
Speaker 2: those words that sounds like pure science fiction mostly beza
Speaker 2: Han solo.
Speaker 3: Let's be real, right, the infamous Kessel run, which as
Speaker 3: a quick aside, was always a unit of distance.
Speaker 2: Not time exactly. Take that Star Wars, But what is
Speaker 2: a parsk in reality?
Speaker 3: In reality, a parsec is simply a unit of distance
Speaker 3: equivalent to about three point twenty six light years or
Speaker 3: roughly nineteen trillion.
Speaker 2: Mile nineteen trillion miles for one parsek.
Speaker 3: Yes, it is derived from a geometric measurement called parallax.
Speaker 3: That's how astronomers measure the distance to relatively nearby stars
Speaker 3: by looking at how they shift against the background as
Speaker 3: the Earth orbits the Sun.
Speaker 2: Right like holding your thumb up and closing one eye
Speaker 2: then the.
Speaker 3: Other, exactly that principle, just on a solar system scale.
Speaker 3: So when an astronomer says a cloud is thirty parsecs across,
Speaker 3: they mean it is about one hundred light years from
Speaker 3: end to end.
Speaker 2: Okay, I want to put one hundred light years in
Speaker 2: perspective for the listener. The distance from our Sun to
Speaker 2: the absolute closest neighboring star, Proxima Centauri, is about four light.
Speaker 3: Years, just over four.
Speaker 2: Yes, and the fastest spacecraft humanity has ever built would
Speaker 2: still take tens of thousands of years to make that
Speaker 2: single four light.
Speaker 3: Year trip, a staggeringly long time.
Speaker 2: And you were saying one of these clouds is one
Speaker 2: hundred light years across, I mean you could stack thousands
Speaker 2: of our solar systems end to end and they would
Speaker 2: just be swallowed up in the.
Speaker 3: Dark, swallowed up completely. You wouldn't even notice them. And
Speaker 3: with that kind of physical volume comes an almost incomprehensible
Speaker 3: amount of mass.
Speaker 2: How much mass are we talking?
Speaker 3: A typical giant molecular cloud contains the equivalent mass of
Speaker 3: hundreds of thousands, and sometimes well over a million of
Speaker 3: our suns.
Speaker 2: A million suns worth of raw material.
Speaker 3: Yes, a million suns. And while the vast overwhelming majority
Speaker 3: of that mass is the molecular hydrogen we just discussed,
Speaker 3: the cloud is definitely not pure. It's got some seasoning
Speaker 3: in it, a lot of seasoning. It is laced with
Speaker 3: an incredibly important mixture of other opponents. Roughly one percent
Speaker 3: of the cloud's mass is made up of interstellar dust.
Speaker 2: When you say dust, you mean like the stuff on
Speaker 2: my bookshelf.
Speaker 3: More like microscopic grains of silicates and carbonaceous material. Think
Speaker 3: soot and sand, but at a microscopic level.
Speaker 2: Okay, soot in sand, got it.
Speaker 3: And then there are trece amounts of other gases too, ammonia,
Speaker 3: carbon monoxide, and even highly complex organic molecules. They are
Speaker 3: really the ultimate cosmic reservoir.
Speaker 2: So we have a reservoir of a million suns. It's
Speaker 2: one hundred light years wide, it is full of the
Speaker 2: exact raw materials needed to build solar systems and it
Speaker 2: is hanging right over our heads in our own galaxy.
Speaker 3: Oh, absolutely all over the galaxy, and.
Speaker 2: In every other galaxy too. So you would think astronomers
Speaker 2: could just point a telescope at the sky and see
Speaker 2: these massive things literally everywhere. You would think so, But
Speaker 2: that leads to one of the most frustrating paradoxes in astrophysics.
Speaker 2: These behemoths are practically invisible.
Speaker 3: It really is the great irony of star formation. The
Speaker 3: raw fuel that creates the brightest, most intensely luminous objects
Speaker 3: in the universe is fundamentally undetectable to standard observational tools.
Speaker 2: It's like they're cloaked. Why is that right? Because it's
Speaker 2: just two of the exact same hydrogen atoms.
Speaker 3: So when it rotates in the freezing cold of a
Speaker 3: dark cloud, it doesn't emit any easily detectable radiation at all.
Speaker 3: It is completely silent to our instruments.
Speaker 2: It's totally dark. You know. To me, it's like trying
Speaker 2: to watch a perfectly clear, rushing river at night.
Speaker 3: That's a really good analogy.
Speaker 2: You know, the river is there, you know, it spans
Speaker 2: for miles and millions of gallons of water are churning
Speaker 2: and carrying massive amounts of force. But because the water
Speaker 2: is totally transparent and there's no light bouncing off of it,
Speaker 2: you stand on the bank and you are just totally blind.
Speaker 3: You can't see the currents, you can't map the flow.
Speaker 2: Right, So if you are a scientist trying to map
Speaker 2: that river, you have to get creative. You essentially have
Speaker 2: to drop a non toxic fluorescent dye into the water upstream. Exactly,
Speaker 2: you can't see the water it's but you can track
Speaker 2: the glowing dye, and by mapping the dye, you map
Speaker 2: the river.
Speaker 3: That river analogy captures the exact methodology of molecular astrophysics perfectly.
Speaker 3: We literally cannot see the molecular hydrogen water. We are
Speaker 3: totally blind to the H two.
Speaker 2: So we need a cosmic dye.
Speaker 1: Yes.
Speaker 3: We must rely on a tracer, and the most ubiquitous,
Speaker 3: reliable dye available in these giant molecular clouds is carbon
Speaker 3: monoxide COO.
Speaker 2: Wait, like the exact same carbon monoxide that comes out
Speaker 2: of a car exhaust or a faulty furnace.
Speaker 3: The very same molecule yes. Now, compared to the vast
Speaker 3: ocean of hydrogen, carbon monoxide is barely a drop in
Speaker 3: the bucket. For every single molecule of COEO, there are
Speaker 3: roughly ten thousand molecules of.
Speaker 2: Hydrogen, so it's a very very faint, dye.
Speaker 3: Very trace. But carbon monoxide has the one crucial feature
Speaker 3: that hydrogen lacks. It is asymmetric.
Speaker 2: Ah, It's made of one carbon in one oxygen exactly.
Speaker 3: Oxygen is more electronegative than carbon, which means it pull
Speaker 3: the shared electrons slightly toward itself.
Speaker 2: It has the imbalance. It has the antenna.
Speaker 3: Precisely because it has that slight electrical imbalance the dipole moment.
Speaker 3: When a carbon monoxide molecule gets bumped by a neighboring
Speaker 3: hydrogen molecule.
Speaker 2: It starts to spin and it hums.
Speaker 3: Yes, as it spins, it emits a very specific, very
Speaker 3: distinct radiofrequency. Specifically, it emits at millimeter and submillimeter wavelengths.
Speaker 2: Even at minus four hundred and forty degrees.
Speaker 3: Even at ten kelvin in the absolute freezing depths of
Speaker 3: the cloud, there is just enough ambient thermal energy from
Speaker 3: those collisions to keep the carbon monoxide rotating and humming.
Speaker 2: So this whole vast invisible cloud of hydrogen is basically
Speaker 2: singing to us, but we can only hear it through
Speaker 2: the voice of the trace carbon monoxide.
Speaker 3: That's beautifully put Yes, where you find carbon monoxide emitting
Speaker 3: these millimeter waves, you are virtually guaranteed to be looking
Speaker 3: at a dense pocket of molecular hydrogen.
Speaker 2: By tuning our instruments to the exact frequency of that
Speaker 2: co hum, we can map the entire invisible river.
Speaker 3: But as you might guess, there is a catch.
Speaker 2: There's always a cat astrophysics. What is it?
Speaker 3: If the dye is glowing specifically in millimeter wavelengths, then
Speaker 3: pointing a regular telescope at it, like the Hubble space telescope,
Speaker 3: which looks primarily at visible and ultraviolet light, is completely useless.
Speaker 2: It's like wearing standard sunglasses to look for a specific
Speaker 2: infrared laser. You just have the wrong lenses.
Speaker 3: You have entirely the wrong lenses. If we want to
Speaker 3: map this massive invisible machinery, we need a machine that
Speaker 3: is specifically built from the ground up to see millimeter waves.
Speaker 2: Which brings us to the Atacoma Large Millimeter Submillimeter Array
Speaker 2: ALMA ALMA, which is, without hyperbole, one of the most
Speaker 2: phenomenal and frankly complex pieces of engineering ever constructed by
Speaker 2: human hands.
Speaker 3: It is the ultimate lens for peering into the dark.
Speaker 3: It's a marvel.
Speaker 2: Let's really dig into LMA because when you look at
Speaker 2: pictures of this facility, it honestly looks like a colony
Speaker 2: on another planet. It does not look like a traditional
Speaker 2: observatory at all.
Speaker 3: No, it doesn't, and it doesn't look like one because
Speaker 3: it operates on entirely different principles than a standard optical telescope.
Speaker 3: ALIMA is not just a single giant mirror housed inside
Speaker 3: a shiny silver dome.
Speaker 2: Right, It's a sprawling network.
Speaker 3: It is an array. It is a network of sixty
Speaker 3: six highly precess individual dish antennas. Most of them are
Speaker 3: twelve meters across, and they weigh over one hundred tons.
Speaker 2: Each one hundred tons each. Wow.
Speaker 3: But the most critical aspect of LMA isn't just the
Speaker 3: dishes themselves. It is where those dishes are physically located, right.
Speaker 2: The Attacama Desert in northern Chile. Yeah, but it's not
Speaker 2: just the desert. They built this thing at an altitude
Speaker 2: of five thousand meters, which is over sixteen four hundred
Speaker 2: feet above sea level. I mean, it is so high
Speaker 2: up that the engineers and the astronomers who maintain it
Speaker 2: literally have to carry supplemental oxygen tanks just to avoid hypoxia.
Speaker 3: It is a brutally hostile environment for human beings.
Speaker 2: So why on Earth do you take a multi billion
Speaker 2: dollar ultrasensitive international science project and stick it on top
Speaker 2: of a freezing oxygen deprived mountain. The logistics alone must be.
Speaker 3: A nightmare are but you do it to escape the
Speaker 3: Earth's atmosphere. Specifically, you are trying to escape the water vapor,
Speaker 3: ah the humidity exactly. Remember that the carbon monoxide die
Speaker 3: we are looking for emits radiation in the millimeter and
Speaker 3: submillimeter range. It turns out that atmospheric water vapor, the
Speaker 3: literal humidity in the air that we breathe down here
Speaker 3: on Earth, is incredibly efficient at absorbing those exact wavelengths,
Speaker 3: so it blocks the signal completely. If you build Alima
Speaker 3: in Florida, or even on a standard mountain in California,
Speaker 3: the moisture in the air would act like an opaque, dense,
Speaker 3: impenetrable wall.
Speaker 2: That's incredibly frustrating to think about.
Speaker 3: Right, The faint hum of the carbon monoxide traveling from
Speaker 3: fifty million light years away, would survive its entire cosmic
Speaker 3: journey across the universe, only to be entirely soaked up
Speaker 3: by a random marine cloud two miles above the telescope.
Speaker 2: It would just hit a brick wall at the very
Speaker 2: last possible.
Speaker 3: Second, exactly, So you have to get above the water.
Speaker 3: The Chajnantur Plateau in the a Kama Desert is one
Speaker 3: of the absolute driest places on the st surface of
Speaker 3: the planet, and.
Speaker 2: It's sixteen four hundred feet you're above most of the
Speaker 2: atmosphere anyway.
Speaker 3: Yes, you are sitting above the vast majority of the
Speaker 3: Earth's atmospheric blanket. The sky up there is exceptionally transparent
Speaker 3: to millimeter waves. It is truly as close to being
Speaker 3: an outer space as you can possibly get while still
Speaker 3: keeping your equipment anchored to the ground.
Speaker 2: Okay, so you have sixty six massive, one hundred ton
Speaker 2: dishes sitting high up in a dry barren desert. But
Speaker 2: you mentioned they form an array, so they don't just
Speaker 2: act like sixty six separate people looking through sixty six
Speaker 2: separate pairs of binoculars. Right, They work as a collective.
Speaker 3: They do, and the technique they used to do this
Speaker 3: is called interferometry. This is where the physics of waves
Speaker 3: becomes incredibly, incredibly useful. Okay, how so, Well, if you
Speaker 3: want to see highly detailed, sharp structures from millions of
Speaker 3: light years away, you fundamentally need a massive telescope. The
Speaker 3: larger the diameter of the dish, the sharper your resolution
Speaker 3: is going to be.
Speaker 2: That makes sense, bigger lens, better picture.
Speaker 3: But physically building a single telescope dish that is saved
Speaker 3: miles across is structurally impossible. It would simply collapse under
Speaker 3: its own weight.
Speaker 2: Gravity gets in the way exactly.
Speaker 3: Interferometry is basically the cheat code that gets around this
Speaker 3: physical limitation, a.
Speaker 2: Cheat code for building a bigger lens. I like that,
Speaker 2: How does the cheat code work?
Speaker 3: By linking multiple smaller dishes together, you can synthesize the
Speaker 3: aperture of a much larger virtual telescope.
Speaker 2: Okay.
Speaker 3: When the faint radiowave from the carbon monoxide in a
Speaker 3: distant galaxy arrives at Earth, it hits one antenna in
Speaker 3: the array a tiny microscopic fraction of a picosecond before
Speaker 3: it hits the next one.
Speaker 2: Because they're physically spread.
Speaker 3: Out right, the antennas are all connected by miles and
Speaker 3: miles of fiber optic cables to a specialized supercomputer which
Speaker 3: is called a correlator.
Speaker 2: The correlator that sounds very intense.
Speaker 3: It is incredibly intense. It is capable of performing quadrillions
Speaker 3: of operations per second.
Speaker 2: Quadrillions.
Speaker 3: Wow. Its entire job is to take the signs from
Speaker 3: all sixty six antennas and cross multiply them, constantly matching
Speaker 3: up the microscopic delays in the arrival times of the radio.
Speaker 2: Waves, so it stitches them together.
Speaker 3: Yes, and by doing this insanely complex math, the array
Speaker 3: acts as if it were a single colossal telescope whose
Speaker 3: overall diameter is equal to the distance between the two
Speaker 3: furthest antennas in the.
Speaker 2: Network, and the antennas aren't bolted to the ground permanently,
Speaker 2: are they. No, they aren't, because I've seen footage of
Speaker 2: these massive, custom built tractor vehicles that literally drive up
Speaker 2: to one hundred ton antenna, pick the whole thing up,
Speaker 2: and drive it across the desert to a new concrete pad.
Speaker 3: Yes, those are the Alma transporters. They're named Auto and Lore.
Speaker 3: They allow the entire array to be constantly reconfigured.
Speaker 2: So you can zoom in and out exactly.
Speaker 3: If astronomers want a wide field zoomed out view of
Speaker 3: the sky, they use the transporters to cluster all the
Speaker 3: antennas closely together. But if they want maximum sharpness, the
Speaker 3: ultimate zoom, they use the transporters to physically spread the
Speaker 3: antenna's across the desert plateau.
Speaker 2: How far apart.
Speaker 3: They can extend the baseline up to sixteen kilometers.
Speaker 2: Across sixteen kilometers, So you are literally computationally building a
Speaker 2: telescope the size of a major city just to stare
Speaker 2: deep into space.
Speaker 3: Yes, and the result of that city sized virtual dish
Speaker 3: is unprecedented angular resolution. When spread out, LMA can resolve
Speaker 3: details down to a fraction of an arcsecond.
Speaker 2: Okay, let's ground that. What does a fraction of an
Speaker 2: arcsecond actually look like.
Speaker 3: Imagine standing in New York City looking through a telescope
Speaker 3: and being able to clearly distinguish the individual dimples on
Speaker 3: a golf ball, sitting on a tee in Los Angeles.
Speaker 3: You are kidding, No, that is the level of pinpoint
Speaker 3: sharpness we are talking.
Speaker 2: About from New York to LA. That is insane, it is.
Speaker 3: And we absolutely need that sharpness because to see the
Speaker 3: fine internal structure of a giant molecular cloud that is
Speaker 3: only a few dozen parsecs across and located inside a
Speaker 3: galaxy tens of millions of light years away, you need
Speaker 3: the ultimate magnifying glass.
Speaker 2: And crucially, because Alima is looking at radio waves, it
Speaker 2: doesn't care about the dust at all. Right, kind of
Speaker 2: in a little bit, Because if you point a normal
Speaker 2: optical telescope at a star forming region, all you see
Speaker 2: is a giant black smudge. The interstellar dust grains just
Speaker 2: physically block the visible light from the stars forming inside.
Speaker 3: Yes, optical telescopes are completely blind to the interior, but
Speaker 3: millimeter waves just slip right around those dust grains. ALMA
Speaker 3: cuts right through the cosmic smog.
Speaker 2: It pierces the veil entirely.
Speaker 3: It does. But honestly, the most powerful aspect of LMA
Speaker 3: isn't just that it takes a clear picture. It is
Speaker 3: that it takes a moving picture.
Speaker 2: What do you mean, like a video?
Speaker 3: Sort of. By observing the specific frequency of the carbon monoxide,
Speaker 3: ALMA is essentially measuring a Doppler shift.
Speaker 2: Okay, like a police siren changing pitch as it drives
Speaker 2: past you on the highway.
Speaker 3: Exactly the same principle, but with light instead of sound.
Speaker 3: If a pocket of gas inside the giant molecular cloud
Speaker 3: is moving toward Earth, the millimeter wave waves of the
Speaker 3: carbon monoxide get compressed, shifting to a slightly higher frequency.
Speaker 2: A blue shift.
Speaker 3: Right. And if the gas is churning away from Earth,
Speaker 3: the waves stretch out to a lower frequency.
Speaker 2: A red shift, and ALMA can detect that.
Speaker 3: ALMA is so precise that it can map these minute
Speaker 3: frequency shifts across the entire cloud simultaneously. So it doesn't
Speaker 3: just see a static blob of gas.
Speaker 2: It maps the internal kinematics.
Speaker 3: Yes, it reads the velocity, the turbulence, and the temperature
Speaker 3: of the gas in real time. It actually shows us
Speaker 3: how the machinery inside the factory is moving.
Speaker 2: Okay, so we have the ultimate tool. We have a
Speaker 2: city sized robotics supercomputing telescope array perched on top of
Speaker 2: the driest mountain in the world, specifically designed to read
Speaker 2: the speed and temperature of invisible gas by tracking trace
Speaker 2: amounts of glowing carbon monoxide.
Speaker 3: That's the summary.
Speaker 2: Yes, now comes the obvious logistical question. Yeah, you have
Speaker 2: this incredible machine. Where do you point it?
Speaker 3: Ah? Yes, the targeting question.
Speaker 2: Because the instinct for anyone would be to say, well,
Speaker 2: we live in the Milky Way. Our galaxy has spiral
Speaker 2: arms completely full of giant molecular clouds. Why not just
Speaker 2: look at our own backyard.
Speaker 3: And for decades that is exactly what astronomers did. We
Speaker 3: have intensely studied the local star forming regions.
Speaker 2: Like the Orion nebula.
Speaker 3: Exactly, regions like the Orion molecular cloud complex, which is
Speaker 3: only about thirteen hundred light years away, or the Taurus
Speaker 3: molecular cloud, or even the incredibly dense chaotic central molecular
Speaker 3: zone right at our galactic core.
Speaker 2: So we have looked close to home.
Speaker 3: We have, and we have learned an immense amount from them.
Speaker 3: But studying the Milky Way from inside the Milky Way
Speaker 3: comes with a fatal flaw. Astronomers refer to it as
Speaker 3: the line of sight problem.
Speaker 2: The line of sight problem. Okay, okay, I try to
Speaker 2: picture it like this. Imagine standing in the middle of
Speaker 2: a massive, incredibly dense old growth forest. Okay, you have
Speaker 2: notepad and your job is to map exactly where every
Speaker 2: single tree is and how big it is. You look
Speaker 2: directly north, you see a massive oak tree right in
Speaker 2: front of you. You write it down, but what you
Speaker 2: absolute we cannot see is whether there are five more
Speaker 2: oak trees lined up perfectly behind that first one. The
Speaker 2: trunk in the foreground completely blocks the background.
Speaker 3: That is the perfect visualization of the problem.
Speaker 2: Because our solar system is embedded deep inside the flat
Speaker 2: disc of the Milky Way, right, So when we look
Speaker 2: out into the galactic plane, we're just looking through the forest.
Speaker 2: We see everything squished and projected onto a single two
Speaker 2: dimensional slice of the sky.
Speaker 3: Yes, if you see a massive emission of carbon monoxide
Speaker 3: in the Milky Way, it is incredibly difficult to know
Speaker 3: if you are looking at one single colossal, giant molecular cloud,
Speaker 3: or if you are looking at three smaller distinct clouds
Speaker 3: that just happen to lie along the exact same line of.
Speaker 2: Sight, just separated by thousands of light years of empty
Speaker 2: space behind each other exactly.
Speaker 3: You have the velocity data from the Doppler shift, which
Speaker 3: helps untangle it a bit, but distance ambiguity is just
Speaker 3: constantly plague galactic astronomy.
Speaker 2: It's just a mess of overlack of data.
Speaker 3: It makes it incredibly difficult to get clean, isolated, true
Speaker 3: three dimensional properties of the clouds. And more importantly, you
Speaker 3: can't get reliable population statistics across the whole galaxy because
Speaker 3: you can never see the whole galaxy at once.
Speaker 2: You are forever stuck in the middle of the trees
Speaker 2: you are, so if you want a perfect map of
Speaker 2: the forest, you have to leave it. And since we
Speaker 2: obviously cannot physically fly a spaceship outside the Milky Way
Speaker 2: to look back down at it, we have to find
Speaker 2: a completely different forest to look at, a forest that
Speaker 2: we can view from a completely different angle.
Speaker 3: Which leads the researchers to target the galaxy NGC thirteen
Speaker 3: eighty seven.
Speaker 2: Let's set the stage with NNGC thirteen eighty seven. Where
Speaker 2: are we looking and why is this specific galaxy the
Speaker 2: holy grail for this kind of mapping.
Speaker 3: NNGC thirteen eighty seven is located in the constellation four
Speaker 3: nax It's it's roughly fifty to sixty million light years
Speaker 3: away from Earth.
Speaker 2: Sixty million light years that is quite the jump from
Speaker 2: our local neighborhood it.
Speaker 3: Is, but structurally it is a barred spiral galaxy somewhat
Speaker 3: similar to our own milk. It has a central structure,
Speaker 3: a bar and an extended disc.
Speaker 2: Well, what makes it so special.
Speaker 3: The absolute defining characteristic that makes ENNGC thirteen eighty seven
Speaker 3: so incredibly valuable is its inclination angle relative to Earth.
Speaker 3: We view it almost entirely face on.
Speaker 2: Oh wow, So instead of looking at the galaxy edge on,
Speaker 2: where it would just look like a thin bright line
Speaker 2: cutting across the sky, which would obviously give us the
Speaker 2: exact same line of sight problem we have here, we
Speaker 2: are essentially hovering above it exactly.
Speaker 3: We are looking down at the face.
Speaker 2: Of a clock that is perfect.
Speaker 3: Yes, the face on top down perspective entirely strips away
Speaker 3: the ambiguity. When LMA points at the disk of NGC
Speaker 3: thirteen eighty seven and detects a giant molecular cloud, we
Speaker 3: know exactly where.
Speaker 2: It is because there's nothing behind it to get confused with.
Speaker 3: Right, We know its exact distance from the center of
Speaker 3: that galaxy. We know we are seeing its true isolated
Speaker 3: boundaries without five other clouds photo bombing it in the
Speaker 3: foreground or background.
Speaker 2: So it's a completely clean data set.
Speaker 3: It allows wowose astronomers to conduct a pure, uncontaminated sensus
Speaker 3: of an entire galactic ecosystem with all the clouds situated
Speaker 3: at a known uniform distance from our telescope.
Speaker 2: Okay, so the team takes Alma. They pointed at fourn
Speaker 2: X and they stared down at the face of NNGC
Speaker 2: thirteen eighty seven. They tuned the receivers to catch the
Speaker 2: carbon monoxide. Hum. What did they actually catch in the net?
Speaker 3: They brought back an absolute treasure trove of data. The
Speaker 3: survey resulted in the rigorous identification of twelve thousand, two
Speaker 3: hundred and eighty five distinct individual giant molecular clouds scattered
Speaker 3: across the rotating gas disc of NNGC thirteen eighty.
Speaker 2: Seven, one thy two hundred and eighty five. That is
Speaker 2: mind boggling.
Speaker 3: It really is a staggering number.
Speaker 2: I mean, they didn't just find a few interesting case
Speaker 2: studies to write a paperon. They cataloged an entire population.
Speaker 2: They essentially mapped the entire industrial sector of a foreign galaxy.
Speaker 3: The word unprecedented gets over used in science a lot,
Speaker 3: but in this case it absolutely applies. To have a
Speaker 3: highly resolved, uniform kinematic map of news nearly thirteen hundred
Speaker 3: distinct star forming factories and a single external galaxy represents
Speaker 3: a massive leap in capability.
Speaker 2: It changes the game entirely.
Speaker 3: It really does. We are moving from studying individual anecdotes
Speaker 3: to doing hard, rigorous population statistics. We can finally ask
Speaker 3: what does a normal molecular cloud actually look like?
Speaker 2: So let's look at the stats. You have twelve thousand,
Speaker 2: two hundred and eighty five clouds on a spreadsheet. What
Speaker 2: happens when you start analyzing their physical properties?
Speaker 3: Well, let's start with their physical footprints across the entire population.
Speaker 3: The mean radius of a cloud is roughly twenty parses
Speaker 3: or about sixty five light years.
Speaker 2: Okay, sixty five light years on average.
Speaker 3: But averages can be very deceiving. The distribution includes massive outliers,
Speaker 3: the true giants, the colossal complexes within the spiral structure
Speaker 3: most radii exceeding one hundred to one hundred and fifty
Speaker 3: light years, and.
Speaker 2: The masses of these structures. Because we said a million
Speaker 2: suns earlier.
Speaker 3: They are equally staggering. The masses range from tens of
Speaker 3: thousands of solar masses at a small diffuse end all
Speaker 3: the way up to well over a million solar masses
Speaker 3: for the largest, most gravitationally dominant complexes.
Speaker 2: But the real insight comes when you look at how
Speaker 2: those masses are distributed across the population.
Speaker 3: Right, Yes, exactly. Because the universe rarely just throws things out.
Speaker 2: Randomly, there's usually a pattern.
Speaker 3: Always when astronomers plot the number of clouds on a
Speaker 3: graph against their respective masses, they don't just see a
Speaker 3: random bell curve. They see a very strict mathematical relationship
Speaker 3: known as a truncated power.
Speaker 2: Law, a truncated power law.
Speaker 3: Specifically, for NNGC thirteen eighty seven, the slope of this
Speaker 3: power law falls between minus one point seven and minus
Speaker 3: one point eight.
Speaker 2: Okay, I want to pause and dissect this because truncated
Speaker 2: power law with the slope of minus one point seven
Speaker 2: sounds intensely like a math exam.
Speaker 3: It does sound a bit dry.
Speaker 2: But I know there is deep physical meaning hidden in
Speaker 2: that phrase. Let's translate it. If I'm understanding this correctly,
Speaker 2: a power law basically dictates a ratio of big things
Speaker 2: to small things.
Speaker 3: That's a good way to frame it.
Speaker 2: So it means you're going to have an enormous number
Speaker 2: of very small clouds, a moderate number of medium clouds
Speaker 2: yea in a tiny, incredibly rare handful of absolute behemoths.
Speaker 2: It is a strict hierarchy. Yes, And the slope that
Speaker 2: minus one point seven is the mathematical rule that tells
Speaker 2: you exactly how much rarer a cloud becomes as you
Speaker 2: scale up the mass.
Speaker 3: That is a perfect translation. The power law describes the
Speaker 3: scale free nature of the gas. But the truly fascinating
Speaker 3: part is why the gas organizes itself according to this
Speaker 3: specific slope.
Speaker 2: Why does it does minus one point seven mean something specific?
Speaker 3: It does? A slope hovering around minus one point seven
Speaker 3: to minus two point zero is a very well known
Speaker 3: mathematical signature in physics. It is the signature of fractal
Speaker 3: supersonic turbulence.
Speaker 2: Fractal turbulence. Let's unpack that when people hear fractal, they
Speaker 2: usually think of those trippy zooming computer graphics where a
Speaker 2: shape perfectly repeats itself no matter how far you zoom
Speaker 2: in right, the mandelbrought sets like the branching of a
Speaker 2: tree or the veins on a fern leave exactly.
Speaker 3: A giant molecular cloud is not just a smooth, uniform
Speaker 3: balloon filled with hydrogen gas. It is a highly complex,
Speaker 3: fractal environment shaped by opposing forces.
Speaker 2: The tut of war.
Speaker 3: Yes, you have the immense gravity of a million suns
Speaker 3: trying to crush the cloud inward. But fighting against that
Speaker 3: gravity is the internal kinetic energy, the turbulence.
Speaker 2: The gas is moving.
Speaker 3: The gas inside the cloud is churning and roiling at
Speaker 3: supersonic speeds. This turbulence creates a fractal structure of shocks
Speaker 3: and eddies. Big turbulent flows break down into smaller turbulent flows,
Speaker 3: which break down into even smaller turbulent.
Speaker 2: Flows, just like the zooming graphic.
Speaker 3: Exactly, This physical cascade of energy naturally partitions the gas,
Speaker 3: creating a lot of small clumps and very few large ones,
Speaker 3: resulting in that exact minus one point seven mathematical slope.
Speaker 2: So the math is just a mirror reflecting the fluid
Speaker 2: dynamics of space. That is just beautiful.
Speaker 3: It really is elegant.
Speaker 2: But you also mentioned the power law was truncated. What
Speaker 2: does truncated mean in this context.
Speaker 3: Well, a standard power law would technically go on forever,
Speaker 3: you would just keep getting bigger and rarer clouds infinitely.
Speaker 3: But physics sets hard limits.
Speaker 2: The universe has rules.
Speaker 3: The truncation point is the upper mass limit. It is
Speaker 3: the point on the graph where the line suddenly plummets to.
Speaker 2: Zero, meaning no clouds exist past that size.
Speaker 3: Right, It tells us that a giant molecular cloud cannot
Speaker 3: grow to ten million or one hundred million solar masses.
Speaker 3: At a certain point, a cloud simply becomes too physically
Speaker 3: large for its own gravity to hold it together against
Speaker 3: the shearing forces of the rotating galaxy.
Speaker 2: The galaxy just rips it apart if it gets too greedy.
Speaker 3: Exactly, the truncation point is essentially the galaxy saying this
Speaker 3: is the maximum allowable size for a star factory, no bigger.
Speaker 2: So we have the outside boundaries, we have the mass limits.
Speaker 2: But what happens when you use Eleme's incredible resolution to
Speaker 2: actually zoom in past the boundary and look at the
Speaker 2: internal architecture of one of these specific clouds. What is
Speaker 2: the actual ecosystem inside?
Speaker 3: It is a deeply structured hierarchy. If you peer deep
Speaker 3: into the interior of the cloud, by passing the diffuse
Speaker 3: outer layers, you find what astronomers call the dense cores.
Speaker 2: The dense cores, these are.
Speaker 3: The hearts of the factory. In these specific regions, the
Speaker 3: density of the gas spikes dramatically reaching thousands or even
Speaker 3: tens of thousands of molecules per cubic centimeter.
Speaker 2: Okay, I need to interject with some terrestrial perspective here,
Speaker 2: because hearing thousands of molecules per cubic centimeter sounds incredibly dense,
Speaker 2: like a solid brick of gas, right. It sounds packed,
Speaker 2: But compared to the air on Earth, it is absolutely nothing.
Speaker 3: Right by terrestrial standards, a dense molecular core is a
Speaker 3: vacuum harder than anything an Earth based laboratory could ever
Speaker 3: dream of engineering.
Speaker 2: Put it in perspective for us, the air in.
Speaker 3: The room you are sitting in right now contains roughly
Speaker 3: ten quintillion molecules per cubic centimeter ten contilion. A giant
Speaker 3: molecular cloud core has ten thousand. It is incomprehensibly sparse to.
Speaker 2: Us, but by the standards of outer space, it's a
Speaker 2: cosmic traffic jam exactly.
Speaker 3: And that relative dense city is all that matters, because
Speaker 3: when the gas gets that crowded relative to its surroundings,
Speaker 3: it can finally shield itself entirely from any external heat.
Speaker 3: It cools to the absolute minimum, with the heat and
Speaker 3: outward pressure basically gone. Gravity finally wins the tug of war,
Speaker 3: the core begins to collapse inward. These dense cores are
Speaker 3: the literal wombs. They are the exact localized sites where
Speaker 3: gravitational collapse becomes imminent, leading to the birth of a protostar.
Speaker 2: But a core can't just sustain itself in a vacuum right,
Speaker 2: and it needs to pull material from the rest of
Speaker 2: the cloud. ALMA also revealed the plumbing system didn't it, Yes, it.
Speaker 3: Did, Connecting these dense cores to the vast wider body
Speaker 3: of the cloud. Are filamentary structures filaments?
Speaker 2: What do they look like?
Speaker 3: They are literal rivers of gas. The ALMA data clearly
Speaker 3: shows these elongated threads routing material through the cloud. The
Speaker 3: supersonic turbulence we discussed earlier compresses the gas into these filaments,
Speaker 3: and gravity.
Speaker 2: Acts as the pump, channeling the material.
Speaker 3: Yes, channeling material down the filaments to constantly feed the
Speaker 3: dense cores. And Surrounding this entire network of rivers and
Speaker 3: cores is the diffuse envelope, a vast lower density halo
Speaker 3: that acts as the transition zone between the freezing molecular
Speaker 3: cloud and the warmer atomic gas of the galaxy.
Speaker 2: So looking at NGC thirteen eighty seven, we have just
Speaker 2: outlined a master blueprint one two hundred and eighty five clouds.
Speaker 2: We know the mass ratios, the fractal turbulent structure, the
Speaker 2: dense cores, the filamentary plumbing. We essentially have the exact
Speaker 2: specs of the factory we do.
Speaker 3: It's a complete structural breakdown.
Speaker 2: So now we can take this massive data set and
Speaker 2: point it at one of the most profound, overarching questions
Speaker 2: in astrophysics. It's something that scientists have debated for decades.
Speaker 3: Universality.
Speaker 2: Yes, are the rules of star formation universal? Does physics
Speaker 2: care where it is?
Speaker 3: That is a big question.
Speaker 2: If I take a million solar masses of molecular hydrogen
Speaker 2: and drop it in the chaotic center of the Milky Way,
Speaker 2: will it behave exactly the same way as a million
Speaker 2: solar masses of hydrogen floating fifty million light years away
Speaker 2: in the quiet suburbs of Foregnax.
Speaker 3: That is the ultimate test. We want to know if
Speaker 3: the recipe for a star is an immutable lot of
Speaker 3: nature or if it changes fundamentally based on the local neighborhood.
Speaker 2: And to test this hypothesis, astrophysicists rely on a historical
Speaker 2: framework known as Larsen's.
Speaker 3: Laws Larson's loss.
Speaker 2: Yes, let's go back into the history of astronomy for
Speaker 2: a second to explain these Where did they come from?
Speaker 3: In nineteen eighty one, an astrophysicist named Richard Larsen published
Speaker 3: a seminal paper. He had been studying the relatively small
Speaker 3: sample of molecular clouds that we could actually observe inside
Speaker 3: the Milky Way at.
Speaker 2: The time, through all the trees exactly.
Speaker 3: Working through the line of sight issues. But through his
Speaker 3: observations he noticed three distinct scaling relationships that seemed to
Speaker 3: govern how these clouds behaved.
Speaker 2: What were the three relationships?
Speaker 3: The first law states that there is a strict relationship
Speaker 3: between a cloud's physical size and its internal velocity dispersion.
Speaker 2: Okay, velocity dispersion, that's simply a measure of how violently
Speaker 2: the gas inside the cloud is churning and moving right.
Speaker 3: Yes, Larson realized that larger clouds have intrinsically higher velocity discursions.
Speaker 3: The bigger the cloud, the faster and more violently the
Speaker 3: gas inside it is swirling.
Speaker 2: Makes sense, more mass, more gravity, more turbulence. What about
Speaker 2: the second law.
Speaker 3: The second law relates a cloud size to its total mass,
Speaker 3: effectively demonstrating that clouds have a roughly uniform calum density
Speaker 3: regardless of their overall volume.
Speaker 2: Okay, and the third law.
Speaker 3: The third law relates to the balance of energies, specifically
Speaker 3: something called the virial theorem.
Speaker 2: The virial theorem, I remember you mentioning this earlier when
Speaker 2: talking about the tug of war in the cloud. Let's
Speaker 2: go that down. So it's not just a jargon term.
Speaker 3: Absolutely, the viial parameter is essentially a ratio. It is
Speaker 3: a way of comparing the kinetic energy of the cloud,
Speaker 3: the turbulence the outward pressure trying to blow the cloud apart,
Speaker 3: against the gravitational potential energy.
Speaker 2: Which is the inward pull trying to crush the cloud
Speaker 2: into a star.
Speaker 3: Exactly, if a cloud isn't what we call v curial equilibrium,
Speaker 3: those two forces are perfectly balanced. The cloud neither collapses
Speaker 3: nor expands. It just hangs there in a stable, steady state.
Speaker 3: It's just chilling, right, And Larson observed that most molecular
Speaker 3: clouds in the Milky Way seem to hover near this
Speaker 3: state of virial equilibrium.
Speaker 2: Okay, So Larson establishes these laws in nineteen eighty one
Speaker 2: using the Milky Way. Fast forward forty something years. You
Speaker 2: have this pristine, massive new data set of twelve thousand,
Speaker 2: two hundred and eighty five clouds from a completely different
Speaker 2: galaxy sixty million light years away.
Speaker 3: A totally fresh data set.
Speaker 2: You apply Larsen's laws to the Fornax clouds. What does
Speaker 2: the math show?
Speaker 3: Astoundingly, the clouds in NNGC thirteen eighty seven fall perfectly
Speaker 3: in line, perfectly perfectly. When the research team plotted the size, mass,
Speaker 3: and molossy dispersion of the twelve two hundred and eighty
Speaker 3: five clouds, the data points trace the exact same scaling
Speaker 3: relationships that Larsen found in the Milky Way.
Speaker 2: Wow.
Speaker 3: The physics mapped cleanly across tens of millions of light years.
Speaker 2: Which provides massive support for the idea that the universe
Speaker 2: really just has one single universal recipe for building a
Speaker 2: star factory.
Speaker 3: It does it heavily implies that the core physics, the
Speaker 3: way a gas cloud supports itself against gravity via internal
Speaker 3: fractal turbulence, and the way it ultimately fragments to build
Speaker 3: dense cores, is governed by fundamental thermodynamic and gravitational constants.
Speaker 2: The basic machinery is identical everywhere, exactly the same. But
Speaker 2: I am going to push back on this just a
Speaker 2: little bit, because my instinct tells me that can't be
Speaker 2: the whole story.
Speaker 3: Oh please do push back.
Speaker 2: If star formation is a perfectly universal, unbreakable law, then
Speaker 2: the local environment doesn't matter at all. That feels wrong
Speaker 2: to me.
Speaker 3: Why does it feel wrong?
Speaker 2: You are telling me that a molecular cloud sitting near
Speaker 2: the chaotic, radiation soaked, hyper dense core of a galaxy
Speaker 2: operates perfectly identically to a cloud floating out in the quiet, empty,
Speaker 2: dark outer suburbs of a spiral arm. The neighborhood has
Speaker 2: to exert some influence.
Speaker 3: Your instinct is spot on, and that exactly tension is
Speaker 3: what makes modern astrophysics so vibrant. The statement that star
Speaker 3: formation is universal is true in the broad strokes, but
Speaker 3: it is incomplete.
Speaker 2: The devil's in the details.
Speaker 3: Always, And this is exactly why having a sample size
Speaker 3: of twelve two hundred and eighty five clouds is so
Speaker 3: absolutely critical. When you have a data set that massive,
Speaker 3: you aren't just looking at the average trend line anymore.
Speaker 3: You can finally observe the statistical deviation got wire. You
Speaker 3: can see the subtle tweaks, and those subtle deviations prove
Speaker 3: that the galactic environment absolutely does matter.
Speaker 2: Okay, so the core engine is the same, but the
Speaker 2: local environment applies the tuning. What kind of environmental tweaks
Speaker 2: are we talking about here? How does the galaxy mess
Speaker 2: with the cloud?
Speaker 3: The most prominent environmental factor is galactic shear. Galactic shear,
Speaker 3: think about how a galaxy rotates. It isn't a solid
Speaker 3: dinner plate spinning on a stick. The inner parts of
Speaker 3: the galaxy orbit much faster than the outer.
Speaker 2: Parts, right, because they're closer to the center.
Speaker 3: Of mass exactly. So, if you have a giant molecular
Speaker 3: cloud that spans one hundred and fifty light years across
Speaker 3: and it is located somewhat near the galactic center, the
Speaker 3: gravitational pull on the side of the cloud closest to
Speaker 3: the core is significantly stronger than the pole on the far.
Speaker 2: Side of the cloud, because the inner edge is physically
Speaker 2: closer to the supermassive black hole and all the dense stars.
Speaker 3: Exactly, this differential gravity, the sheer force physically pulls on
Speaker 3: the cloud. It stretches it. It actively elongates the gas, pulling
Speaker 3: it out of a spherical shape into a sneered oval.
Speaker 2: It's like stretching caffee.
Speaker 3: Yes. And it can also induce massive violent rotation into
Speaker 3: the cloud structure itself.
Speaker 2: So the galaxy is literally kneading the cloud like bread dough.
Speaker 3: It is, and the deep galactic potential, the overall gravitational
Speaker 3: field of the galaxy center can drive external energy directly
Speaker 3: into the cloud. This forces the internal velocity dispersion we
Speaker 3: talked about to spike wildly.
Speaker 2: It makes it more turbulent, much more.
Speaker 3: The ALMA data from NGNGC thirteen eighty seven specifically highlights
Speaker 3: regions exhibiting a extreme supersonic line wits.
Speaker 2: Okay, let's clarify supersonic line wits. We touched on this briefly,
Speaker 2: but it means the gas inside the cloud is literally
Speaker 2: moving faster than the speed of sound.
Speaker 3: Yes.
Speaker 2: Now, on Earth at sea level, the speed of sound
Speaker 2: is about seven hundred and sixty miles per hour. But
Speaker 2: I assume the speed of sound in a molecular cloud
Speaker 2: at minus four hundred and forty degrees fahrenheit is vastly different.
Speaker 3: It is vastly slower. In a ten kelvin molecular gas,
Speaker 3: the speed of sound is only a fraction of a
Speaker 3: kilometer per second.
Speaker 2: Okay, so it's very low barred across.
Speaker 3: But the gas inside these clouds is churning at several
Speaker 3: kilometers per second. It is perpetually, constantly breaking the sound barrier.
Speaker 2: So the inside of this cloud is just a continuous,
Speaker 2: violent network of sonic booms. It's a chaotic storm of
Speaker 2: shockwaves just crashing into each other over and over.
Speaker 3: It is absolute chaos, yes, but it is a highly
Speaker 3: productive chaos, productive hound. Remember the filamentary rivers we discussed
Speaker 3: the plumbing. Those filaments are physically carved out by these
Speaker 3: intersecting supersonic shockways. When two shockwaves collide, they violently compress
Speaker 3: the gas between them, creating a dense threadlike river.
Speaker 2: So the shockwaves build the rivers.
Speaker 3: This filamentary accretion is the cosmic plumbing system in action.
Speaker 3: The severe turbulence actually acts as a support mechanism, preventing
Speaker 3: the entire million solar mass cloud from collapsing all at
Speaker 3: once in a catastrophic freefall, while simultaneously forcing gas down
Speaker 3: the narrow filaments to feed the dense cores.
Speaker 2: Okay, let's just step back for a second and look
Speaker 2: at the picture we've painted here. Yeah, because it's a lot.
Speaker 3: It's a very complex system.
Speaker 2: You have a massive structure one hundred late years across.
Speaker 2: It possesses the gravity of a million suns. It has
Speaker 2: highly organized, dense cores acting as literal wounds. It has
Speaker 2: supersonic shockwaves carving out rivers to efficiently funnel raw fuel
Speaker 2: directly into the ignition zones. When you describe the mechanics
Speaker 2: like that, a giant molecular cloud sounds like the most
Speaker 2: ruthlessly efficient factory ever conceived. You would expect it to
Speaker 2: just rapidly convert all of that million solar mass gas
Speaker 2: into a million stars in a brilliant flash of causing productivity.
Speaker 3: You would certainly expect that.
Speaker 2: But the reality is the exact opposite, isn't it.
Speaker 3: This is one of the most counterintuitive and arguably the
Speaker 3: most crucial facts about galactic evolution. Starbirth is staggeringly inefficient.
Speaker 2: Despite millions of solar masses of raw.
Speaker 3: Fuel, despite gravity working tirelessly to crush it altogether. Yes,
Speaker 3: the factory is by most metrics of failure.
Speaker 2: How much of a failure if I have a cloud
Speaker 2: with one million solar masses of pristine hydrogen gas, how
Speaker 2: many solar masses actually become stars?
Speaker 3: The standard metric across astrophysics, which the NNGC thirteen eighty
Speaker 3: seven data strongly supports, is the one to ten percent rule.
Speaker 2: One to ten percent of the.
Speaker 3: Total initial mass of a giant molecular cloud, only about
Speaker 3: one percent to ten percent actually successfully condenses to form
Speaker 3: a star.
Speaker 2: That is just That is the ultimate AHA paradox to me.
Speaker 2: You have the perfect factory. You have a million tons
Speaker 2: of raw material ready to go on the assembly line,
Speaker 2: and before the shift is over, ninety ninety nine percent
Speaker 2: of the raw material is just thrown out the window
Speaker 2: into the void unused. It doesn't get used. Why what
Speaker 2: on Earth is powerful enough to stop a million son's
Speaker 2: worth of gravity from finishing the job.
Speaker 3: The only thing powerful enough to stop a star factory
Speaker 3: is a star.
Speaker 2: Okay, Now that sounds like poetry.
Speaker 3: It's physics. The phenomenon is called stellar feedback.
Speaker 2: Stellar feedback, let's delve deep into the destruction of the cloud.
Speaker 2: How do the stars destroy their own cradle?
Speaker 3: It primarily comes down to timing and mass. When a
Speaker 3: cloud begins to fragment and collapse. It does not create
Speaker 3: a million identical stars all at exactly the same time.
Speaker 2: Hi it's not perfectly synchronized.
Speaker 3: The mass of the newly born stars follows a distribution
Speaker 3: called the initial mass function. This function dictates that while
Speaker 3: the cloud will create thousands of tiny, dim red dwarf stars,
Speaker 3: it will also create a tiny handful of absolute monsters
Speaker 3: to heavyweights of the universe, the O type and early
Speaker 3: B type stars. These stars are tens or even hundreds
Speaker 3: of times more massive than our.
Speaker 2: Sun, and because they are so massive.
Speaker 3: Their core temperatures are unimaginably hot. The moment nuclear fusion
Speaker 3: ignites in the core of an O type star, it
Speaker 3: unleashes a cataclysmic torrent of energy directly into the surrounding cloud.
Speaker 2: So the moment the factory turns on, the machinery immediately
Speaker 2: starts melting.
Speaker 3: Literally melting. The first phase of destruction is radiation. These
Speaker 3: massive stars emit blistering lethal levels of ultraviolet radiation UV light.
Speaker 3: This UV light slams into the freezing cold molecular hydrogen
Speaker 3: that surrounds the star. The radiation is so intense that
Speaker 3: it physically strips the electrons off the hydrogen molecules, dissociating
Speaker 3: the H two back into single atoms and then completely
Speaker 3: ionizing them.
Speaker 2: Oh wow, it unmakes the molecules.
Speaker 3: Yes, this creates a rapidly expanding bubble of superheated plasma
Speaker 3: called an HII region. The freezing ten kelvin gas is
Speaker 3: suddenly flash heated to ten thousand kelvin.
Speaker 2: So the baby stars are literally vaporizing their own food source.
Speaker 3: They absolutely are. But the UV radiation is just the
Speaker 3: opening act of the destruction.
Speaker 2: There's more.
Speaker 3: Oh. Yes, These massive stars also generate ferocious stellar.
Speaker 2: Winds, like solar winds, but bigger.
Speaker 3: Much bigger. These are continuous streams of charged particles blowing
Speaker 3: off the star's surface at millions of miles per hour.
Speaker 3: These winds act like a cosmic hurricane, physically slamming into
Speaker 3: the dense gas of the cloud and violently pushing it outward,
Speaker 3: physically clearing out the factory.
Speaker 2: Floor, just sweeping the gas away. And because these supermassive
Speaker 2: O type stars burn so hot, they burn through their
Speaker 2: nuclear fuel incredibly fast. Right, They don't live for billions
Speaker 2: of years like our sun, not at all.
Speaker 3: They live fast and die young. An O type star
Speaker 3: might only live for three to five million years.
Speaker 2: In galactic terms. That is literally the blink of an eye.
Speaker 3: It is nothing. And when they run out of fuel,
Speaker 3: they do not go quietly. They die in spectacularly violent
Speaker 3: supernova explosions.
Speaker 2: And that's the finale.
Speaker 3: The shockwave from a supernova travels outward at thousands of
Speaker 3: kilometers per second. When that shockwave hits the remaining structure
Speaker 3: of the giant molecular cloud, it is the final death blow.
Speaker 2: The blast physically rips the cloud apart.
Speaker 3: Violently ejecting the remaining ninety percent of the unconsumed pristine
Speaker 3: molecular gas back out into the interstellar medium.
Speaker 2: The cradle is just completely shattered. The factory is permanently
Speaker 2: shut down before it could even finish processing its raw inventory.
Speaker 2: That is just an incredibly poetic but violent image.
Speaker 3: It is the brutal reality of star formation.
Speaker 2: And I imagine that having this exhaustive catalog of two
Speaker 2: hundred and eighty five clouds from NGNGC thirteen eighty seven
Speaker 2: gives astrophysicists the exact tool they need to study this
Speaker 2: battle between gravity and stellar feedback.
Speaker 3: Right it serves as the ultimate forensic laboratory because we
Speaker 3: now have a comprehensive map of all the gas clouds
Speaker 3: in the galaxy. And we can also use optical telescopes
Speaker 3: to see exactly where the young, brightly growing stellar clusters are.
Speaker 3: We can match them up.
Speaker 2: Oh, you can overlay them out exactly.
Speaker 3: Astronomers can look at a specific cloud, measure its mass,
Speaker 3: its surface density, and its urial parameter with ALMA, and
Speaker 3: then look with an optical telescript to see if a
Speaker 3: star cluster has ignited inside it yet.
Speaker 2: So you can see the before, during, and after.
Speaker 3: By looking at hundreds of these regions at various stages
Speaker 3: of their life cycle, researchers can essentially watch a time
Speaker 3: lapse of the destruction. They can test incredibly complex theoretical
Speaker 3: models to see exactly how many million years it takes
Speaker 3: for a cluster of massive stars to entirely disassemble a
Speaker 3: giant molecular cloud.
Speaker 2: Okay, so the massive stars throw a tantrum, they go supernova,
Speaker 2: and they blast ninety percent of the cloud's gas back
Speaker 2: out into the void. Right, But that gas doesn't just disappear.
Speaker 2: The factory is destroyed, but the raw material survives. It
Speaker 2: gets pushed somewhere else. It feels like This is the
Speaker 2: exact moment we really need to zoom out from the
Speaker 2: individual cloud, look at the macro picture. How does this
Speaker 2: endless cycle impact the entire galaxy.
Speaker 3: Zooming out is absolutely essential here because giant molecular clouds
Speaker 3: are not just isolated local phenomena that live and die
Speaker 3: without consequence. They are the primary engines of evolution for
Speaker 3: the entire galaxy.
Speaker 2: The engines of evolution.
Speaker 3: You can accurately think of the total molecular gas reservoir
Speaker 3: as the fuel gauge for a galaxy's lifespan.
Speaker 2: The fuel gauge, so as long as there is molecular gas,
Speaker 2: the galaxy is alive.
Speaker 3: Yes, the availability of this gas, how it is distributed
Speaker 3: across the spiral arms, and crucially, the rate at which
Speaker 3: it is consumed and destroyed totally dictates the morphological evolution
Speaker 3: of the galaxy over billions of years.
Speaker 2: It dictates its shape, its shape.
Speaker 3: Its brightness, everything. It also dictates the entire history of
Speaker 3: its chemical enrichment.
Speaker 2: Let's really focus on that chemical enrichment for a second,
Speaker 2: because this is where the cosmic recycling program comes in.
Speaker 2: The phrase astronomers use is metallicity, right, Yes, metallicity which
Speaker 2: is deeply confusing to lay people. Yeah, because to an astronomer,
Speaker 2: literally anything heavier than helium is considered a metal.
Speaker 3: It's a very old quirk of astronomical terminology, I admit,
Speaker 3: but the concept is crucial. During the Big Bang, the
Speaker 3: universe essentially only produced hydrogen and a bit of helium.
Speaker 2: Nothing else.
Speaker 3: Nothing else. Every single heavier element carbon, oxygen, nitrogen, iron, silicon,
Speaker 3: every single one of them had to be forged later
Speaker 3: inside the burning cores of massive stars.
Speaker 2: So when that O type star we just talked about
Speaker 2: reaches the end of its life and explodes into supernova,
Speaker 2: it doesn't just blow away the original hydrogen cloud.
Speaker 3: No, it violently ejects all of those newly forged heavy
Speaker 3: elements out into the interstellar medium along with the gas.
Speaker 2: It seeds the galaxy with the good stuff exactly.
Speaker 3: That newly enriched gas, now carrying traces of carbon and oxygen,
Speaker 3: drifts through the galaxy. Eventually, over millions of years, it
Speaker 3: gets swept up again, cools down, and forms a brand
Speaker 3: new giant molecular cloud.
Speaker 2: But this new cloud has a slightly higher metallicity than
Speaker 2: the one before.
Speaker 3: It, Right, it has more trace elements and the next
Speaker 3: generation of stars that form from this cloud will have
Speaker 3: more heavy elements built into them. It is an endless,
Speaker 3: billion year cycle of cosmic recycling, slowly enriching the galaxy
Speaker 3: generation after generation, and.
Speaker 2: The physical shape of the galaxy plays a massive role
Speaker 2: in how this gas is moved around and recycled.
Speaker 3: Right, the shape is incredibly important.
Speaker 2: Let's go back to n GC thirteen eighty seven. We
Speaker 2: mentioned at the very beginning that it is a barred spiral.
Speaker 2: Our Milky Way is also a barred spiral. Let's explain
Speaker 2: what that bar actually does to the gas. It isn't
Speaker 2: just a static, pretty shape in the center of the galaxy,
Speaker 2: is it not at all?
Speaker 3: The central bar of a galaxy, which is a dense,
Speaker 3: elongated structure of older stars cutting right through the galactic core,
Speaker 3: is a highly dynamic physical funnel well funnel. The physics
Speaker 3: of how gas orbits within a galaxy are complex. In
Speaker 3: a normal unbarred spiral disc, gas clouds orbit and relatively stable,
Speaker 3: mostly circular paths, but the intense asymmetrical gravitational field of
Speaker 3: the central bar acts like a break.
Speaker 2: It disrupts the orbit.
Speaker 3: It creates torque that actively rob the giant molecular clouds
Speaker 3: of their angular momentum.
Speaker 2: Meaning the clouds can no longer maintain their stable circular orbits.
Speaker 3: Precisely because they lose their orbital momentum, the gas clouds
Speaker 3: are literally forced to migrate. They funnel steadily inward, sliding
Speaker 3: down the gravitational well toward the absolute center of the galaxy.
Speaker 2: So the bar is literally a conveyor belt relentlessly dumping
Speaker 2: millions of solar masses of cold gas directly into the
Speaker 2: galactic core. What happens when all that gas piles up
Speaker 2: in the center.
Speaker 3: The results are spectacular. The immense concentration of molecular gas
Speaker 3: in the central region can trigger violent, massive bursts of
Speaker 3: star formation, completely changing the luminosity of the galactic core.
Speaker 2: It lights up.
Speaker 3: It lights up tremendously, but more profoundly. If the galaxy
Speaker 3: hosts a supermassive black hole at its absolute center, this
Speaker 3: bar driven funneling of molecular clouds is exactly the mechanism
Speaker 3: required to feed.
Speaker 2: It, because the black hole needs fuel too.
Speaker 3: Yes, when the black hole consumes this gas, it unleashes
Speaker 3: staggering amounts of energy, transforming the core into an active
Speaker 3: galactic nucleus. Or agn. The radiation from an agn can
Speaker 3: be so intense that it outshines the rest of the
Speaker 3: galaxy combined.
Speaker 2: So by mapping the kinematics of the clouds in NNGC
Speaker 2: Thirteen eighty seven, we are literally watching the physical mechanism
Speaker 2: that dictates whether a supermassive black hole starves or feeds.
Speaker 3: We are watching the feeding tube.
Speaker 2: It is just incredible how interconnected it all is. A
Speaker 2: cloud forms, it makes stars, the stars blow it up.
Speaker 2: The bar funnels the remnants to the black hole. But
Speaker 2: there is another layer to this entirely. You mentioned earlier
Speaker 2: that mapping these relatively local galaxies like foreign acts at
Speaker 2: sixty million light years is essential for a completely different
Speaker 2: field of astronomy.
Speaker 3: Yes, cosmology.
Speaker 2: It helps us look at the dawn of time. How
Speaker 2: does studying a modern factory help us understand the early universe?
Speaker 3: It acts as a totally necessary calibration tool. Right now,
Speaker 3: modern astronomy is obsessed with pushing our observational boundaries as
Speaker 3: well far back as physically possible.
Speaker 2: We want to see the beginning.
Speaker 3: We want to see the epoch of reionization. We want
Speaker 3: to look back over thirteen billion years and see the
Speaker 3: very first primordial galaxies forming out of the dark ages
Speaker 3: of the early universe.
Speaker 2: And we are building insane new machines to do this.
Speaker 3: Yes, mega facilities are coming online in the coming decades,
Speaker 3: like the next generation very large array, the NGVLA or
Speaker 3: the square kilometer array of the sk These arrays will
Speaker 3: be vast, spanning entire continents.
Speaker 2: Cotton in size telescopes.
Speaker 3: It's wild, but there is a fundamental limit to observation.
Speaker 3: When these future super telescopes capture a radio signal from
Speaker 3: a galaxy that is thirteen billion light years away, that
Speaker 3: signal is going to be incredibly faint, and the spatial
Speaker 3: resolution will be.
Speaker 2: Poor because it's so unimaginally far away. Even with a
Speaker 2: telescope the size of a continent, the early galaxy is
Speaker 2: just going to look like a few blurry pixels of data.
Speaker 3: On a screen exactly. They will not be able to
Speaker 3: see the fine details. They won't see individual giant molecular
Speaker 3: clouds like we do in format. They will just see
Speaker 3: a faint, generalized smudge of carbon monoxide emission.
Speaker 2: So if it's just a smudge, the critical question for
Speaker 2: an astronomer is, how do you know what physical processes
Speaker 2: are actually happening inside that blurry smudge.
Speaker 3: Right, you need a decoder ring. A decoder ring, you
Speaker 3: need a gold standard template, and that is exactly what
Speaker 3: the NGC thirteen eighty seven data set provides. By exhaustively
Speaker 3: mapping the two hundred and eighty five clouds in our
Speaker 3: local universe at high resolution, we understand the exact mechanics.
Speaker 2: You know how it works locally.
Speaker 3: We know exactly how the total gas mask correlates to
Speaker 3: the rate of star formation. We know how the internal
Speaker 3: velocity dispersion behaves. So when a future astronomers look at
Speaker 3: that blurry smudge from the dawn of time, they will
Speaker 3: apply the mechanical rules we learned from NGC thirteen eighty seven.
Speaker 3: They will extrapolate our local high fidelity knowledge to interpret
Speaker 3: the physics of the primordial universe.
Speaker 2: That is a brilliantly practical scientific strategy. We basically spend
Speaker 2: years perfectly apping out the mechanics of the engine sitting
Speaker 2: in our neighbor's driveway. We learn every valve, every piston,
Speaker 2: so that when we see a blurry engine racing on
Speaker 2: the other side of the planet through a para binoculars,
Speaker 2: we already know exactly how it works inside.
Speaker 3: That is exactly what we're doing.
Speaker 2: But before we crown LMA as the flawless, omniscient god
Speaker 2: of astronomy, we really have to talk about the blind spots.
Speaker 2: Because as perfect as this twelve and eighty five cloud
Speaker 2: data set scenes, the methodology actually has a glaring flaw.
Speaker 2: LMA doesn't see everything.
Speaker 3: That is a vital caveat, and it is something astronomers
Speaker 3: have to rigorously mathematically account for. No instrument in existence
Speaker 3: is perfect, and interferometers like LMA suffer from a very
Speaker 3: specific structural blind spot.
Speaker 2: The fundamenta comes down to how the mathematics of synthesizing
Speaker 2: a virtual telescope works. Doesn't it it does.
Speaker 3: It goes back to the baselines, the physical distance between
Speaker 3: the sixty six antenna dishes sitting out in the desert.
Speaker 3: Explain that because LMA uses the distance between its antennas
Speaker 3: to achieve its razor sharp ultra high resolution, the instrument
Speaker 3: is highly optimized to detect small, distinct, high contrast structures.
Speaker 2: It likes sharp edges.
Speaker 3: Yes, it is phenomenally good at seeing the dense molecular
Speaker 3: cores and the sharp filamentary rivers. But the mathematical process
Speaker 3: of cross correlating the signals essentially acts as a spatial
Speaker 3: filter in the Fourier plane.
Speaker 2: Okay, let's break that down with an analogy, because Fourier
Speaker 2: planes can get incredibly denser. People, Please do imagine you
Speaker 2: have a highly specialized, perfectly focused macro camera lens. Yeah,
Speaker 2: you pointed at a massive oak tree. The lens is
Speaker 2: so specifically designed to capture fine detail that it takes
Speaker 2: a flawless, incredibly sharp picture of the individual veins on
Speaker 2: a single leaf. Right. But because it is so hyper
Speaker 2: focused on the sharp edges, it physically cannot record the massive, smooth,
Speaker 2: vast blue sky sitting directly behind the leaf. The sky
Speaker 2: has no sharp contrast, so the lens just zeros it out.
Speaker 2: The sky becomes invisible in the data.
Speaker 3: That does a highly accurate way to visualize it. In
Speaker 3: radio astronomy, this is known as the missing flux problem.
Speaker 2: Missing flux giant.
Speaker 3: Molecular clouds do not just exist in a vacuum. They
Speaker 3: are often surrounded by and embedded within, vast, smoothly distributed,
Speaker 3: highly diffuse envelopes of gas that span across the.
Speaker 2: Galactic arms, and Alma misses it.
Speaker 3: Because this gas is smooth and lacks sharp contrast. Alima's
Speaker 3: high resolution array simply filters it out. It doesn't see it.
Speaker 2: Which means if you just look at the ALMA data alone,
Speaker 2: you might be missing a massive chunk of the galaxy's
Speaker 2: total fuel supply.
Speaker 3: You absolutely are a significant percentage of the total molecular
Speaker 3: gas in NGNGC thirteen eighty seven might not be locked
Speaker 3: up in the dense, easily visible GMCs. It might be
Speaker 3: out in that diffuse, invisible component.
Speaker 2: So how do you fix that?
Speaker 3: To capture that missing piece of the puzzle and to
Speaker 3: get the true total gas mass of the galaxy, a
Speaker 3: dronomers cannot rely on LMA alone. They had to combine
Speaker 3: LMA's high resolution maps with separate observations from large single
Speaker 3: dish telescopes.
Speaker 2: Because single dish works differently.
Speaker 3: A single dish telescope doesn't have the sharpness to see
Speaker 3: the cores, but it is excellent at measuring the total
Speaker 3: broad brush brightness of the diffuse sky. By merging the
Speaker 3: two data sets, you finally get the complete picture.
Speaker 2: So there is still heavy lifting to do just to
Speaker 2: count the basic gas mass. But there is another frontier
Speaker 2: here that we only briefly touched on. At the very
Speaker 2: beginning of the show, and I really want to dive
Speaker 2: deep into it because it borders on astrobiology and chemistry.
Speaker 2: The chemistry we mentioned that these clouds are mostly hydrogen
Speaker 2: with the trace of carbon monoxide dye, but there are
Speaker 2: other things hiding in the dark, complex organic molecules comms.
Speaker 3: Yes, and this is arguably one of the most exciting
Speaker 3: and rapidly expanding fields in modern astrophysics astrochemistry. It turns
Speaker 3: out that giant molecular clouds are not just cold storage units.
Speaker 3: They are highly active chemical laboratories.
Speaker 2: But wait, how we just established that the core of
Speaker 2: the cloud is ten kelvin. It is minus four hundred
Speaker 2: and forty degrees. At that temperature, chemical reactions should basically
Speaker 2: be frozen solid. There's no heat to drive the chemistry.
Speaker 3: That was the assumption for a very long time. Gas
Speaker 3: phase chemistry, where two atoms bump into each other in
Speaker 3: the void and bond is incredibly slow at these temperatures. Right,
Speaker 3: But the key is the dust. Remember the microscopic grains
Speaker 3: of silicate and carbon suit we mentioned earlier.
Speaker 2: The one percent of the cloud.
Speaker 3: Yes, these dust grains are the secret catalysts.
Speaker 2: How does dust change the chemistry in a freezing cloud.
Speaker 3: In the freezing depths of the cloud, stray atoms of oxygen, carbon,
Speaker 3: and nitrogen drift around until they collide with a grain
Speaker 3: of dust. When they hit the dust, they stick to it.
Speaker 2: They freeze to the surface.
Speaker 3: Over thousands of years, the dust grain becomes coated in
Speaker 3: a microscopic mantle of ice, and not just water ice,
Speaker 3: but frozen ammonia, frozen methane, and frozen carbon monoxide.
Speaker 2: It's like a tiny snowball of chemicals.
Speaker 3: The surface of the dust grain acts as a tiny
Speaker 3: work bench. The atoms are trapped closely together on the surface,
Speaker 3: allowing them to interact and form much more complex bonds.
Speaker 2: But they still need an energy to react, don't they.
Speaker 2: Where does the spark come from if there are no
Speaker 2: stars yet.
Speaker 3: The energy comes from cosmic rays. Cosmic rays these are
Speaker 3: high energy protons zipping through the galaxy at nearly the
Speaker 3: speed of light. They penetrate deep into the dark cloud
Speaker 3: and slam directly into the ice mantles.
Speaker 2: On the dust grains like tiny bullets.
Speaker 3: Exactly the impact of a cosmic ray shatters the simple
Speaker 3: molecules in the ice, creating highly reactive free radicals. These
Speaker 3: radicals immediately combine to form complex organic molecules.
Speaker 2: Even at minus four hundred and forty degrees.
Speaker 3: Through this exact process, even in the absolute freezing vacuum
Speaker 3: of space, these clouds are synthesizing molecules like methanol, ethanol,
Speaker 3: dimethyl ether, and formamide formamide.
Speaker 2: Wait, those are the precursors. Those are the literal chemical
Speaker 2: building blocks of amino acids.
Speaker 3: Exactly, they are the foundation of prebiotic chemistry. These giant
Speaker 3: molecular clouds are pre baking the ingredients for life, long
Speaker 3: before a planet ever even exists. When the cloud eventually
Speaker 3: collapses to form a star, a swirling disk of leftover
Speaker 3: gas and dust forms around the new Sun. That protoplanetary
Speaker 3: disk eventually clumps together to form planets, and it brings
Speaker 3: those pre baked complex organic molecules with it, delivering.
Speaker 2: Them directly to the surface of the new world. Precisely so,
Speaker 2: the alcohol, the sugars the building blocks of RNA. They
Speaker 2: are forged on the warm surface of a planet. They're
Speaker 2: forged in the freezing, violent dark of the molecular cloud.
Speaker 2: And LMA can see these molecules.
Speaker 3: It can a lemma has been revolutionary for local astrochemistry.
Speaker 3: It has detected dozens of complex organic molecules in giant
Speaker 3: molecular clouds inside our own Milky Way.
Speaker 2: So what's next?
Speaker 3: The next great frontier, the bleeding edge of this science
Speaker 3: is extragalactic chemistry.
Speaker 2: Taking LMA and pointing it at the twelve two hundred
Speaker 2: and eighty five clouds in NGNGC thirteen eighty seven and
Speaker 2: looking for the building blocks of life sixty million light
Speaker 2: years away.
Speaker 3: Precisely, we want to know how the chemical makeup of
Speaker 3: these clouds varies across different galactic environments. Does a molecular
Speaker 3: cloud located near the violent, radiation heavy center of a
Speaker 3: Barred's spiral galaxy produce more or fewer complex organics than
Speaker 3: a quiet, isolated cloud floating out in the outer disk.
Speaker 2: That's a huge question.
Speaker 3: Are certain regions of a galaxy chemically more suited to
Speaker 3: eventually harboring biological life. Mapping the extragalactic distribution of comms
Speaker 3: is the next major step in understanding our place in
Speaker 3: the universe, And.
Speaker 2: As we look to the future, ALMA isn't going to
Speaker 2: be operating in a vacuum anymore. We are currently entering
Speaker 2: the Golden Age of observational astronomy. Because LMA now has
Speaker 2: the ultimate tag team partner sitting out in space.
Speaker 3: You are referring to the James Web Space Telescope JWST.
Speaker 2: Yes, JWST. The synergy between LMA and JWST is poised
Speaker 2: to completely revolutionize our understanding of star formation physics over
Speaker 2: the next decade.
Speaker 3: It absolutely is.
Speaker 2: Let's explicitly lay out why they are such a perfect
Speaker 2: pairing because they look at completely different things.
Speaker 3: Right, They are completely complementary, precisely because they operate in
Speaker 3: totally different realms of the electromagnetic spectrum.
Speaker 2: Let's review. ALMA does millimeter waves right.
Speaker 3: As we've discussed extensively, ALMA operates in the millimeter and
Speaker 3: submillimeter wavelengths. It is the undisputed master of mapping the
Speaker 3: cold gas. It sees the invisible hydrogen via the carbon
Speaker 3: monoxide dye.
Speaker 2: It maps the kinematics, the turbulence the filamentary rivers exactly.
Speaker 3: LMA shows us the raw ingredients and the mixing bowl
Speaker 3: of the giant molecular cloud before and during the collapse.
Speaker 2: But JAWST is an infrared telescope. It looks for heat.
Speaker 3: Yes, JWST is specifically designed to capture infrared radiation while
Speaker 3: ALMA is mapping the freezing cold gas on the outside.
Speaker 3: JAWST can peer right through the dense, opaque dust of
Speaker 3: the core to see the heat of the warm glowing
Speaker 3: objects buried deep inside. So you point them at the
Speaker 3: exact same spot exactly, So LMA can look at a
Speaker 3: specific core in NNGC thirteen eighty seven and tell us
Speaker 3: exactly how fast the cold gas is collapsing inward. SIMULTANEOUSLYBST
Speaker 3: can look at the exact same coordinates and image the
Speaker 3: brightly glowing emerging protostar that is just igniting in the center.
Speaker 2: Wow.
Speaker 3: LM maps the gas falling in and JWST maps the
Speaker 3: radiation and stellar winds pushing the gas back out.
Speaker 2: It's like LMA shows up the dough being needed and
Speaker 2: JWST peers into the oven to show us the final
Speaker 2: baked cake as it rises. Together, they provide astronomers with
Speaker 2: a near complete, end to end high resolution picture of
Speaker 2: the entire cosmic assembly line.
Speaker 3: It truly is a golden age when we pull all
Speaker 3: these disparate threads together, the fractal power laws, the supersonic turbulence,
Speaker 3: the inefficient stellar feedback, the chemistry on the dust grains,
Speaker 3: the galact procycling. The resulting perspective is just profoundly humbling.
Speaker 2: Humbling is the right word.
Speaker 3: Giant molecular clouds are not just inert, cold voids sitting
Speaker 3: in the background of the universe. They are the vital, churning,
Speaker 3: dynamic laboratories of the cosmos. Every single heavy element forged
Speaker 3: in the nuclear furnaces of dying stars billions of years
Speaker 3: ago eventually find its way into the dark belly of
Speaker 3: a giant molecular cloud.
Speaker 2: To be reused.
Speaker 3: Yes, the cloud gathers those elements, compresses them through a
Speaker 3: chaotic network of supersonic shock waves, laces them with the
Speaker 3: chemical precursors to life, and recycles them into new suns
Speaker 3: and new planetary systems.
Speaker 2: It is the great billion year engine of cosmic evolution.
Speaker 2: If you are listening to this right now, I genuinely
Speaker 2: hope that the next time you walk outside and look
Speaker 2: up at the stars, the sky looks completely different to you.
Speaker 2: I hope so too, because we as a species now
Speaker 2: possess the sheer technological audacity to build a robotic supercomputing
Speaker 2: eye on top of a freezing desert mountain pier sixty
Speaker 2: million light years across the void and map out the
Speaker 2: exact violent machinery that builds the universe. We can literally
Speaker 2: catalog the wombs of the next generation of stars.
Speaker 3: It's an incredible achievement.
Speaker 2: But I want to leave you with one final, deeply
Speaker 2: personal thought to turn over in your mind. If it
Speaker 2: is true that these massive dark clouds are the great
Speaker 2: recyclers of the cosmos, If every single heavy element in
Speaker 2: your body right now, the iron carrying oxygen in your blood,
Speaker 2: the calcium fortifying your bones, the carbon that makes up
Speaker 2: your very DNA, was once gathered up, frozen, and churned
Speaker 2: through the violent, turbulent heart of a giant molecular cloud,
Speaker 2: exactly like the twelve two hundred and eighty five we
Speaker 2: just mapped in n GC thirteen eighty seven. We are
Speaker 2: part of that cycle, then, aren't we, as conscious beings
Speaker 2: building city sized telescopes to look back at the stars
Speaker 2: simply the universe's way of finally turning around to look
Speaker 2: at its own birthplaces. We are the stardust looking back
Speaker 2: at the factory. And if that is the case, it
Speaker 2: begs a really fascinating question. What might an astronomer sitting
Speaker 2: on a rocky planet sixty million light years away in
Speaker 2: four nex, pointing their own version of LMA directly at
Speaker 2: the Milky Way. Be seeing in our clouds right now,