# A Young Solar System Reveals How Comets Could Seed Planets With Water

An episode of [Bedtime Astronomy](https://invisiblenetwork.ai/podcast/1736397134), 11 Sep 2026, 24 min.

Audio: https://dts.podtrac.com/redirect.mp3/api.spreaker.com/download/episode/74859125/cometsp.mp3

Astronomers have discovered exocomets orbiting the young star PDS 70, offering a rare glimpse into planetary systems during their formation. Their inward migration may reveal how comets transported water and other essential ingredients toward developing planets—and perhaps how similar processes shaped the early Earth. Thank you for listening to Bedtime Astronomy — your guide to the cosmos. New episodes on space exploration, NASA missions & the latest astronomy breakthroughs. This episode includes AI-generated content.

## Transcript

[0:03] Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
[0:07] Speaker 1: with our soothing Bedtime Astronomy podcast. Each episode offers a
[0:12] Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
[0:16] Speaker 1: unwinding after a long day. Let's travel through the mysteries
[0:20] Speaker 1: of the universe as you drift off into a peaceful
[0:22] Speaker 1: slumber under the night sky.
[0:27] Speaker 2: You know, it's funny how we look at a glass
[0:29] Speaker 2: of water or like the vast oceans that cover 70
[0:32] Speaker 2: percent of our planet. And we just kind of accept
[0:35] Speaker 2: it as this completely ordinary part of the world.
[0:37] Speaker 3: Oh, absolutely. We take it totally for granted every single day. Right.
[0:41] Speaker 2: But we rarely stop to think about the sheer mechanical
[0:45] Speaker 2: absurdity of that water even being here. Because if you
[0:47] Speaker 2: roll the clock back about four and a half billion
[0:50] Speaker 2: years to when the Earth was first forming, our planet
[0:53] Speaker 2: was essentially this glowing hot molten rock.
[0:56] Speaker 3: Yeah, turbulent, searing, hot furnace. Just a chaotic, violent environment.
[1:01] Speaker 2: Exactly. So you're forced to ask this fundamental question. Where
[1:05] Speaker 2: did Earth's oceans actually come from? How on Earth did
[1:08] Speaker 2: this delicate, life-sustaining liquid arrive on a newly formed planet
[1:12] Speaker 2: without just, you know, instantly boiling off into the infinite
[1:15] Speaker 2: void of space?
[1:16] Speaker 3: It's wild to think about, and it remains one of
[1:18] Speaker 3: those compelling paradoxes in planetary science. Because a young terrestrial
[1:23] Speaker 3: planet Well, it's incredibly hostile. The surface temperatures are extreme.
[1:26] Speaker 3: You have this young sun blasting the inner system with
[1:30] Speaker 3: intense solar winds.
[1:31] Speaker 2: Right, which sounds like a terrible place for water.
[1:33] Speaker 3: It is the absolute last place you would expect to
[1:36] Speaker 3: find volatile substances like liquid water just hanging around. Because
[1:40] Speaker 3: any original water present during the Earth's violent accretion phase,
[1:44] Speaker 3: it would have been vaporized, just completely stripped away.
[1:47] Speaker 2: So mathematically, you're required to find a delivery mechanism. The
[1:52] Speaker 2: planet had to be restocked somehow.
[1:55] Speaker 3: Precisely. There had to be a cosmic supply chain that
[1:58] Speaker 3: brought the water in much later after the surface began
[2:01] Speaker 3: to cool down. And it had to arrive in a
[2:03] Speaker 3: format that actually protected that water during transit.
[2:07] Speaker 2: And uncovering that specific supply chain is our central mission today.
[2:11] Speaker 2: We are looking at a recent groundbreaking discovery in astronomy
[2:14] Speaker 2: that essentially functions as like a time machine. It allows
[2:17] Speaker 2: us to watch this restocking process happen in real time.
[2:20] Speaker 3: Which is incredibly rare.
[2:21] Speaker 2: Yeah, it's amazing. We are traveling to a distant infant
[2:24] Speaker 2: planetary system called PDS-70, but analyzing the activity around this
[2:29] Speaker 2: specific star, we're basically watching a live-action prequel to our
[2:32] Speaker 2: own solar system.
[2:33] Speaker 3: Getting a chance to witness firsthand how massive, icy comets
[2:38] Speaker 3: might act as these heavy-duty cosmic delivery trucks, actively transporting
[2:42] Speaker 3: water across the void to forming planets.
[2:45] Speaker 2: Okay, let's unpack this. Hmm. Because to really understand the
[2:48] Speaker 2: physics of this delivery mechanism, we first need to get
[2:51] Speaker 2: a clear picture of the destination itself. Right. We have
[2:54] Speaker 2: to travel 370 light years away and really set the
[2:57] Speaker 2: scene at PDS 70.
[2:59] Speaker 3: So 370 light years. I mean, it's a substantial distance
[3:02] Speaker 3: for a human. Yeah. But in the grand architectural scale
[3:05] Speaker 3: of the Milky Way, it's practically in our galactic backyard.
[3:08] Speaker 2: Just down the street, cosmically speaking? Exactly.
[3:11] Speaker 3: The light we observe from PDS-70 left that system roughly
[3:14] Speaker 3: around the time Galileo was building his very first telescopes.
[3:18] Speaker 3: But what we see when that light finally hits our
[3:20] Speaker 3: modern instruments is a system that is an absolute newborn.
[3:23] Speaker 2: Right.
[3:23] Speaker 3: PDS-70 is only about 5 million years old.
[3:26] Speaker 2: Which is just a cosmic blink of an eye. For context,
[3:28] Speaker 2: if our 4.6 billion-year-old solar system is, say, a middle-aged adult...
[3:33] Speaker 2: PDS-70 is a newborn that was delivered just a few
[3:36] Speaker 2: hours ago. It is still heavily entrenched in its planetary infancy.
[3:39] Speaker 3: Yeah, and the central star itself is actually quite similar
[3:41] Speaker 3: to our own sun, just slightly cooler and a bit
[3:44] Speaker 3: less massive.
[3:45] Speaker 2: Yeah.
[3:45] Speaker 3: But because it's only 5 million years old, it's still
[3:47] Speaker 3: surrounded by this massive circumstellar disk.
[3:50] Speaker 2: That's the swirling chaotic halo of primordial gas and dust, right?
[3:55] Speaker 2: The stuff that hasn't been cleared out or absorbed yet.
[3:58] Speaker 3: Right, exactly. But within that messy disk, Massive structural development
[4:02] Speaker 3: is already underway. We have definitively identified at least two
[4:07] Speaker 3: massive gas giants in there.
[4:09] Speaker 2: Kind of like our Jupiter and Saturn.
[4:11] Speaker 3: Very similar, yeah. And they are actively orbiting that central star,
[4:14] Speaker 3: literally carving massive gaps in the dust cloud as they move.
[4:18] Speaker 2: Okay, so we have a relatively cool sun-like star, a
[4:21] Speaker 2: messy disk of primordial dust, and two massive gas giants
[4:25] Speaker 2: already throwing their weight around. But the major mystery, the
[4:27] Speaker 2: spark that ignited this specific investigation, actually happened back in 2023.
[4:31] Speaker 3: Oh, right. The water vapor detection.
[4:34] Speaker 2: Yes. Astronomers pointed their instruments at PDS-70 and detected the
[4:38] Speaker 2: distinct signature of water vapor. And they didn't just find
[4:41] Speaker 2: it out in the freezing outer edges where you would
[4:43] Speaker 2: expect ice to safely survive.
[4:45] Speaker 3: No, they found it right in the inner part of
[4:47] Speaker 3: the system, relatively close to the star.
[4:49] Speaker 2: Which is the critical inner region where terrestrial rocky planets
[4:54] Speaker 2: like Earth exist. typically form. So think of this young
[4:58] Speaker 2: five million year old system like a massive, messy cosmic
[5:01] Speaker 2: construction site.
[5:02] Speaker 3: I like that analogy.
[5:03] Speaker 2: The raw building materials are scattered everywhere. But that inner
[5:06] Speaker 2: zone right next to the stellar furnace is incredibly hot,
[5:10] Speaker 2: swept by stellar winds and just highly turbulent.
[5:14] Speaker 3: Very hostile.
[5:14] Speaker 2: Right. So if volatile materials like water are out there,
[5:18] Speaker 2: how are they surviving? Or more accurately, since planets form
[5:21] Speaker 2: in these hot, turbulent inner regions, How does water survive
[5:26] Speaker 2: or get there in the first place without boiling away?
[5:28] Speaker 3: What's fascinating here is that catching a five million year
[5:31] Speaker 3: old system in this specific transitional phase is just immensely
[5:35] Speaker 3: valuable to astrophysics. Normally, astronomers are stuck playing historical detective.
[5:41] Speaker 2: Right. Looking at old evidence.
[5:42] Speaker 3: Exactly. We look at mature, stable systems like our own
[5:45] Speaker 3: and try to run the computer models backward. Or we
[5:48] Speaker 3: look at formless, dark molecular clouds and try to guess
[5:52] Speaker 3: how they'll eventually collapse into a star.
[5:54] Speaker 2: So PDS-70 basically removes the guesswork.
[5:57] Speaker 3: It really does. It provides a live-action snapshot of active
[6:00] Speaker 3: planetary development. It gives us the laboratory we need to
[6:03] Speaker 3: literally test our theories about how volatile substances maneuver through
[6:09] Speaker 3: a young, chaotic environment.
[6:10] Speaker 2: It's like the difference between analyzing a finished skyscraper to
[6:13] Speaker 2: guess how the plumbing was installed versus just pulling up
[6:16] Speaker 2: a lawn chair and watching the cranes drop the pipes
[6:19] Speaker 2: into the foundation in real time.
[6:20] Speaker 3: Yeah, it is a perfect way to look at it.
[6:22] Speaker 2: Yeah.
[6:23] Speaker 3: The 2023 detection was a monumental clue, but it was
[6:26] Speaker 3: really only half the puzzle. Detecting water vapor near the
[6:29] Speaker 3: star proved that the water successfully arrived in the inner system.
[6:33] Speaker 2: It told us the destination, but not the journey. Right.
[6:36] Speaker 3: It provided zero mechanical data on how it actually got there.
[6:39] Speaker 3: The water vapor is just the resulting exhaust. To track
[6:43] Speaker 3: the actual transport mechanism to find those cosmic delivery trucks
[6:46] Speaker 3: you mentioned earlier, researchers had to engage in some incredibly
[6:49] Speaker 3: clever observational physics.
[6:51] Speaker 2: And that leads us to the breakthrough from a team
[6:53] Speaker 2: of researchers at Lund University in Sweden. This was led
[6:57] Speaker 2: by astronomy researcher Aline Nové, who published their findings in
[7:01] Speaker 2: Nature Communications.
[7:02] Speaker 3: An absolutely brilliant piece of detective work.
[7:04] Speaker 2: Truly. The brilliance of their approach was that to track
[7:07] Speaker 2: the water, they completely stopped looking for water. Instead, they
[7:10] Speaker 2: hunted for a totally different element, which was sodium.
[7:13] Speaker 3: Yeah, because tracking water vapor directly as it moves dynamically
[7:17] Speaker 3: through a system is notoriously difficult. Water molecules just don't
[7:22] Speaker 3: always leave the cleanest, most visible signatures against the really
[7:25] Speaker 3: complex backdrop of a star's light.
[7:27] Speaker 2: What comets do, right?
[7:29] Speaker 3: Exactly. Comets are those ancient, dirty snowballs made of ice, rock,
[7:33] Speaker 3: and organic dust. They carry a wide cocktail of elements,
[7:36] Speaker 3: and they carry a significant amount of sodium. In the
[7:39] Speaker 3: realm of astrophysics, sodium is an exceptional tracer element.
[7:43] Speaker 2: Because it shows up so clearly. Yeah.
[7:45] Speaker 3: Its atomic structure interacts with starlight in highly specific, aggressively
[7:49] Speaker 3: visible ways.
[7:50] Speaker 2: So Noves and her team went back to the archives.
[7:53] Speaker 2: They analyzed highly detailed spectroscopic observations of PDS 70 taken
[7:58] Speaker 2: back in 2018. And when they analyzed the light from
[8:01] Speaker 2: the star, they found distinct variations in sodium gas.
[8:05] Speaker 3: Moving incredibly fast, too. Right.
[8:07] Speaker 2: Clocking in at several kilometers per second relative to the star.
[8:11] Speaker 2: But the crucial detail wasn't just the speed. It was
[8:13] Speaker 2: the behavior. The sodium gas wasn't a permanent stationary cloud.
[8:18] Speaker 2: It was appearing, lingering, and then completely disappearing over the
[8:23] Speaker 2: course of just a few nights.
[8:24] Speaker 3: And that rapid transient appearance and disappearance is the behavioral
[8:28] Speaker 3: smoking gun. It perfectly mirrors the mathematical models of how
[8:31] Speaker 3: a comet behaves. when it aggressively passes in front of
[8:34] Speaker 3: a star on a highly elliptical orbit, and then just
[8:37] Speaker 3: moves rapidly out of view.
[8:38] Speaker 2: Okay, wait, let me play the step dick for a
[8:40] Speaker 2: second because we need to bridge a gap here for
[8:42] Speaker 2: the listener. We do not have a photograph of a
[8:44] Speaker 2: comet with a glowing tail flying around PDS-70.
[8:47] Speaker 3: No, our telescopes just aren't that powerful yet. Right.
[8:50] Speaker 2: So wait, if we can't actually see the icy comets,
[8:53] Speaker 2: how does disappearing sodium gas prove that comets are flying around?
[8:58] Speaker 2: Couldn't we just be looking at, I don't know, a
[9:00] Speaker 2: random glowing clump of gas floating through the system?
[9:04] Speaker 3: It's a fair question. But the mechanics of the observation
[9:07] Speaker 3: rule out a random clump. It really comes down to
[9:10] Speaker 3: understanding the physics of a process called sublimation within a vacuum.
[9:14] Speaker 2: Okay, break that down for us.
[9:16] Speaker 3: So imagine the life cycle of this comet. It forms
[9:19] Speaker 3: in the extreme, freezing, dark outer edges of the planetary system.
[9:23] Speaker 3: Out there, the water, the sodium, and the other volatiles
[9:26] Speaker 3: flow are all locked together in a rock-hard frozen state.
[9:29] Speaker 2: Right.
[9:30] Speaker 3: But as this icy body gets pulled inward, it approaches
[9:33] Speaker 3: the intense heat of the central star.
[9:35] Speaker 2: And because space is a vacuum, this isn't like leaving
[9:37] Speaker 2: an ice cube on a hot sidewalk where it slowly
[9:39] Speaker 2: melts into a puddle.
[9:40] Speaker 3: No, not at all. The lack of atmospheric pressure changes
[9:43] Speaker 3: the physics entirely. In the vacuum of space, ice cannot
[9:47] Speaker 3: exist in a liquid state. So as the comet heats
[9:50] Speaker 3: up rapidly from the star's thermal radiation, the ice skips
[9:53] Speaker 3: the liquid phase entirely.
[9:54] Speaker 2: It just vaporizes.
[9:56] Speaker 3: It violently transitions from a solid directly into a mass
[10:00] Speaker 3: expanding cloud of gas. That transition is sublimation. It basically erupts.
[10:04] Speaker 3: And when that comet erupts, it violently ejects the sodium
[10:08] Speaker 3: that was trapped within its ice. Oh, wow.
[10:10] Speaker 2: So it creates this massive expanding halo of sodium gas
[10:15] Speaker 2: that physically positions itself between our telescopes here on Earth
[10:19] Speaker 2: and the central star of PDS-70.
[10:22] Speaker 3: Exactly. And the process we use to see it is
[10:24] Speaker 3: called absorption spectroscopy. Basically, every element on the periodic table
[10:28] Speaker 3: absorbs specific wavelengths or colors of light.
[10:31] Speaker 2: Right, like a fingerprint.
[10:32] Speaker 3: Yeah. So when the star's full spectrum of light shines
[10:35] Speaker 3: through that erupting cloud of sodium gas, the sodium atoms
[10:38] Speaker 3: act like a sponge. They absorb very specific wavelengths. When
[10:42] Speaker 3: that starlight finally reaches our telescopes, we run it through
[10:45] Speaker 3: a spectrograph. which spreads the light out into a rainbow.
[10:47] Speaker 2: And because the sodium absorbed its specific colors, there are
[10:51] Speaker 2: literally black lines missing from that rainbow. It creates a
[10:54] Speaker 2: measurable barcode.
[10:55] Speaker 3: You got it.
[10:56] Speaker 2: It's almost like throwing a highly specific colored filter in
[10:59] Speaker 2: front of a camera lens for just a few nights
[11:01] Speaker 2: and then violently ripping it away as the comet moves past.
[11:04] Speaker 3: That is the exact mechanism. We are not seeing the
[11:07] Speaker 3: physical three-mile-wide rock of the comet itself. We are detecting
[11:12] Speaker 3: the massive temporary shadow cast by its erupting gas cloud.
[11:16] Speaker 2: That is so cool.
[11:18] Speaker 3: And the speed of the shadow, combined with the fact
[11:20] Speaker 3: that it disappears after a few days, perfectly aligns with
[11:23] Speaker 3: the velocity and trajectory of an inward-falling comet.
[11:26] Speaker 2: Here's where it gets really interesting. Finding this sodium shadow
[11:29] Speaker 2: isn't just a neat observational trick. This is the very
[11:33] Speaker 2: first time astronomers have ever found evidence of exocomets. You know,
[11:37] Speaker 2: comets operating outside our solar system orbiting a relatively cool,
[11:40] Speaker 2: sun-like star.
[11:42] Speaker 3: The magnitude of that simply cannot be overstated. We've detected
[11:45] Speaker 3: signatures of exocomets before, but almost exclusively around much hotter, brighter,
[11:50] Speaker 3: more massive stars.
[11:51] Speaker 2: Like Beta Pictoris, right?
[11:52] Speaker 3: Right, Beta Pictoris, where the thermal environment is so extreme
[11:56] Speaker 3: that the sublimation is incredibly violent and just much easier
[12:00] Speaker 3: to spot. But detecting this around a sun-like star... brings
[12:04] Speaker 3: the phenomenon right to our own doorstep.
[12:06] Speaker 2: It proves the mechanism happens in systems that look just
[12:08] Speaker 2: like ours. And as Noves pointed out, this is the
[12:12] Speaker 2: absolute youngest system where exocomet activity has ever been proposed.
[12:16] Speaker 3: We're watching the cosmic delivery system boot up for the
[12:19] Speaker 3: very first time in a nascent solar system.
[12:22] Speaker 2: The trucks are officially on the highway.
[12:23] Speaker 3: Exactly. And the discovery of the traffic inevitably forces us
[12:27] Speaker 3: to examine the physics of the highway itself.
[12:30] Speaker 2: Which is the next major hurdle. Because, okay, we have
[12:34] Speaker 2: the spectroscopic evidence of these sublimating comets right near the
[12:37] Speaker 2: hot star. But comets are born in the freezer.
[12:40] Speaker 1: Right.
[12:41] Speaker 3: Out in the dark.
[12:42] Speaker 2: They form in the extremely cold outer rim of a
[12:45] Speaker 2: planetary system where water can safely exist as a solid
[12:48] Speaker 2: chunk of ice. So how do you strip an icy
[12:51] Speaker 2: body of its orbital momentum so drastically that it plunges
[12:55] Speaker 2: toward the star?
[12:56] Speaker 3: Because they don't just catch a breeze and float inward.
[12:58] Speaker 2: Exactly. Orbits are governed by inertia. To bridge the immense
[13:02] Speaker 2: gap between the freezing outer system and the hot inner system,
[13:06] Speaker 2: you need an engine. You need an immense amount of
[13:09] Speaker 2: force to alter their trajectory.
[13:11] Speaker 3: Because orbits in the outer system are generally quite stable.
[13:13] Speaker 3: I mean, unless a kinetic impact or a massive gravitational
[13:16] Speaker 3: disruption occurs, an icy body will happily orbit in the
[13:20] Speaker 3: dark outer rim for billions of years.
[13:22] Speaker 2: And this brings us back to the Lund University team,
[13:25] Speaker 2: because they didn't stop at just analyzing the light shadows.
[13:28] Speaker 2: To find that gravitational engine, they ran highly complex n-body
[13:32] Speaker 2: orbital simulations of the entire PDS-70 system.
[13:36] Speaker 3: Which takes a lot of computing power.
[13:38] Speaker 2: Oh, yeah. These simulations involve plugging in the estimated masses, velocities,
[13:42] Speaker 2: and gravitational fields of all the known objects, and then
[13:45] Speaker 2: just fast-forwarding the math over millions of years to see
[13:48] Speaker 2: how things physically interact. And the key players in those
[13:51] Speaker 2: simulations are the two massive gas giants we established at
[13:55] Speaker 2: the beginning.
[13:55] Speaker 3: Right, because the gas giants are already fully formed. They
[13:58] Speaker 3: possess immense mass, which means they wield incredible gravitational influence
[14:03] Speaker 3: over the rest of the disk.
[14:04] Speaker 2: The simulations reveal that those gas giants are not just
[14:07] Speaker 2: passively orbiting. The best way to visualize the mechanics of
[14:11] Speaker 2: PDS-70 is to picture the entire system as a massive
[14:14] Speaker 2: cosmic pinball machine.
[14:16] Speaker 3: I love that visual.
[14:17] Speaker 2: Right. The comets are the pinballs slowly drifting around in
[14:21] Speaker 2: the cold outer rim. But those two massive gas giants
[14:25] Speaker 2: are acting exactly like the flippers. As a comet's orbit
[14:28] Speaker 2: slightly overlaps with the territory of a gas giant, it
[14:32] Speaker 2: enters that massive gravitational field.
[14:34] Speaker 3: And gravity from a Jupiter-sized planet is an incredibly potent
[14:38] Speaker 3: kinetic tool. When a smaller object approaches a massive planet,
[14:43] Speaker 3: it doesn't just quietly get captured. Depending on the angle,
[14:46] Speaker 3: it can undergo a gravitational assist, basically a slingshot effect.
[14:48] Speaker 2: It just whips it around. Yes.
[14:50] Speaker 3: The planet's gravity violently alters the comet's momentum and vector.
[14:53] Speaker 2: It aggressively yanks these distant icy comets out of their
[14:56] Speaker 2: stable orbits and violently flings them inward, turning an outer-room
[15:00] Speaker 2: ice cube into an inward-bound projectile aimed right at the
[15:03] Speaker 2: inner system.
[15:04] Speaker 3: If we connect this to the bigger picture, the implications
[15:06] Speaker 3: for planetary formation are absolutely staggering. What we are observing
[15:10] Speaker 3: is that gravitational bullying by gas giants... is a highly
[15:14] Speaker 3: efficient vital transport mechanism.
[15:16] Speaker 2: They're doing the heavy lifting.
[15:18] Speaker 3: The gas giants are the heavy machinery of the supply chain.
[15:21] Speaker 3: They are actively harvesting water, sodium and other volatile building
[15:26] Speaker 3: blocks from the frozen, sterile wastelands of the outer system
[15:30] Speaker 3: and channeling them directly into the inner zone.
[15:33] Speaker 2: The habitable zone. The exact region where terrestrial rocky planets
[15:38] Speaker 2: are trying to form. Because, like we said, the inner
[15:40] Speaker 2: region is far too hot for water to just condense
[15:43] Speaker 2: and stay there on its own during the early stages.
[15:45] Speaker 3: Right.
[15:45] Speaker 2: But if you constantly bombard that inner construction site with
[15:48] Speaker 2: massive icy comets flung inward by the gas giants, you're
[15:52] Speaker 2: fundamentally overriding the thermal limits of that zone. You're forcefully
[15:56] Speaker 2: delivering the water precisely where it needs to be for
[15:59] Speaker 2: a cooling rocky planet to eventually capture it.
[16:02] Speaker 3: It is a brilliantly chaotic process. It's violent, random, and
[16:06] Speaker 3: incredibly effective.
[16:08] Speaker 2: So we've solved the mystery of the moving water in PDS-70.
[16:12] Speaker 2: We have broken down the spectroscopy of the sodium shadows,
[16:16] Speaker 2: and we've modeled the cosmic pinball machine. But if we
[16:19] Speaker 2: pull back, the crucial question is, what does a 370
[16:24] Speaker 2: light-year distant pinball game actually have to do with us?
[16:27] Speaker 3: It matters deeply, because analyzing PDS-70 is functionally identical to
[16:32] Speaker 3: looking into a mirror that reflects our own deep geological past.
[16:36] Speaker 2: Alexandra Stockwell Murphy, an astronomer at Lund University who collaborated
[16:40] Speaker 2: on this research, highlighted this connection perfectly. She pointed out
[16:43] Speaker 2: that this exact transport process, massive gas giants slinging icy
[16:48] Speaker 2: comets inward, is highly reminiscent of the dominant theories regarding
[16:52] Speaker 2: our own early solar system.
[16:53] Speaker 3: Because the origin of Earth's water is still a rigorously
[16:56] Speaker 3: debated topic in both geology and astronomy. We established earlier
[17:00] Speaker 3: that the early Earth was a molten hellscape, totally incapable
[17:03] Speaker 3: of holding surface water. So how did the Pacific Ocean
[17:06] Speaker 3: get here?
[17:06] Speaker 2: We needed a delivery. Now, to be fair to the
[17:08] Speaker 2: broader science, water-rich asteroids from the relatively nearby asteroid belt
[17:12] Speaker 2: are strongly considered as a primary source for Earth's oceans.
[17:16] Speaker 1: True.
[17:16] Speaker 3: They are a huge piece of the puzzle.
[17:18] Speaker 2: But this observational data from PDS-70 massively strengthens the theory
[17:22] Speaker 2: that early comets played a critical, simultaneous role. It provides
[17:26] Speaker 2: tangible evidence that our own gas giants, specifically Jupiter and Saturn,
[17:31] Speaker 2: likely acted as our local pinball flippers.
[17:34] Speaker 3: They were the gravitational engines.
[17:35] Speaker 2: Yeah, flinging ancient icy comets inward from the Kuiper Belt
[17:39] Speaker 2: and the Oort Cloud, delivering the water that now makes
[17:42] Speaker 2: up the Atlantic Ocean, the rain falling outside your window,
[17:45] Speaker 2: and even the water inside your own cells.
[17:48] Speaker 3: And that observation provides empirical physical backing to what was
[17:52] Speaker 3: mostly a theoretical mathematical model of our own history. We
[17:56] Speaker 3: are no longer just running computer simulations guessing that Jupiter
[18:00] Speaker 3: might have flung comets at early Earth.
[18:01] Speaker 2: We're seeing it happen.
[18:02] Speaker 3: Exactly. Exactly. We are aiming our telescopes at another young
[18:05] Speaker 3: system and verifying that the mechanism actively happens in nature.
[18:09] Speaker 2: So what does this all mean? If we have proven
[18:12] Speaker 2: the delivery mechanism exists, the next logical step feels like
[18:16] Speaker 2: we need to see the package actually arriving.
[18:18] Speaker 3: That's the holy grail, yeah.
[18:19] Speaker 2: But looking for a tiny, dark, rocky planet buried inside
[18:24] Speaker 2: a dusty, turbulent disk 370 light years away seems physically
[18:29] Speaker 2: impossible with our current technology. How do we actually prove
[18:33] Speaker 2: the inner planets are catching this water?
[18:35] Speaker 3: The future of this specific investigation requires a massive leap
[18:39] Speaker 3: in optical technology. And Jens Heumakers, another astronomy researcher at Lund,
[18:44] Speaker 3: laid out the precise roadmap for this.
[18:46] Speaker 2: Okay, what's the plan?
[18:47] Speaker 3: The next major breakthrough relies on an unprecedented piece of
[18:50] Speaker 3: hardware called the Extremely Large Telescope, or ELT, which is
[18:56] Speaker 3: currently under construction in the high deserts of Chile.
[18:58] Speaker 2: When astronomers name things, they really don't mess around. The ELT.
[19:02] Speaker 3: The naming is highly accurate, I promise you. To understand
[19:04] Speaker 3: why we need it, you have to look to the
[19:06] Speaker 3: limitations of our current telescopes. When Noveas and her team
[19:09] Speaker 3: found the comets, they relied on detecting expanding gas clouds
[19:12] Speaker 3: because the comets themselves are just too small.
[19:14] Speaker 2: Right, the shadows. Yeah.
[19:16] Speaker 3: And rocky planets in the early stages of formation are
[19:19] Speaker 3: also relatively small, and they emit very little light. So
[19:22] Speaker 3: when you try to find a small, dark rock hidden
[19:24] Speaker 3: within the incredibly bright glare of the central star... And
[19:27] Speaker 3: all that thick, dusty mess of a young planetary disk,
[19:31] Speaker 3: current telescopes simply do not have the angular resolution or
[19:34] Speaker 3: the light-gathering power to separate the planet from the background noise.
[19:38] Speaker 2: To put this into perspective for you, the James Webb
[19:40] Speaker 2: Space Telescope, which is currently the most powerful observatory humanity
[19:44] Speaker 2: has ever built, has a primary mirror that is about 6.5
[19:48] Speaker 2: meters across.
[19:49] Speaker 3: Which is huge. for space.
[19:50] Speaker 2: It is. But the extremely large telescope is going to
[19:53] Speaker 2: have a primary mirror that is over 39 meters across.
[19:57] Speaker 2: That is a single telescope mirror roughly the size of
[19:59] Speaker 2: a baseball diamond.
[20:01] Speaker 3: The surface area difference is just exponential. That massive light bucket,
[20:05] Speaker 3: combined with advanced adaptive optics, which physically deform the mirror
[20:09] Speaker 3: thousands of times a second to cancel out the blurring
[20:12] Speaker 3: effect of Earth's atmosphere that will provide a resolution that
[20:14] Speaker 3: we have never had access to before.
[20:16] Speaker 2: Unbelievable.
[20:17] Speaker 3: Furthermore, the ELT is highly optimized for infrared observation.
[20:21] Speaker 2: Which means it isn't just looking for visible light, right?
[20:23] Speaker 2: It's looking for heat signatures. It can peer straight through
[20:26] Speaker 2: the cold dust of the primordial disk and detect the
[20:29] Speaker 2: faint thermal glow of a rocky planet that is still
[20:32] Speaker 2: hot from the friction of its own formation.
[20:35] Speaker 3: Precisely. With that unprecedented capability, once the ELT becomes operational
[20:40] Speaker 3: late in this decade, astronomers will point it right back
[20:43] Speaker 3: at PDS-70.
[20:44] Speaker 2: To look for the planets themselves.
[20:46] Speaker 3: Exactly. We have already proven the water is being transported.
[20:49] Speaker 3: We know the icy comets are flying inward. The ELT
[20:51] Speaker 3: will finally allow us to pierce the veil of the
[20:54] Speaker 3: inner system and see if there are hidden, newly forming,
[20:57] Speaker 3: rocky terrestrial planets sitting right there, actively being bombarded and
[21:02] Speaker 3: catching this incoming water.
[21:03] Speaker 2: We could literally watch an alien world acquiring its very
[21:07] Speaker 2: first oceans in real time. To synthesize this entire journey
[21:11] Speaker 2: for you, we started by questioning the origin of Earth's oceans,
[21:15] Speaker 2: looking at the water in our own backyard. And that
[21:18] Speaker 2: simple question led us to analyze the physics of disappearing
[21:21] Speaker 2: sodium shadows 370 light years away. By decoding those spectral shadows,
[21:27] Speaker 2: we uncovered a massive, chaotic gravitational transport system driven by
[21:32] Speaker 2: giant planets acting as cosmic flippers, forcibly delivering the chemical
[21:36] Speaker 2: building blocks of life to the inner solar system.
[21:38] Speaker 3: The chain of discovery is phenomenal. But taking a step back,
[21:43] Speaker 3: the mechanics of this transport system leave us with a
[21:45] Speaker 3: deeply profound, almost unsettling implication about the chaotic luck required
[21:50] Speaker 3: for planet formation.
[21:52] Speaker 2: Unsettling in what way?
[21:53] Speaker 3: Well, Analyze the precise tolerances of the mechanism we just outlined.
[21:57] Speaker 3: The delivery of water to the inner system relies entirely
[22:00] Speaker 3: on the immense gravitational strength and the specific orbital positioning
[22:04] Speaker 3: of those outer gas giants. If the gas giants in
[22:07] Speaker 3: PDS-70 had formed with just a little less mass, their
[22:10] Speaker 3: gravitational reach wouldn't be strong enough to violently alter the
[22:12] Speaker 3: comet's trajectories. Or if they had formed in slightly different,
[22:16] Speaker 3: more distant orbital tracks, their gravitational fields might not overlap
[22:20] Speaker 3: with the icy comet reservoirs in the exact right way.
[22:23] Speaker 2: Ah, I see. The flippers would completely miss the pinballs.
[22:26] Speaker 3: Exactly. If the architecture of that system was tweaked by
[22:29] Speaker 3: even a fraction of a percent, those gas giants wouldn't
[22:32] Speaker 3: fling those icy comets inward. The comets would remain safely,
[22:36] Speaker 3: permanently frozen in the outer rim. And the inner system,
[22:40] Speaker 3: where the rocky planets are attempting to form, would be
[22:42] Speaker 3: completely starved to volatiles. It would remain totally and permanently dry.
[22:46] Speaker 2: Just barren, sterile rock forever.
[22:49] Speaker 3: Which fundamentally challenges how we view our place in the universe.
[22:53] Speaker 3: We tend to search for water worlds with the baseline
[22:55] Speaker 3: assumption that oceans are a natural, expected byproduct of standard
[22:59] Speaker 3: planetary evolution.
[23:00] Speaker 2: Like it's just meant to happen.
[23:01] Speaker 1: Right.
[23:02] Speaker 3: But the mechanics of PDS-70 demonstrate how incredibly fragile and
[23:06] Speaker 3: conditional the process truly is. It forces us to ask,
[23:10] Speaker 3: is a life-sustaining, water-rich planet like Earth actually a cosmic inevitability?
[23:16] Speaker 3: Or are we simply the incredibly fortunate winners of a
[23:18] Speaker 3: completely random, high-stakes game of gravitational pinball? Think about it.
[23:23] Speaker 3: If our own Jupiter had been just a little bit
[23:25] Speaker 3: smaller or formed a little further out, Earth might just
[23:28] Speaker 3: be another dry, dead rock floating in the dark.
[23:31] Speaker 2: That is a staggering perspective to leave you with. Every
[23:34] Speaker 2: single time you look at the ocean or simply turn
[23:37] Speaker 2: on your kitchen tap, you might just be looking at
[23:38] Speaker 2: the jackpot of a chaotic cosmic lottery that played out
[23:42] Speaker 2: billions of years ago. Thank you for joining us for
[23:44] Speaker 2: this exploration today. Keep looking up, keep asking questions, and
[23:48] Speaker 2: we will catch you next time.

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