Extreme Exoplanets: Molten Worlds Around Red Dwarfs

Welcome to Bedtime Astronomy. Explore the wonders of the cosmos with our soothing Bedtime Astronomie podcast. Each episode offers a gentle journey through the stars, planets, and beyond, perfect for unwinding after a long day. Let's travel through the mysteries of the universe as you drift off into a peaceful slumber under the night sky.

I want you to just close your eyes for a second. Try to imagine the absolute most extreme environment you can possibly conceive of. Oh wow, okay, yeah, And I don't just mean like a place that's uncomfortably hot. I want you to picture an entirely different physical reality.

Right, like completely alien exactly.

Imagine you're standing on a shoreline, but the ocean stretching out in front of you, it isn't made of water. It is this vast, churning sea of molten silicate rock, just glowing this deep orange in the dark.

That is terrifying it is.

And you look up and the sky isn't blue, It's this thick, suffocating, opaque haze. And the smell, the smell of the air around you is just punishingly toxic. It's overwhelmingly dominated by the scent of rotting eggs.

It is a literal sensory nightmare. I mean, it's a hellscape of the highest order where the very concept of a solid surface basically ceases to exist.

It really does. But the crazy thing is we are talking about a very real place. It's a super earth known as L ninety eight fifty nine DY, which.

Is about thirty five light years away from us, right, yeah, the constellation Vila.

Yeah, exactly thirty five light years. But we aren't going on a mental journey to this world today just for the novelty of, you know, looking at a bizarre, stinky planet.

No, definitely not. There's a much bigger reason, right, We.

Are looking at this specific world because it actually happens to be the smoking gun that solves one of the most frustrating cold cases in modern astronomy.

Oh absolutely, it's a total game changer.

So before we even talk about the molten notions or the toxics guy, we kind of need to set the stakes for you because for years planetary scientists have basically been staring at this massive glaring hole in our map of the galaxy.

Yeah, the Radius Valley, or some people call it the Fulton Gap that was the original name when the Kepler Space telescope data first brought it to light, the Fulton Gap, and it is one of the most profound mysteries in

But instead the graph looks, well, it looks like a mountain range with this massive canyon carved right down the middle of it.

It's so weird, it really is a canyon.

Yeah. So we see this huge peak of rocky planets that are about the size of Earth up to maybe like one point four times Earth's radius, right the terrestrial worlds, and then further down the graph we see another huge peak of planets that are bigger around two to three times Earth's radius.

The mini Neptunes. Those are the ones with thick, puffy atmospheres.

AGAs exactly, but right in the middle between one point five and two times the size of Earth. The population of planets just absolutely plummet.

It's complete dead zone.

It's just empty.

Yeah, the planets simply go missing in that size bracket. And the thing is, it is statistically impossible for that gap to be an accident of our observation methods.

Like, it's not just a glitch in the telescopes.

No, not at all. The universe is actively preventing planets from staying in that specific size range. Or and this was the leading idea, it's rapidly stripping them down so they fall into the smaller category.

Right, So the leading theory for a long time was atmospheric.

Loss yep photo evaporation, the idea being that a planet might form with a thick hydrogen envelope, which puts it in that larger mini neptune category, but if it orbits too close to its host star, the.

Intense radiation just eventually boils that atmosphere away.

It boils away, the planet shrinks, crosses that forbidden zone of the radius valley really quickly. It ends up just a bare, rocky core on the other.

Side, exactly. And so the assumption for decades was that planetary evolution is fundamentally a story of subtractions attraction.

Right, you start big, the star strips you, you end up small.

It was this really neat binary framework. Path one you somehow hold onto your gas, maybe you're far enough away from the star and you stay a mini neptune. And path two, Path two is your star strips you naked and you become a bare rock, which.

Is so intuitive it makes perfect physical sense.

It does, especially based on how aggressive we know young stars can be, particularly the en dwarfs, the red dwarf stars.

And those are the most common stars in our galaxy.

Right by far, and they are notorious for violent stellar flares and this intense extreme ultraviolet radiation that basically acts like a blow torch on planetary atmosphere.

A blow to That's a great way to put it, which brings us back to our target. L ninety eight fifty nine D yes the rule breaker.

Because this specific planet, in this specific star system just completely breaks that binary framework. It literally forces us to rewrite the fundamental physics of how planets evolve and survived.

It really does, and the whole unraveling of this mystery, it actually started with a cosmic weight problem.

A weight problem. I love that the severe density anomaly.

Right, so L ninety eight fifty nine D was first discovered back in twenty nineteen by NASA's Tests satellite.

Tests the Transiting Exoplanet Survey.

Satellite exactly and tests uses the transit photometry method. It basically stares at a patch of sky and just waits for a star's light to.

Dim just a tiny fraction of a percent, right, Yeah, a microscopic dip in light, and that indicates that a planet has crossed in front of it. And based on how much light is blocked, we can calculate the physical volume the size of the planet, and.

Test told us that L ninety eight to fifty nine DY is roughly one point six times the size.

Of Earth, which drops it squarely into the danger zone right in the middle of a canyon. It's sitting right on the edge of that forbidden radius valley. It is in the transition zone.

But just knowing the physical volume of a planet is only the first step.

Right, to understand what a planet is actually made of, you need its mass.

You need to weigh it exactly.

And for that astronomers use ground based spectrographs to measure the radial velocity. That's the tiny, tiny gravitational wobble. The planet induces on its host star.

So the planet pulls on the star.

A little bit. It does, and when you have the volume from the transit and you have the mass from.

The wobble, you can calculate the overall bulk density.

BINGO, and the density of L ninety eight to fifty nine D immediately set off alarm bells for everyone looking at the data.

Because if you have a planet that's one point six times the size of Earth and it's sitting incredibly close to its host star, you expect a very specific composition.

You really do. The radiation environment is so brutal there that any primordial fluffy envelope of hydrogen and helium it should have been photo evaporated away billions of years ago.

So you expect to find a dense, bare terrestrial rock like an iron core surrounded by a solid silicate mantle, right.

But the radio velocity measurements revealed something entirely different. The mass of the planet was just far, far too low for its physical.

Size, so it's huge, but it's really light.

The density was abnormally low. It was much lighter than a pure rocky world of that diameter.

Should ever be Okay, let's unpack this for a second. It's like it's like picking up a bowling ball right and expecting it to be super heavy, but you realize it weighs as much as a styrofoam block.

That is a perfect analogy.

Your brain immediately knows something is just fundamentally wrong with the recipe. The math just doesn't add up.

It really doesn't. You have this massive volume but missing mass. Wow, And the traditional models they basically leave you with two options for a low density world.

Okay, what's option A.

Option eight is the gas dwarf scenario. We just discussed a small rocky with a huge, puffy hydrogen atmosphere.

Well, we already ruled that out right exactly.

We ruled it out because the red dwarf's high energy X ray and UV emissions would have stripped a lightweight hydrogen atmosphere away eons ago.

I mean, the system is five billion years old. A primordial hydrogen envelope simply cannot survive there.

It's physically impossible. The stellar wind would act like a sand blaster over those timescales. The retention of a primordial envelope at that orbital distance is just untenable.

Okay, so option A is out. That leaves option B for a low density planet, the water world.

Right, the water world.

A planet with a smaller rocky core, but it's enveloped by this massive, deep ocean of liquid water, or maybe an incredibly thicked shell of high pressure ice.

And that makes sense on paper because water is significantly less dense than iron and silicate rock.

So incorporating a huge fraction of water into the planet's bulk composition perfectly explains the missing mass. Right. It expands the volume without adding heavy metals.

It solves the density equation beautifully.

But there's always a butt.

There's always a butt. In astronomy, the problem is the thermodynamic reality of the planet's orbit. L ninety eight fifty nine D is tuck in so incredibly close to its star that the stellar irradiation it receives is just astronomical.

Oh right, We're talking surface temperatures estimated around nineteen hundred degrees celsius.

Over thirty five hundred degrees fahrenheit.

Liquid water cannot exist in that regime, not even close.

No way. I mean, even if the planet had somehow formed further out in the star system, like beyond the snow line and then migrated inward over millions of years.

Water wouldn't stick around, it would.

Not remain stable. It would vaporize into this massive steam atmosphere, and water vapor in the upper atmosphere is highly susceptible to photoed association.

Wait, photo association explain that process.

Basically, the intense UV light from the red dwarf would act like a hammer. It would literally shatter the water molecules apart in to hydrogen and oxygen.

Oh wow, so it just breaks the water apart exactly.

The lighter hydrogen escapes into space, the heavier oxygen falls down and oxidizes the crust, and eventually the entire planet desiccates.

It just rusts and dries out completely if the dead end. So it can't be rock because it's too light, right. It can't be a gas dwarf because the stellar wind would strip the hydrogen right again. And it can't be a water world because the temperature would boil the oceans and the star would shatter the steam exactly. So what is it? I mean? The planetary science community was essentially

But resisting the blow torch of the red dwarf star for five billion years. It's just wild.

How do you even begin to solve that?

Well, honestly, it was an intractable problem with the observatories we had available in twenty nineteen.

Because we only had tests and ground based telescopes.

Right, we could measure sure the bulk parameters, you know, the mass and the radius. Yeah, but those numbers only offered contradictory boundary conditions.

They just told us what it could be exactly.

To figure out what was actually inflating this planet, we had to stop looking at its gravitational footprint and start looking directly at its chemistry.

We needed to read the chemical bar code of whatever envelope was clinging to this.

World, which requires transmissions Pictrosky.

And doing that on a small, rocky super Earth thirty five light years away, I mean, that is an entirely different ballgame than looking at a giant, puffy hot Jupiter.

Oh, it's exponentially harder. The atmospheric signal you were trying to isolate is microscopic. The scale of the measurement is.

Just staggering right, because when L ninety eight to fifty nine D transits its host star, the solid body of the planet blocks a fraction of the.

Starlight, but the atmosphere, assuming it even has one, is just a razor thin halo around that solid sphere.

Okay, I have an analogy for this. To visualize this, I want you to imagine holding up a thick piece of stained glass to a blindingly bright searchlight.

Oh, I like this.

So the solid metal frame of the glass blocks the light entirely right, It casts a hard shadow, but the translucent colored glass lets a tiny, tiny fraction of that search light bleed through.

Yep.

And if you stand far enough back and analyze the exact wavelengths of light that make it through the glass, you can reverse engineer the chemical dyes used to color it.

Because certain chemicals absorb red light and others absorb blue.

Exactly, the missing colors tell you the composition of the barrier.

That is precisely the essence of transmission spectroscopy. It's so cool, it really is. As the starlight from the red dwarf filters through the incredibly thin atmospheric limb of L ninety eight fifty nine D. The specific molecules suspended in that alien air act as chemical filters.

Just like the stained glass.

Exactly like the stained glass, they absorb very specific, quantifiable wavelengths of infrared light.

And to see that, we needed a serious upgrade in our tech.

We need it the James Webb Space Telescope. When JWST captures that filtered starlight, its near infrared spectram graph in iro spec disperses the light into a high resolution spectrum, and we just looked for the absorption.

Bands, the missing slivers of light.

Missing slivers exactly, and this signal.

To noise ratio required to detect those missing slavers on a planet this small. I mean, that's literally why we had to wait for a ten billion dollar Berrillium Mirror observatory parked a million miles from Earth.

Previous telescopes just didn't have the sensitivity in the infrared to see through the glare of the host star. JWFT represents a total paradigm shift to our diagnostic capabilities.

So what happened when they actually pointed JWST at it.

Well, the international team led by researchers at the University of Oxford, they pointed jawst at this system analyze the transmission spectrum, and the absorption features that popped out of the data were entirely unexpected.

Like they didn't find the lightweight signatures of primordial hydrogen and helium Nope, none, And they didn't find a saturated signal of water vapor right right.

What they found were profound undeniable absorption bands corresponding to heavy sulfur compounds sulfur specifically sulfur dioxide and hydrogen sulfide.

Hydrogen sulfide. Okay, here's where it gets really interesting. For anyone who has ever been near a geyser or a volcanic vent or you know, simply smelled or rotting egg.

You know the visceral impact of hydrogen sulfide.

It is a highly toxic, incredibly pungent gas. Finding it out in the cosmos isn't necessarily strange, right, Like we see sulfur in planetary nebulas and young star forming regions.

Sure, sulfur is common, but finding it dominating the thick atmosphere of a blazing hot super Earth that changes the entire physical model of the planet.

Because it immediately resolves the density anomaly.

It does, but and this is a big butt. It introduces a severe dynamic paradox.

Okay, let's break that down. How does it resolve the density?

Well, a heavily metallic, volatile rich atmosphere like one dominated by sulfur to oxide and hydrogen sulfide has a much higher mean molecular weight than a hydrogen helium envelope.

So it's heavier, it's denser.

It's denser, it hugs the planet tighter, and it is significantly harder for the stellar wind to strip away.

It's like wearing heavier armor. It resists the photo of operation blow towards much better than fluffy hydrogen exactly.

And the sheer volume of this thick, heavy, hazy sulfur envelope explains why the planet is puffed up to one point six times the size of Earth without adding the mass of solid rock.

So the static math works. The puzzle pieces finally fit together.

The static math works, Yes, but planetary atmospheres are not static, especially not in a compact orbit around a red dwarf.

Right, because even with the heavier molecular weight of sulfur compounds the extreme ultraviolet radiation and the relentless stellar wind over five billion years, it would still inexorably erode that atmosphere.

It might be harder to strip than hydrogen, but over billions of years, it should still be gone.

It has to be bleeding into space. The physics of the stellar wind literally demand it.

They do. Therefore, the fact that JWST observes a thick, opaque sulfur envelope today, five billion years into the system's lifespan, implies a terrifying reality. The atmosphere is not a primordial remnant. It is not a leftover shell of gas from the planet's berth. It is being actively, aggressively and continuously replenished.

Wow, so the planet is bleeding sulfur into the sky faster than the star can strip it away.

Exactly. It is a planetary scale out gassing engine.

And to fuel an engine that massive, to continuously pump millions of tons of hydrogen, sulfide and sulfur dioxide into the atmosphere for five eons, you need a reservoir of unthinkable proportions.

Right. You can't just have a few active volcanoes dotting a solid crust. That wouldn't cut it.

A localized volcanic network would exhaust its volatile supply way too quickly.

Far too quickly, And that's where the geodynamic simulations come in. The model presented in the March twenty twenty six Nature Astronomy paper takes the jawst atmospheric data and couples it with interior geodynamic simulations.

They basically calculated what kind of internal structure is actually required to sustain this level of outgassing, and.

The simulations converged on a singular extreme structural model.

The permanent magma ocean.

A global, deep seated layer of molten silicate rock.

And we aren't just talking about a surface phenomenon right now.

No, No. The nineteen hundred degree surface temperature guarantees that the crust itself is a glowing liquid. Sure, but the simulations dictate that this molten state extends thousands of kilometers deep into the planet's mantle.

Okay, wait, I want to pause here and really dig into the geophysics, because when you say the word ocean, the human brain immediately defaults to the mechanics of water.

Of course, you picture waves, right.

We picture a sloshing fluid sphere, but a magma ocean extending thousands of kilometers down into a super Earth involves pressure regimes that fundamentally alter how matter behaves, oh completely. So how does a planet maintain its structural integrity if half of its volume is essentially a liquid like Why doesn't the tidal stress or the centrifugal force of its rotation just tear it apart into space?

That is a great question. It comes down to the concept of reology. Reology, Yeah, reology the study of how matter flows under pressure. As you descend into the interior of L ninety eight fifty nine D, the gravitational pressure increases exponentially.

Because there's so much weight pressing down from above.

Exactly so, even though the temperature is high enough to melt silicate rock at the surface, the immense pressure at depth actively combats that melting.

Because pressure forces atoms together, fighting the thermal energy that is trying to spread them apart.

Spot on, and the result is a state of matter that is partially molten. It isn't a low viscosity liquid like water. The mantle is often described in these high pressure, high temperature regimes.

As a mush, a mush that sounds unappealing.

It behaves more like an unimaginably dense, glowing molasses.

Glowing molasses. Okay, that's a brilliant visual.

It flows, it convects, it churns, but it possesses enough viscosity and structural cohesion, bound by the immense gravity of the core, to maintain a perfect spherical shape.

So the planet is essentially a giant convecting sphere of ultra pressurized, mushy liquid rock. Yes, but how does this molten state solve the sulfur problem? Like, how does glowing molasses act as a reservoir for toxic.

Gas because magma is an incredibly efficient solvent for volatiles.

A solvent.

Okay, think back to when this planet was forming from the protoplanetary disc five billion years ago. It created a huge inventory of building blocks, dust, rock, and massive amounts of volatile elements like sulfur, hydrogen, carbon.

And oxygen, all smashed together.

Right now, if the planet had cooled down and solidified like Earth or like Venus, what would have happened to those volatiles.

Well, solidification forces volatiles out of the crystal lattice of the rock. Right as magma crystallizes into solid stone, the gases are expelled.

Exactly, they bubble up to the surface in a massive initial pulse of out gassing, forming a thick primordial atmosphere.

And then the red dwarf star hits that atmosphere with its X ray blowtorch, strips it entirely and leaves behind a dead, solid barren rock.

The path two scenario we talked about earlier, the fast track cross the redisalid if L.

Ninety eight fifty nine did never solidified.

It never solidified because it remained a deep, churning magma ocean. The crystallization process never completed. The magma ocean acts as a planetary scale.

Sponge, a sponge for the gas.

It traps the volatile elements, the sulfur and the hydrogen in solution deep within the liquid silicate melt. The magma physically holds onto the gases.

Okay, it's like a sealed bottle of sparkling water. The carbon dioxide is trapped in the liquid. You can't see the gas, but it's held in solution by the pressure.

That is exactly it. And as the magma slowly convects, hotter material from deep within the planet rises toward the surface, where the pressure is slightly lower.

The solubility of the magma decreases, it can no longer hold as much gas.

The bottle is uncapped. Boom the magma to gases. The sulfur and hydrogen bubble out of the glowing molasses, rising through the thousands of kilometers of molten mantle and continuously erupt into the atmosphere.

It is a slow, steady, relentless release, A billion year exhalation, A billion year exhalation.

I love that.

And that is the planetary engine. The star is constantly scraping the top of the atmosphere away into the void, but the deep magma ocean is constantly burping up a fresh supply of hydrogen sulfide from the bottom to replace it.

It's an equilibrium, a beautifully brutal equilibrium.

But wait, this entire engine, this whole paradigm of Path three evolution. It relies on one foundational requirement, doesn't.

It It does. The mantle must remain liquid. The outgassing stops the exact moment the planet freezes solid.

Which brings us to the thermodynamics of the system. Because five billion years is a phenomenally long time to keep a rocky planet completely melted.

It really is.

I mean even sitting close to a star. Space is an infinite heat sink. The planet is constantly radiating thermal energy into the void. It should have cooled, crystallized, and dyed eons ago.

It absolutely should have to keep an.

Engine running for five billion years. You need an incredible continuous power source. You need a perfect storm of heat.

And the nature. Astronomy researchers model the heat budget of L ninety eight fifty nine D extensively to figure out how this is possible and what did they find. They found that a single heat source is simply insufficient to maintain a mantle deep magma ocean over geological time scales. It requires a trifecta.

A trifecta three distinct intersecting pillars of thermal energy working in concert. Okay, let's dissect the heat budget. Pillar one is the primordial heat of accretion, right, the violent birth of the planet.

Yes, the kinetic energy d of planetary formation is immense. When planetesimals and protoplanetary chunks smashed together under the force of gravity to form a super Earth, all.

That kinetic energy is converted into thermal energy. The entire mass of the newly formed planet is superheated.

It starts its life as a literal ball of liquid fire. And for a planet one point six times the size of Earth, the sheer volume of material means it takes a very long time for that initial primordial heat to radiate away into space.

Because the core is heavily insulated by the thousands of kilometers of rock above it.

Right, and radiogenic heating also plays a minor role here. You know, the decay of radioactive isotopes deep in the.

Core sure like a slow nuclear reactor.

But even combined with the primordial heat, the models show it is not enough. Left entirely to its own devices, a super Earth of this mass would eventually form a solid lithosphere, a crust.

Would form, the mantle would stiffen into solid rock, and the outgassing would shoke to a halt.

So the planet needs insulation to slow down that cooling process.

And it needs an active heater to inject new energy into the system.

Yes, so the insulation is pillar two. The atmospheric greenhouse.

Effect, the sulfur greenhouse because the sulfur rich atmosphere we detected with JWST isn't just a byproduct of the magma ocean. It is its protector exactly.

I mean, we understand the greenhouse effect on Earth, right, yeah, trace amounts of carbon dioxide methane trapping the infrared radiation trying to escape the surface.

But the greenhouse effect on l ninety eight fifty nine D is operating on a fundamentally different scale.

A completely different scale. We are talking about a thick, opaque haze of heavy sulfur dioxide and hydrogen sulfide. It acts as an extreme heavy duty thermal blanket.

So as the primordial heat from the deep interior slowly conducts its way to the surface ocean of lava, it tries to radiate into space, but the.

Sulfur blanket intercepts that infrared energy, absorbs it, and radiates it back down toward the surface.

It creates a thermal feedback loop.

It does. The magma out gases the sulfur. The sulfur forms the atmospheric blanket, and the blanket traps the heat required to keep the magma liquid so it can continue out gassing.

That is an incredible symbiotic relationship. It's almost biological in its elegance.

It really is. Again, but even the best thermal blanket in the universe eventually loses heat. A blanket doesn't generate energy, it only delays its escape.

Right, you don't warm up a cold bed just by throwing a blanket on it.

Exactly, to keep a thousands of kilometers deep ocean of rock molden for five billion years, you absolutely must have an active heater plugged into the wall.

You need a mechanism that physically injects new thermal energy into the planet's interior.

And this is where the orbital dynamics of the L ninety eight to fifty nine system become the critical key to the entire mystery. This brings us to pillar three, tidal heating.

Tidal heating. Now, when we say tides, we have to strip away the terrestrial bias for a second. We aren't talking about the Moon gently pulling on the oceans to give us high tide the beach.

No. No, we are talking about gravitational forces so profound they physically deform the solid structure of the planet.

Because L ninety eight fifty nine is not a lonely star system, it is a compact multiplanet system.

There are at least four planets crammed into orbits that are incredibly close to the host star, they are orbiting in a tight, crowded.

Neighborhood, and because they are so close to each other, their gravitational fields interact constantly right constantly.

The host star has a massive gravitational grip on L ninety eight fifty nine D, locking it in a tight orbit. But as the other planets in the system race around the star on their own orbits, they constantly pass by L ninety eight fifty nine D.

And every time a neighboring planet swings past its gravity tugs on our super Earth.

It pulls it slightly out of a perfect circular orbit, making the orbit elliptical or eccentric.

The eccentricity is the engine of the tidal heating.

Exactly because the orbit is slightly elliptical. The gravitational pull from the host star changes.

Constantly on where the planet is in its path.

When the planet is at its closest point to the star, the periastron, the gravitational tug is immense. It physically stretches the planet, elongating it along the equator like squeezing a rubber ball perfect analogy. Then, as the planet swings further away to the distant edge of its elliptical orbit the apostron, The star's gravitational grip relaxes slightly.

And the planet snaps back toward a more perfectly spherical shape.

Squeeze, release, squeeze, release, every single orbit.

And these orbits are incredibly fast. We are talking about a year that lasts just a few earth days.

The planet is being relentlessly rhythmically needed like a ball of dense dough.

Wow.

And this continuous deformation affects the entire thousands of kilometers deep mantle of glowing molasses. The internal layers of partially molten rock are constantly sliding against each other, grinding, stretching and compressing.

And all of that kinetic energy, all of that internal friction, it's converted directly into thermal energy.

Exactly. The gravitational dance of the neighboring planets is acting as a massive planetary scale friction heater. It is injecting colossal amounts of energy directly into the mantle.

This is the mechanism that keeps the pot boiling.

It is the tidal heating generates the energy. The primordial heat provides the baseline temperature. The sulfur greenhouse effect insulates the system.

This perfectly balanced trifecta maintains the magma ocean, which allows the continuous out gasing which replenishes the rotten egg atmosphere against the relentless stripping of the stellar wind.

It is a clockwork masterpiece of planetary physics.

A machine built out of gravity, heat, and chemistry. It really is beautiful and understanding. This machine is exactly what allowed the researchers in the Nature Astronomy paper to drop a bomb on the concept of the radius valid oh totally, because we talked earlier about the missing planets problem, the assumption that planets either keep their gas and stay big or lose their gas, shrink and become bare rocks.

The binary framework path one and path two right.

But L ninety eight fifty ninety proves the existence of an entirely new evolutionary roadmap. It proves that the universe is not limited to subtraction.

It introduces path three.

The internalized atmosphere.

Exactly what the data from L ninety eight to fifty ninety demonstrates is that a planet does not need to hold onto a fragile primordial envelope of hydrogen to maintain a bloated radius and a load density.

It can literally store its atmosphere inside its own body.

It absorbs the volatile inventory during formation, sequesters it in a deep magma ocean fueled by tidal heating, and then slowly continuously bleeds it out over billions of.

Years, the planet creates its own secondary atmosphere from the inside out.

And this completely changes how we interpret the demographic map of the galaxy.

Because when we look at that massive gap in the Radius valley, now we can no longer assume that every planet sitting near that forbidden zone is just a dead rock that lost its hydrogen.

We have to consider internal plumbing. A planet sitting on the edge of the Radius valley might not be a bare core. It might be a highly active, actively outgassing magma world wrapped in a dense shroud of heavy metallic volatiles.

It is puffing itself up with sulfur.

The size of the planet is being dictated by its internal geodynamics just as much as by the external radiation of its star.

We have to stop judging planets by their covers. We can't just measure the mass, measure the radius, calculate the density and put it in a box.

No, we really can't. We have to understand the specific orbital mechanics that drive its internal heat budget. The complexity of planetary evolution just gained an entirely new dimension.

And the implications of this extend far beyond just solving a quark in a demographic graph, right, because the statistical reality of path three evolution is actually staggering. Oh it is, let's one the numbers on that because L ninety eight fifty ninety is just one planet, but it orbits an M dwarf a red dwarf star, and.

M dwarfs are the undisputed rulers of the Milky Way. They account for roughly seventy to seventy five percent of all stars in our.

Galaxy and twenty five percent. Our Sun is a G type main sequence star, which makes it a minority. The galaxy is fundamentally a red dwarf galaxy.

It is, And what do we know about the planetary systems that form around red dwarfs?

Thanks to missions like Kepler and tests, we know that compact multiplanet systems are incredibly common around M dwarfs.

Right, Systems like Trappist one or L ninety eight fifty nine, where you have three four or seven rocky planets huddled in tight fast orbits close to the host star.

So we have a galaxy dominated by red dwarfs, and those red dwarfs are frequently surrounded by tight clusters of rocky super earths.

Which means the specific conditions that created L ninety eight to fifty ninety are not rare. They are ubiquitous.

The intense high energy radiation from the young star to strip the primordial hydrogen ubiquitous. The close proximity to neighboring planets to generate intense tidal heating ubiquitous. The initial accretion of volatile.

Rich material also ubiquitous.

The perfect storm isn't a freak accident, it is a standard weather pattern in the.

Milky Way exactly, which means Path three isn't just a quirky alternative lifestyle for a planet. It might be one of the most common planetary end states in the entire universe.

Wait, really one of the most common.

It is highly probable that the galaxy is teeming with these worlds, sulfur rich, permanently molten hellscapes wrapped in toxic, hazy atmospheres.

So we may be looking at a dominant class of exoplanets that we simply couldn't identify until the James Webs based telescope gave us the capability to read their chemical fingerprints.

This single observation effectively creates an entirely new category in the catalog of.

Worlds, and it highlights just how wild the universe is compared to our local terrestrial bias. I mean, we grew up on a planet with a solid crust, liquid water oceans, and a nice nitrogen oxygen atmosphere.

We kind of assume that rocky planets generally follow the rules we see in our own Solar.

System, right like Venus and Mars are just variation on a theme. But L ninety eight fifty nine D is playing a different sport entirely.

It forces a severe pivot in observational astronomy. Now that we know what the signature of a magma outgassing world looks like. You know, the heavy sulfur absorption bands, that density anomaly, the compact orbital architecture.

We know exactly what to look for we do.

The follow up campaigns for this specific planet are going to be intense, but the broader surveys of similar compact systems will be revolutionary.

So what are the immediate next steps? Because JWST isn't done with the system right. The Nature Astronomy paper is a monumental leap, but it's based on initial transmission spectra. There has to be more data to extract from that stinky sky.

Oh. JWST will undoubtedly conduct more transit observations, utilizing different instruments and observing across broader wavelength ranges.

Okay, what will they be looking for?

The current detection focus is heavily on the sulfur compounds, but astronomers will push the limits of the signal to noise ratio to search for traces.

They'll be hunting for water again.

Precisely because the magma ocean should also be an efficient reservoir for hydrogen and oxygen.

Ah, is there trace water vapor being outgassed alongside the hydrogen sulfide yes?

And if so, is the stellar radiation destroying it instantly or is it lingering in the lower atmosphere. The presence or absence of water vapor will further refine the models of mantle rheology and volatile solubility.

I also wonder about variability, like if this planet's atmosphere is being sustained by a churning, convecting ocean of glowing molasses. The outgassing shouldn't be.

Perfectly uniform, no, it would be.

It shouldn't be a smooth static release.

You would definitely expect episodic variations, major convective overturns in the mantle, or localized spikes and tidal heating due to orbital resonance cycles. Those could trigger massive planet wide eruptive.

Events supervolcanic outgassing pulses.

Exactly, if JWST observes the planet transitting multiple times over a period of years and the atmospheric composition or the transit depth changes, like if the sulfur dioxide signal suddenly spikes, it would provide real time observational evidence of active catastrophic volcanic churning in the magma ocean.

We would literally be watching the planet's internal plumbing operate in real time.

We would and won't just be GWST doing the heavy lifting either.

Well. Right, ground based scopes.

Now that the target is painted, ground based observatories with massive next generation mirrors like the extremely large telescope currently under construction, will be able to join the hunt.

What can they do that JWST can't.

They can use ultra high resolution spectroscopy to confirm the exact volatile ratios and even track the atmospheric as cape rates as the wind blows the sulfur away.

The synergy between space based infrared observatories and massive ground based spectrographs is going to rapidly accelerate our mapping of these path three worlds.

We are transitioning from the era of simply finding planets to the era of deeply characterizing their geophysical mechanic.

It's an incredible timeline to think about. I mean, a decade ago, a planet thirty five light years away was just a dip in a light.

Curve, a shadow, a twenty shadow.

We could guess its size and maybe it's mass, and we argued about whether it was a rock or a gas ball. And today we are diagnosing the viscosity of its molten mantle and smelling its rotten egg atmosphere. We are dissecting its internal thermodynamics.

It's a testament to the sheer, relentless ingenuity of the people who build these instruments. It really underscores the power of empirical observation to humble our theoretical models. We build neat boxes based on what we know path one or path two. Then the universe presents us with a world that shatters those boxes, forcing us to expand our understanding of physics and chemistry to accommodate a much wilder reality.

It's so true. We started this conversation looking at a world that is objectively terrifying, a glowing, toxic, boiling hellscape where life as we understand it cannot possibly exists.

Right. The radiation would fry you, the heat would melt you, and the atmosphere would suffocate you. It is the ultimate anti Earth.

But I want to look at this mechanism from a slightly different angle before we wrap up. Okay, let's take a step back from the extreme nightmare of L ninety eight fifty nine D and look purely at the planetary engine we just spent the last hour unpacking. We have an engine driven by tidal and primordial heat, maintaining a deep magma ocean that acts as an incredibly stable, billion

Okay, I see where you're going with this.

Now take that exact same internal machinery, like exact same magma de gassing engine, but mentally move the planet further away from the host star.

Moved out of the blood towards zone.

Exactly place it safely in the habitable zone where the surface temperature is actually cool enough for liquid water to exist, but the internal tidal friction keeps the mantle active and convecting. Oh wow, could this exact mechanism, this slow billion year exhalation of trapped volatiles from a deep internal reservoir, Could that be the very engine that jump starts prebiotic chemistry?

I mean, yes, we know that early Earth had a magma ocean phase.

We know that outgassing from our own mantle built our secondary atmosphere and provided the raw chemical building blocks for the primordial soup. So by analyzing the extreme lethal overdrive version of this planetary engine on L ninety eight fifty nine, dy, are we actually reverse engineering the very machinery that creates the conditions for life on truly habitable worlds?

Are we looking at the monstrous, high speed prototype of the system that breathes life into our own planet.

Exactly. It is a profound possibility to consider. We study the extremes to understand the middle, and the deeper we peer into the chemistry of these hostile worlds, the closer we get to understanding the delicate, more miraculous balance required to build a world like ours.

That is. That's a beautiful way to think about it. It really is.

It is something to think about the next time you look up at the night sky, past the glare of the city lights into the vast, populated darkness of the Milky Way. Absolutely, thank you so much for joining us on this exploration of the cosmos. The search for diversity in the universe continues, and discoveries like this make it brilliantly clear that we have only begun to scratch the surface of what is out there. Until next time, teachers, the

Gay Chara