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: I want you to close your eyes for a second.
Speaker 2: We're going to do something a little dark to start
Speaker 2: things off today.
Speaker 3: Oh I'm intrigued.
Speaker 2: I want you to imagine the absolute worst case scenario.
Speaker 2: And I'm not talking about a stock market crash or
Speaker 2: a hurricane, or even a zombie apocalypse. I'm talking about
Speaker 2: the ultimate cosmic end game, the big one, the death
Speaker 2: of a solar system.
Speaker 3: It is a scale of destruction that is genuinely hard
Speaker 3: for the human mind to process. I mean, we are
Speaker 3: talking about physics on a scale that makes our most
Speaker 3: powerful nuclear weapons look like tiny firecrackers popping in the
Speaker 3: distance exactly.
Speaker 2: And I think when most people picture this the end
Speaker 2: of the world or the end of a star system,
Speaker 2: they think of science chittus.
Speaker 3: A death star.
Speaker 2: You think of the death star, right it's a giant
Speaker 2: laser beam, a sudden green flash and explosion and boom,
Speaker 2: the planet has gone instant darkness. But the reality, the
Speaker 2: actual science of it, is actually much slower and much
Speaker 2: more insidious, and honestly, it is a lot scarier.
Speaker 3: It is not an explosion.
Speaker 2: It's a suffocation.
Speaker 3: That is a very very apt way to put it.
Speaker 3: It's the slow, inevitable swelling of a star, the transition
Speaker 3: to the red giant phase.
Speaker 2: The red giant just the name sounds menacing. Picture of
Speaker 2: star are maybe running out of fuel. It gets angry,
Speaker 2: It starts expanding outward like a balloon being overinflated. It
Speaker 2: swallows everything in its path. Mercury gone, Venus toast toast.
Speaker 2: Earth will get to Earth later. And it's not a
Speaker 2: pretty picture. But for a long time, the assumption in
Speaker 2: astronomy was that this is basically a death sentence for
Speaker 2: the entire neighborhood. If your star goes red giant, it's
Speaker 2: game over.
Speaker 3: That has been the prevailing wisdom for decades. When a
Speaker 3: star sheds its outer layers and swells up, the gravitational
Speaker 3: and thermal forces are so extreme that we generally assume
Speaker 3: planetary systems are wiped clean.
Speaker 2: The slate is wipe blank exactly.
Speaker 3: The star expands, consumes the inner planets, destabilizes the outer ones,
Speaker 3: and leaves nothing but dust.
Speaker 2: But and this is why we are here today. There's
Speaker 2: a twist, you plot twist in the story of stellar death.
Speaker 2: H It turns out not everyone dies. There are survivors,
Speaker 2: party survivors, and that is the mystery we are unpacking today.
Speaker 2: How do you survive being swallowed or scorched by your
Speaker 2: own son? And more importantly, who are these survivors? Because
Speaker 2: we have some brand new informations literally hot off the breast,
Speaker 2: that changes how we look at this.
Speaker 3: It really is brand new. I mean we are looking
Speaker 3: into data that came out essentially yesterday, February fourth, twenty
Speaker 3: twenty six.
Speaker 2: It doesn't get fresher than that. Yeah, So what are
Speaker 2: we looking at? What's the source?
Speaker 3: This is a new study published in Astronomy and Astrophysics
Speaker 3: and it's currently making waves on the ARCSIV server. The
Speaker 3: title is predicted incidents of Jupiter like planets around white dwarfs.
Speaker 2: Predicted incidents. It's very polite.
Speaker 3: Academic titles always hide at the drama, don't they. But
Speaker 3: the lead author is alex Mars Soriano from the DEPARTMENTA
Speaker 3: of Phisica at the University DoD Technica Federico Santa Maria
Speaker 3: in Valpariso, Chile, Okay. And what they have done is fascinating.
Speaker 3: They haven't just looked for these planets with a telescope,
Speaker 3: They've built a comprehensive simulation of the Milky Way to
Speaker 3: predict them.
Speaker 2: So our mission today is to look at this census
Speaker 2: of the survivors. We want to know, out of all
Speaker 2: the planets that face this fiery apocalypse, how many actually
Speaker 2: make it through to the other side.
Speaker 3: And we aren't just looking at pretty pictures of space here,
Speaker 3: we are digging into the physics. Yeah, we need to
Speaker 3: figure out exactly how rare these survivor planets are. Are
Speaker 3: they one in a million, one in ten?
Speaker 2: Right? And why does one planet survive while its neighbor
Speaker 2: gets completely vaporized?
Speaker 3: And here is the So what for you listening right now?
Speaker 3: This isn't just about some distant star light years away.
Speaker 3: This is a preview.
Speaker 2: It's a trailer.
Speaker 3: It's a trailer for the future of our own Solar system.
Speaker 3: We are basically looking at the fate of Jupiter and Saturn.
Speaker 2: That is exactly right. By studying these distant systems, we
Speaker 2: are essentially looking into a crystal ball for our own neighborhood.
Speaker 2: We're seeing our own future played out on a galactic stage.
Speaker 3: Yeah, future, that's about what five six billion years away,
Speaker 3: But still it's written in the stars.
Speaker 2: So let's unpack this. Before we get to the survivors.
Speaker 2: We have to understand the killer. We need to talk
Speaker 2: about the mechanism of destruction. Why is survival so incredibly hard?
Speaker 3: To understand the destruction, you have to understand the life
Speaker 3: cycle of a star. Most stars, like our Sun, spend
Speaker 3: the vast majority of their lives in what we call
Speaker 3: the main sequence.
Speaker 2: That's the happy, stable time, the prime of life.
Speaker 3: Correct, it's burning hydro into helium in its core. It's stable.
Speaker 3: Gravity is pulling in trying to crush the star, but
Speaker 3: the energy from fusion is pushing out, and everything is
Speaker 3: in a perfect hydrostatic balance, a standoff. It's a standoff
Speaker 3: between two tightened forces, and as long as there is fuel,
Speaker 3: the standoff holds. But eventually the hydrogen runs.
Speaker 2: Out, the fuel tank gets empty, and when the gas
Speaker 2: tank is empty in a car, the car stops.
Speaker 3: Right in a car, Yes, in a star, it's the opposite.
Speaker 3: When the fuel runs out in the core, the engine
Speaker 3: goes haywire. Core starts to collapse because there's no outward
Speaker 3: pressure to hold it up to more. But as the
Speaker 3: core collapses, it gets hotter, much much hotter. This new
Speaker 3: intense heat pushes the outer layers of the star away, so.
Speaker 2: The outer parts stop listening to gravity.
Speaker 3: They stop listening to gravity, they start to expand drastically.
Speaker 3: The star transitions from a main sequence star into a
Speaker 3: red giant.
Speaker 2: I always like the analogy of a marshmallow in a microwave.
Speaker 3: That is surprisingly accurate.
Speaker 2: Go on, you know what I mean. You put a
Speaker 2: regular hence marshmallow and you hit start. It heats up
Speaker 2: from the inside and it just starts expanding. It gets huge,
Speaker 2: it gets fluffy, It takes up the whole microwave.
Speaker 3: But unlike a marshmallow, which is delicious.
Speaker 2: A red giant is incredibly dangerous. If you are orbiting nearby.
Speaker 3: It is lethal. The radius of the star can increase
Speaker 3: by a factor of one hundred or even more. Our
Speaker 3: Sun will swell up to roughly the orbit of Earth.
Speaker 3: It physically takes up more space and This leads to
Speaker 3: the three ways a planet can die, the three.
Speaker 2: Methods of execution. Let's go through them, because this really
Speaker 2: sets the stakes. It's not just one thing that kills you.
Speaker 2: It's a triple threat.
Speaker 3: The first and most obvious is engulfment, which is just
Speaker 3: what it sounds like. It's exactly what it sounds like.
Speaker 3: The star physically expands past the planet's orbit. The planet
Speaker 3: literally flies inside the star's atmosphere, and.
Speaker 2: Space is a vacuum, so there's usually no friction. But
Speaker 2: inside a star, that's a different story.
Speaker 3: It's a very different story. It's gas. It's thick. The
Speaker 3: friction from the gas the drag. It slows the planet down,
Speaker 3: it loses orbital speed, spirals into the core, and is obliterated. Wow,
Speaker 3: this is the likely fate of mercury and venus in
Speaker 3: our own system. They will simply be swallowed whole.
Speaker 2: And possibly Earth. But we'll pinachaotic maybe on that for now.
Speaker 2: So that's engulfment being eaten alive. What's the second way
Speaker 2: to die?
Speaker 3: Tidal forces? This one is a bit more subtle, but
Speaker 3: just as.
Speaker 2: Destructive, like the tides of the ocean.
Speaker 3: Same principle, but on a mind boggling scale. As the
Speaker 3: star loses mass because it's puffing out these layers into space,
Speaker 3: it's gravity changes. But also because the star is so
Speaker 3: huge and you're so close, the gravitational pull on the
Speaker 3: side of the planet facing the star is much stronger than.
Speaker 2: The pole on the far side, so it gets stretched.
Speaker 3: Ripped apart. Really, we call this spaghettification when we talk
Speaker 3: about black holes, but a similar thing happens here. These
Speaker 3: intense gravitational poles can physically disassemble a planet before it
Speaker 3: even gets engulfed.
Speaker 2: It just crumbles under the stress.
Speaker 3: The planet's own gravity isn't strong enough to hold it
Speaker 3: together against the pull of the star. It's like pulling
Speaker 3: a piece of bread apart.
Speaker 2: Okay, so you can be eaten or you can be
Speaker 2: ripped to shreds. Not great options.
Speaker 3: And the third vaporization, the transition from a main sequence
Speaker 3: star to a red giant involves intense heat spikes. The luminosity,
Speaker 3: the brightness of the star skyrockets, so it's not just bigger,
Speaker 3: it's also hotter incredibly, so the radiation can be so
Speaker 3: intense that it boils the planet away. It strips the atmosphere,
Speaker 3: then boils the oceans and melts the rock. It's like
Speaker 3: holding a candle to an ice cube, but the candle
Speaker 3: is a star and the ice cube is a planet.
Speaker 2: So it's a gauntlet you have to dodge being eaten,
Speaker 2: being torn apart, and being.
Speaker 3: Boiled precisely, And if a planet manages to survive all
Speaker 3: of that, if it survives the red giant phase, the
Speaker 3: star eventually sheds all those outer pucky layers.
Speaker 2: Where do they go?
Speaker 3: They drift away into space, creating what we call a
Speaker 3: planetary nebula, which ironically is often beautiful to look at.
Speaker 2: I've seen pictures. They're gorgeous, but it's really a stellar graveyard.
Speaker 3: It is, and what is left behind is the core,
Speaker 3: a dense, hot, tiny remnant called.
Speaker 2: A white dwarf, the corpse of the star.
Speaker 3: A very hot corpse, but yes, about the size of Earth,
Speaker 3: but with the mass of the Sun, incredibly dense. A
Speaker 3: teaspoon of it would weigh tons.
Speaker 2: So if we look up at the sky with our
Speaker 2: telescopes and we see a white dwarf and we see
Speaker 2: a planet orbiting it, that planet is a veteran.
Speaker 3: It is a survivor of a stellar war. It witnessed
Speaker 3: the expansion. It survived the tides, it endured the heat,
Speaker 3: and it is still standing. It has a story to tell.
Speaker 2: That makes them incredibly special. It means they have a
Speaker 2: story to tell. But for a long time, we didn't
Speaker 2: know if any planets actually could survive this. It was
Speaker 2: all theoretical math on a chalkboard exactly.
Speaker 3: We had the models, but we didn't have the proof,
Speaker 3: so we were just guessing. We were guessing until about
Speaker 3: fifteen years ago. We hoped they existed, but we hadn't
Speaker 3: seen one. We weren't sure it was even possible.
Speaker 2: But then we found evidence, and this takes us to
Speaker 2: the second part of our journey. Today we know they exist.
Speaker 2: This isn't just math anymore.
Speaker 3: No, we have direct observations. The first major clue came
Speaker 3: back in twenty eleven.
Speaker 2: Take us back to twenty eleven. What did they find?
Speaker 3: Astronomers discovered an exoplanet orbiting a white dwarf. It was massive,
Speaker 3: about eight times the mass of Jupiter.
Speaker 2: That is a beast of a planet that's bordering on
Speaker 2: a brown dwarf. Isn't it one of those failed stars?
Speaker 3: It's getting there but still classified as a planet. But
Speaker 3: the key detail wasn't its size, it was its location.
Speaker 3: It was orbiting at a distance of about twenty five
Speaker 3: hundred astronomical units AU.
Speaker 2: Okay, let's put that in respective for everyone. One AU
Speaker 2: is the distance from the Earth to the Sun. That's
Speaker 2: our yardstick. Jupiter is about five AU out right.
Speaker 3: And Pluto, which we all think of as being way
Speaker 3: out there, is about forty AU on average.
Speaker 2: And the voyager probes the furthest things humans have ever
Speaker 2: sent are only about one hundred and fifty to one
Speaker 2: hundred and sixty AU out right now, and they've been
Speaker 2: traveling for decades.
Speaker 3: So this thing at twenty five hundred AU was way
Speaker 3: way out there.
Speaker 2: That is lonely. That is deep deep space, that is
Speaker 2: practically in the interstellar void.
Speaker 3: It is incredibly far, but that distance is exactly why
Speaker 3: it survived. We call this survival tactic the distant observer
Speaker 3: self explanatory. It was simply too far away to be
Speaker 3: touched by the Red Giant's expansion. The star swelled up,
Speaker 3: but the planet was sitting way back in the cheap
Speaker 3: seats watching the fireworks, completely safe.
Speaker 2: So the strategy there is simple avoidance. Just be really
Speaker 2: really far away.
Speaker 3: Exactly. It's the safest bet. If you aren't near the explosion,
Speaker 3: you don't get hurt. Problem solved.
Speaker 2: But then in twenty twenty we got a second clue
Speaker 2: that really complicated the picture.
Speaker 3: The plot thickens because nature is never that simple.
Speaker 2: Never what happened in twenty twenty.
Speaker 3: Astronomers found another Jupiter sized gas giant around a white dwarf.
Speaker 3: But this one was orbiting very close to the star.
Speaker 2: How close are we talking?
Speaker 3: Close enough that it completes an orbit in just a
Speaker 3: few days, not years. It was hugging the star well
Speaker 3: well within where Mercury's orbit would be in our Solar system.
Speaker 2: Wait, hang on, if it's that close, it should have
Speaker 2: been eaten. We just established that when the star was
Speaker 2: a red giant, it would have expanded way past that orbit,
Speaker 2: way past it should be inside the star's stomach, effectively exactly.
Speaker 2: That is the puzzle. It could not have survived the
Speaker 2: red giant phase at its current distance. It would have
Speaker 2: been engulfed and destroyed instantly, no question. So how is
Speaker 2: it there? Is it a ghost planet? Did it form afterwards?
Speaker 2: Like a phoenix rising from the ashes?
Speaker 3: Unlikely to form afterwards? There isn't usually enough material left
Speaker 3: in the disk around a white dwarf to build a giant.
Speaker 2: Planet from scratch, it was the theory.
Speaker 3: The leading theory is that this planet is the migrator.
Speaker 3: It didn't start there. It survived the red giant phase
Speaker 3: by being further out, maybe in that safe zone we
Speaker 3: talked about beyond a few au Okay.
Speaker 2: So as a distant observer at first.
Speaker 3: Yes, But then after the star shrank down into a
Speaker 3: white dwarf and things calmed down, something caused the planet
Speaker 3: to spiral inward.
Speaker 2: So it moved into the empty house after the fire
Speaker 2: was put out.
Speaker 3: That's a great way to put it. It survived the
Speaker 3: danger zone, then migrated in later. Usually this happens because
Speaker 3: of scattering. Maybe another massive planet in the system gave
Speaker 3: it a gravitational kick, or the disc of debris left
Speaker 3: over from the star's death dragged it in.
Speaker 2: So we have two pathways to survival. Pathway one the
Speaker 2: distant observer stay far away and don't move. Pathway two
Speaker 2: the migrator stay far away during the danger, then move
Speaker 2: in close when it's safe.
Speaker 3: Those seem to be the two main options. If you
Speaker 3: stay close and don't move, you die.
Speaker 2: Simple rules for a complicated universe. But here's the problem,
Speaker 2: and this leads us right into the new research from
Speaker 2: Max Soriano. We found these two examples, right, A couple
Speaker 2: others maybe, but we haven't found many.
Speaker 3: That is the issue. We have found thousands of exoplanets
Speaker 3: around normal stars, thousands, we find them everywhere we look.
Speaker 3: But planets around white dwarfs we have a literal handful.
Speaker 2: So the question is are they missing because they are rare,
Speaker 2: or are they missing because we just aren't good at
Speaker 2: seeing them.
Speaker 3: This is the classic servational bias problem in astronomy. It's
Speaker 3: a huge question.
Speaker 2: Maybe they're there, but we just can't spot them.
Speaker 3: It's possible white dorks are dim. Planets are dim. Maybe
Speaker 3: the glare from the white dwarf, even though it's faint,
Speaker 3: hides them. Maybe we just haven't looked at enough of
Speaker 3: them for long enough. It's like looking for a needle
Speaker 3: in a haystack, but we aren't sure if we're even
Speaker 3: holding a magnet.
Speaker 2: And this is where Max Soriano and the team from
Speaker 2: Chili come in. They decided to stop guessing and start simulating.
Speaker 3: Right. Instead of just relying on our limited telescope data,
Speaker 3: they used stellar evolution codes. They essentially built a physics
Speaker 3: engine of the Milky Way.
Speaker 2: I love when scientists do this. We can't find it,
Speaker 2: so let's build a universe where we can calculate it.
Speaker 2: It's like playing some city, but with solar systems.
Speaker 3: It's an incredibly powerful tool. They factored in everything mass
Speaker 3: loss from the star, how gravity changes, the tidal forces,
Speaker 3: which we'll get to, the metallic makeup of stars. They
Speaker 3: ran the numbers to predict how many of these survivors
Speaker 3: should exist.
Speaker 2: So they're not observing, therefore casting exactly.
Speaker 3: They simulated the entire life cycle from birth to death
Speaker 3: for millions of scenarios to see what the end result
Speaker 3: should be, and they.
Speaker 2: Came back with a number, a specific percentage of white
Speaker 2: dwarfs that should have a Jupiter like survivor orbiting them.
Speaker 3: They did, and that number is less than three percent.
Speaker 2: Wow, less than three percent. Yes, that means for every
Speaker 2: one hundred dead stars you look at, ninety seven of
Speaker 2: them are alone or at least they don't have a
Speaker 2: gas giant survivor.
Speaker 3: It is a massacre out there. The vast, vast majority
Speaker 3: of planets do not make it.
Speaker 2: That feels incredibly low. I mean, we look at our
Speaker 2: Solar System. We see Jupiter and Saturna. They seem so
Speaker 2: big and permanent. We think of them as the kings
Speaker 2: of the Solar System. We assume they are invincible. But
Speaker 2: you're saying, in the grand scheme of stellar evolution, keeping
Speaker 2: a planet like that is a rarity.
Speaker 3: It is. The transition to a white dwarf is a chaotic,
Speaker 3: violent event. It cleans house. Now there is a small
Speaker 3: caveat the researchers point out, which is important. If we
Speaker 3: look at what they call the local age metallicity relation,
Speaker 3: basically stars that are similar to our Sun and in
Speaker 3: our local neighborhood of the galaxy, that number might creep
Speaker 3: up to roughly eight percent.
Speaker 2: Okay, eight percent is better than three percent, but it's
Speaker 2: still single digits. It's still a tiny minority.
Speaker 3: Absolutely. It implies that a white dwarf with a planet
Speaker 3: is the exception, not the rule. The default state for
Speaker 3: a dead star is loneliness.
Speaker 2: And another thing that study noted, ninety five percent of
Speaker 2: these survivors are gas giants like Jupiter, not brown dwarfs.
Speaker 3: That's an important distinction. Brown dwarfs are these failed stars.
Speaker 3: They are heavier than planets anywhere from thirteen to eighty
Speaker 3: times the mass of Jupiter, but not heavy enough to
Speaker 3: ignite fusion in their cores.
Speaker 2: You would think being heavier and tougher they would survive better.
Speaker 3: Yeah, logic would suggest the biggest kid on the playground
Speaker 3: doesn't get pushed around. If you're heavier, you should be
Speaker 3: harder to push into the star. Right, more inertia, you'd think,
Speaker 3: But the simulation shows that planets seem to survive better
Speaker 3: than brown dwarfs in this specific context. It's a nuanced
Speaker 3: interplay of a few things.
Speaker 2: Like what well.
Speaker 3: First, Brown corps are rare to begin with compared to
Speaker 3: gas giants, but more importantly, they interact with tides differently.
Speaker 3: They raise much stronger tides on the star because they.
Speaker 2: Are so massive ah, and stronger tides create more.
Speaker 3: Drag exactly, more drag which pulls them in faster. So
Speaker 3: being big can actually be a disadvantage here. You're too
Speaker 3: good at slowing yourself down and spiraling to your doom.
Speaker 2: So if you want to survive the apocalypse, be a
Speaker 2: gas giant, don't be a brown dwarf, and definitely don't
Speaker 2: be a rocky planet like Earth.
Speaker 3: Correct, Rocky planets are usually too close, they get swallowed.
Speaker 3: Being small and close is a death sentence.
Speaker 2: Okay, so we know it's rare, we know it's dangerous.
Speaker 2: But let's dig into the survivor's handbook. Because even though
Speaker 2: only three percent make it, some do make it. Who
Speaker 2: are they? What makes them special? The paper breaks this
Speaker 2: down into specific factors they did.
Speaker 3: They identified several key factors. Think of this as the
Speaker 3: checklist for survival. If you are a planet and you
Speaker 3: want to live, you need to check these boxes.
Speaker 2: Factor're number one, the parent stars mass.
Speaker 3: This is crucial. It turns out there's a Goldilock zone
Speaker 3: for the star itself. Not too hot, not too cold,
Speaker 3: not too big, not too small.
Speaker 2: Okay.
Speaker 3: Survival peaks when the resulting white dwarf ends up being
Speaker 3: between point five to three and point sixty six solar masses.
Speaker 2: Okay, those are numbers. Translate that. What does that mean
Speaker 2: for the star before it died, when it was in
Speaker 2: its prime.
Speaker 3: It corresponds to a progenitor, the original star having a
Speaker 3: mass of about one to three times the mass of
Speaker 3: our sun.
Speaker 2: So you don't want a star that was too huge
Speaker 2: to begin with, right.
Speaker 3: If the star is really massive, say eight or ten
Speaker 3: solar masses. It doesn't go out with a whimper. It
Speaker 3: goes out with a bang.
Speaker 2: It goes supernova.
Speaker 3: Yeah, and nobody survives as supernova nearby. That's just a bomb.
Speaker 3: It sterilizes the entire system.
Speaker 2: Right.
Speaker 3: But if the star is too small, like a red dwarf,
Speaker 3: it takes trillions of years to evolve. The universe isn't
Speaker 3: old enough for those to have turned into white dwarfs yet.
Speaker 3: So you need a star like the Sun or a
Speaker 3: bit bigger. That is the sweet spot for creating a
Speaker 3: white that might still have a planet. You need a
Speaker 3: star that lives a normal life span and dies a
Speaker 3: relatively gentle death.
Speaker 2: Okay, so fac to one pick a medium sized star
Speaker 2: like ours, good start for us. Factor two the age
Speaker 2: of the system.
Speaker 3: This was interesting. They found that younger systems, those between
Speaker 3: one and six billion years old, have higher survival rates.
Speaker 3: They are above that three percent baseline.
Speaker 2: Wait, how can a young system have a dead star?
Speaker 2: That sounds contradictory. If it's young, shouldn't the star still
Speaker 2: be burning?
Speaker 3: Young is relative in astronomy. A more massive star, say
Speaker 3: three solar masses, burns through its fuel much faster. It
Speaker 3: guzzles gas.
Speaker 2: It lives fast and dies young exactly.
Speaker 3: So you can have a system that is only two
Speaker 3: billion years old. But the star was big, so it
Speaker 3: burned through its fuel and a flash went through its
Speaker 3: red giant phase, died and became a white dwarf.
Speaker 2: I see. So the system itself is young, even if
Speaker 2: its star is already dead.
Speaker 3: Correct. And the study suggests that in these younger old
Speaker 3: systems more planets survive.
Speaker 2: Why why does age hurt survival?
Speaker 3: Well, the paper doesn't say for certain, but we can
Speaker 3: speculate maybe in much older systems ten twelve billion years old,
Speaker 3: there's just been more time for things to go wrong. Entropy, chaos,
Speaker 3: orbits destabilize over eons, Other stars pass by in the galaxy,
Speaker 3: and their gravity can nudge things around. The longer you
Speaker 3: hang around, the more likely you are to get kicked
Speaker 3: out of the system or crash into something else. It's
Speaker 3: dynamic instability.
Speaker 2: Given enough time, gravity finds a way to ruin your day.
Speaker 3: That's a good way of putting it.
Speaker 2: So speed matters. Get the apocalypse over with quickly if
Speaker 2: you want to keep your planets.
Speaker 3: In a manner of speaking, Yes.
Speaker 2: All right. Factor three. This one seems obvious, but we
Speaker 2: need the numbers orbital separation the safe zone.
Speaker 3: The data is very clear here. Surviving companions are usually
Speaker 3: found between three and twenty four AU.
Speaker 2: Let's context that again, Jupiter is at five AU.
Speaker 3: So Jupiter is right at the inner edge of this
Speaker 3: survival belt.
Speaker 2: That makes me nervous for Jupiter, it's barely safe. It's
Speaker 2: standing right next to the fire exit.
Speaker 3: It is on the edge. But three AU seems to
Speaker 3: be the cutoff. Anything closer than three AU usually gets
Speaker 3: swallowed by the red giant expansion.
Speaker 2: And what about the outer edge twenty four AU. What
Speaker 2: happens beyond that?
Speaker 3: Well, anything further out than twenty four AU is safer
Speaker 3: from the expansion for sure, but it might be less
Speaker 3: common just due to how planets form in the first place.
Speaker 3: You don't get as many giant planets forming way way
Speaker 3: out there in the protoplanetary disk. The gas and dust
Speaker 3: are too thin to clump together efficiently.
Speaker 2: So the survival belt is three to twenty four AU.
Speaker 2: If you are in there, you have a fighting chance.
Speaker 3: Correct, it's the sweet spot.
Speaker 2: And finally, fact four. This one sounded like a heavy
Speaker 2: metal band. Metallicity.
Speaker 3: Ah Yes, metallicity in astronomy, we have a very funny
Speaker 3: periodic table. It confuses the chemists to no end. Also,
Speaker 3: to an astronomer, there is hydrogen, there is helium, and
Speaker 3: everything else is a metal.
Speaker 2: Carbon, metal, oxygen, metal, nitrogen, iron, all metals.
Speaker 3: So when we talk talk about a star with high metallicity,
Speaker 3: we mean a star that has a lot of heavier
Speaker 3: elements in it, elements that aren't the primordial hydrogen or
Speaker 3: helium from the Big Bang.
Speaker 2: And why does that help a planet survive.
Speaker 3: It's not so much that it helps them survive the fire.
Speaker 3: It helps them exists in the first place. High metallicity
Speaker 3: stars are more likely to form planets, especially giant ones.
Speaker 2: It's a numbers game exactly.
Speaker 3: You need the raw materials, the dust, the rock, the
Speaker 3: ice to build a gas giant core. If a star
Speaker 3: is rich in metals, it has more building blocks available
Speaker 3: in its initial discs.
Speaker 2: It's like trying to build a lego castle. If you
Speaker 2: have three buckets of bricks, you can build a bigger,
Speaker 2: better castle than if you only have three bricks.
Speaker 3: Perfect analogy. If a star is rich in metals, it
Speaker 3: builds more planets and bigger planets. So if you start
Speaker 3: with more planets, statistically you end up with more survivors.
Speaker 2: The quote in the paper was something like, progenitors with
Speaker 2: higher metallicities simply form more planets.
Speaker 3: Simple logic. More lottery tickets means a higher chance of winning.
Speaker 2: So to recap the survivor's handbook, pick a sun likes
Speaker 2: don't be too old as a system, orbit between three
Speaker 2: and twenty four AU, and make sure your star is
Speaker 2: made of heavy stuff.
Speaker 3: That is your best bet for making it through. But
Speaker 3: even then, there is an invisible killer we haven't discussed yet,
Speaker 3: a variable that could ruin everything.
Speaker 2: The invisible killer. This sounds ominous, it is.
Speaker 3: We mention it briefly in the death list, but we
Speaker 3: need to go deeper. We need to talk about tides.
Speaker 2: This was a big part of the new paper, right,
Speaker 2: the physics of tides. Now, when I think of tides,
Speaker 2: I think of the beach, the moon pulls the water,
Speaker 2: high tide, low tide. It's peaceful.
Speaker 3: That is the basic concept gravity from one object stretching another.
Speaker 3: But now scale it up to a star that is
Speaker 3: swelling to the size of Earth's orbit. Okay, not peaceful,
Speaker 3: not peaceful at all. As the star swells, it becomes fluffy.
Speaker 3: It's not a dense ball anymore. It's a diffuse, turbulent
Speaker 3: cloud of hot gas what we call the convective envelope marshmallow.
Speaker 2: Again.
Speaker 3: Yes, Now, imagine a planet orbiting through the outer edges
Speaker 3: of that fluff. We're just near it. The planet raises
Speaker 3: tides on the star. It gravitationally pulls the gas toward it,
Speaker 3: and the star raises tides on the planet.
Speaker 2: It's a gravitational tuggle war.
Speaker 3: It is. But here is the catch, tidal lag. The
Speaker 3: star is spinning and the planet is orbiting. They aren't
Speaker 3: perfectly syncd The bulge of gas that the planet pulls
Speaker 3: up it doesn't point directly at the planet because of
Speaker 3: the star's rotation. It lags behind or pulls ahead.
Speaker 2: Okay, so they are at a sink. What does that do?
Speaker 3: And that misalignment creates torque, It creates friction, It creates.
Speaker 2: Drag drag like air resistance.
Speaker 3: It's a very similar concept. Think of it like this.
Speaker 3: If the planet is orbiting through empty space, it glides
Speaker 3: effortlessly forever. But if the star swells up and the
Speaker 3: planet starts interacting with those powerful tidal forces, it's like
Speaker 3: the planet is suddenly wading through molasses that slows it down,
Speaker 3: and in orbital mechanics, if you slow down, you drop,
Speaker 3: your orbit decays, you spiral.
Speaker 2: Inward toward the center of the star, toward destruction. So
Speaker 2: the tides act like a break, dragging the planet to
Speaker 2: its two exactly.
Speaker 3: But here is the controversy in the paper, and it's
Speaker 3: a huge deal. The researchers had to choose between two
Speaker 3: different mathematical formulas for tides. Because we don't know exactly
Speaker 3: how thick or sticky that interaction is.
Speaker 2: You can't test it.
Speaker 3: We don't have a red giant nearby to test it on.
Speaker 3: So it's a big debate. In astrophysics. There are weak
Speaker 3: tides based on a model by a. Villaver and Lvio
Speaker 3: from two thousand and nine, and there are strong tides
Speaker 3: suggested by Ratio and colleagues back in nineteen ninety six.
Speaker 2: What's the difference in the outcome?
Speaker 3: It's enormous. Imagine the difference between wading through water versus
Speaker 3: wading through quicksand that is the difference between weak and
Speaker 3: strong tides.
Speaker 2: So if the tides are weak, the planet.
Speaker 3: Experiences less drag, it's more likely to stay in its orbit.
Speaker 3: The survival rate effectively doubles in.
Speaker 2: Their simulation, doubles just from that one variable.
Speaker 3: Yes, and if the tides are strong.
Speaker 2: Then planet gets dragged in.
Speaker 3: The drag is immense. The planet gets pulled in and
Speaker 3: destroyed much much more easily. The survival rate plummets.
Speaker 2: So the fate of these planets literally hangs on a
Speaker 2: variable in a math equation that we aren't one hundred
Speaker 2: percent sure about.
Speaker 3: Yet it does. The paper has this fascinating graph. They
Speaker 3: call it the island of probability in the strong tide scenario.
Speaker 3: The graph shows just this tiny, tiny island of mass
Speaker 3: and distance where a planet can live. Everywhere else is
Speaker 3: a sea of death.
Speaker 2: And if you turn up the tides even a little
Speaker 2: bit more than that.
Speaker 3: The island sinks. The survival rate drops to almost zero.
Speaker 2: That is terrifyingly fragile. It means survival is on a
Speaker 2: razor's edge.
Speaker 3: It highlights just how chaotic this transition is. It's not
Speaker 3: a gentle process. It is a violent, turbulent restructuring of
Speaker 3: gravity and matter. One small change in the physics can
Speaker 3: be the difference between life and death for an entire world.
Speaker 2: So we have the simulation saying survival is rare, less
Speaker 2: than three percent. But let's go back to the reality check.
Speaker 2: We have telescopes, we have the James Web, we have
Speaker 2: giant ground based observatories. Why aren't we seeing more of
Speaker 2: these survivors?
Speaker 3: The paper addresses this directly. They ask is this a
Speaker 3: detection problem or an existence problem?
Speaker 2: Meaning are they there and we just can't see them,
Speaker 2: or are they just not there in the first place?
Speaker 3: Right? Direct imaging Taking a picture of a planet is
Speaker 3: incredibly hard. It depends on contrast. You need a bright
Speaker 3: planet and a dim star, and.
Speaker 2: White dwarfs change over time, don't they They do.
Speaker 3: They're born incredibly hot, glowing white or blue, but they're
Speaker 3: not generating new energy. They're just cooling off. A young
Speaker 3: white dwarf is relatively bright and hot. An old one
Speaker 3: is cold and dim.
Speaker 2: And the planet cools down too.
Speaker 3: I assume exactly, it's not getting much energy from its
Speaker 3: dead stars. If you have a cold, faint planet orbiting
Speaker 3: a cold faint star, it's like trying to spot a
Speaker 3: piece of coal in a dark cellar from a mile away. Impossible,
Speaker 3: very very difficult. So the older the system, the harder
Speaker 3: it is to see a surviving planet.
Speaker 2: So are we missing them?
Speaker 3: Is that the answer, the conclusion in the paper is no,
Speaker 3: or at least not entirely. They argue that even when
Speaker 3: you account for how hard it is to see them,
Speaker 3: the number are still too low. Our current surveys should
Speaker 3: have found more by now if they were common.
Speaker 2: So the scarcity is real. The simulation is likely correct.
Speaker 3: Yes, the low number of detections isn't just because the
Speaker 3: eyes are bad. It reflects reality. They really are that rare.
Speaker 3: Most planets simply die.
Speaker 2: That is a sobering thought.
Speaker 3: It is It validates the simulation. The universe is a
Speaker 3: graveyard of planetary systems.
Speaker 2: Well on that cheerful note. Yeah, let's bring this home,
Speaker 2: literally home to our Solar system, because we started this
Speaker 2: by saying this is a trailer for our future.
Speaker 3: Yes, let's apply these findings to us. Let's run the
Speaker 3: diagnostics on the Solar system using their survivor's handbook.
Speaker 2: We have the Sun. It's a main sequence star. In
Speaker 2: about five billion years give or take, it runs out
Speaker 2: of hydrogen in its core. It goes red giant.
Speaker 3: Correct, Phase one of the end begins.
Speaker 2: Let's do the roll call Mercury and venus.
Speaker 3: Engulfed, vaporized, gone. They don't stand a chance. They are
Speaker 3: deep inside the furnace. Earth is right on the bubble.
Speaker 3: The Sun will expand almost exactly to Earth's orbit. Some
Speaker 3: models say it stops just short, some say it swallows us.
Speaker 2: And even if it stops short, even.
Speaker 3: If it stops just short, the heat will be so
Speaker 3: intense it will strip our atmosphere and boil the oceans dry.
Speaker 3: Earth as a living planet is dead. That happens way
Speaker 3: before the red giant phase, actually just from the Sun
Speaker 3: getting brighter. But Earth as a rock maybe it survives,
Speaker 3: but likely those tidal forces we talked about, they will
Speaker 3: drag it in.
Speaker 2: So don't buy real estate for the year five million,
Speaker 2: twenty six.
Speaker 3: Not a recommended long term investment.
Speaker 2: Mars.
Speaker 3: Mars is further out. It will almost certainly escape the engulfment,
Speaker 3: but the radiation will toast it. It will be a
Speaker 3: burnt cinder. It's thin atmosphere long gone.
Speaker 2: And then we get to the big boys, Jupiter and Saturn.
Speaker 3: This is where the paper gives us hope. Jupiter is
Speaker 3: at five AU, Saturn is at nine point five AU.
Speaker 2: They are in that three to twenty four AU survival beilt.
Speaker 3: They are smack in the middle of it, and the
Speaker 3: Sun is a one solar mass star that fits the
Speaker 3: progenitor criteria perfectly, and we.
Speaker 2: Have decent metal city. Our Sun has all those metals
Speaker 2: we do.
Speaker 3: The Sun is a relatively metal rich star, which is
Speaker 3: why we have a robust planetary system in the first place.
Speaker 2: So Jupiter and Saturn to check all the boxes, they're
Speaker 2: the designated survivors.
Speaker 3: Statistically, yes, we are likely in that lucky three percent,
Speaker 3: or given our local conditions, that more hopeful eight percent.
Speaker 3: When our Sun becomes a white dwarf six or seven
Speaker 3: billion years from now, our inner solar system will be
Speaker 3: a ghost town, but Jupiter and Saturn will likely still
Speaker 3: be there.
Speaker 2: Orbiting a tiny white point of light in the cold.
Speaker 3: In the dark. The Sun will be the size of Earth,
Speaker 3: casting a pale, weak light, no brighter than the full
Speaker 3: moon does on Earth today. Jupiter will be freezing, but
Speaker 3: it will be there.
Speaker 2: There is something hauntingly beautiful about that, a quiet, lonely vigil.
Speaker 3: It is a solar system of two.
Speaker 2: I want to leave our listeners with a final thought. Today,
Speaker 2: we often look up at the night sky and think
Speaker 2: about life and civilizations and beginnings. We think about the
Speaker 2: Goldilock zone for liquid water and biology. There is an
Speaker 2: end to the story too.
Speaker 3: The universe is constantly changing. Nothing stays in the main
Speaker 3: sequence forever.
Speaker 2: I want you to picture that final white dwarf system,
Speaker 2: a burnt out star no bigger than Earth but super dense,
Speaker 2: a cold, dark universe around it, and there, silently orbiting
Speaker 2: in the dark is a massive gas giant, maybe Jupiter,
Speaker 2: with its great red spot long faded, a silent witness exactly.
Speaker 2: It's the last witness to a solar system that once
Speaker 2: hosted life. It's the tombstone, but it's also the legacy,
Speaker 2: the last thing standing.
Speaker 3: And if an alien astronomer looks at our dead solar
Speaker 3: system seven billion years from now, that is what they
Speaker 3: will see. They won't see the pyramids, they won't see
Speaker 3: our skyscrapers, they won't see the Great Wall of China.
Speaker 2: They'll see a white dwarf.
Speaker 3: And they will see Jupiter, and if their instruments are
Speaker 3: good enough, maybe Saturn, and they will know this system
Speaker 3: once was, this system survived.
Speaker 2: So next time you look at Jupiter through a backyard
Speaker 2: telescope or just see that bright, steady dot in the sky,
Speaker 2: don't just see a planet see the survivor, the one
Speaker 2: that makes it to the end.
Speaker 3: Of the book, the hearty survivor.
Speaker 2: Thanks for joining us for this exploration. It's a big
Speaker 2: universe out there, and sometimes it's good to know what
Speaker 2: makes it to the end.
Speaker 3: Indeed, keep looking up.
Speaker 2: Get you next time, Sai.