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 just take a second, close your
Speaker 2: eyes maybe, and think about our moon, Luna, how absolutely
Speaker 2: vile it is. It's just it's so big, so close,
Speaker 2: it feels fundamental. You know, we kind of take it
Speaker 2: for granted. We see the tide, sure, we see the moonlight,
Speaker 2: but do we really stop to think that if Earth
Speaker 2: hadn't captured that giant companion way back when life like us, complex,
Speaker 2: long lived life, it might never have even gotten started. Seriously,
Speaker 2: we could have been just this unstable spinning rock, wobbling
Speaker 2: all over the place with a crazy axial tilt, no
Speaker 2: stable climate, no chance. And that thought brings us right
Speaker 2: into this huge paradox. In our search for life out there,
Speaker 2: we found thousands of exoplanets, thousands, the galaxy seems packed
Speaker 2: with them, But exo moons where are they? Logically they
Speaker 2: have to be out there, right. We have zero confirmed ones, none,
Speaker 2: just maybe a couple of interesting candidates that we're still
Speaker 2: squinting at. Finding them is tough, really tough. So astronomers
Speaker 2: have been focusing on where moons might matter most for habitability,
Speaker 2: and for a long time that meant looking at planets
Speaker 2: around m dwarfs, you know, the old red dwarf stars.
Speaker 2: They make up most of the stars in the galaxy.
Speaker 2: But it turns out the physics in those systems it
Speaker 2: might be incredibly harsh, really destructive. So today we're diving
Speaker 2: into some fascinating new research. It's led by Sean Patel
Speaker 2: and the paper's title really says it all tidally torn
Speaker 2: why the most common stars may lack large habitable zone moons.
Speaker 2: We're going to unpack the well terrifying orbital mechanics of
Speaker 2: these red dwarf systems and find out why the very
Speaker 2: conditions that might seem good for life could actually be destroying.
Speaker 2: The moon's life might need to hang on long term. Okay,
Speaker 2: so let's get into this. Is it possible that the
Speaker 2: most commonplaces for planets in the galaxy are just moonless
Speaker 2: or at least lack the big moons. What does that
Speaker 2: mean for finding another Earth.
Speaker 3: It's a really pivotal question right now in astrobiology, absolutely,
Speaker 3: because we use the Earth Moon system as our benchmark,
Speaker 3: our sort of end of one example for a habitable world.
Speaker 3: And when you compare our moon Luna to basically any
Speaker 3: other moon in our own solar system, the difference is
Speaker 3: just striking. Relative to Earth's size, Our moon is enormous.
Speaker 3: That mass ratio planet to moon, it's way off the
Speaker 3: charts compared to Jupiter's moons or Saturns. And that sheer size,
Speaker 3: that's where it's incredible stabilizing power comes from.
Speaker 2: Right, It's not just a pretty nihild. It's doing heavy
Speaker 2: lifting gravitationally.
Speaker 4: Speaking, exactly.
Speaker 3: The scientific consensus really is that without Luna Earth's history,
Speaker 3: Life's history would look fundamentally different if life even got
Speaker 3: going in the first place, which is a big if.
Speaker 3: We can kind of break down its key jobs for
Speaker 3: habitability into two main things, and we need to grasp
Speaker 3: both to really see what might be missing around those
Speaker 3: m dwarfs.
Speaker 2: Okay, let's start with a big one, the one that
Speaker 2: gives us stable climates over long, long periods, axeal tilt stability.
Speaker 3: Yes, first up is axeal stability. Earth tilts on its
Speaker 3: axis about twenty three point five degrees right now. That
Speaker 3: gives us our regular seasons, predictable climate zones. Our moon
Speaker 3: acts like this giant gravitational gyroscope. Basically it keeps that
Speaker 3: tilt the planet's obliquity from swinging wildly over millions, even
Speaker 3: billions of years without that big moon acting as an anchor.
Speaker 3: Models suggest Earth's tilt could wobble chaotically, maybe from like
Speaker 3: zero degrees so no seasons at all, all the way
Speaker 3: up to eighty five degrees where the poles are practically
Speaker 3: pointing straight.
Speaker 4: At the sun.
Speaker 2: WHOA, okay, eighty five degrees. What happens to a planet
Speaker 2: if its axis is swinging around like that? What are
Speaker 2: the consequences?
Speaker 3: Uh? Cataclysmic is probably the right word. The climate shifts
Speaker 3: would be extreme. If the tilt gets too low, close
Speaker 3: to zero, the poles stay freezing, cold, ice cacs grow huge.
Speaker 3: Maybe you trigger a runaway snowball Earth scenario. But if
Speaker 3: it swings the other way, it's really extreme. You could
Speaker 3: get these incredibly rapid violent climate swings, cycles of oceans
Speaker 3: potentially boiling near the equator and then global deep freezes.
Speaker 2: Yeah, trying to evolve anything more complix than maybe some
Speaker 2: hardy microbes in that kind of environment, Yeah, it sounds impossible.
Speaker 3: It's hard to imagine. The Moon essentially gives us billions
Speaker 3: of years of relative climate stability. That consistent seasonality is
Speaker 3: probably crucial for complex life to emerge, diversify, and thrive.
Speaker 3: You just have to look at Mars. It only has
Speaker 3: these tiny little moons, Phobos and demos. They do basically
Speaker 3: nothing for stability. And Mars's axial tilt it's known to
Speaker 3: have shifted dramatically over geological time.
Speaker 2: Okay, so that's the climate regulation, billions of years of stability.
Speaker 2: What's the second critical function, the one we see every day.
Speaker 3: That's the more immediate biological driver.
Speaker 4: Tidal action.
Speaker 3: The Moon pulls on Earth's oceans, creating the tides, and
Speaker 3: this has really profound biological effects, especially thinking about early
Speaker 3: life and the transition for from water to land, or
Speaker 3: it's complexity in general. Those zones that get repeatedly covered
Speaker 3: and uncovered by water, the intertidal zones, they're incredible mixing
Speaker 3: bowls for nutrients. They constantly expose life forms to both
Speaker 3: water and air, driving really important adaptations.
Speaker 2: Early on, I remember reading about that. Some theories suggest
Speaker 2: tidal pools or these area cycle by tides, or maybe
Speaker 2: key for concentrating the building blocks of life, the organic
Speaker 2: molecules needed to kick things off. So it's not just biodiversity.
Speaker 2: Later on, it could be about the origin itself.
Speaker 3: Absolutely, there's a strong case to be made there. The
Speaker 3: tides dump enormous amounts of mechanical energy into the oceans
Speaker 3: and coastal areas. They stir things up. So whether life
Speaker 3: got its start near deep sea hydrothermal vents or in
Speaker 3: shallow sunlit pools, that constant mixing and movement driven by
Speaker 3: the moon is likely a critical factor, which is why
Speaker 3: when astronomers are looking out at other star systems, just
Speaker 3: finding a rocky planet in the habitable zone, well.
Speaker 4: It might not be enough.
Speaker 3: We really need to find systems that also have these big, stabilizing,
Speaker 3: potentially life stirring moons.
Speaker 2: And this isn't just a fringe idea, right The search
Speaker 2: for exomoons is becoming pretty mainstream in the astronomy community.
Speaker 2: They see the need.
Speaker 3: Oh, definitely, it's moved from theoretical wish lists, right into
Speaker 3: actual observing plans for our best telescopes, I mean prime
Speaker 3: observing time on the James webspased telescope JAWST has been
Speaker 3: specifically allocated to hunt for an exomoon.
Speaker 2: Really, which system are they looking at?
Speaker 3: They're targeting a planet called TOI seven hundred D. It's
Speaker 3: a rocky world, looks like it's smack in the middle
Speaker 3: of its stars habitable zone, and there are some let's say,
Speaker 3: intriguing hints nothing confirmed yet, but hints that it might
Speaker 3: host a large Luna like moon.
Speaker 2: Wow. So if JDABST actually confirmed a big moon there,
Speaker 2: that would be huge game chance.
Speaker 3: We'd be revolutionary overnight. Suddenly, the idea of habitable worlds
Speaker 3: needing moons wouldn't just be based on our one example.
Speaker 3: We'd have another data point. But and this is the
Speaker 3: big butt from the Patel research we're talking about. The
Speaker 3: study suggests that these very systems were most interest in
Speaker 3: the M dwarf systems like TOI seven hundreds might be
Speaker 3: fundamentally unable to keep a large moon like that for
Speaker 3: very long.
Speaker 2: Okay, let's dive into that tension. Why M dwarfs, Why
Speaker 2: are they both the most common places to look statistically
Speaker 2: and maybe the worst places for moons to survive physically. So,
Speaker 2: just to set the scene again, M dwarfs red dwarfs,
Speaker 2: small stars, cool, not very bright, but and this is key,
Speaker 2: they make up something like three quarters of all stars
Speaker 2: in the Milky Way. They're just everywhere, and we know
Speaker 2: from Kepler and tests and other surveys that they often
Speaker 2: have rocky planets orbiting them, including planets in their habitable zones.
Speaker 2: So purely by numbers, M dwarfs look like prime real estate.
Speaker 3: Statistically, yes, absolutely, if you're playing the numbers game, M
Speaker 3: dwarfs are where you place your bets. But the physics,
Speaker 3: the physics gets tricky. The biggest issue comes directly from
Speaker 3: them being so dim. Remember the habitable zone, the Goldilock zone.
Speaker 3: Its distance is said by how much heat the star
Speaker 3: puts out. Because En dwarfs are so faint, their habitable
Speaker 3: zones are in incredibly close to the star Way, way
Speaker 3: closer than Earth's orbit around our Sun.
Speaker 2: Okay, put that in perspective, how close are we talking?
Speaker 3: Well, if you think about Earth being at one astronomical
Speaker 3: unit ninety three million miles from our Sun, the habitable
Speaker 3: zone around a typical en dwarf might be more like uh,
Speaker 3: inside Mercury's orbit, maybe only a few million miles out
Speaker 3: from the star in some cases.
Speaker 2: Wow, Okay, that is close, and being that close has
Speaker 2: major consequences for a planet and especially for its moon. Right,
Speaker 2: tidal sources must be immense.
Speaker 3: Exactly, you get two huge tidal consequences.
Speaker 2: The first one we hear about a lot within boar
Speaker 2: of planets is tidal locking. Yeah, where the planet always
Speaker 2: shows the same face to the star.
Speaker 3: Correct, That close proximity makes it almost inevitable that the
Speaker 3: planet becomes tidally locked, just like our moon is locked
Speaker 3: to Earth. So you get one side perpetually baked by
Speaker 3: the star and the other side locked in permanent freezing
Speaker 3: night life might maybe find a niche in the terminator zone,
Speaker 3: that twilight ring around the edge, but that's a whole
Speaker 3: other challenge for habitability.
Speaker 2: Okay, so tidal locking of the planet is one consequence.
Speaker 2: What's the second, the one that's critical for this research
Speaker 2: about moons.
Speaker 3: The second consequence is the raw power of the stellar
Speaker 3: tides acting on the Moon. Because the habitable zone planet
Speaker 3: is orbiting so incredibly close to the M dwarf, the
Speaker 3: star zone gravity exerts this immense disruptive pull on any
Speaker 3: moon orbiting that planet. The star is basically in a constant,
Speaker 3: fierce gravitational competition with the planet trying to steal its moon.
Speaker 2: It really does sound like a cosmic tug of war.
Speaker 2: The planet's trying to hold onto its moon, but this
Speaker 2: huge star nearby keeps yanking on the rope.
Speaker 3: That's a great way to picture it. And since we
Speaker 3: obviously can't sit and watch this gravitational battle play out
Speaker 3: over billions of years in real time, we have to
Speaker 3: simulate it.
Speaker 2: Right, which brings up the question, how do you even
Speaker 2: model that three massive object star, planet, moon, all pulling
Speaker 2: on each other plus tides. It sounds computationally intense.
Speaker 3: Oh, it is immensely so simple two body gravity, like
Speaker 3: just a planet and a star, planet and a moon.
Speaker 3: That's relatively straightforward. We have nice equations for that. But
Speaker 3: add that third body, the star pulling on the Moon,
Speaker 3: the moon pulling on the star, everything interacting. It blows
Speaker 3: up into the classic three body problem. There's generally no
Speaker 3: neat simple mathematical solution you can just write down.
Speaker 2: So no easy formula. How do they figure out if
Speaker 2: the moon stays or goes and for how long.
Speaker 3: The only practical way is through what are called n
Speaker 3: body simulations. It's a numerical technique. Basically, you telecomputer the
Speaker 3: initial positions and velocities of the star, planet and moon.
Speaker 3: Then the simulation calculates the gravitational force every object exerts
Speaker 3: on every other object over a tiny little timestep, maybe
Speaker 3: just minutes of simulated time. It figures out how those
Speaker 3: forces change their paths, moves them to their new positions,
Speaker 3: and then it repeats again and again for millions or
Speaker 3: even billions of simulated years.
Speaker 2: So they're essentially playing out a high speed, high precision
Speaker 2: video game of orbital mechanics, step by tiny step over
Speaker 2: cosmic time scales.
Speaker 4: Pretty good analogy.
Speaker 3: Yeah, And for this particular study by Patel and his team,
Speaker 3: they couldn't just model the simple point mass gravity. They
Speaker 3: had to include the really complex effects of tidal forces.
Speaker 3: The star raises tides on the planet and the moon
Speaker 3: the planet raises tides on the moon. These tides act
Speaker 3: like friction, They dissipate energy, they cause orbits to change.
Speaker 4: It all has to go into the simulation.
Speaker 2: And what were the key things they changed in these simulations?
Speaker 2: To see what mattered.
Speaker 3: Most, they varied two main factors. The mass of the
Speaker 3: host planet. They looked at planets around one Earth mass
Speaker 3: up to maybe two Earth masses, like a super Earth.
Speaker 3: And crucially, they varied the planet's orbital distance its semi
Speaker 3: major access within the habitable zone.
Speaker 2: That distance seems like it would be critical because the
Speaker 2: further the planet is from the star, the less the
Speaker 2: star interferes. Right. That defines the plant's gravitational.
Speaker 3: Turf precisely, and that turf has a technical name that's
Speaker 3: central to this whole problem, the Hillsphere.
Speaker 2: Okay, the Hillsphere explain that what is it.
Speaker 3: Visually imagine the planet is surrounded by an invisible bubble.
Speaker 3: Inside that bubble, the planet's own gravity is the dominant force.
Speaker 3: It's strong enough to hold on to an orbiting moon
Speaker 3: even with the star pulling from farther away. That bubble
Speaker 3: is the hill sphere. If the Moon orbits nice and
Speaker 3: deep inside the hill sphere, it's relatively safe. But if
Speaker 3: its orbit takes it too close to the edge of
Speaker 3: that bubble, or if the bubble itself shrinks, the spar's
Speaker 3: gravity can become dominant and it can pull the Moon away.
Speaker 2: Okay, so how does the hillsphere behave in these tight
Speaker 2: Endorf systems compared to say, our Solar system.
Speaker 3: Well, here, Earth is quite far from the Sun, so
Speaker 3: our hillsphere is pretty large, about one point five million
Speaker 3: kilometers across, plenty of room for the Moon, which orbits
Speaker 3: well inside that, but around an em dwarf the habitable zone.
Speaker 4: Planet is so close to the.
Speaker 3: Star that powerful stellar gravity constantly squeezes the planet's hill sphere,
Speaker 3: shrinking its zone of influence. The closer the planet orbits
Speaker 3: the star, the smaller its hill sphere becomes, and the
Speaker 3: smaller the hill sphere, the easier it is for any
Speaker 3: slight nutt or orbital evolution to push the Moon outside
Speaker 3: that boundary where the star can just snatch it.
Speaker 2: So the setup itself is precarious. The planet might be
Speaker 2: at the right temperature for liquid water, but it's in
Speaker 2: absolutely the worst gravitational neighborhood for keeping a large moon safe.
Speaker 2: The deck is stacked against the Moon from the start.
Speaker 4: That's the fundamental challenge.
Speaker 3: The simulations were designed to quantify, and the results, well,
Speaker 3: they paint a pretty bleak picture for the idea of
Speaker 3: Earth like worlds, with Luna like moons being common around.
Speaker 4: Most red dwarfs. The headline finding.
Speaker 3: The general rule that emerged is that rocky planets like
Speaker 3: Earth orbiting and the habitable zones of M dwarf stars
Speaker 3: are highly likely to lose any large lunicized moons they
Speaker 3: might form, and they lose them fast, typically within the
Speaker 3: first billion years of the system's life.
Speaker 2: A billion year sounds like a long time, but in
Speaker 2: planetary evolution terms maybe not.
Speaker 3: Compared to the four point five billion years Earth has
Speaker 3: had its moon. No, a billion years is short, but
Speaker 3: it gets much much worse when you drill down into
Speaker 3: the specific types of endwarf.
Speaker 2: Right, we can't just say M dwarfs. They range from hotter,
Speaker 2: brighter ones to much cooler, dimmer ones, and that classification
Speaker 2: M zero down to M nine must be critical here
Speaker 2: because it dictates how close that habitable zone.
Speaker 3: Is absolutely critical. The classification basically tells you the star's
Speaker 3: temperature and brightness. M zero stars are the hottest and
Speaker 3: brightest M dwarfs. Relatively speaking, M nine's are at the
Speaker 3: other end, tiny, ultra cool incredibly dim. Since the habitable
Speaker 3: zone location depends entirely on the star's heat output. This
Speaker 3: classification directly tells you how close an eight Z planet
Speaker 3: has to orbit, and M nine's habitable zone is practically
Speaker 3: skimming the star's surface compared to an M zero.
Speaker 2: And closer means stronger stellar tides, more hillsphere, squeezing more
Speaker 2: danger for the moon.
Speaker 3: Precisely so, the researchers ran detailed simulations, focusing initially on
Speaker 3: systems around M four dwarfs. These are kind of typical
Speaker 3: middle of the road red dwarfs. They simulated these star
Speaker 3: planet moon setups for two hundred million years to see
Speaker 3: what happened.
Speaker 2: Ok M four systems was the verdict? How long did
Speaker 2: those Luna like moons typically last? This feels like the
Speaker 2: moment of truth.
Speaker 3: The results were frankly shocking. For these typical M four
Speaker 3: dwarf systems. The simulation showed the average lifetime for a
Speaker 3: large Luna like moon was less than ten million years.
Speaker 2: Wait, ten million, not billion million, ten.
Speaker 3: Million years, ten mere. It's an incredibly short timescale. Cosmically speaking,
Speaker 3: it's basically instantaneous. The moon forms maybe and then puff.
Speaker 2: It's gone, Okay, wow, I need to process that ten
Speaker 2: million years. Let's put that against Earth's history again, Life's history.
Speaker 2: What does ten million years get you?
Speaker 3: Almost nothing in terms of complex evolution. Earth is four
Speaker 3: point five billion years old. It took hundreds of millions
Speaker 3: of years just for the planet to cool down, for
Speaker 3: oceans to form, for the atmosphere to stabilize somewhat. Simple,
Speaker 3: single celled life appeared relatively early, maybe within the first
Speaker 3: billion years. But complex life, multicellular organisms, animals, that'sok, billions
Speaker 3: of years. The entire Cambrian Explosion, the big diversification of
Speaker 3: animal life, happened around five hundred and forty million years ago.
Speaker 3: Dinosaurs existed for one hundred and sixty five million years.
Speaker 3: Ten million years.
Speaker 4: It's just a blip.
Speaker 2: So any benefits that moon might provide, the stable tilt
Speaker 2: the ocean tides stirring things up, they'd vanish before life
Speaker 2: had any real chance to take advantage of them for
Speaker 2: the long haul. The stability needed for billions of years
Speaker 2: is only there for millions.
Speaker 3: That's the devastating implication. The researchers explicitly state that ten
Speaker 3: million years is very short compared to the astrobiological, geological,
Speaker 3: or astrophysical time scales. It means the mood is effectively
Speaker 3: useless for fostering the kind of long term stable conditions
Speaker 3: complex life seems to require.
Speaker 2: And if that's the case for M four stars, what
Speaker 2: about the even cooler, dimmer ones, the M fives, M six's,
Speaker 2: all the way to M nine's, where the habitable zone
Speaker 2: is even closer.
Speaker 3: The prognosis gets even worse. Patel and the team extrapolate
Speaker 3: from their findings, they expect that habitable zone planets around
Speaker 3: those later type M dwarfs M five through M nine
Speaker 3: will lose their large moons even faster than ten million years.
Speaker 3: The stellar tides are just too overwhelming that close in.
Speaker 3: They rip the moon away almost immediately.
Speaker 2: So for the vast majority of red dwarfs, the most
Speaker 2: common stars. If planet forms with a big moon and
Speaker 2: the habitable zone, that moon is doomed, its lifespan is
Speaker 2: negligible on cosmic time scales. The system is actively hostile
Speaker 2: to it.
Speaker 3: That really seems to be the takeaway for mphorism later,
Speaker 3: and it's important to connect this finding the tidal tearing
Speaker 3: with other research that looked at a different problem, tidal heating.
Speaker 2: Ah right, So even if the moon somehow survived being
Speaker 2: ripped away, it might cook itself from the inside.
Speaker 4: Out potentially yes.
Speaker 3: Other studies suggested that even if a large moon managed
Speaker 3: to hang on for a while in that intense gravitational environment,
Speaker 3: the constant flexing and stretching from both the stars and
Speaker 3: the planet's gravity could generate enormous amounts of internal heat
Speaker 3: through friction. If it's an icy moon, maybe that creates
Speaker 3: a subsurface ocean, which sounds good like Europa, But the
Speaker 3: heating could be so extreme it makes the ocean too
Speaker 3: hot or drives runaway volcanism, rendering moon itself uninhabitable.
Speaker 2: So it's the double whammy for big moons around most
Speaker 2: e M dwarfs, they either get tidally torn away very quickly,
Speaker 2: or they get tidally heated into oblivion, a real lose
Speaker 2: lose situation.
Speaker 3: That phrase general fragility of exa moons in M dwarf
Speaker 3: systems really captures it well. For M four through M nine,
Speaker 3: the outlook seems incredibly poor. If you need a large
Speaker 3: stabilizing moon for planetary habitability.
Speaker 2: It's hard not to feel a bit deflated by that. Yeah,
Speaker 2: billions upon billions of star systems potentially hostile to the
Speaker 2: one feature that made Earth so stable, But science always
Speaker 2: has nuances, right? Were there any scenarios in the simulations
Speaker 2: where moons lasted longer? Any exceptions to this grim rule?
Speaker 3: Yes, thankfully there were. The simulations didn't just paint a
Speaker 3: picture of destruction. They also pinpointed the specific, somewhat rare
Speaker 3: configurations where large moons could survive for significantly longer periods.
Speaker 3: And the key factor, again was the star type.
Speaker 2: Okay, so where did they find more hope? Which M
Speaker 2: dwarfs offer a better chance?
Speaker 3: The hope lies almost entirely with the earliest, hottest and
Speaker 3: brightest en dwarfs, the M zero stars.
Speaker 2: M Zero's what makes them different enough to potentially save
Speaker 2: a moon?
Speaker 3: It all comes down to distance again. Being the brightest
Speaker 3: type of M dwarf, an M zero star's habitable zone
Speaker 3: is pushed significantly further out compared to an M four
Speaker 3: or an M nine. It's still closer than Earth's orbit,
Speaker 3: but it's far enough to provide a crucial buffer. That
Speaker 3: extra distance dramatically weakens the star's tidal pull on the Moon.
Speaker 3: It gives the planet its own gravity its hill sphere
Speaker 3: a much better chance to hold on.
Speaker 2: Okay, so moving the habitable zone outwards is key how
Speaker 2: much longer could a moon last around an M zero
Speaker 2: in the simulations?
Speaker 3: Significantly longer. The simulation showed that for a standard Earth
Speaker 3: mass planet orbiting in the habitable zone of an M
Speaker 3: zero dwarf, a large lunar like moon could survive for
Speaker 3: up to one billion years dear one billion years. Okay,
Speaker 3: that's one hundred times better than the ten millionyears for
Speaker 3: the M four scenario. That's starting to sound more useful.
Speaker 2: Maybe it's definitely a huge much improvement. As the researchers
Speaker 2: put it, the increased distance weakens the stellar tide and
Speaker 2: leaves a large part of the tidal action to the
Speaker 2: Moon's tide that dispins the host planet. Basically, the star
Speaker 2: becomes less of a bully, allowing the planet moondance to
Speaker 2: continue for much longer before the inevitable disruption. Did they
Speaker 2: try to find the absolute best case scenario, like tweaking
Speaker 2: the planet.
Speaker 4: Size to they did.
Speaker 3: They push the parameters to find the maximum possible survival time.
Speaker 3: They simulated a more massive planet, a super earth of
Speaker 3: about two Earth masses, also orbiting in the habitable zone
Speaker 3: of an M zero dwarf. In that specific optimized scenario,
Speaker 3: biggest plausible planet mass orbiting the safest type of M
Speaker 3: dwarf M zero, the Moon could last for a calculated
Speaker 3: maximum of one point three five billion years.
Speaker 2: One point three five billion years. Okay, that's the absolute
Speaker 2: ceiling form moon stability in any M dwarf haftable zone.
Speaker 2: According to these models, we need to anchor that number again.
Speaker 2: Put one point three five billion years into Earth's timeline.
Speaker 2: Where does that landis? Is it long enough?
Speaker 3: Well, it's still problematic. Even at the maximum, Earth has
Speaker 3: had had Luna stabilizing it for four point five billion years.
Speaker 3: If our moon had vanished one point three five billion
Speaker 3: years after Earth formed, that would put its disappearance somewhere
Speaker 3: deep in the Proterozoic eon. We're talking about a time
Speaker 3: when oxygen was only just starting to really accumulate in
Speaker 3: the atmosphere during or after the Great Oxidation event. It's
Speaker 3: long before complex animals appeared. It's certainly way before the
Speaker 3: Cambrian explosion around five hundred and forty million years ago,
Speaker 3: which marked that huge burst of diverse, multicellular life.
Speaker 2: So even in the absolute best, most favorable M dwarf scenario,
Speaker 2: imaginable hottest AM dwarf, biggest planet, perfect orbit the stabilizing
Speaker 2: moon is likely gone before complex life really gets going
Speaker 2: and needs that long term stability the most the clock
Speaker 2: runs out too soon.
Speaker 3: The stability it offers is significant, but ultimately transient. It
Speaker 3: provides a decent runway, maybe long enough for simple life
Speaker 3: to get established, but it sets a firm expiration date
Speaker 3: well before the time scale over which complex Earth life
Speaker 3: evolved and relied on that stability. It forces us to question,
Speaker 3: does planetary habitability require billions of years of stability from
Speaker 3: a large moon or can life adapt? These simulations strongly
Speaker 3: suggest that if you do need that long term lunar
Speaker 3: anchor M dwarfs, even the best M zero's probably aren't
Speaker 3: the place to find it.
Speaker 2: That's a profound adjustment to how we think about the
Speaker 2: search for life. M dwarfs abundant, yes, but maybe gravitationally
Speaker 2: unsuitable for Earth style habitability.
Speaker 3: That seems to be the core message regarding large moons.
Speaker 3: The study was focused on Luna sized moons because those
Speaker 3: are the ones massive enough to significantly stabilize a planet's
Speaker 3: tilt and drive strong tides, But the researchers did acknowledge
Speaker 3: something important. What about small moons?
Speaker 2: Ah right, moons like Mars's foes and daimos, or maybe
Speaker 2: asteroid sized moons like Series. Could they survive exactly?
Speaker 3: The simulations and the physics suggest that much smaller moons
Speaker 3: could potentially survive for billions of years, even around the
Speaker 3: cooler m dwarfs.
Speaker 4: Their small mass means.
Speaker 3: The stars tidal forces just don't have the same leverage
Speaker 3: to disrupt their orbits. They're gravitationally less significant. The star
Speaker 3: barely notices them. So it's possible these mdoor planets could
Speaker 3: be orbited by swarms of small stable moons for eons.
Speaker 2: But can we even see those? Are they detectable?
Speaker 4: And that's the huge caveat No.
Speaker 3: Moons that small are currently completely beyond our detection capabilities.
Speaker 3: They don't create a strong enough gravitational wobble TTV or
Speaker 3: block enough light transit depth variation for us to spot
Speaker 3: them with current methods.
Speaker 2: The big stabilizing moons are likely gone fast, especially around
Speaker 2: most endors. Smaller moons might survive, but we can't see
Speaker 2: them yet. It really does push the focus for finding
Speaker 2: Earth like stability towards other types of stars, doesn't it.
Speaker 3: It strongly suggests that if long term stability from a
Speaker 3: large moon is a requirement. We probably need to focus
Speaker 3: more on stars like our own sung G type stars,
Speaker 3: or maybe even slightly hotter F type stars. Around those stars,
Speaker 3: the habitable zones are much farther out. There's just more
Speaker 3: breathing room. The star's tidal influence at that distance is far.
Speaker 3: We can allowing a planet to comfortably hold on to
Speaker 3: a large moon within its hill sphere for billions and
Speaker 3: billions of years, plenty of time for complex life to
Speaker 3: potentially evolve under stable conditions.
Speaker 2: So this study isn't saying moons are rare everywhere. It's
Speaker 2: saying large moons are likely rare and short lived, specifically
Speaker 2: in the habitable domes of the most common stars, the
Speaker 2: M dwarfs. The system architecture itself is the problem there precisely.
Speaker 3: It highlights that the stability of the entire star planet
Speaker 3: moon system might be the critical bottleneck, maybe even more
Speaker 3: so than just having a planet in the right temperature zone.
Speaker 3: You need both proximity for warmth and distance for gravitational peace,
Speaker 3: and for M dwarfs, those two needs seem fundamentally incompatible
Speaker 3: for large moons.
Speaker 2: Okay, So the theory in the simulations paint a compelling,
Speaker 2: if somewhat challenging picture, But theory needs observation. Where do
Speaker 2: we stand on actually finding any exo moons, large or small.
Speaker 4: Well, that's the ongoing challenge.
Speaker 3: As we said at the start, despite thousands of exoplanets,
Speaker 3: we still have have zero definitively confirmed X and wounds zero.
Speaker 2: And detecting them is just incredibly hard technically. You mentioned
Speaker 2: the methods transit timing variations ttvs and transit duration variations tdvs?
Speaker 2: Can you explain those a bit more? How subtle are
Speaker 2: the signals we're looking for?
Speaker 3: They are unbelievably subtle. Imagine watching a planet pass in
Speaker 3: front of its star that's a transit.
Speaker 4: If that planet has.
Speaker 3: A moon, the moon's gravity constantly tugs on the planet,
Speaker 3: pulling it slightly ahead or behind in its orbit. So
Speaker 3: instead of the transit's happening with perfect clockwork regularity, they
Speaker 3: might occur a few seconds or minutes early one time,
Speaker 3: then a bit late the next. That tiny wobble in
Speaker 3: the timing is the TTV signal. Similarly, the moon's gravity
Speaker 3: can slightly alter the planet's path during the transit itself,
Speaker 3: making the transit last a tiny bit longer or shorter
Speaker 3: than expected.
Speaker 2: That's the TDV signal seconds or minutes difference over journeys
Speaker 2: that take days or weeks viewed from light years away. Yeah,
Speaker 2: I could see why that's tough. It must be incredibly
Speaker 2: easy to mistake noise or interference from other plantets for
Speaker 2: a moon's signal.
Speaker 3: Exactly distangling a faint moon signal from instrumental noise, stellar activity,
Speaker 3: or the gravitational nudges of other unseen planets in the
Speaker 3: system is a massive data analysis challenge. We have candidates
Speaker 3: like the one around Kepler sixteen twenty five B or
Speaker 3: Kepler seventeen oh eight B, but confirming them beyond doubt
Speaker 3: has proven extremely difficult.
Speaker 2: But technology doesn't stand still. Are there new telescopes or
Speaker 2: instruments coming online soon that might finally give us the
Speaker 2: breakthrough we need. Can we test these simulation results from
Speaker 2: Betel's team directly?
Speaker 3: That's the big hope for the next decade or two.
Speaker 3: There are some potentially game changing facilities on the horizon,
Speaker 3: both in space and on the ground. In space, the
Speaker 3: big one being discussed is the Habitable World's Observatory HWO.
Speaker 3: This is envisioned as NASA's next flagship astrophysics mission after
Speaker 3: Web and Roman. If it gets built, its primary goals
Speaker 3: to directly image earthlike exoplanets around sunlike stars. It would
Speaker 3: likely feature a large mirror maybe six to eight meters across,
Speaker 3: and crucially advanced technolology like a coronagraph or a separate
Speaker 3: star shaped spacecraft. These are designed to block out the
Speaker 3: overwhelming glare.
Speaker 4: Of the host star.
Speaker 2: Okay, blocking the starlight. Why is that so critical for
Speaker 2: finding Moon?
Speaker 3: Specifically because moons don't produce their own light, they only
Speaker 3: reflect their stars light, and that reflected light is incredibly faint,
Speaker 3: billions of times dimmer than the star itself. It gets
Speaker 3: completely lost in the stars glare with current telescopes. By
Speaker 3: suppressing the starlight very effectively, HWO could potentially allow us
Speaker 3: to not just detect the indirect gravitational wobble TDV, but
Speaker 3: maybe even directly see the faint light reflected off a
Speaker 3: large exomoon orbiting an exoplanet, or at least characterize the
Speaker 3: planet Moon system much better.
Speaker 2: Direct imaging of an exomoon that would be incredible. What
Speaker 2: about ground based telescope? So the new giant telescope's going to.
Speaker 3: Help absolutely on the ground. We're looking forward to the
Speaker 3: next generation of extremely large telescopes, like the Giant Magellan
Speaker 3: Telescope GMT in Chile. This beast will have a primary mirror,
Speaker 3: effectively twenty four point five meters across, huge light collecting power.
Speaker 3: While ground based telescopes have to deal with Earth's atmosphere
Speaker 3: blowing the view, the GMT will use sophisticated adaptive optic
Speaker 3: systems to correct for that distortion in real time.
Speaker 2: So sharper images from the.
Speaker 3: Ground incredibly sharp. The combination of its sheer size and
Speaker 3: advanced optics should allow GMT, expected to start observations in
Speaker 3: the twenty thirties, to directly image some nearby exoplanets, especially
Speaker 3: larger ones orbiting a bit further from their stars. And
Speaker 3: if you can directly image of the planet, you can
Speaker 3: track its motion very precisely if it's wobbling due to
Speaker 3: an unseen moon. GMT might be able to detect that
Speaker 3: wobble with much higher fidelity than current instruments, potentially confirming
Speaker 3: moon candidates or even discovering new ones, especially around closer
Speaker 3: stars where the angular separation.
Speaker 2: Is larder so between HWO and space, potentially giving us
Speaker 2: direct light and GMT on the ground, giving us ultra
Speaker 2: precise motion tracking. The next ten to fifteen years could
Speaker 2: be really exciting for exomoon science. We might finally get
Speaker 2: observational data to compare against these theoretical predictions about endwars.
Speaker 3: That's exactly the goal. We need to bridge the gap
Speaker 3: between these sophisticated simulations and actual observations.
Speaker 4: We need to see if.
Speaker 3: Large moons really are rare around M zero stars and
Speaker 3: essentially nonexistent around M four M nine's, as Patel's work suggests,
Speaker 3: or maybe nature has found a way we haven't anticipated,
Speaker 3: and finding them is so important for two big reasons
Speaker 3: related to the search for life. First, as we've hammered home,
Speaker 3: a large moon might make its planet habitable through stability
Speaker 3: and tithes, like Luna does for Earth. But second, there's
Speaker 3: the flip side. The Moon itself could be a habitable world.
Speaker 3: We can't ignore that possibility, like.
Speaker 2: The icy moons in our own outer Solar system Europa
Speaker 2: Enceladus exactly.
Speaker 3: Even if an exomoon is in a system where it
Speaker 3: experiences significant tidal heating, maybe too much for the planet
Speaker 3: or even too much for surface life on the Moon,
Speaker 3: that internal heat could potentially maintain a liquid water ocean
Speaker 3: beneath an icy shell. We're actively exploring whether such subsurface
Speaker 3: ocean on Europa or Enceladus could harbor life rate here.
Speaker 3: The same potential exists for exo moons, possibly even some
Speaker 3: of those tidally heated moons around M dwarfs if they
Speaker 3: manage to survive long enough in some configuration.
Speaker 2: So finding exo moons opens up two potential avenues for
Speaker 2: life beyond Earth. Wow. Okay, let's try to tie this
Speaker 2: all together. If we step back and look at the
Speaker 2: big picture from this research, I think.
Speaker 3: The core message connecting everything is that planetary habitability isn't
Speaker 3: just about being in the right temperature zone. The stability
Speaker 3: of the entire system's architecture, especially concerning large moons, seems
Speaker 3: to be a critical prerequisite, at least for Earth like life.
Speaker 3: And this study by Ptel and his colleagues really challenges
Speaker 3: the long held assumption that M dwarfs are the prime
Speaker 3: targets just because they're numerous and have each Z planets.
Speaker 3: If that potential life needs the long term stabilizing hug
Speaker 3: of a massive moon, the intense gravitational environment close to
Speaker 3: these common stars appears to be fundamentally hostile. It tears
Speaker 3: those moons away.
Speaker 2: It suggests that finding that sweet spot enough for warmth
Speaker 2: but far enough for gravitational stability for a moon might
Speaker 2: be much rare than we thought. That specific architecture might
Speaker 2: be the real bottleneck.
Speaker 4: It could very well be.
Speaker 3: Maybe having a large, stable, long lived moon is one
Speaker 3: of the rarest variables in the drink equation, if you will.
Speaker 4: We need the observations to find out.
Speaker 2: This has been absolutely fascinating really digging into the physics
Speaker 2: of these tiny, turbulent star systems. Okay, let's quickly recap
Speaker 2: the main takeaways you've gotten from our discussion on this
Speaker 2: tidally torn research. First, you understand now just how crucial
Speaker 2: a large moon like ours is for keeping Earth's tilt
Speaker 2: stable over billions of years and for driving ocean tides
Speaker 2: that might be linked to life's origins and complexity. Second,
Speaker 2: you know that m dwarfs, the most common stars, have
Speaker 2: habitable zones snuggled up incredibly close, and that closeness means
Speaker 2: the star's gravity reeks havoc on any large moons, creating
Speaker 2: intense tidal forces. Third, the simulations show that for typical
Speaker 2: M dwarfs like M four's, these crucial large moons likely
Speaker 2: last less than ten million years. That's just far too
Speaker 2: short for complex Earth like life to evolve needing that stability. Fourth,
Speaker 2: there are rare exceptions around the hottest end dwarfs and
Speaker 2: zero's where the HD is further out. The moon might
Speaker 2: last up to maybe one point three five billion years
Speaker 2: in the best case scenario, but even that's likely not
Speaker 2: long enough compared to Earth's four point five billionears of
Speaker 2: lunar partnership. So Fifth, you now see why the search
Speaker 2: for planets with long term moon stabilized habitability might need
Speaker 2: to shift focus slightly away from the most common stars
Speaker 2: and more towards stars like our Sun, where there's more
Speaker 2: gravitational room for moons to survive long term. But here's
Speaker 2: a final thought. I want to leave you with something
Speaker 2: sparked by our conversation about those other moons. The study
Speaker 2: focused on the big Luna like moons needed to stabilize
Speaker 2: a planet. We also mentioned that tiny moons, maybe series
Speaker 2: size or phobo size, could potentially survive for billions of years,
Speaker 2: even around M dwarfs, although we can't detect them yet. Now,
Speaker 2: what if, What if? Those small, stable, currently invisible moons
Speaker 2: are habitable in their own right. Maybe they have subsurface
Speaker 2: oceans kept liquid by just enough tidal heating, not the
Speaker 2: runaway kind, but a gentle, long term warmth. If that's possible.
Speaker 2: Are we perhaps looking for life in the wrong place entirely?
Speaker 2: Should we be thinking less about moons that help their
Speaker 2: planets and more about tiny moons that managed to survive
Speaker 2: and thrive despite their chaotic planetary instellar neighborhood. Just something
Speaker 2: to ponder next time you look up the pass