Speaker 1: You know, the thermal models were just completely wrong. That
is really the only place we can start today.
Speaker 2: Yeah, completely wrong. It's a well, it's a crisis in
the modeling, but honestly in the best possible way.
Speaker 1: Right because if you look at the standard commentary physics
we've relied on for decades, I mean, the Whipple models,
the sublimation curves, they all predicted that three il lasts
would peak, put on a modest show, and it just
sort of fade away as it rounded the Sun exactly.
Speaker 2: But the data we're looking at now, this post perihelion
analysis that just dropped from the combined Hubble and jada
Ust teams, it's completely invalidates those initial projections. We aren't
just looking at a rock that behaved unexpectedly. We are
looking at a fundamental disconnect between how we thought interstellar
objects age and how they actually behave when they wake up.
Speaker 1: And for you listening, that is the hook. We have
a visitor that traveled light years in complete silence, basically
ignored the Sun during its closest approach, and then when
it's supposed to be cooling down, it erupted with a
violence that defies all the low thermodynamic norms.
Speaker 2: It is the delayed fuse scenario, and it is cracked
open a trove of chemical data that we frankly had
no business sing.
Speaker 1: Welcome to thrilling Threads. I am your host, and today
we are pulling on a thread that leads all the
way back to a stellar nursery billions of years old
and light years.
Speaker 2: Away, and I am here to help navigate the orbital
mechanics and the deep chemistry of that journey.
Speaker 1: We are, of course talking about the third interstellar object
three IA LASS. Now, for those of you who track
the minor Planet Center circulars, you probably know the basics,
but the mainstream headlines, you know, the one screaming comment
breaks up or alien rock, they really do not capture
the nuance of this massive new data set. We're looking
at a synthesis of observation spanning late twenty twenty five
all the way through February twenty twenty six.
Speaker 2: Right, this is the comprehensive update. We have photometry, spectroscopy, radar,
cross section analysis, everything. It's a mountain of data from
some of our best instruments.
Speaker 1: So let's just skip the preambling gets straight into the physics.
Because for months three Italia was essentially a ghost. We
had the astrometry, we knew exactly where it was, but
we didn't really know what it was. We couldn't resolve
the nucleus.
Speaker 2: And that is the standard frustration with any active commet.
You have a solid body, the nucleus, which is the
actual thing you want to measure, but as soon as
it gets anywhere near the frost line, it starts sublimating.
It surrounds itself in a coma.
Speaker 1: Just a massive cloud of gas.
Speaker 2: And dust exactly. It's an optical depth problem. The signal
to noise ratio heavily favors the glowing gas, not the
dark rock hiding inside it.
Speaker 1: It is like trying to measure the exact dimensions of
a light bulb while it is shining through an incredibly
heavy fog. You see the glow, you don't see the glass.
Speaker 2: That is a perfect analogy. The coma can be thousands
of kilometers wide while the nucleus is tiny. But the
Hubble team, specifically the group using the wide field camera three,
they applied a new subtraction technique in this latest study
that finally pierced that vein, and.
Speaker 1: This wasn't just taking a better picture, right. They had
to computationally strip away the gas.
Speaker 2: Right. They took a series of exposures and used a
point spread function subtraction to digitally remove the coma. It
is a brilliant piece of image processing. They modeled the
gas distribution based on the solar wind vectors, subtracted that
glow from the pixel data, and were left with the
point source, the naked nucleus itself.
Speaker 1: And this is where the first major revision to our
understanding comes in the size, because early estimates were just
all over the map, but the subtraction data gives us
a much tighter constraint. We're looking at a radius of
one point three kilometers.
Speaker 2: Which gives us a diameter of roughly two point six kilometers.
Speaker 1: Let's put that into context for you listening, because that
is significantly larger than the initial small fragment theories were suggesting.
If you compare that to sixty seven p the churim
Moffcrasamanco comet, which was the target of the Rosetta mission,
that was about four kilometers across on its longest axis,
so three ils absolutely in the same way it is.
Speaker 2: It is a substantial world, And we have to remember
that size s it hinges entirely on the albedo the
surface reflectivity. These specific calculations assume a geometric albedo of
about point zero four to point zero.
Speaker 1: Five, which is standard for commentary nuclei. They are darker
than fresh asphalt. They are darker than coal.
Speaker 2: Yes, they are incredibly unreflective. Now, if the surface were brighter,
say if it had a lot of fresh shiny ice expose,
the object would actually have to be smaller than one
point three kilometers to reflect that specific amount of light
we measured. But given the spectral data we'll get into later,
the dark organic crud model really holds up. So two
point six kilometers is a very solid working number, but.
Speaker 1: It is not a sphere. The light curve analysis, which
is tracking how the brightness dips and peaks as it
rotates tumbling through space, it shows an axis ratio of
two to one.
Speaker 2: Yes, this is the shape derived from the amplitude of
that light curve. It is getting twice as bright and
then twice as dim as it spins. That tells us
definitively that it is elongated, which.
Speaker 1: Is fascinating because it sits in this weird morphological valley
between the two previous interstellar visitors we've had. We had Umuamua,
which was extreme a ten to one cigar or maybe
a pancake shape, and then we had Borisov, which was
seemingly spherical, almost indistinguishable from a standard Solar System comet.
Speaker 2: And three I Atlas is right in the middle. It
is not an extreme splinter, but it's definitely not a
round potato either. It is a prolate spheroid significantly.
Speaker 1: Stretched, a thick baget, if you will.
Speaker 2: A very large, very dark baguette hurtling through the void.
And the shape is important because it hints at either
its formation history or its erosional history. To get that
two to one ratio, it likely underwent some significant tidal
stresses in its home system, or perhaps a really violent
collision event before it was ejected into interstellar space.
Speaker 1: Or it could just be a fragment of a much
larger body that got shattered.
Speaker 2: That is a very strong possibility as well.
Speaker 1: Now, the size and the shape are the stats, but
the behavior is a real story here. You mentioned earlier
that the thermal models failed really dig into this delayed
fusee anomaly.
Speaker 2: This is the part that had everyone scratching their heads.
In a standard cometary approach, activity which is the sublimation
of ices turning into gas, tracks very predictably with heliocentric distance.
As the distance to the Sun decreases, the temperature increases
and gas production goes up. The peak usually happens right
at or just slightly after perihelion.
Speaker 1: Because that is when the heat flucks from the Sun
is at its absolute highest.
Speaker 2: Right, it is simple thermodynamics. But three ilists did not
do that. It swung past the Sun, its perihelium was
reasonably close, well inside the orbit of Mars, and it
was just quiet.
Speaker 1: I remember reading the papers from late twenty twenty five.
The headlines were all saying, three ietless underwhelms. Is it
a dud? Has it lost all its ice?
Speaker 2: It was active technically, but the production rates were strangely low.
It looked like a highly evolved comet, something that had
been around the Sun hundreds of times and had already
lost most of its volatile ices.
Speaker 1: But then post perihelium, when it is moving away from
the Sun. Late October early November, the activity curve just
goes vertical.
Speaker 2: Completely vertical. We saw a surge and water production that
completely defied the cooling trend. By December, the production rate
of water jumped by a factor of.
Speaker 1: Forty forty times the output while actively moving away from
the heat source. That is wild.
Speaker 2: The so Swan instrument recorded rates hitting one point eight
times ten to the twenty eighth molecules per second.
Speaker 1: Let's translate that number ten to the twenty eighth molecules
per second into something we can visualize. We often hear
the Olympic swimming pools metric in these press releases. I
think the number was two pools per hour.
Speaker 2: That's the volumetric equivalent. Yes, it was ejecting about five
million liters of water every single hour. But scientifically speaking,
that specific production rate puts it firmly in the category
of a hyperactive comet.
Speaker 1: And hyperactive usually means a really significant percentage of the
surface area is actively venting.
Speaker 2: Right, yes, exactly. For most local commets, the act diffraction
of the surface is actually very small. One to five
percent of the surface is vent in gas. The rest
is covered in an inert layer of dust. To get
these kinds of numbers from a two point six kilometer object,
a much much larger portion of the surface had to
detonate and vent simultaneously.
Speaker 1: So why the delay. Why did it wait until it
was heading back out into the freezing cold to suddenly
turn into a massive geyser.
Speaker 2: This brings us to the irradiation mental hypothesis, or, as
we've been casually calling it, the crust theory. But we
need to be very specific about what this crust actually is.
It is not just a layer of rock, right.
Speaker 1: We aren't talking about a mineral shell like a turtle.
We're talking about complex chemistry.
Speaker 2: We're talking about the effects of galactic cosmic rays GCRs.
These are highly energetic protons and atomic nuclei moving at
nearly the speed of light in the interstellar medium. When
you are outside the protective magnetic bubble of a star,
an object is constantly bombarded by these GCRs for millions,
sometimes billions of years.
Speaker 1: And when those high energy particles slam into the surface
ices like methane, ammonia, water, what actually happens chemically?
Speaker 2: They literally break the chemical bonds apart. Specifically, they knock
the hydrogen atoms right out of the molecular lattice. This
process is called dehydrogenation. And when you strip the hydrogen away.
The remaining carbon atoms are left looking for something to
bond with, so they bond with each other, they polymerize.
Speaker 1: So you are basically taking simple ices and forcing them
to turn into complex, long chain carbon structures.
Speaker 2: Exactly, you create a thick layer of highly disordered carbon.
It is essentially an asphalt or a tar like substance.
It is incredibly dark, it is hard, and structurally it
is very strong. This is the crust, and it can
easily be ten to fifteen meters thick, depending on exactly
how long the object drifted in the void.
Speaker 1: Okay, so three I at leaves arrives in our solar
system wearing this fifteen meter thick suit of armor made
of cosmic asphalt.
Speaker 2: And that cosmic asphalt happens to be an absolutely excellent insulator.
It has a very very low thermal conductivity.
Speaker 1: I see. So the sun shines on the comet, the
outer surface gets hot, maybe pushing three hundred kelvin, but
that heat does not immediately reach the pristine ice buried below,
not at all.
Speaker 2: It takes a significant amount of time for that thermal
wave to propagate down through fifteen meters of disorganized insulating carbon. Material,
there is a massive thermodynamic lag the lang.
Speaker 1: Okay, so the delayed fuse we were talking about is
literally just the travel time of the heat wave moving
through the crust.
Speaker 2: That fits the observational data perfectly. It took months for
the intense heat pulse from perihelium to finally conduct its
way down to the pristine ice layer. By the time
it actually hit that volable reservoir, the comet was already
physically moving away from the Sun, but the heat had
finally arrived.
Speaker 1: And when that intense heat finally hits super volatile interstellar
ice that has been trapped under immense pressure for billions
of years.
Speaker 2: It sublemates instantly. The phase change from solid ice to
gas creates a massive sudden spike in internal pressure. The crust,
which is rigid and can't really expand, fails. It is
a catastrophic structural failure. The shell cracks wide open, and
you get that sudden forty X surge and outgassing activity.
Speaker 1: It is quite literally a pressure cooker explosion in space.
Speaker 2: It is. And what's truly fascinating is that this validates
the idea that interstellar objects have fundamentally different surfaces than
our local commets, our local comments haven't been exposed to
deep space GCRs for that long. They just don't have
this thick, blackened polymerized armor.
Speaker 1: So three I Alis is essentially a pristine time capsule
wrapped in thick asphalt. And when it finally cracked open,
we got a fresh sample of what was locked inside.
And this is where the James Webb Space Telescope really
flexed its muscles.
Speaker 2: The spectral analysis from JWST was just breathtaking.
Speaker 1: We've seen water obviously, we talked about the swimming pools,
but the trace gases are where the real story of
its origin lies. The detection of methane is the absolute
headline here.
Speaker 2: It is the first definitive detection of methane in an
interstellar comment. And this is critical for you to understand.
Because methane is hyper volatile, its sublimation temperature is incredibly low.
We're talking around thirty kelvin.
Speaker 1: Thirty kelvin that is barely above absolute zero.
Speaker 2: Right, if this object had ever gotten warm, even slightly warm,
during its billions of years of travel, or even during
its initial formation, that methane should be completely gone. It
should have outgassed eons ago.
Speaker 1: So the fact that we are seeing it now means
what exactly.
Speaker 2: It means two very important things. One, the crust theory
is absolutely correct. It was hermetically sealed in that tarshell.
And two, this object formed in a very very cold environment.
We're talking about the extreme outer fringes of a protoplanetary disc,
far far beyond the co line of its home star.
It formed in the d freeze, the absolute DeFreeze, and
it stayed there. It was likely ejected from its home
star system very early on in its life, well before
it could migrate inward and lose those precious volatiles.
Speaker 1: The report also dives into a really strange ratio of
nickel time iron, and the gaseous emissions. Now, I know
metallicity is basically a fingerprint for stars.
Speaker 2: Right it is in our Solar system we have a
very specific ratio of heavy elements because everything here formed
from a specific cloud of gas that was enriched by
specific previous supernova. When we look at the vaporized metals
coming off three ilus, specifically the atomic nickel and iron
emission lines, the ratio is completely skewed compared to our
solar value.
Speaker 1: It is definitely not the solar standard.
Speaker 2: No, not at all. It is enriched in certain heavy
elements and severely depleted in others. This tells us definitively
that the star system three Ilis originally came from had
a totally different chemical recipe than ours. Maybe the molecular
cloud it formed from was seated by a different type
of supernova, or it just had a different initial abundance
of elements.
Speaker 1: Overall, we are effectively doing remote archaeology on a star
system we have never even seen.
Speaker 2: We are we're tasting the soup and realizing the chef
used a completely different set of spices.
Speaker 1: There is another aspect of the material coming off this
comment that caught my eye. The dust. The polarization curves
the teams recorded were just really weird, right.
Speaker 2: So, polarization measures the geometry of how light scatters off particles.
It tells you a lot about the surface roughness and
crucially the size of those particles.
Speaker 1: Usually, comet dust is micron sized, right, like superfine talicumpowder
or cigarette smoke.
Speaker 2: Correct, But the polarization phase curve for three IAD lists
was noticeably flatter and deeper than typical solar system commets.
This implies that the scattering particles are unusually large.
Speaker 1: How large are we talking.
Speaker 2: We're looking at models suggesting grains that are millimeters across,
maybe even up to centimeters in some cases.
Speaker 1: Oh wait, so it is not ejecting a cloud of smoke.
It is ejecting a cloud of gravel or what we.
Speaker 2: Call fluffy aggregates. Think of cosmic dust bunnies, large highly
porous clumps of material that have been stuck together. And
this perfectly supports the idea of the crust breaking up violently.
We aren't just seeing the gentle sublimation of ice. We
are seeing the mechanical, violent sintegration of that solid irradiation mantle.
Speaker 1: It is shedding its skin in giant.
Speaker 2: Chunks, which, by the way, would make a flyby mission
incredibly dangerous. If you flew a probe through that tail
trying to get a sample, you wouldn't just get dusted,
your spacecraft would get completely sam blasted.
Speaker 1: That is an amazing image. But let's pivot to the
topic that inevitably comes up. Whenever we find something strange
with an object this shape and with this bizarre delayed
fuse behavior, the question of artificiality is always going to
be on the table the classic von Neumann probe hypothesis.
Speaker 2: And it is a completely valid scientific question to ask.
If you were sending a probe between stars, you might
very well coat it in a protective shield. You might
even see non gravitational acceleration as it maneuvers.
Speaker 1: So we looked. The astronomical community didn't just ignore the possibility.
The Green Bank Telescope and the Allen Telescope array did
some serious heavy lifting here.
Speaker 2: They absolutely did. This wasn't just a casual listen for
a few hours. They dedicated significant premium observation time to
perform a highly rigorous narrowband search.
Speaker 1: Explain the concept of narrowband for us. Why is that
considered the absolute gold standard for finding techno signatures.
Speaker 2: Well, nature is inherently broadband. When a star, a pulsar,
or a quasar amidst radio waves, it is messy. It's
spread across a huge range of frequencies. Technology, on the
other hand, is narrowband. When we transmit a signal, we
squeeze all that energy into a very specific tight frequency
like one oh one point five fm to maximize efficiency.
If you see a signal that is only a few
hurts wide, Nature simply did not make that.
Speaker 1: So they scan the one to ten gigahertz range looking
for that tight signal.
Speaker 2: Yes, the classic waterhole frequencies and well beyond, and the
sensitivity they achieved was just extraordinary. They could have detected
an omnidirectional transmitter with a power output of just zero
point one watts.
Speaker 1: You own one watts. Let that sink in for a second. Yeah,
that is less power than the little led flashlight on
my smartphone.
Speaker 2: It's roughly the transmit power of a standard self pe handset.
If there is a piece of electronics sitting on that rock,
even just in a low power standby mode, trying to
ping a signal.
Speaker 1: Home, we would have heard it loud and clear.
Speaker 2: Absolutely. The Green Bank telescope is an absolute monster. It's
a one hundred meter dish. The game is.
Speaker 1: Immense and the result of all that listening.
Speaker 2: Completely null results.
Speaker 1: But I read the report and it did mention candidate signals.
People hear that in their minds go.
Speaker 2: Wild, right, But in radio astronomy you always get candidate signals.
That's just RFI radio frequency interference. It's our own technology
bouncing back at US Starlink satellites GPS signals, aircraft, radar,
even researchers using microwave ovens down the hall. The key
to filtering that out is looking for the Doppler drift, because.
Speaker 1: The comet is physically moving relative.
Speaker 2: To us exactly. The comet is moving very fast relative
to Earth, so any actual signal originating from it should
show a distinct Doppler drift. The frequency should slightly change
over time as it moves, like the pitch of a
siren passing by terrestrial interference is mostly stationary relative to
the ground. When the teams applied the Doppler filters to
those candidates, every single one of them disappeared, So.
Speaker 1: No aliens today. It is a rock.
Speaker 2: It is a rock, a genuinely fascinating, chemically complex, violently
erupting rock. But it is definitively not a.
Speaker 1: Machine, which honestly I find almost more compelling in a
way because it means nature alone is capable of manufacturing
these incredible imposters that mimic our ideas of technology.
Speaker 2: It means the galaxy is wonderfully messy. It creates things
that look structured or behave oddly just through the sheer
chaos of formation, ejection, and billions of years of radiation.
Speaker 1: Three a Alis is currently on its way up. We
missed the chance for a rendezvous, but there was a
moment in the orbital projections where the dynamics got very,
very spicy.
Speaker 2: The Jupiter encounter OH March twenty twenty six. The trajectory
takes it out to about thirty six AU, but the
key metric we looked at was the hyperbolic excess velocity.
It is moving incredibly fast.
Speaker 1: But it passes tantingly near Jupiter's hill sphere right.
Speaker 2: The hillsphere is the specific volume of space where a
planet's gravity completely dominates over the Sun's gravity. If an
object enters that sphere with low enough kinetic energy, it
gets captured. It ceases to be a comet and becomes
a temporary or sometimes permanent moon.
Speaker 1: We've seen this happen with local commets before, right like
comet Shoemaker Levy nine, which was captured by Jupiter right
before it famously crashed into it.
Speaker 2: Correct, Jupiter is the great vacuum cleaner of our Solar system.
The trajectory analysis showed that three I lists passed incredibly
close to that exact capture threshold. If it had entered
the Jovian System just a few kilometers per second.
Speaker 1: Slower, Jupiter would have grabbed it out of the sky.
Speaker 2: We would have had a permanent, or at least semi
permanent interstellar satellite, or didting Jupiter.
Speaker 1: Just think about the mission potential of that. We wouldn't
have to chase it down into deep space. We could
have sent a dedicated sample return mission. We could have
landed on it, drilled through that asphalt crust.
Speaker 2: It would have been the scientific prize of the century,
a captive interstellar laboratory. But unfortunately it just had too
much kinetic energy. It is doing a hyperbolic flyby and
actually gaining a gravity assist out of the Solar System.
Speaker 1: The Obirth effect in action right there.
Speaker 2: Effectively, Yes, it stole a tiny bit of angular momentum
from Jupiter and is currently flinging itself back into the
interstellar void even faster than before.
Speaker 1: So let's zoom out for a minute and recap what
we have here. We have a two point six kilometer object.
It is shaped like a giant dark baguette. It has
a thick crust of cosmic gas, fold baked by billions
of years of radiation it's full of ancient hypervoltle methane
and nickel rich gas that proves it came from a
different star, and when it finally got warm, it erupted
a cloud of gravel.
Speaker 2: That is the complete peer reviewed profile.
Speaker 1: So what does this tell us about the actual population
of these things out there? Because this is the third
one we've seen in less than a decade. We had
Umoa in twenty seventeen, Boresov in twenty nineteen, and now ATLS.
Speaker 2: Statistically, it suggests the number density of interstellar objects floating
out there is much much higher than we ever previously estimated.
But there is a massive catch to that assumption. Three
Ils and Borisov were highly active eventually, and Umongole was
weirdly shiny and tumbling in a way that caught the light.
Speaker 1: They drew attention to themselves, they made themselves visible.
Speaker 2: Exactly, which brings up a relatively new concept in the
community known as the dark River.
Speaker 1: The dark River that sounds incredibly.
Speaker 2: Ominous, It is a bit haunting. The idea is that
for every active interstellar object like three Als that eventually
lights up and releases enough gas for us to spot,
there might be one hundred or even a thousand that
are truly dead. They have those thick tar crusts, but
their crusts simply never crack. They passed through our solar
system completely dark and silent.
Speaker 1: Because if they don't outgas, they never form a coma.
They don't form a coma, they don't reflect much sunlight,
and if their bare surface is as dark as coal,
we never see them.
Speaker 2: There are perfect stealth transits.
Speaker 1: That is a deeply haunting thought. We are sitting here
in this lit room our solar system, and we tend
to think we're alone in the dark, but they are
ghosts passing through the room constantly. We just can't see
them because they don't reflect the light.
Speaker 2: The galaxy is absolutely teeming with debris. We are only
seeing the ones that scream.
Speaker 1: So the next great mission is to figure out how
to find the quiet ones.
Speaker 2: The Verra Reuben Observatory, which is finally coming online fully,
is going to be our best bet for that. It's
specifically designed to spot these incredibly faint, fast moving transients
that previous surveys would just miss entirely.
Speaker 1: I want to leave you listening with a thought on
that crust theory we discussed. We so often think of
deep space as just being empty and inert, But this
object proves that the emptiness is actually chemically active. It
processes matter over eons. It actively builds armor on these
drifting rocks.
Speaker 2: It transforms them completely. The object that originally left its
home Star billions of years ago is not the exact
same object that arrived here. The journey itself changed its
fundamental nature.
Speaker 1: I really want to hear from you guys on this one,
because the implications are huge. If a comic can be
shielded by a crust that hides its true nature until
the very last moment, how many other totally dark objects
pass through our system unnoticed because they never wake up?
Are we surrounded by dormant interstellar travelers?
Speaker 2: And also, how do you feel about that near miss
with Jupiter? Does the physics of a lost opportunity sting?
Or is it just the way orbital mechanics crumbles?
Speaker 1: Drop your thoughts down in the comments. We read the papers,
but we also love reading the comments. It is where
the best theories sometimes pop up.
Speaker 2: Honestly, sometimes the comments are harder to decipher than the
academic papers.
Speaker 1: Ain't they have the truth? Three at Aisles is heading
out but the sky is big, and our surveys are
getting better every single day. It won't be long until
number four shows up.
Speaker 2: Keep looking up, everyone.
Speaker 1: Stay curious, and stay thrilled. We'll see you in the
next thread.