# A Rare Brown Dwarf Could Finally Reveal How These Strange Objects Form

An episode of [Bedtime Astronomy](https://invisiblenetwork.ai/podcast/1736397134), 31 Aug 2026, 46 min.

Audio: https://dts.podtrac.com/redirect.mp3/api.spreaker.com/download/episode/73978780/reddwarfp.mp3

NASA’s TESS mission has helped astronomers identify the rare brown dwarf HIP 61637 b, orbiting an aging A-type star. Located in the mysterious “brown dwarf desert,” this object could help scientists determine whether brown dwarfs form more like stars or giant planets. Its unusual properties offer new clues about how diverse worlds and stellar objects emerge. Thank you for listening to Bedtime Astronomy — your guide to the cosmos. New episodes on space exploration, NASA missions & the latest astronomy breakthroughs. This episode includes AI-generated content.

## Transcript

[0:03] Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
[0:07] Speaker 1: with our soothing Bedtime Astronomie podcast. Each episode offers a
[0:12] Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
[0:16] Speaker 1: unwinding after a long day. Let's travel through the mysteries
[0:20] Speaker 1: of the universe as you drift off into a peaceful
[0:22] Speaker 1: slumber under the night sky.
[0:26] Speaker 2: You know, human beings just have this absolute obsession with taxonomy.
[0:31] Speaker 3: Oh for sure. It's how we process everything, right.
[0:34] Speaker 2: It is like wires so deeply into our cognitive architecture.
[0:37] Speaker 2: You walk into a room, you look around, and your
[0:40] Speaker 2: brain is instantly sorting the world into these discrete, manageable boxes.
[0:46] Speaker 3: Yeah, you see a chair, a table.
[0:48] Speaker 2: Exactly, that is a chair, That is a plant.
[0:50] Speaker 3: Yeah.
[0:50] Speaker 2: We crave that categorization because it creates a sense of
[0:54] Speaker 2: order out of all the chaos.
[0:56] Speaker 3: You know, is survival mechanism, really it is.
[0:59] Speaker 2: And when we look up the night sky we apply
[1:03] Speaker 2: the exact same psychological architecture to the cosmos.
[1:06] Speaker 3: We can't help ourselves, we really can't.
[1:07] Speaker 2: So we had this box and it's labeled planets, and
[1:10] Speaker 2: these are well, they're the cold, relatively small rocky or
[1:14] Speaker 2: gaseous bodies that just orbit around the light source.
[1:16] Speaker 3: Right, the passengers of the system, Yes, the passengers.
[1:19] Speaker 2: And then we have another box labeled stars. And these
[1:22] Speaker 2: are the massive, self limitous blazing infernos.
[1:26] Speaker 3: Powered by sustained nuclear fusion in their cores.
[1:29] Speaker 2: Exactly, And those categories they feel really robust, right like
[1:33] Speaker 2: they feel binary. You are either the engine or you
[1:36] Speaker 2: are the passenger.
[1:37] Speaker 3: It is a very comfortable framework, I mean, assigning those
[1:39] Speaker 3: distinct labels. It allows us to build models of how
[1:43] Speaker 3: the universe actually.
[1:44] Speaker 2: Operates because you know what rules to apply.
[1:46] Speaker 3: Exactly. If we see a star, we apply stellar physics.
[1:49] Speaker 3: If we see a planet, we pull out the planetary
[1:52] Speaker 3: science rule book.
[1:53] Speaker 2: Makes total sense.
[1:53] Speaker 3: The problem, however, is that nature fundamentally rejects rigid boundaries.
[1:59] Speaker 3: The universe is a continuous spectrum, not a filing cabinet.
[2:03] Speaker 3: When you start peering really closely at the boundaries between
[2:06] Speaker 3: those neat little boxes, the whole taxonomy just completely breaks down,
[2:09] Speaker 3: which brings.
[2:10] Speaker 2: Us to the core of what we are. What we're
[2:12] Speaker 2: unpacking today, because we are traveling roughly three hundred and
[2:15] Speaker 2: ninety six million years back in cosmic time to examine
[2:19] Speaker 2: a newly discovered celestial body.
[2:21] Speaker 3: And it is a fascinating one.
[2:22] Speaker 2: It really is. It essentially drives a bulldozer right through
[2:24] Speaker 2: our standard definitions. We are looking at a system centered
[2:28] Speaker 2: around a world known as Hip six one six three
[2:31] Speaker 2: seven B. And the deeper you look at this specific object,
[2:35] Speaker 2: the more you realize it is just an absolute structural paradox.
[2:38] Speaker 3: Hip six one sixty three seven B is. Well, it's
[2:42] Speaker 3: a phenomenal stress test for.
[2:44] Speaker 2: Astrophysics stress tests. I like that.
[2:46] Speaker 3: That's really what it is. What we have here is
[2:48] Speaker 3: an object situated in an orbital regime where our prevailing
[2:52] Speaker 3: models insists it should not be able to survive.
[2:54] Speaker 2: It's orbiting this massive, rapidly evolving star.
[2:57] Speaker 3: Exactly, and the physical characteristics of this object are forcing
[3:00] Speaker 3: the entire astronomical community to completely rethink the extreme limits
[3:05] Speaker 3: of both planetary accretion and stellar formation.
[3:09] Speaker 2: So let's start with the identity crisis itself. Yeah. To
[3:12] Speaker 2: really understand why Hip sixty one sixty three says B
[3:15] Speaker 2: is causing such a headache, we need to examine the
[3:17] Speaker 2: category it technically falls into, the brown dwarf. The brown
[3:20] Speaker 2: dwarf right, for decades, the astronomical community has sort of
[3:24] Speaker 2: treated brown dwarfs as the ultimate cosmic middle children.
[3:27] Speaker 3: They really are the misfits.
[3:28] Speaker 2: Yeah, they are too massive to be classified as plants,
[3:31] Speaker 2: but they lack the necessary mass to initiate and sustain
[3:34] Speaker 2: the fusion of ordinary hydrogen in their cores.
[3:37] Speaker 3: Which is of course the singular defining characteristic of a
[3:40] Speaker 3: true main sequence star.
[3:42] Speaker 2: Right, So how did we historically define these things?
[3:46] Speaker 3: Well, the way we have historically defined brown dwarfs highlights
[3:50] Speaker 3: that exact taxonomic flaw you mentioned earlier. We define them
[3:54] Speaker 3: almost exclusively by mass.
[3:56] Speaker 2: Boundaries, just putting them on a cosmic scale basically.
[3:59] Speaker 3: Yeah, and since this has generally been that, if an
[4:01] Speaker 3: object sits somewhere between say, thirteen and eighty times the
[4:05] Speaker 3: mass of Jupiter, we drop it into the brown dwarf box.
[4:09] Speaker 2: Okay, so why thirteen and why eighty? What is the
[4:12] Speaker 2: significance of those specific numbers.
[4:14] Speaker 3: It comes down to internal pressure and heat. The thirteen
[4:18] Speaker 3: jupiter mass lower limit is roughly where an object has
[4:21] Speaker 3: enough internal pressure to fuse deuterium, which.
[4:23] Speaker 2: Is like a heavier isotope of hydrogen.
[4:25] Speaker 3: Well, exactly, it has a neutron in the nucleus along
[4:27] Speaker 3: with the proton, so it fuses a bit easier than
[4:30] Speaker 3: normal hydrogen.
[4:31] Speaker 2: But it's just a brief period of fusion, right, it
[4:33] Speaker 2: doesn't last.
[4:34] Speaker 3: Right, it's a fleeting phase. Now, the eighty jupiter mass
[4:37] Speaker 3: upper limit, that is the hard threshold where core temperatures
[4:40] Speaker 3: and pressures become extreme enough to sustain the proton chain reaction.
[4:44] Speaker 2: So that's fusing normal hydrogen into helium.
[4:46] Speaker 3: Yes, and at that exact point it officially becomes a star.
[4:51] Speaker 2: But you know, if I'm looking at that purely from
[4:53] Speaker 2: a mass perspective, it feels incredibly reductive.
[4:57] Speaker 3: It is entirely reductive.
[4:58] Speaker 2: It completely ignores the evil utionary history of the object.
[5:02] Speaker 2: Two celestial bodies might both tip the scales at exactly
[5:06] Speaker 2: forty jupiter masses, but how they accumulated that mass could
[5:10] Speaker 2: be entirely different.
[5:11] Speaker 3: That is the critical blind spot in defining objects solely
[5:14] Speaker 3: by their mass. It is a strictly phenomenological definition rather
[5:19] Speaker 3: than a genetic one.
[5:20] Speaker 2: It doesn't tell you the origin story.
[5:21] Speaker 3: Not at all. Consider human physiology as an analog. You
[5:24] Speaker 3: could have two individuals who both weigh exactly two hundred pounds. Okay, sure,
[5:28] Speaker 3: if your only diagnostic tool is a bathroom scale. They
[5:32] Speaker 3: are identical data points. They both say two hundred. But
[5:36] Speaker 3: one might be an elite powerlifter, hyperdense muscle mass, a
[5:40] Speaker 3: very specific macronutrient diet, years of heavy resistance training.
[5:44] Speaker 2: Feel like a tank exactly.
[5:46] Speaker 3: The other person might be completely sedentary, with an entirely
[5:50] Speaker 3: different metabolic profile, lower bone density, totally different cardiovascular capacity.
[5:55] Speaker 2: Yeah, the scale tells you literally nothing about the underlying
[5:59] Speaker 2: mechanics or the journey that resulted in that final number.
[6:02] Speaker 3: Right, Their underlying blueprints are totally different.
[6:05] Speaker 2: I always think about it like vehicles. It is like
[6:08] Speaker 2: looking at a luxury battery electric suv and then looking
[6:11] Speaker 2: at a specialized commercial dump truck that just happen to
[6:14] Speaker 2: have the exact same curb weight.
[6:16] Speaker 3: That's a great way to picture it.
[6:17] Speaker 2: If you categorize them only by tonnage, you miss the
[6:20] Speaker 2: fact that they have entirely different powertrains, different chassis architecture,
[6:25] Speaker 2: and fundamentally different purposes.
[6:27] Speaker 3: Exactly.
[6:27] Speaker 2: You can't use the dumb truck for a quiet family
[6:30] Speaker 2: road trip, No.
[6:30] Speaker 3: You cannot.
[6:31] Speaker 2: Yeah, and you definitely can't use the luxury suv to
[6:33] Speaker 2: haul three tons of gravel.
[6:34] Speaker 3: It would ruin the suspension instantly.
[6:37] Speaker 2: Yeah, the mass is literally the least interesting thing about them.
[6:40] Speaker 2: So if mass is a fundamentally lazy diagnostic tool for
[6:43] Speaker 2: these celestial objects, the obvious question is what is the alternative?
[6:48] Speaker 3: Well, we have to shift our focus from the current
[6:50] Speaker 3: state of the object to its formation mechanism. The origin
[6:53] Speaker 3: story is the true DNA of a celestial body.
[6:56] Speaker 2: Okay, so how do we trace that DNA?
[6:58] Speaker 3: When you look at the astrophysics of that intermediate mass range,
[7:01] Speaker 3: that thirteen to eighty jupiter mass window, there are two
[7:05] Speaker 3: completely distinct, physically contrasting thermodynamic pathways that can produce an
[7:11] Speaker 3: object of that size, and.
[7:12] Speaker 2: We colloquially refer to them as the star method and
[7:15] Speaker 2: the planet method.
[7:16] Speaker 3: Right pathway one and pathway two.
[7:17] Speaker 2: Okay, let's pull apart the mechanics of pathway one first,
[7:20] Speaker 2: the star method. When we say an object forms like
[7:23] Speaker 2: a star, what are the actual physical steps of that process.
[7:27] Speaker 3: The star method is fundamentally a top down process. It's
[7:30] Speaker 3: driven entirely by gravitational collapse.
[7:33] Speaker 2: So starting big and shrinking down.
[7:34] Speaker 3: Yes, it begins in a giant molecular cloud. These are massive, sprawling,
[7:39] Speaker 3: incredibly cold regions of space filled mostly with hydrogen gas
[7:43] Speaker 3: and interstellar.
[7:44] Speaker 2: Dust just floating out there.
[7:45] Speaker 3: It's floating, and these clouds are delicately balanced. It's a
[7:49] Speaker 3: constant struggle. The thermal pressure of the cold gas is
[7:52] Speaker 3: pushing outward, trying to expand the cloud, while the self
[7:56] Speaker 3: gravity of all that massive amount of material is pulling in,
[8:00] Speaker 3: trying to collapse it.
[8:01] Speaker 2: It's a hydrostatic tug of war.
[8:02] Speaker 3: That is the exact term, a hydrostatic tug of war.
[8:06] Speaker 3: And if something tips the scales, say a shockwave from
[8:10] Speaker 3: a distant supernova compresses the gas, or maybe the cloud
[8:13] Speaker 3: simply crosses a critical mass threshold, gravity wins.
[8:17] Speaker 2: Gravity always wins.
[8:18] Speaker 3: Eventually, it usually does. So a dense pocket within the
[8:21] Speaker 3: cloud begins to collapse inward, and as it collapses, the
[8:24] Speaker 3: conservation of angular momentum dictates that any slight rotation in
[8:29] Speaker 3: that initial cloud is amplified.
[8:31] Speaker 2: Like an ice skater pulling their arms.
[8:32] Speaker 3: In perfect analogy, it spins faster and faster, causing the
[8:36] Speaker 3: collapsing pocket to flatten out into a disk structure. Concurrently,
[8:40] Speaker 3: the gravitational potential energy of all that collapsing gas is
[8:43] Speaker 3: converted into thermal energy.
[8:44] Speaker 2: So the core heats up dramatically. As it gets.
[8:46] Speaker 3: Squeezed dramatically, it is frantically accumulating material, increasing the core
[8:51] Speaker 3: pressure in temperature, trying desperately to cross that eighty Jupiter
[8:55] Speaker 3: mass threshold to ignite sustained hydrogen fusion. Wants to be
[8:59] Speaker 3: a star, that is the goal of the collapse. But
[9:02] Speaker 3: in the case of a brown dwarf forming via this pathway,
[9:05] Speaker 3: the initial pocket of gas simply wasn't massive enough.
[9:08] Speaker 2: You're out of fuel to pull from exactly it.
[9:11] Speaker 3: It creates all the available material in its immediate vicinity,
[9:14] Speaker 3: but the final Tallie just falls short.
[9:16] Speaker 2: So what happens to the core?
[9:17] Speaker 3: The core temperature might reach a few million degrees that's
[9:21] Speaker 3: enough to briefly fuse deuterium, perhaps even lithium, but it
[9:25] Speaker 3: never hits the critical temperature needed for sustained hydrogen fusion,
[9:29] Speaker 3: so it's a dud. Essentially, the object becomes incredibly hot,
[9:32] Speaker 3: it radiates thermal energy, but without an internal nuclear engine
[9:36] Speaker 3: to generate outward pressure, it just slowly cools and contracts
[9:40] Speaker 3: over billions of years.
[9:41] Speaker 2: But wait, because it's so massive, it doesn't collapse infinitely. Right,
[9:45] Speaker 2: there has to be a structural limit to how far
[9:47] Speaker 2: gravity can crush it.
[9:49] Speaker 3: Correct, the collapse is eventually halted by something called electron
[9:52] Speaker 3: degeneracy pressure.
[9:53] Speaker 2: Okay, break that down for us.
[9:55] Speaker 3: The atoms in the core are squeezed together so tightly
[9:58] Speaker 3: that quantum mechanics take over. The poly exclusion principle dictates
[10:03] Speaker 3: that no two electrons can occupy the exact same quantum state.
[10:07] Speaker 2: They just refuse to overlap.
[10:08] Speaker 3: They physically resist being compressed any further. That quantum resistance
[10:13] Speaker 3: is what actually holds the brown dwarf up against its
[10:15] Speaker 3: own immense gravity.
[10:17] Speaker 2: Wow, that is a staggering visual. It's not held up
[10:21] Speaker 2: by the heat of a nuclear furnace like a star.
[10:23] Speaker 2: It's held up by the fundamental quantum refusal of electrons
[10:26] Speaker 2: to overlap.
[10:27] Speaker 3: It's a bizarre state of matter, truly.
[10:30] Speaker 2: Now contrasts that incredibly violent, rapid top down collapse with
[10:34] Speaker 2: Pathway two, the planet method. This has to be a
[10:37] Speaker 2: completely different physical environment.
[10:38] Speaker 3: It is entirely different. Pathway two is a bottom up.
[10:41] Speaker 2: Process building from scratch.
[10:43] Speaker 3: Yes, in this scenario, a massive true star has already
[10:47] Speaker 3: successfully formed via that collapse method we just discussed, But
[10:50] Speaker 3: the formation of that central star is sloppy.
[10:53] Speaker 2: Nature is a messy.
[10:54] Speaker 3: Eater very messy. Not all the material in the collapsing
[10:57] Speaker 3: pocket falls directly into the star, significant percentage of the
[11:01] Speaker 3: gas and dust retains too much angular momentum and ends
[11:05] Speaker 3: up orbiting the newborn star, creating a disc, creating a
[11:09] Speaker 3: vast flattened structure known as a protoplanetary accretion disc.
[11:13] Speaker 2: I always picture this like a massive cosmic centrifuge. You've
[11:17] Speaker 2: got the wazing newborn star in the center and this
[11:21] Speaker 2: incredibly broad, relatively thin disk of material just spinning around it.
[11:26] Speaker 3: That's the architecture, and compared to the turbulent, violent collapse
[11:29] Speaker 3: of a molecular cloud, the interior of a protoplanetary disc
[11:33] Speaker 3: is a highly structured, relatively orderly environment.
[11:36] Speaker 2: Because everything is flowing in the same direction right.
[11:39] Speaker 3: The gas and dust are orbiting in coplearian motion.
[11:41] Speaker 2: Meaning the inner part's orbit faster than the outer.
[11:43] Speaker 3: Part exactly right, which does create sheer forces, but overall
[11:47] Speaker 3: it's a stable disc. Within this disk, microscopic dust grains
[11:51] Speaker 3: begin colliding. At first, they just stick together through simple
[11:54] Speaker 3: electrostatic forces like static cling. Yes, exactly like dust Bunny
[11:58] Speaker 3: is accumulating under a bed.
[12:00] Speaker 2: But you can't build a forty Jupiter mass object with
[12:03] Speaker 2: static electricity.
[12:04] Speaker 3: No, the electrostatic forces only get you so far. As
[12:08] Speaker 3: the aggregates grow into pebbles and then into boulders, they
[12:11] Speaker 3: become subject to gas drag within the disc like wind resistance, Yes,
[12:16] Speaker 3: and that wind resistance can cause them to lose momentum
[12:19] Speaker 3: and spiral inward toward the star. This is actually a
[12:23] Speaker 3: major hurdle in planetary formation models. It's often referred to
[12:27] Speaker 3: as the meter sized barrier.
[12:28] Speaker 2: Because objects that are about a meter across get dragged
[12:31] Speaker 2: into the star and destroyed.
[12:33] Speaker 3: Right. But if the material can rapidly clump together, perhaps
[12:37] Speaker 3: getting trapped in localized pressure bumps within the disc, they
[12:40] Speaker 3: can grow massive enough that their own gravity begins to dominate.
[12:44] Speaker 2: They graduate from pebbles to actual gravitational bodies.
[12:47] Speaker 3: They become planetesimals and eventually a solid planetary core.
[12:50] Speaker 2: And once that core hits a certain critical mass, the
[12:54] Speaker 2: physics shift again, don't they. It's not just sweeping up
[12:56] Speaker 2: dust anymore.
[12:57] Speaker 3: Exactly. Once the solid core reaches somewhere between say, ten
[13:01] Speaker 3: and twenty times the mass of the Earth, its gravitational
[13:04] Speaker 3: pull becomes incredibly strong, strong enough to start accreting the
[13:08] Speaker 3: abundant hydrogen and helium gas directly from the disc.
[13:11] Speaker 2: It starts vacuuming up the atmosphere.
[13:13] Speaker 3: It initiates a phase called runaway gas secretion. The more
[13:17] Speaker 3: gas it pulls in, the more massive it becomes. The
[13:19] Speaker 3: more massive it becomes, the stronger it's gravity, allowing it
[13:22] Speaker 3: to pull in gas from an even wider radius.
[13:25] Speaker 2: It's an exponential growth loop.
[13:26] Speaker 3: It just balloons in mass, growing into a gas giant,
[13:30] Speaker 3: and potentially, if the disc has enough material and survives
[13:33] Speaker 3: long enough, it can cross that thirteen jupiter mass threshold
[13:37] Speaker 3: and become a brown dwarf.
[13:39] Speaker 2: So, just to recap the two origin stories, Pathway one
[13:42] Speaker 2: is a rapid, dramatic collapse from a massive cloud down
[13:45] Speaker 2: to a dense core. Pathway two is a slow, methodical
[13:48] Speaker 2: accumulation of mass, starting from microscopic dust grains and building
[13:52] Speaker 2: upward inside a structured disc over millions of years.
[13:55] Speaker 3: That is the perfect summary, and the key.
[13:57] Speaker 2: For astrophysicists is that these two wildly different origin stories
[14:03] Speaker 2: should leave behind structural evidence, specifically in the mechanics of
[14:07] Speaker 2: their orbits.
[14:08] Speaker 3: Right, the orbital mechanics are the primary diagnostic tool we
[14:12] Speaker 3: have to differentiate between the two formation pathways.
[14:15] Speaker 2: After the fact, because we can't be there to watch
[14:17] Speaker 2: them form.
[14:17] Speaker 3: We can't, so we look at how they move. If
[14:19] Speaker 3: a brown dwarf forms via the star method the direct
[14:23] Speaker 3: cloud collapse, it rarely forms an isolation. Molecular clouds typically
[14:27] Speaker 3: fragment into multiple collapsing cores simultaneously.
[14:31] Speaker 2: Like a litter of puppies.
[14:32] Speaker 3: Yeah, and you end up with a highly chaotic, dense
[14:34] Speaker 3: cluster of protostars and brown dwarfs all interacting gravitationally.
[14:38] Speaker 2: It's an n body problem. You have multiple massive objects
[14:41] Speaker 2: all pulling on each other, exchanging momentum. It sounds like
[14:44] Speaker 2: a gravitational moshpit.
[14:46] Speaker 3: A mosh pit is a very accurate way to describe it.
[14:48] Speaker 3: Through those complex dynamical interactions, objects slingshot past one another.
[14:53] Speaker 3: The lighter objects like brown dwarfs often have their orbits
[14:56] Speaker 3: violently perturbed.
[14:57] Speaker 2: They get kicked around.
[14:58] Speaker 3: Some are ejected from the cl luster entirely becoming rogue
[15:02] Speaker 3: objects just floating freely through the galaxy.
[15:05] Speaker 2: Wow.
[15:06] Speaker 3: But those that remain bound to a heavier central star
[15:08] Speaker 3: typically end up in highly eccentric orbits.
[15:11] Speaker 2: Which means the orbit is not a circle. The eccentricity
[15:14] Speaker 2: is a measure of how stretched out the orbit is right.
[15:16] Speaker 3: Right, and the centric orbit has a high degree of ellipticity.
[15:20] Speaker 3: There is a point where the brown dwarf swings incredibly
[15:23] Speaker 3: close to the host star we call that the periapsis,
[15:27] Speaker 3: and a point where it is flung far out into
[15:29] Speaker 3: the outer reaches of the system, the apoapsis.
[15:32] Speaker 2: It is a highly dynamic, highly variable path Yeah, like
[15:35] Speaker 2: a comet.
[15:36] Speaker 3: Yes, very comet like now. On the other hand, if
[15:38] Speaker 3: an object forms via the planet method pathway two, it
[15:42] Speaker 3: inherits the kinematic properties of the protoplanetary.
[15:45] Speaker 2: Disk because the disc itself is already in a stable
[15:47] Speaker 2: near circular rotation around the star.
[15:50] Speaker 3: Yes, the gas and dust in the disc move in
[15:52] Speaker 3: nearly circular coullplanar orbits. As the protoplanet grows within the disc,
[15:57] Speaker 3: the surrounding gas acts as a dampening agent, like shok
[15:59] Speaker 3: ofs exactly any slight eccentricities are quickly smoothed out by
[16:04] Speaker 3: aerodynamic drag and gravitational interactions with the disc material itself. Consequently,
[16:09] Speaker 3: objects born via the core accretion method almost invariably maintain
[16:13] Speaker 3: low eccentricity near circular orbits.
[16:15] Speaker 2: So looking at this Structurally, we have a seemingly perfect
[16:18] Speaker 2: diagnostic tool. We observe a brown dwarf. We track its orbit.
[16:23] Speaker 2: If the orbit is a highly stretched out ellipse, it
[16:25] Speaker 2: formed via cloud collapse in gravitational scattering.
[16:27] Speaker 3: Correct.
[16:28] Speaker 2: If the orbit is a clean, stable circle, it formed
[16:31] Speaker 2: inside a disc via core accretion. We don't even need
[16:34] Speaker 2: to worry about the mass boundaries anymore. The orbit tells
[16:36] Speaker 2: us the genetic history.
[16:38] Speaker 3: In a static universe, that logic would be absolutely flawless.
[16:41] Speaker 2: Ah, but we don't live in a static universe.
[16:44] Speaker 3: We do not The orbital fingerprint would be permanent if
[16:47] Speaker 3: things didn't change, but the universe is highly dynamic over
[16:51] Speaker 3: long time scales. This brings us to a mechanical process
[16:54] Speaker 3: that deeply frustrates.
[16:55] Speaker 2: Astronomers, the cosmic eraser.
[16:57] Speaker 3: Yes, tidal circularization. It acts as a cosmic eraser, slowly
[17:02] Speaker 3: destroying the very orbital evidence we rely on to figure
[17:05] Speaker 3: out how these things formed.
[17:06] Speaker 2: Okay, let's dig into the physics of this cosmic eraser.
[17:10] Speaker 2: Because when we talk about tidal forces, I think most
[17:13] Speaker 2: people immediately think of the Moon's gravity pulling on Earth's
[17:18] Speaker 2: oceans to create tides.
[17:20] Speaker 3: That's the most familiar example, right.
[17:22] Speaker 2: But how does a tidal force literally alter the geometric
[17:26] Speaker 2: shape of an entire orbit over millions of miles. That
[17:29] Speaker 2: seems insane.
[17:30] Speaker 3: It fundamentally comes down to the inverse square law of gravity.
[17:34] Speaker 3: The strength of the gravitational force between two objects drops
[17:38] Speaker 3: off exponentially as the distance between them increases. Okay, when
[17:41] Speaker 3: you have a massive object like a brown dwarf swinging
[17:44] Speaker 3: into the periapsis of a highly eccentric orbit, it gets
[17:47] Speaker 3: very close to its massive host star.
[17:50] Speaker 2: That's the close approach, right.
[17:51] Speaker 3: And because the brown dwarf itself has a phytical radius,
[17:54] Speaker 3: I mean maybe it's one hundred thousand kilometers across the
[17:56] Speaker 3: side of the brown dwarf facing the star is physically
[17:59] Speaker 3: closer to the star than the side facing away.
[18:01] Speaker 2: Right by one hundred thousand kilometers exactly.
[18:03] Speaker 3: And because of that difference in distance, the near side
[18:06] Speaker 3: of the brown dwarf experiences a significantly stronger gravitational pull
[18:10] Speaker 3: from the star than the far side does.
[18:12] Speaker 2: The gravity is literally uneven across the body of the planet.
[18:15] Speaker 3: It is this differential gravitational gradient physically deforms the brown dwarf.
[18:21] Speaker 3: It stretches the object along the axis pointing toward the star,
[18:24] Speaker 3: creating a massive tidal.
[18:26] Speaker 2: Bulge, so the spherical object becomes slightly ovoid like a football.
[18:31] Speaker 3: Like a football, it is literally pulling the physical matter
[18:34] Speaker 3: of the object out of shape.
[18:36] Speaker 2: That has to be violently disruptive.
[18:38] Speaker 3: It is. But as the brown dwarf continues along its
[18:41] Speaker 3: highly eccentric path, swinging away from the star and heading
[18:45] Speaker 3: back out toward Apopsis, the distance increases, the gravitational gradient weakens.
[18:50] Speaker 2: So the football goes back to being a sphere.
[18:52] Speaker 3: The tidal bulge collapses, and the brown dwarf relaxes back
[18:55] Speaker 3: into a more spherical shape due to its own self
[18:58] Speaker 3: gravity squeeze. At relax it undergoes this massive physical deformation
[19:04] Speaker 3: every single time it completes an orbit.
[19:05] Speaker 2: But the brown dwarf isn't a rigid solid, and it's
[19:08] Speaker 2: not a perfect fluid either. There has to be immense
[19:11] Speaker 2: resistance inside the object as millions of tons of gas
[19:15] Speaker 2: and material are being forced to shift in flex.
[19:17] Speaker 3: That resistance is the key. The interior of the brown
[19:20] Speaker 3: dwarf has viscosity. As the material flexes, that internal friction
[19:25] Speaker 3: generates an enormous amount.
[19:27] Speaker 2: Of heat, just like rubbing your hands together.
[19:29] Speaker 3: Exactly. The first law of thermodynamics tells us that energy
[19:32] Speaker 3: cannot be created or destroyed, it must be conserved. So,
[19:36] Speaker 3: if the flexing of the Brown dwarf is generating massive
[19:39] Speaker 3: amounts of thermal energy, where is that energy coming from.
[19:43] Speaker 2: It has to be bleeding it from somewhere. Is it
[19:44] Speaker 2: coming from the kinetic energy of the orbit itself.
[19:47] Speaker 3: Yes, the energy dissipated as internal heat is siphoned directly
[19:51] Speaker 3: from the object's orbital energy. Crucially, this energy dissipation is
[19:56] Speaker 3: highly localized because the tidal forces are exponent stronger when
[20:00] Speaker 3: the objects are close together. Almost all of the energy
[20:04] Speaker 3: drain occurs during that brief window when the Brown dwarf
[20:07] Speaker 3: is at periapsis.
[20:08] Speaker 2: Wait, if you were draining energy from the orbit, wouldn't
[20:11] Speaker 2: the Brown dwarf just spiral inward and eventually crash into
[20:14] Speaker 2: the star.
[20:15] Speaker 3: It's a great question, But no. While orbital energy is
[20:19] Speaker 3: being dissipated, angular momentum must be conserved. The physics dictate
[20:24] Speaker 3: that losing orbital energy at periapsis doesn't pull the periapsis
[20:27] Speaker 3: closer to the star. Instead, it lowers the epoapsis.
[20:31] Speaker 2: It pulls the far end of the orbit inward precisely.
[20:35] Speaker 3: Over millions or billions of years, the relentless siphoning of
[20:39] Speaker 3: energy at periapsis continuously trims the extreme edges of the
[20:43] Speaker 3: elliptical orbit. The orbit becomes less and less eccentric, until
[20:46] Speaker 3: eventually it circularizes completely.
[20:49] Speaker 1: Wow.
[20:50] Speaker 2: So the closest point stays the same, but the furthest
[20:53] Speaker 2: point just gets dragged in closer and closer until it's
[20:56] Speaker 2: a perfect circle.
[20:56] Speaker 3: Right. And once the orbit is perfectly circular, the distance
[20:59] Speaker 3: between the the star and the brown dwarf remains constant.
[21:02] Speaker 3: The gravitational gradient is constant, the tidle bulge becomes locked
[21:05] Speaker 3: in place, the flexing stops, and the energy drain ceases.
[21:08] Speaker 3: The system reaches an equilibrium, so.
[21:10] Speaker 2: A brown dwarf could be borne in a chaotic cluster
[21:12] Speaker 2: via cloud collapse. Pathway one gets slingshotted into a wildly
[21:16] Speaker 2: eccentric orbit, and then over a billion years, the internal
[21:20] Speaker 2: friction caused by tidal flexing slowly sands down the orbit
[21:24] Speaker 2: into a perfect stable circle, making it look exactly like
[21:27] Speaker 2: pathway too.
[21:28] Speaker 3: Yes, and that is why tidal circularization is the cosmic eraser.
[21:33] Speaker 3: If we observe a brown dwarf today and see that
[21:35] Speaker 3: it has a near circular orbit. We cannot definitively say
[21:39] Speaker 3: it formed via the planet method and a disc It
[21:42] Speaker 3: very well could have formed via the star method, and
[21:45] Speaker 3: the tidal forces have simply scrubbed away the kinematic evidence
[21:48] Speaker 3: over billions of years.
[21:50] Speaker 2: It reminds me of forensic trace evidence. Imagine you are
[21:53] Speaker 2: walking along a pristine shoreline, right where the tide meets
[21:56] Speaker 2: the sand. If a dog runs past, it leads a
[21:58] Speaker 2: very specific bile mechanical signature.
[22:00] Speaker 3: In the sand four pause claw marks right.
[22:03] Speaker 2: If a human walks past, the footprint is entirely different.
[22:06] Speaker 2: If you observe the tracks immediately, the diagnostic evidence is perfect.
[22:09] Speaker 2: You know exactly what walked by.
[22:10] Speaker 3: But if you arrive three hours later, exactly.
[22:13] Speaker 2: If you arrive three hours later, after the incoming tide
[22:15] Speaker 2: has continually washed over that exact spot, the mechanical energy
[22:19] Speaker 2: of the waves has redistributed the sand, the surface is
[22:22] Speaker 2: perfectly smooth. The waves act as the tidal circularization.
[22:26] Speaker 3: That analogy holds up perfectly.
[22:28] Speaker 2: When you look at that smooth sand, you have absolutely
[22:31] Speaker 2: no way of knowing whether a dog or a human
[22:33] Speaker 2: walked there. The historical data has been completely erased.
[22:36] Speaker 3: The relentless action of gravity washes away the orbital eccentricity,
[22:41] Speaker 3: just like the waves wash away the footprints. So the
[22:44] Speaker 3: observational challenge becomes incredibly steep. How do you catch one
[22:49] Speaker 3: of these objects before the evidence is erased? How do
[22:51] Speaker 3: you peer beneath the smooth.
[22:53] Speaker 2: Sand to do that? To even find these intermediate mass
[22:56] Speaker 2: objects orbiting close to their host stars before billions of
[22:59] Speaker 2: years of pace, we need a massive unlinking eye in
[23:02] Speaker 2: the sky, and that requires a deep dive into the
[23:05] Speaker 2: engineering and methodology of the Transiting Exoplanet Survey Satellite or Test.
[23:09] Speaker 3: TESTS is fundamentally revolutionizing our catalog of the local universe.
[23:13] Speaker 3: Deployed in twenty eighteen, its primary architecture is designed to
[23:17] Speaker 3: survey hundreds of thousands of the brightest stars in the
[23:20] Speaker 3: solar neighborhood. It's an incredible machine, it is, but it
[23:23] Speaker 3: is vital to understand the precise mechanics of what TESTS
[23:26] Speaker 3: is actually doing. It is not an optical telescope taking
[23:30] Speaker 3: direct high resolution photographs of brown dwarfs or exoplanet.
[23:34] Speaker 2: Right because the contrast ratio makes direct imaging nearly impossible
[23:38] Speaker 2: for close in objects. You are trying to resolve a
[23:40] Speaker 2: relatively dim object sitting right next to a star that
[23:44] Speaker 2: might be a million times brighter.
[23:45] Speaker 3: Exactly, the glare of the host star completely overwhelms any
[23:49] Speaker 3: photons emitted or reflected by the companion object. You just
[23:52] Speaker 3: see a blinding light.
[23:53] Speaker 2: So how does it actually work?
[23:55] Speaker 3: Instead of pictures, tests utilizes highly sensitive charred coupled device
[23:59] Speaker 3: or CC photometers. It operates on the transit method. Test
[24:03] Speaker 3: essentially stares at a wide feel of stars and constantly
[24:06] Speaker 3: measures the incoming photon flux, the raw brightness, yes, the
[24:10] Speaker 3: raw brightness from each individual star, plotting that data over
[24:13] Speaker 3: time to create a continuous light curve.
[24:15] Speaker 2: So for the vast majority of stars, that light curve
[24:18] Speaker 2: is just a flat line or maybe a slightly noisy line,
[24:21] Speaker 2: depending on the star's natural activity.
[24:23] Speaker 3: Correct. But if a star system is aligned such that
[24:26] Speaker 3: the orbital plane of a companion object is viewed almost
[24:29] Speaker 3: exactly edge on from our perspective here in the Solar system,
[24:33] Speaker 3: meaning an inclination angle very close to ninety degrees, that
[24:36] Speaker 3: companion will periodically pass directly between its host star and
[24:40] Speaker 3: the test cameras.
[24:41] Speaker 2: It physically blocks a portion of the star's photosphere, it
[24:45] Speaker 2: casts a shadow.
[24:46] Speaker 3: It creates an eclipse, albeit a microscopic one. As the
[24:49] Speaker 3: object transits the stellar disc test records a minute temporary
[24:53] Speaker 3: drop in the photon flux. The light curve DIPS remains
[24:56] Speaker 3: depressed for the duration of a transit, which could be
[24:59] Speaker 3: hours or days, and then returns to its baseline flux
[25:02] Speaker 3: once the object completes its passage, and.
[25:04] Speaker 2: The geometry of that DIP contains physical data, doesn't it.
[25:07] Speaker 2: The shape of the light curve isn't just a binary yes,
[25:10] Speaker 2: no signal.
[25:10] Speaker 3: Oh not at all. The morphology of the transit light
[25:13] Speaker 3: curve is incredibly data rich. The depth of the dip
[25:17] Speaker 3: exactly what percentage of the star's light is blocked, tells
[25:20] Speaker 3: us the physical ratio between the cross sectional area of
[25:23] Speaker 3: the companion and the cross sectional area of the star.
[25:26] Speaker 2: So if we know how big the star is, we
[25:27] Speaker 2: know exactly how big the planet is.
[25:29] Speaker 3: Yes, if we know the radius of the star, we
[25:31] Speaker 3: can calculate the exact physical radius of the transiting object. Furthermore,
[25:36] Speaker 3: the duration of the transit and the exact shape of
[25:38] Speaker 3: the ingress and egress the slopes of the DIP as
[25:41] Speaker 3: the object enters and exits the stellar disc allow us
[25:44] Speaker 3: to constrain the orbital velocity and the exact inclination of
[25:47] Speaker 3: the orbit.
[25:48] Speaker 2: That is where the precision requirement becomes just mind bending.
[25:52] Speaker 2: I try to visualize the physical scale of what tests
[25:54] Speaker 2: is measuring. A Jupiter sized object passing in front of
[25:57] Speaker 2: a sun like star might only block one percent of
[25:59] Speaker 2: the light. A smaller object might block a tenth of
[26:02] Speaker 2: a percent.
[26:03] Speaker 3: It's an incredibly small signal.
[26:05] Speaker 2: We're basically tasked with staring at a massive stadium floodlight
[26:08] Speaker 2: from hundreds of miles away and trying to detect the
[26:11] Speaker 2: momentary fractional dimming caused by a moth flying across the lens.
[26:15] Speaker 3: That is exactly the scale of the challenge.
[26:18] Speaker 2: So how do astrophysicists filter out the noise? How do
[26:22] Speaker 2: you know that dip in the light curve isn't just
[26:23] Speaker 2: an instrumental glitch or like a sunspot rotating across the
[26:28] Speaker 2: surface of the star.
[26:29] Speaker 3: The signal to noise ratio is the greatest adversary in
[26:32] Speaker 3: transit photometry. To overcome it, you need rigorous validation. A
[26:36] Speaker 3: single transit event is classified merely as a candidate.
[26:39] Speaker 2: It's just a maybe right.
[26:41] Speaker 3: To confirm it, you first need to observe the transit
[26:44] Speaker 3: repeat at strict predictable intervals, which confirms periodicity and rules
[26:48] Speaker 3: out random instrumental noise because a.
[26:50] Speaker 2: Glitch won't happen every four point two days exactly exactly.
[26:53] Speaker 3: But even with a perfectly repeating transit signal, a sun
[26:56] Speaker 3: spot or a background eclipsing binary star could theoretically mimic
[27:00] Speaker 3: the light curve of a planetary transit, so.
[27:03] Speaker 2: You need a second method to double check yes.
[27:05] Speaker 3: To achieve absolute conformation and to fully characterize the object,
[27:09] Speaker 3: you must move from the space based photometry of tests
[27:12] Speaker 3: to ground based high resolution spectroscopy.
[27:15] Speaker 2: Okay, let's break down spectroscopy because this is where the
[27:18] Speaker 2: actual mass of the object is derived. Right, tests gives
[27:22] Speaker 2: us the radius how big the shadow is, but it
[27:24] Speaker 2: tells us nothing about how heavy the object is.
[27:27] Speaker 3: That's the degeneracy we have to break.
[27:29] Speaker 2: Because a highly inflated fluffy gas giant and a super
[27:32] Speaker 2: dense brown dwarf could have the exact same physical radius
[27:36] Speaker 2: and cast the exact same shadow precisely.
[27:39] Speaker 3: Test measures the volumemetric size, but tectroscopy measures the gravitational mass.
[27:45] Speaker 3: Think of the light emitted by a star as a
[27:47] Speaker 3: continuous spectrum of electromagnetic radiation. When we capture that light
[27:51] Speaker 3: with a spectrograph, we disperse it into its component.
[27:54] Speaker 2: Wavelengths like a prism, making a rainbow.
[27:56] Speaker 3: Like a prism. Because the outer atmosphere of the star
[27:59] Speaker 3: is cooler than its interior, atoms in the stellar atmosphere
[28:02] Speaker 3: absorb specific wavelengths of light based on their chemical composition.
[28:06] Speaker 2: So when you look at the dispersed spectrum, you see
[28:08] Speaker 2: dark bands absorption lines cutting across the rainbow of light.
[28:12] Speaker 2: It looks like a chemical barcode.
[28:13] Speaker 3: A barcode is the perfect analogy. Every star has a
[28:17] Speaker 3: unique spectral barcode. Now we have to consider the orbital
[28:21] Speaker 3: mechanics of the system. While we often say the Brown
[28:24] Speaker 3: Dwarf orbits the star, that isn't strictly true. Newton's laws
[28:28] Speaker 3: dictate that both the star and the Brown dwarf orbit
[28:31] Speaker 3: their common center of mass, known as the Berry center.
[28:34] Speaker 2: Because gravity is bidirectional, the star pulls on the planet,
[28:38] Speaker 2: but the planet also pulls on the.
[28:39] Speaker 3: Star exactly the massive host star dominates, so the Berry
[28:44] Speaker 3: center is usually deep inside the star itself, but the
[28:47] Speaker 3: Brown Dwarf's gravity still pulls on the star, causing the
[28:50] Speaker 3: star to wabble slightly in space. It does a little dance,
[28:54] Speaker 3: it does, and as the star wabbles around that Berry center,
[28:57] Speaker 3: its movement relative to Earth causes a Doppler shift in.
[29:00] Speaker 2: Its light, just like an ambulance siren changing pitch as
[29:03] Speaker 2: it drives past you.
[29:04] Speaker 3: Yes, the exact same principle, but with light waves instead
[29:07] Speaker 3: of sound waves. When the star's wobble pulls it slightly
[29:10] Speaker 3: toward our telescopes, the light waves are compressed, shifting the
[29:14] Speaker 3: entire spectral bar code towards the blue end of the spectrum.
[29:17] Speaker 3: The blue shift, and as the star wobbles away from us,
[29:21] Speaker 3: the light waves are stretched and the barcode shifts toward
[29:24] Speaker 3: the red end of the spectrum. This is called the
[29:26] Speaker 3: radial velocity method.
[29:28] Speaker 2: So astrophysicists are monitoring this chemical barcode, watching the dark
[29:32] Speaker 2: lines rhythmically slide left to right, blue to red in
[29:36] Speaker 2: perfect synchronization with the transit dips observed by tests.
[29:39] Speaker 3: Exactly the periodicity of the Doppler shift matches the orbital
[29:44] Speaker 3: period derived from the transits. More importantly, the amplitude of
[29:48] Speaker 3: that shift, exactly how fast the star is wobbling toward
[29:52] Speaker 3: and away from US is directly proportional to the gravitational
[29:55] Speaker 3: mass of the unseen companion.
[29:57] Speaker 2: Because a heavier object pulls harder and makes the star
[30:00] Speaker 2: wobble faster.
[30:01] Speaker 3: A massive brown dwarf will induce a much larger radial
[30:05] Speaker 3: velocity shift than a low mass planet.
[30:08] Speaker 2: So you take the physical radius calculated from the depth
[30:10] Speaker 2: of the test shadow, and you take the mass calculated
[30:13] Speaker 2: from the amplitude of the spectroscopic wobble. You combine them
[30:16] Speaker 2: and suddenly you have the exact bolt density of the object.
[30:19] Speaker 3: You know exactly what you were looking at without ever
[30:21] Speaker 3: actually seeing it.
[30:22] Speaker 2: It is a triumph of deductive physics. And it was
[30:25] Speaker 2: exactly this combination of test photometry and ground based radial
[30:29] Speaker 2: velocity spectroscopy that led a team at Harvard University spearheaded
[30:34] Speaker 2: by Ninoephramids to isolate a signal that defies our current
[30:38] Speaker 2: astrophysical models.
[30:40] Speaker 3: They identified the shadow of Hip six' one six three SEVEN.
[30:44] Speaker 2: B let's dig into the specifics of this rule, breaker
[30:47] Speaker 2: because it isn't just the physical properties of the brown
[30:50] Speaker 2: dwarf that make it, bizarre it's the specific orbital neighborhood
[30:53] Speaker 2: it in. Habits The harvard team found this object sitting
[30:57] Speaker 2: in a region of parameter space that astrophysicists ominously call
[31:01] Speaker 2: The Brown dwarf.
[31:02] Speaker 3: Desert The Brown dwarf desert is one of the most
[31:04] Speaker 3: persistent statistical anomalies in exoplanet.
[31:07] Speaker 2: Demographics why is it a? Desert, well when we plot.
[31:10] Speaker 3: The mass of discovered companions against their orbital distance from
[31:13] Speaker 3: their host, stars we find thousands of massive gas giants
[31:16] Speaker 3: in very close, orbits and we find numerous brown dwarfs
[31:19] Speaker 3: in very wide distant. Orbits but if you look at
[31:22] Speaker 3: the close in intermediate mass, regimes specifically objects between thirteen
[31:27] Speaker 3: and roughly sixty jupiter masses with orbital periods of less
[31:30] Speaker 3: than one hundred, days the data is incredibly. Sparse it
[31:34] Speaker 3: is a statistical.
[31:35] Speaker 2: Void so why does the desert. Exist is it a
[31:38] Speaker 2: formation problem where the physical conditions close to a star
[31:41] Speaker 2: prevent objects of that specific mass from, forming or is
[31:45] Speaker 2: it a survival problem where they form further, out migrate,
[31:48] Speaker 2: inward and then just get completely swallowed by the host.
[31:51] Speaker 3: Star it is fiercely, debated but the current consensus leans
[31:55] Speaker 3: toward a combination of rapid migration and tidal. Engulfment as
[31:59] Speaker 3: massive objects formed within the gas, disc gravitational interactions with
[32:03] Speaker 3: the spiral density waves in the disk can cause them
[32:06] Speaker 3: to lose angular momentum and migrate, inward.
[32:08] Speaker 2: A process known as type two.
[32:09] Speaker 3: Migration, exactly if an object is massive, enough like a brown,
[32:13] Speaker 3: dwarf the tidal forces from the star become extreme as
[32:15] Speaker 3: it migrates. Closer the energy dissipation we discussed earlier not
[32:19] Speaker 3: only circularizes the, orbit but can also decay the semi major.
[32:22] Speaker 2: Axis so it spiral's the death, spiral.
[32:25] Speaker 3: Yes causing the brown dwarf to spiral inward until it
[32:28] Speaker 3: crosses The roche limit and is shredded or is simply
[32:31] Speaker 3: engulfed by the expanding envelow of the.
[32:33] Speaker 2: Star the physics actively conspire to clear that specific orbital
[32:38] Speaker 2: region of massive, objects and Yet hip six one six
[32:43] Speaker 2: three SEVEN b is sitting right, there heavily, populated right
[32:47] Speaker 2: in the middle of the desert define the. Odds but
[32:49] Speaker 2: the environment is even more hostile than a typical star
[32:52] Speaker 2: system because of the host star.
[32:54] Speaker 3: Itself the host star is an absolutely crucial variable in this.
[32:57] Speaker 3: Paradox it is an a type main ste.
[33:00] Speaker 2: Sequence, star which is very different from Our sun.
[33:02] Speaker 3: Drastically different from OUR g type. SUN a type stars
[33:05] Speaker 3: are significantly more, massive incredibly, hot and extremely. Luminous the
[33:09] Speaker 3: host star Of hip six one six three SEVEN b
[33:12] Speaker 3: is nearly three times the mass of The.
[33:14] Speaker 2: Sun with that much, mass the core pressure and temperature
[33:17] Speaker 2: must be, immense which means the rate of nuclear fusion
[33:20] Speaker 2: is hyperaccelerated.
[33:21] Speaker 3: Exactly the luminosity of a star scales roughly with the
[33:24] Speaker 3: cube of its. Mass because they brain through their hydrogen
[33:27] Speaker 3: reserve so, voraciously MASSIVE a type stars have very short
[33:31] Speaker 3: main sequence life.
[33:32] Speaker 2: Spans they essentially live fast and die.
[33:34] Speaker 3: Young they, do but from an observational, standpoint that short
[33:37] Speaker 3: life span is actually a massive diagnostic.
[33:40] Speaker 2: Advantage because the star evolves so, rapidly you can track
[33:44] Speaker 2: its biological clock with much greater precision than a slow burning.
[33:47] Speaker 3: Star that is the golden key to unraveling the origin
[33:51] Speaker 3: Of hip six one six three SEVEN. B stellar evolution
[33:55] Speaker 3: models FOR a type stars are highly. Refined by analyzing
[33:59] Speaker 3: the stars current effective, temperature its surface, gravity and its
[34:02] Speaker 3: luminosity via, spectroscopy The harvard team could pinpoint exactly where
[34:06] Speaker 3: the star is on its evolutionary.
[34:08] Speaker 2: Track they checked its, Vitals they.
[34:10] Speaker 3: Did they determined that it is nearing the end of
[34:12] Speaker 3: its main sequence, life transitioning toward the subgiant. Phase this
[34:16] Speaker 3: allowed them to lock down the age of the entire
[34:18] Speaker 3: system with remarkable, confidence.
[34:20] Speaker 2: And the age they derived was roughly three hundred and
[34:22] Speaker 2: ninety six million years.
[34:23] Speaker 3: Old three hundred and ninety six million years in the
[34:26] Speaker 3: context of stellar, evolution that is practically.
[34:29] Speaker 2: Infancy for, comparison Our solar system is roughly four point
[34:32] Speaker 2: six billion years.
[34:33] Speaker 1: Old.
[34:33] Speaker 3: Exactly finding a transiting brown dwarf in a system with
[34:37] Speaker 3: such a, robust constrained age is phenomenally. Rare HiPE six
[34:42] Speaker 3: one six thirty SEVEN b is only the seventh such
[34:45] Speaker 3: object ever documented where the age is known with this
[34:48] Speaker 3: level of.
[34:48] Speaker 2: Precision, OKAY i see the dominoes falling. Here let's go
[34:51] Speaker 2: back to the cosmic, eraser the tidal forces circularizing the
[34:55] Speaker 2: orbit and destroying the genetic evidence of whether it formed
[34:58] Speaker 2: like a star or like a. Planet the problem with
[35:00] Speaker 2: the eraser is. Time, right if you wait billions of,
[35:04] Speaker 2: years the orbit is completely smoothed out, Right but if
[35:07] Speaker 2: we know with absolute certainty that this system is only
[35:09] Speaker 2: three hundred and ninety six million years, old that fundamentally
[35:12] Speaker 2: changes the.
[35:12] Speaker 3: Math it allows us to reverse engineer the title dissipation.
[35:16] Speaker 3: Timescale because we have the precise mass of the host,
[35:19] Speaker 3: star the mass of The brown dwarf from the radial velocity,
[35:22] Speaker 3: data and the exact orbital distance from the test, transits
[35:25] Speaker 3: we can calculate the exact magnitude of the title forces
[35:28] Speaker 3: acting on the.
[35:29] Speaker 2: System you know exactly how much mechanical energy the title
[35:32] Speaker 2: flexing can dissipate per.
[35:33] Speaker 3: Orbit, Yes and because we know the absolute maximum time
[35:37] Speaker 3: those forces have been operating three hundred and ninety six million,
[35:39] Speaker 3: years we can calculate the maximum possible change in orbital
[35:43] Speaker 3: eccentricity that could have occurred since the system.
[35:46] Speaker 2: Formed we can calculate how much sand the waves could
[35:49] Speaker 2: have possibly moved.
[35:50] Speaker 3: Precisely and when The harvard team ran those, calculations the
[35:53] Speaker 3: orbital dynamics revealed something. Striking what do they? Find the
[35:57] Speaker 3: test data show That hip six one six thirty SEVEN
[36:00] Speaker 3: b is currently in a near circular, Orbit but the
[36:04] Speaker 3: tidal dissipation calculations prove conclusively that three hundred and ninety
[36:08] Speaker 3: six million years is nowhere near enough time for tidal
[36:11] Speaker 3: forces to have circularized a highly eccentric orbit for an
[36:15] Speaker 3: object of this mass at this orbital, distance.
[36:17] Speaker 2: The waves haven't been washing long enough to erase the footprints.
[36:20] Speaker 3: Exactly the physics demand that the near circular orbit we
[36:23] Speaker 3: observe today is essentially the original primordial. Orbit The Brown
[36:26] Speaker 3: dwarf was born in that circular, configuration.
[36:29] Speaker 2: And if the orbit has always been, circular that unequivocally
[36:33] Speaker 2: points toward pathway. Too it Means hip six one six
[36:36] Speaker 2: thirty SEVEN b could not have formed via the, violent
[36:40] Speaker 2: chaotic gravitational collapse of a gas, cloud because that would
[36:43] Speaker 2: have left it in a highly eccentric orbit that hasn't
[36:45] Speaker 2: had time to smooth. Out it must have formed via core,
[36:48] Speaker 2: accretion gradually building up mass within the stable circular flow
[36:53] Speaker 2: of a protoplanetary.
[36:54] Speaker 3: Disc the kinematics heavily favor the insitu disc formation. Model
[36:58] Speaker 3: everything about its movement suggests it is mechanically, speaking an overgrown.
[37:02] Speaker 2: Planet but here is where the entire model crashes into
[37:05] Speaker 2: a brick. Wall we have the mass derived from the
[37:07] Speaker 2: spectroscopic radial velocity. Wabble what is the actual mass Of
[37:11] Speaker 2: hip six one six three SEVEN.
[37:13] Speaker 3: B the radio velocity amplitude dictates a mass equivalent to
[37:17] Speaker 3: forty eight.
[37:18] Speaker 2: Jupiters forty Eight jupiter. Masses we need to pause and
[37:20] Speaker 2: establish the physical scale of that number because it is.
[37:23] Speaker 2: Terrifying jupiter itself is already a gravitational. Behemoth it is
[37:26] Speaker 2: roughly three hundred and eighteen times more massive than The.
[37:29] Speaker 2: Earth you could fit over a thousand earth's Inside jupiter's.
[37:31] Speaker 2: Volume it's mass hip six one six thirty SEVEN b
[37:35] Speaker 2: is forty eight times more massive Than. Jupiter we're talking
[37:39] Speaker 2: about an object containing roughly fifteen Thousand earth masses of
[37:43] Speaker 2: material sitting in a close circular orbit around a massive.
[37:47] Speaker 3: Star the sheer density of the object is difficult to
[37:50] Speaker 3: conceptualize because of the electron degeneracy pressure we discussed. Earlier
[37:54] Speaker 3: adding mass to a brown dwarf beyond roughly the Massive,
[37:57] Speaker 3: jupiter it doesn't actually make its physical radius much. Larger
[38:00] Speaker 3: it just compresses the, interior making it incredibly.
[38:03] Speaker 2: Dense so you have forty Eight jupiter masses packed into
[38:05] Speaker 2: a sphere roughly the size Of.
[38:07] Speaker 3: Jupiter, exactly and that staggering mass figure is what creates
[38:10] Speaker 3: the central, paradox.
[38:11] Speaker 2: Because if the circular orbit dictates that it formed inside
[38:14] Speaker 2: a protoplanetary disc via core. Accretion the physics of the
[38:18] Speaker 2: disk have to be able to actually build an object
[38:20] Speaker 2: of that. Size is it physically possible for a disc
[38:23] Speaker 2: to supply forty eight jupiter masses of material to a single.
[38:25] Speaker 3: Core according to our current theoretical, frameworks it stretches the
[38:29] Speaker 3: limits of possibility to the breaking. Point the core reccretion
[38:32] Speaker 3: model fundamentally struggles with objects above roughly ten to fifteen jupiter.
[38:36] Speaker 2: Masses why is?
[38:37] Speaker 3: That the problem is a combination of mass availability and disc,
[38:41] Speaker 3: stability which is often modeled using the TUMBARATE q.
[38:44] Speaker 2: Parameter, okay let's explore the TUMOR q. Parameter what forces
[38:49] Speaker 2: is it balancing within the?
[38:50] Speaker 3: Disc the tumor criterion assesses whether a differentially rotating disc
[38:54] Speaker 3: of gas will remain stable or fragment under its own.
[38:57] Speaker 3: Gravity it balances three primary. Forces, first you have the
[39:02] Speaker 3: thermal pressure of the, gas which is trying to puff
[39:05] Speaker 3: the disc up and stabilize.
[39:06] Speaker 2: It the heat pushing outward.
[39:08] Speaker 3: Yes, second you have the couplearian, shear the fact that
[39:11] Speaker 3: the inner disc rotates faster than the outer, disk which
[39:14] Speaker 3: acts to tear collapsing clumps apart also stabilizing the disc.
[39:18] Speaker 2: And fighting against both the thermal pressure and the shear
[39:21] Speaker 2: is the self gravity of the disk.
[39:23] Speaker 3: Material, exactly which is actively trying to pull the gas
[39:26] Speaker 3: together into, dense collapsing. Clumps if the mass of the
[39:29] Speaker 3: gas disc is relatively, low thermal pressure and sheer, dominate
[39:33] Speaker 3: the disc is, stable and core accretion can proceed slowly
[39:36] Speaker 3: building planets pebble.
[39:37] Speaker 2: By pebble like pathway too supposed to, work.
[39:40] Speaker 3: Right but to build an object of forty eight jupiter
[39:43] Speaker 3: masses via core, accretion the initial protoplanetary disk must contain
[39:48] Speaker 3: an absolutely massive reservoir of gas and.
[39:51] Speaker 2: Dust but wouldn't a host star that is three times
[39:54] Speaker 2: the mass of The sun naturally possess a proportionally massive protoplanetary.
[39:59] Speaker 3: Disc but there is a hard physical limit to how
[40:02] Speaker 3: massive a disc can be before the self gravity of
[40:05] Speaker 3: the gas overwhelms the thermal pressure and The caplearian. Shear
[40:09] Speaker 3: if the disc becomes too, heavy the TUMOR q parameter
[40:13] Speaker 3: drops below a critical.
[40:14] Speaker 2: Threshold the scale tips to.
[40:15] Speaker 3: Gravity, yes the disc becomes gravitationally.
[40:18] Speaker 2: Unstable and what happens when a massive disc goes gravitationally?
[40:22] Speaker 2: Unstable does it just feed the growing planet?
[40:24] Speaker 3: Faster, no the disc fundamentally changes its. Architecture instead of
[40:28] Speaker 3: smoothly feeding material onto a central planetary, core the massive
[40:32] Speaker 3: spiral arms of the disc fragment localized pockets of gas
[40:35] Speaker 3: become so dense that they collapse violently under their own.
[40:38] Speaker 2: Gravity, wait a violent gravitational collapse of a gas. Pocket
[40:41] Speaker 2: that's pathway. One that's the star. Method.
[40:44] Speaker 3: Exactly the extreme mass required in the disk to build
[40:46] Speaker 3: a forty eight jupiter mass object via slow core accretion
[40:50] Speaker 3: almost guarantees that the disc would instead fragment and trigger
[40:54] Speaker 3: direct gravitational. Collapse the star method forming small companion stars
[40:59] Speaker 3: or brown dwarfs out in the disc completely bypassing the
[41:03] Speaker 3: slow accretion, process which.
[41:04] Speaker 2: Would result in chaotic end body interactions sling shotting those
[41:08] Speaker 2: objects into highly eccentric.
[41:10] Speaker 3: Orbits you see the.
[41:11] Speaker 2: Paradox the structural contradiction is. Staggering if we look At
[41:15] Speaker 2: hip sixty one six thirty SEVEN b through the lens
[41:18] Speaker 2: of its mass forty eight jupiters the physics of disk,
[41:21] Speaker 2: stability the Tumor cu parameter demand that it must have
[41:24] Speaker 2: formed via violent gravitational. Collapse the disc simply couldn't have
[41:28] Speaker 2: remained stable long enough to accrete that much mass. Slowly
[41:31] Speaker 2: but if we look at its orbit a stable near
[41:34] Speaker 2: circular path that hasn't had enough time to be circularized
[41:36] Speaker 2: by tidal, forces the kinematics demand that it formed via
[41:39] Speaker 2: slow core accretion within a stable.
[41:41] Speaker 3: Disc it possesses the kinematic geometry of an accreted, planet
[41:44] Speaker 3: but the physical mass of a collapsed. Star it completely
[41:48] Speaker 3: violated the mutually exclusive boundaries of our two primary formation.
[41:51] Speaker 2: Models it is the astrophysical equivalent of a. Chimera it's
[41:55] Speaker 2: like finding a creature with the skeletal structure of a,
[41:57] Speaker 2: bird but it weighs as much as an elephant and
[42:00] Speaker 2: possesses the genetic markers of a. Reptile it just refuses
[42:04] Speaker 2: to fit into the mathematical boxes we have. Constructed it's
[42:07] Speaker 2: a true rule. Breaker so where does this leave the astrophysics.
[42:10] Speaker 2: Community if both models are mutually exclusive and this object
[42:14] Speaker 2: breaks both of, them does it mean our understanding of
[42:17] Speaker 2: accretion discs is fundamentally.
[42:18] Speaker 3: BROKEN i wouldn't say, broken but it unequivocally demonstrates that
[42:22] Speaker 3: our models are. Incomplete this single data point forces a
[42:25] Speaker 3: radical re evaluation of the upper limits of planetary. Formation
[42:29] Speaker 3: we must ask difficult theoretical questions like what is there
[42:33] Speaker 3: a mechanism of rapid gas secretion that can bypass the
[42:36] Speaker 3: fragmentation limits of the tumor criterion in disks around MASSIVE
[42:40] Speaker 3: a type. Stars can a disc remain stable just long
[42:43] Speaker 3: enough to gorge a core to forty eight jupiter masses before, Dissipating.
[42:47] Speaker 2: Or, conversely is there some unknown dynamical friction mechanism that
[42:52] Speaker 2: can take an object form via violent collapse and dampen
[42:55] Speaker 2: its orbit into a perfect circle almost, instantaneously completely passing the,
[43:00] Speaker 2: slow billion year process of tidal.
[43:02] Speaker 3: Circularization both avenues require physics that we currently do not fully.
[43:07] Speaker 3: Understand the observation by The harvard team is a massive
[43:11] Speaker 3: wrench in the gears of traditional stellar and planetary formation.
[43:14] Speaker 3: Theory it proves that the universe is capable of engineering
[43:17] Speaker 3: structures that exceed the constraints of our current mathematical, models.
[43:21] Speaker 2: Which makes this entire discussion incredibly. Thrilling we started by
[43:25] Speaker 2: examining humanities intrinsic need for. Taxonomy our flawed rigid box
[43:30] Speaker 2: is based entirely on an object's. Mass we look at
[43:33] Speaker 2: how a thirteen to eighty jupiter mass definition completely ignores
[43:36] Speaker 2: the structural thermodynamics of how an object actually, forms whether
[43:39] Speaker 2: through the top down violence of a collapsing cloud or
[43:41] Speaker 2: the patient bottom up accretion within a protoplanetary.
[43:44] Speaker 3: Disk we explored the mechanics of the cosmic, eraser how
[43:47] Speaker 3: the inverse square law of gravity and internal viscosity drive
[43:51] Speaker 3: tidal circularization relentlessly smoothing out eccentric orbits and destroying the
[43:56] Speaker 3: kinematic evidence of an object's.
[43:58] Speaker 2: Origin we look at the sheer engineering triumph of tests
[44:02] Speaker 2: utilizing high precision photometry to detect the microscopic transits of these,
[44:05] Speaker 2: objects and how combining that gmetric data with ground based
[44:09] Speaker 2: radio voltzcity spectroscopy allows us to isolate the exact mass
[44:13] Speaker 2: and radius of bodies sitting right in the middle of
[44:15] Speaker 2: the Brown dwarf.
[44:16] Speaker 3: Desert and all of that deductive reasoning and technological prowess
[44:19] Speaker 3: led us directly to the paradox Of hip sixty one
[44:22] Speaker 3: six thirty SEVEN, b a system pinned by stellar evolution
[44:25] Speaker 3: models to a mirror three hundred and ninety six million years,
[44:28] Speaker 3: old harboring an impossibly dense forty eight jupiter mass behemoth
[44:31] Speaker 3: that defies categorization.
[44:33] Speaker 2: An object that moves with the, calm circular grace of
[44:35] Speaker 2: a planet born in a, disk but possesses a mass
[44:38] Speaker 2: that should theoretically trigger gravitational instability and destroy the very
[44:42] Speaker 2: disk it needed to. Form the beautiful part of this
[44:45] Speaker 2: paradox is that tests is still. Operating it is still
[44:49] Speaker 2: staring unblinkingly at the celestial, sphere capturing the photon flux
[44:53] Speaker 2: of hundreds of thousands of, stars hunting for the next.
[44:56] Speaker 3: Shadow as the test mission, continues and as follow up
[44:59] Speaker 3: spectroscopy build our, catalog we will inevitably discover more of
[45:02] Speaker 3: these extreme transitional. Objects we will populate The Brown Dwarf
[45:06] Speaker 3: desert with more data, points more constrained, ages and more kinematic. Maps,
[45:10] Speaker 3: slowly the statistical void will fill, in and the underlying
[45:13] Speaker 3: physics of how these chimeras form will begin to.
[45:15] Speaker 2: Resolve it leads you with a profound linkering question about
[45:18] Speaker 2: the nature of. Discovery we spend so much energy trying
[45:22] Speaker 2: to force anomalist objects like hip six, one, six three
[45:25] Speaker 2: SEVEN b into our pre existing. Boxes we constantly ask
[45:28] Speaker 2: is it a failed star that experienced an impossibly rapid orbital,
[45:31] Speaker 2: dampening or is it an overgrown planet that somehow circumvented
[45:35] Speaker 2: the gravitational fragmentation limits of its Disc we desperately want
[45:39] Speaker 2: it to be one or the. Other but what if
[45:41] Speaker 2: the anomaly is actually the. Rule if an object can
[45:43] Speaker 2: blur the physical lines so, completely perhaps the structural flaw
[45:46] Speaker 2: isn't the object. Itself perhaps the flaw is the architecture
[45:49] Speaker 2: of our. Boxes what if objects Like hip six one
[45:52] Speaker 2: six three thirty SEVEN b represent an entirely distinct third
[45:55] Speaker 2: physical category of celestial, creation of thrown dynamic recipe that
[45:59] Speaker 2: we haven't even begun to fream of.
[46:00] Speaker 1: Yet

Shows are listed from Apple Podcasts' charts and directory, and Podcast Index where it is used. Every show and episode belongs to its publisher and plays from the publisher's own feed; this site hosts none of them.