Speaker 1: Welcome to Bedtime Astronomy. Explore the wonders of the cosmos
Speaker 1: with our soothing Bedtime Astronomie podcast. Each episode offers a
Speaker 1: gentle journey through the stars, planets, and beyond, perfect for
Speaker 1: unwinding after a long day. Let's travel through the mysteries
Speaker 1: of the universe as you drift off into a peaceful
Speaker 1: slumber under the night sky.
Speaker 2: We are starting today with a pretty cosmic mandate, really
Speaker 2: trying to find our closest earthlike neighbors out there. And
Speaker 2: for this deep dive, we're looking into the future of
Speaker 2: space explorations, specifically at the machine designed to do just that,
Speaker 2: the Habitable World's Observatory. You'll hear it called HWO. Now.
Speaker 2: HWO is slated to be the next great observatory, you know,
Speaker 2: following the footsteps of giants like Hubble and Web. But
Speaker 2: it has this incredibly specific central mission. It needs to
Speaker 2: analyze the atmospheres of at least twenty five exoplanets earth
Speaker 2: like ones, searching for biosignature basically signs of life. For
Speaker 2: a long time, the main strategy for HWO has really
Speaker 2: hinged on using an extremely powerful coronagraph that's well the
Speaker 2: specialized tool designed to block out the overwhelming light of
Speaker 2: a star so you can actually see hopefully the faint
Speaker 2: little planet orbiting next to it. But here's the snag.
Speaker 2: Finding twenty five worlds like that, especially when you don't
Speaker 2: even know for sure where most of them are hiding.
Speaker 2: That's a massive targeting problem.
Speaker 3: It absolutely is. It's an issue of well efficiency and
Speaker 3: just sheer astronomical legwork. You could waste so much time
Speaker 3: pointing at the wrong places, and that difficulty, that strategic
Speaker 3: challenge is exactly what Fibiu Malbad and his colleagues are
Speaker 3: tackling in some new research. They're proposing that hw needs
Speaker 3: a bit of an upgrade, really a powerful secondary instrument,
Speaker 3: one that could frankly revolutionize how HWO picks its targets
Speaker 3: for that crucial atmospheric analysis. Yeah, the big idea is
Speaker 3: adding a cutting edge, super high precision astrometry instrument to
Speaker 3: hwo's toolkit. And this isn't just like a minor tweak.
Speaker 3: It's a genuine leap in capability. If they do this,
Speaker 3: this instrument could potentially identify confirmed Earth sized planets orbiting
Speaker 3: hundreds of nearby stars. Think about that. It would instantly
Speaker 3: feed the HWO chronograph. This like perfectly curated list of
Speaker 3: prime targets.
Speaker 2: Okay, wow, let's unpack that straight away, because I mean
Speaker 2: the implications they are pretty stunning. So this add on
Speaker 2: dramatically boosts hwo's chances of hitting its main goal finding
Speaker 2: those biosignatures, obviously, but you're saying it also gives us
Speaker 2: this remarkable, almost separate scientific bonus that this incredibly precise
Speaker 2: planet hunter could actually double as a tool for cosmology,
Speaker 2: helping us map, maybe even solve, one of the biggest
Speaker 2: riddles out there, how cold dark matter CDM is spread
Speaker 2: out precisely.
Speaker 3: That's the unexpected twist. So for you listening, what we'll
Speaker 3: do in this dive is unpack the amazing tech precision
Speaker 3: needed for this. We're talking measurements down to half of
Speaker 3: micro arc second, just incredibly fine. We'll explore why that
Speaker 3: jump in sensitivity so critical, the kind of engineering tricks
Speaker 3: that might make it possible, and you know what discovering
Speaker 3: all these plans and potentially mapping dark matter could mean
Speaker 3: for understanding our place in the cosmos and the universe's
Speaker 3: basic structure.
Speaker 2: All right, let's start with HWO itself and its core
Speaker 2: job it's a biosignature hunter. Fundamentally, that means it needs
Speaker 2: to gather light from a planet potentially dozens of light
Speaker 2: years away, break that light down and look for the
Speaker 2: chemical fingerprints of things like oxygen, methane, water, vapor, things
Speaker 2: that could indicate life. And doing that takes a long time,
Speaker 2: hours and hours of telescope time focused on just one
Speaker 2: single target. So picking the right targets efficiently, that's everything.
Speaker 3: It really is. The coronagraph, as amazing as it is,
Speaker 3: needs good intel beforehand. It needs to know exactly where
Speaker 3: to point and ideally know the planet's orbit pretty well
Speaker 3: so it can track it effectively. And that leads us
Speaker 3: right into this, well, this significant gap in what we
Speaker 3: currently know about planets right here in our own stellar backyard.
Speaker 3: Just think about the stars within say sixty five light
Speaker 3: years of Earth. That's our immediate cosmic neighborhood, right These
Speaker 3: are prime candidates for HWO to look at. But of
Speaker 3: the sun like stars in that local bubble, we currently
Speaker 3: only know if planet's orbiting about twelve percent of them.
Speaker 2: Only twelve percent, And that low number isn't even the
Speaker 2: most critical part of the story, is it, No, not
Speaker 2: at all?
Speaker 3: The really crucial detail is the kind of planets we've
Speaker 3: found so far around those nearby stars. Every single one
Speaker 3: of the confirmed planets in that local sixty five light
Speaker 3: year zone is a gas giant. We're talking worlds like
Speaker 3: Jupiter or even bigger. As of today, we haven't confidently
Speaker 3: identified a single rocky Earth sized exoplanet orbiting a nearby
Speaker 3: Sun like star.
Speaker 2: Not one, right, So let me just make sure I'm
Speaker 2: getting the straight for everyone listening. In this huge volume
Speaker 2: of space right around us, a space where we assume
Speaker 2: there should be plenty of smaller rocky worlds, our best
Speaker 2: technology so far just hasn't been able to confirm any.
Speaker 2: It almost sounds wrong.
Speaker 3: It's purely a function of our instruments limitations, not necessarily
Speaker 3: a reflection of what's actually out there. It doesn't mean
Speaker 3: those Earth sized worlds aren't there. I mean all our
Speaker 3: theories of planet formation suggest they should be pretty common. Actually,
Speaker 3: it just means the signals they pretty, whether it's their
Speaker 3: reflected light or their gravitational tug, are currently getting drowned
Speaker 3: out by the noise. You know, if you're trying to
Speaker 3: spot a tiny firefly right next to a giant searchlight,
Speaker 3: your camera needs incredible contrast and stability.
Speaker 2: Same idea here, and that brings us squarely to this
Speaker 2: precision problem and the limits of our current best tool
Speaker 2: for this kind of work. The Gaya Space Observatory. Guy's
Speaker 2: been amazing for mapping stars in the Milky Way, absolutely revolutionary,
Speaker 2: but for finding these tiny earth like worlds nearby, it
Speaker 2: kind of hits a sensitivity wall.
Speaker 3: Guya really is the gold standard for current astrometry. It
Speaker 3: measures the positions and movements of stars with phenomenal accuracy,
Speaker 3: but its absolute best precision, its limit is around twenty
Speaker 3: to thirty micro arc seconds. We usually write that as ice.
Speaker 2: Okay, twenty or thirty micro arc seconds. That sounds incredibly
Speaker 2: tiny already. Why does that still fall short for finding
Speaker 2: an Earth? Twin? What's the physical scale here that we're missing?
Speaker 3: Well, to grasp the challenge, you need to visualize the
Speaker 3: star's actual movement. It's wobble. See when a planet orbits
Speaker 3: a star, they both actually orbit a common center of mass.
Speaker 3: It's called the Barry center. Now, a really massive planet
Speaker 3: like Jupiter makes our Sun move quite a bit, pulls
Speaker 3: the Sun around and a loop that's what about two
Speaker 3: million kilometers across even from sixty five light years away.
Speaker 3: That's a relatively large angular displacement on the sky. It's
Speaker 3: something Guy that can measure, and that's why Guy is
Speaker 3: great at finding gas giants. Okay, but now picture an
Speaker 3: Earth mass planet orbiting a sun like star. That tiny
Speaker 3: planet only makes it star wobble by maybe a few
Speaker 3: thousand kilometers let's say enter ten thousand kilometers over its
Speaker 3: whole orbit. Now translate that tiny physical movement into an
Speaker 3: angle on the sky as seen from sixty five light
Speaker 3: years away. That angular shift, the wobble we need to
Speaker 3: detect it works out to be less than one micro second.
Speaker 2: Ah. Okay, So Guya's best measurement twenty to thirty onens
Speaker 2: is just way too coarse. It's like trying to measure
Speaker 2: something a millimeter wide with a ruler marked only in centimeters.
Speaker 2: We're hunting for a wiggle that might be, say, thirty
Speaker 2: times smaller than the inherent error the noise level in
Speaker 2: our current best.
Speaker 3: Instruments exactly that twenty to thirty on's level is effectively
Speaker 3: the noise floor of today's technology for this specific task.
Speaker 3: And hiding beneath that noise floor we think are potentially
Speaker 3: hundreds of habitable Earth sized worlds right next door. So
Speaker 3: the only way to really enable hwo's primary mission to
Speaker 3: give it those targets is to dramatically, drastically lower that
Speaker 3: noise floor.
Speaker 2: Right. So, if the coronagraph is the tool for the
Speaker 2: deep dive, the detailed atmospheric sniffing, then astrometry, this wobble
Speaker 2: measuring technique sounds like the perfect tool for the initial
Speaker 2: survey for finding the worlds and figuring out their basic properties. First,
Speaker 2: can you give us a quick, clear definition of astrometry
Speaker 2: against specifically how it helps us find exoplanet sure?
Speaker 3: At its heart, astrometry is simply the science of measuring
Speaker 3: the precise positions and motions of stars over time very accurately.
Speaker 3: When we apply it to finding exoplanets, we're looking for
Speaker 3: that tiny, repetitive periodic shift in a star's parent position
Speaker 3: on the sky. That shift is caused by the gravitational
Speaker 3: pull of an orbiting planet tugging the star back and
Speaker 3: forth as they both orbit that common center of mass,
Speaker 3: the Barry Center. We're basically tracking the star's side of
Speaker 3: that orbital.
Speaker 2: Dance, and the beauty of it is the size of
Speaker 2: that wobble directly relates to the mass of the planet
Speaker 2: doing the tugging right, bigger wobble, bigger planet.
Speaker 3: Mass exactly right. And that's the huge advantage of astrometry
Speaker 3: because that gravitational relationship is so well understood based on physics.
Speaker 3: If you can measure that wobble with extremely high precision,
Speaker 3: you can calculate the exoplanet's entire orbital solution, its orbital period,
Speaker 3: how far it is from the star on average, a
Speaker 3: semi major axis, even how elliptical its orbit is. You
Speaker 3: basically get a complete map of its path, which tells
Speaker 3: you exactly where that planet will be at any given time.
Speaker 3: And that's absolutely critical for pointing the coronograph later on.
Speaker 2: Okay, so that's the practical benefit better targeting knowing where
Speaker 2: to look makes sense. But you also mention a fundamental
Speaker 2: scientific advantage, something that other main planet finding methods like
Speaker 2: the transit method or radial velocity can't quite deliver with
Speaker 2: the same certainty.
Speaker 3: Yes, and this is key. Astrometry allows you to determine
Speaker 3: the exo planet's absolute mass, not just a minimum mass,
Speaker 3: but it's actual mass. See the radio velocity method, which
Speaker 3: measures the stars wobble towards and away from us only
Speaker 3: gives you a minimum possible mass for the planet. That's
Speaker 3: because the signal depends on the tilt of the planet's
Speaker 3: orbit relative to our line of sight, and usually we
Speaker 3: don't know that tilt precisely. Astrometry, though, measures the side
Speaker 3: to side wobble on the sky. That measurement directly gives
Speaker 3: you the true, unambiguous mass of the planet. And why
Speaker 3: is knowing the true mass so important? We'll think about
Speaker 3: Hwo's goal finding life. To assess if a planet could
Speaker 3: host life, we first need to know if it's even rocky. Right.
Speaker 3: If you can combine that absolute mass from astrometry with
Speaker 3: the planet's radius, which you might get if you're lucky
Speaker 3: and the planet also happens to transit passing in front
Speaker 3: of it star from our view, then mass plus radius
Speaker 3: gives you density. And density is the killer metric. It's
Speaker 3: what fundamentally tells you if you're looking at a dense,
Speaker 3: rocky world like Earth or Venus, or a puffy, low
Speaker 3: density gas or ice giant like Jupiter or Neptune, which are,
Speaker 3: let's face it, much less likely places to find life
Speaker 3: as we know it. So astramistry provides that foundational piece
Speaker 3: of the puzzle for figuring out if the planet is
Speaker 3: even potentially habitable in the first place.
Speaker 2: Okay, so it all comes back to the main challenge
Speaker 2: getting sensitive enough to measure that incredibly tiny wobble from
Speaker 2: an Earth mass planet Gia. Our current best is stuck
Speaker 2: at around twenty thirty oins. What's the leap in precision
Speaker 2: that doctor Malbat's proposal is calling for. How much better
Speaker 2: do we need to be?
Speaker 3: The instrument they're suggesting aims for an operational precision of
Speaker 3: I get this zero point five micro arc seconds.
Speaker 2: Half of microrost. Wow. Okay, just comparing that to Gaya,
Speaker 2: which is already state of the area. You're talking about
Speaker 2: making this new instrument on EAHWO something like four hundred
Speaker 2: to six hundred times more sensitive than Guya. That's that's
Speaker 2: not just like the next step up. That's like skipping
Speaker 2: two whole generations of technology. It completely changes the game
Speaker 2: for hwo's mission.
Speaker 3: It really does. Just to give you a sense of scale,
Speaker 3: foer point five targets, that's roughly the angular size of
Speaker 3: a single human hair viewed from about five hundred miles away.
Speaker 3: It's an unbelievably fine measurement we're talking about making from
Speaker 3: space and achieving that level of sensitivity that point five
Speaker 3: tarrets is the absolute key. It's what unlocks potentially hundreds
Speaker 3: of new Exo Earth candidates right in our solar neighborhood.
Speaker 3: It means hwo's giant coronagraph doesn't have to waste precious
Speaker 3: time searching blindly or inefficiently. Instead, it gets handed this
Speaker 3: highly optimized, pre vetted list of confirmed targets, complete with
Speaker 3: their masses and orbital details, making it much much easier
Speaker 3: to efficiently tick off that primary mission goal finding those
Speaker 3: twenty five biosignatures.
Speaker 2: Okay, boosting precision by a factor of say four hundred
Speaker 2: or six hundred, that obviously means you have to overcome
Speaker 2: some equally huge technical challenges. If doing astronotry at point
Speaker 2: five highs was easy, presumably we'd have done it by now.
Speaker 2: So what's the main weakness? What makes these astrometers so
Speaker 2: prone to error that we need to fix?
Speaker 3: Well, even out in the relative stability of space, astronomers
Speaker 3: are inherently susceptible to what we call systematic errors. You're
Speaker 3: trying to measure an angular shift on the sky. That's
Speaker 3: smaller than the width of a virus. Right, So, every
Speaker 3: tiny physical imperfection in the instrument itself, whether it's in
Speaker 3: the detector chip, tiny misalignments in the mirrors, slight changes
Speaker 3: do to temperature, all these things can combine and create
Speaker 3: noise that swamps the signal you're looking for. The main
Speaker 3: offenders are usually imperfections in the detector and just thermal instability.
Speaker 3: The sensor, typically a CMOS chip like in your phone camera,
Speaker 3: but much more advanced, isn't mathematically perfect. The pixels aren't
Speaker 3: all identical squares. They have tiny variations and how sensitive
Speaker 3: they are, their exact size, their electrical behavior. That's due
Speaker 3: to the manufacturing process, and it's called fixed pattern noise. Now,
Speaker 3: if that sensor shifts even minutely relative to the incoming starlight,
Speaker 3: or if it's temperature fluctuates by even a tiny fraction
Speaker 3: of a degree, those built in imperfections create errors in
Speaker 3: your position measurement, and those errors very quickly add up
Speaker 3: and overwhelm the sub microarc second signal you're desperately trying
Speaker 3: to detect. That inherent instrumental noise floor is basically why
Speaker 3: we've been stuck around that twenty thirty oin limit for
Speaker 3: so long.
Speaker 2: Okay, So to break through that barrier and actually hit
Speaker 2: zero point five noise, Malvot's team is proposing a kind
Speaker 2: of two pronged attack, right, a strategy to cancel out
Speaker 2: both those predictable systematic errors from the hardware itself and
Speaker 2: also the unpredictable random noise from the environment. Let's start
Speaker 2: with the first part, the clever bit of technology, the
Speaker 2: detector calibration unit or DCU. What does that do?
Speaker 3: The DCU is a really neat piece of engineering. It's
Speaker 3: designed specifically to tackle that fixed pattern noise problem on
Speaker 3: the CMOS sensor head on. So you've got your sensor,
Speaker 3: which is basically this grid of millions of tiny light
Speaker 3: collecting pixels. The DCU generates a set of extremely precise,
Speaker 3: stable reference patterns, think of them like light and dark
Speaker 3: interference fringes, or a super high resolution grid pattern, and
Speaker 3: it projects these known patterns directly onto the face of
Speaker 3: the CMO sensor itself while you're observing.
Speaker 2: Ah. Okay, so it's like shining a perfect unchanging calibration
Speaker 2: ruler directly onto the detector every time you take a
Speaker 2: picture exactly.
Speaker 3: That's a great analogy the DCU allows the system to
Speaker 3: isolate and map the precise physical location and the specific
Speaker 3: response characteristics of every single pixel in that detector array.
Speaker 3: And this calibration isn't just done once. It's done constantly
Speaker 3: or very frequently. It effectively corrects for all those tiny
Speaker 3: pixel to pixel variations, any slight geometric distortions introduced by
Speaker 3: the telescope's optics, and even tiny changes in the detector's
Speaker 3: own internal shape or geometry caused by minute thermal expansions
Speaker 3: or vibrations. What it does basically is create a perfectly
Speaker 3: stable internal coordinate system right on the detector itself, so
Speaker 3: when the light from the target star hits that sensor,
Speaker 3: the DCU calibration ensures that any measured shift in the
Speaker 3: star's apparent position is a real angular movement due to
Speaker 3: its gravitational wobble, and not just some artifact caused by
Speaker 3: the telescope hardware warming up by a thousandth of a
Speaker 3: degree or a pixel behaving slightly differently than its neighbor.
Speaker 3: It aims to drive that systematic air contribution down to
Speaker 3: almost zero.
Speaker 2: Okay, that sounds like it tackles the predictable flaws in
Speaker 2: the hardware pretty effectively. But even with a perfect DCU,
Speaker 2: you're still going to have some residual fuzziness, right, random
Speaker 2: errors from things like stray background light, maybe a cosmic
Speaker 2: ray hitting the detector, tiny thermal jitters. So this requires
Speaker 2: the second ingredient in the recipe, basically statistical brute force.
Speaker 2: You need lots and lots of data.
Speaker 3: You need a massive amount of data. The estimate they
Speaker 3: provide to the paper suggests that to really nail down
Speaker 3: the conformation of an Earth mass planet and to average
Speaker 3: down all those random errors to achieve that overall zero
Speaker 3: point five arrow precision goal, HWO would probably need to
Speaker 3: collect over one hundred separate high precision measurements of that
Speaker 3: particular star system.
Speaker 2: And these aren't just one hundred snapshots taken one after another.
Speaker 2: I assume you need to spread them out over time
Speaker 2: to actually see the orbit absolutely correct.
Speaker 3: These hundred plus measurements would need to be distributed over
Speaker 3: the course of hwo's planned operational lifetime, which is typically
Speaker 3: expected to be around three to four years. You need
Speaker 3: that longtime baseline to actually track this are through a
Speaker 3: significant portion, ideally more than one full cycle of its
Speaker 3: gravitational wobble caused by the planet. That's how you confirm
Speaker 3: the orbital period accurately, and the reason for needing so
Speaker 3: many images. The statistics part is pretty straightforward. Even the
Speaker 3: brilliant DCU can't stop every single random, unpredictable error. A
Speaker 3: stray photon here, a tiny vibration there. These are stochastic events.
Speaker 3: But the magic happens when you take a hundred or
Speaker 3: maybe one hundred and fifty of these individual measurements. The
Speaker 3: central limit theorem from statistics starts to work in your favor.
Speaker 3: Random errors are by definition random. They scatter. So if
Speaker 3: what measurement happens to have a random error that nudges
Speaker 3: the stars measure positions slightly to the north, it's likely
Speaker 3: that another measurement taken later will have a roughly equal
Speaker 3: and opposite random error that nudges the position slightly to
Speaker 3: the south right.
Speaker 2: So by combining and averaging all those hundreds of measurements together,
Speaker 2: you effectively force those random plus and minus errors to
Speaker 2: statistically cancel each other out over the long run, leaving
Speaker 2: behind only the consistent underlying signal that tiny, stable, repeatable
Speaker 2: gravitational wobble of the star caused by the planet.
Speaker 3: That's exactly the rationale. It's this combination, this marriage of
Speaker 3: highly sophisticated real time technical calibration that's the DCU with
Speaker 3: the sheer power of statistical averaging from taking lots and
Speaker 3: lots of pictures that gives us confidence we can actually
Speaker 3: stabilize the final result down to that incredibly demanding zero
Speaker 3: point five a's of precision level. It transforms a mission
Speaker 3: initially conceived around just a coronagraph into potentially the definitive
Speaker 3: surveyor of nearby planetary masses as well.
Speaker 2: Okay, now we pivot to the part that for me,
Speaker 2: really elevates this whole proposal. It goes beyond just making
Speaker 2: HWO better at its main job. The idea that an
Speaker 2: instrument fine tuned to measure a star wobbling by just
Speaker 2: a few thousand kilometers could also give us real leverage
Speaker 2: on one of the universe's biggest mysteries, cold dark matter.
Speaker 2: That's pretty amazing.
Speaker 3: It is a truly remarkable example of how pushing the
Speaker 3: technological envelope in one area of science can suddenly unexpectedly
Speaker 3: on block brand new capabilities in a completely different field.
Speaker 3: Hwo's proposed astrometer if built to this point five and
Speaker 3: spec could provide crucial observational data to directly test the
Speaker 3: standard model of cold dark matter. Specifically, it could help
Speaker 3: resolve a long standing puzzle about how dark matter is
Speaker 3: actually distributed right in the centers of galaxies.
Speaker 2: Right, and this gets into the famous cusp versus core debate,
Speaker 2: doesn't it? If dark matter is cold, meaning it moves
Speaker 2: slowly and mostly non interacting except through gravity, which is
Speaker 2: the standard CDM picture, what should happen to it near
Speaker 2: the super dense center of a galaxy? What does theory predict?
Speaker 3: The standard CDM theory is pretty unequivocal on this. It
Speaker 3: should form a cusp because dark matter particles in this
Speaker 3: model only really feel gravity. They should just keep getting
Speaker 3: pulled deeper and deeper into the galaxies gravitational Well, this
Speaker 3: process should cause the density of dark matter to continuously
Speaker 3: increase the closer you get to the very center, creating
Speaker 3: a really steep, sharp spike in density right at the core,
Speaker 3: like a pointy cut.
Speaker 2: Okay, so theory predicts this sharp density peak, But what
Speaker 2: do our observations actually show us, Especially when we look
Speaker 2: at smaller dwarf galaxies where the dark matter signal is
Speaker 2: often clearer, less mixed up with normal matter.
Speaker 3: Well, that's where the tension arises. Observations, particularly from studying
Speaker 3: how stars orbit in the outer parts of galaxies, and
Speaker 3: especially in these smaller dwarf galaxies, they frequently suggest something different.
Speaker 3: The data often indicates that the dark matter density profile
Speaker 3: tends to flatten out in the very center. Instead of
Speaker 3: that sharp cusp, we seem to see a core, basically
Speaker 3: a region where the dark matter density is more or
Speaker 3: less constant, or at least doesn't spike up dramatically right
Speaker 3: at the galactic heart.
Speaker 2: So theory predicts a steep point. Observation suggests more of
Speaker 2: a flat plateau in the middle. That's a pretty significant disagreement,
Speaker 2: and the existence of these apparent cores implies something's going
Speaker 2: on that isn't in the simplest CDM model right. Either
Speaker 2: are assumptions about dark matter or wrong, or something else
Speaker 2: is messing with its distribution exactly.
Speaker 3: These cores are real and common. It means something must
Speaker 3: be acting to sort of smooth out or push that
Speaker 3: dark matter away from the very center. What could it be, Well,
Speaker 3: one possibility is astrophysical feedback from normal matter things like
Speaker 3: massive bursts of star formation and powerful supernova explosions. These
Speaker 3: events can violently expel gas and energy, potentially pushing the
Speaker 3: dark matter outwards too, dynamically creating a core over time.
Speaker 3: Or maybe point to something fundamental about the dark matter
Speaker 3: particles themselves. Perhaps dark matter isn't completely non interacting. Maybe
Speaker 3: it's self interacting dark matter or SIDM, where dark matter
Speaker 3: particles can actually collide and scatter off each other occasionally.
Speaker 3: That kind of self interaction would naturally tend to smooth
Speaker 3: out the central density peak, turning a CUSP into a core.
Speaker 2: And this is where hwo's super precise astrometer comes back
Speaker 2: into the picture. We're not looking for a star's wobble anymore.
Speaker 2: We're talking about using that same incredible point five visos
Speaker 2: precision to detect the subtle gravitational effects of those predicted
Speaker 2: dark matter cusps themselves, if they exist. How does that work?
Speaker 2: How does measuring star positions help us see? A dark
Speaker 2: matter cusp.
Speaker 3: Would use the phenomenon called gravitational lensing, or more specifically,
Speaker 3: gravitational deflection of light. Any concentration of mass like the
Speaker 3: dense dark matter cusp predicted by CDM theory will bend
Speaker 3: the path of light that passes near it. Now we
Speaker 3: can't see the dark manner directly, of course, but we
Speaker 3: can see distant background stars or quasars whose light has
Speaker 3: to travel past or through these potential dark matter concentrations
Speaker 3: in nearby galaxies on its way to us. If a
Speaker 3: dense dark matter cusp is sitting there between HWO and
Speaker 3: some distant background star, the gravity of that cusp will
Speaker 3: slightly deflect the light from the background star. This deflection
Speaker 3: causes a tiny, tiny shift in the apparent position of
Speaker 3: that background star as seen by HWO. That predicted shift
Speaker 3: caused by the lengthening effect of a standard CDM cusp
Speaker 3: is incredibly small. Calculation suggests it's right around the level
Speaker 3: of you guessed a zero point five micro arc seconds.
Speaker 3: Only an instrument with the kind of precision being proposed
Speaker 3: for hw a's astrometer would actually be sensitive enough to
Speaker 3: reliably detect these minute skilled deflections caused specifically by the
Speaker 3: presence of a dark matter.
Speaker 2: Cusp ah I see. So the logic is if this
Speaker 2: astrometer looks at millions of background stars shining through the
Speaker 2: centers of nearby galaxies, and it consistently fails to find
Speaker 2: those tell tale point five thitdistic positional shifts that a
Speaker 2: cusp should produce. Then that provides strong evidence that the
Speaker 2: cusps aren't there and the dark matter must be arranged
Speaker 2: in cores instead.
Speaker 3: It would provide potentially definitive, clean observational evidence. Yes, that
Speaker 3: kind of data. A null result across many targets would
Speaker 3: really force cosmologists to seriously re evaluate the standard, simplest
Speaker 3: CDM model. It would lend powerful support either to alternative
Speaker 3: dark matter theories like self interacting dark matter, or to
Speaker 3: models where astrophysical feedback processes are extremely efficient at flattening
Speaker 3: alcocentral densities. So this one instrument, borne out of the
Speaker 3: very practical need to find nearby Earth like planets suddenly
Speaker 3: becomes this fundamental probe for understanding the distribution of dark
Speaker 3: matter and the very structure of galaxies.
Speaker 2: It really is quite something, the solution to a tricky
Speaker 2: planetary measurement problem potentially unlocking answers to a deep cosmological mystery. Now,
Speaker 2: this proposal sounds incredibly powerful, almost essential, giving these potential
Speaker 2: twins scientific payoffs better exoplanet hunting and insights into dark matter.
Speaker 2: But space missions are notoriously complex, incredibly expensive, and take
Speaker 2: decades to plan and build. So let's put this idea
Speaker 2: into context a bit. How developed is this concept? Is
Speaker 2: it brand new or does it have some history? And
Speaker 2: why does it make sense to try and tack it
Speaker 2: onto HWO.
Speaker 3: Now, well, that's a good point, and the idea is
Speaker 3: actually highly mature technically speaking. It didn't just spring up
Speaker 3: out of nowhere for HWO. Doctor Malbitt, who led the
Speaker 3: recent paper, was also a key figure behind a much earlier,
Speaker 3: very detailed mission proposal called THEA.
Speaker 2: THEA I remember hearing about that. That was basically envisioned
Speaker 2: as a dedicated space telescope whose entire purpose was going
Speaker 2: to be ultra high precision astrometry. Right, using essentially the
Speaker 2: same core technology concept.
Speaker 3: That's exactly right. THEO was designed from the ground up
Speaker 3: as a standalone mission, completely separate from the lineage at
Speaker 3: the great observatories like Hubble Web or HWO. The THEA
Speaker 3: team spent years meticulously developing the concept, working through the
Speaker 3: incredibly demanding error budgets, figuring out how to control systematic errors,
Speaker 3: and designing the specialized hardware needed, including crucial calibration systems
Speaker 3: like that detector calibration unit of the DCU we discussed. Now,
Speaker 3: ultimately THEA wasn't selected by the funding agencies to move
Speaker 3: forward and actually launch, but all that detailed engineering work,
Speaker 3: the simulations, the technical solutions, that knowledge base still exists
Speaker 3: and is highly valuable.
Speaker 2: Okay, So if you look at it strategically, then since
Speaker 2: the really hard groundwork for achieving this kind of super
Speaker 2: precision astrometry has largely already been done for THEA, it
Speaker 2: seems incredibly logical, maybe even efficient, to try and incorporate
Speaker 2: that already developed capability into HDI. You avoid the huge
Speaker 2: cost and complexity of launching a whole, separate, dedicated mission
Speaker 2: like THEO was planned to be, while at the same
Speaker 2: time you significantly boost hwo's ability to achieve its own
Speaker 2: primary goal. Kind of a win win.
Speaker 3: It really does look like a way to maximize the
Speaker 3: scientific return on investment for a single major flagship mission
Speaker 3: like HWO. I mean, any instrument that can quickly and
Speaker 3: definitively find and confirm potentially hundreds of Earth mass planets
Speaker 3: right in our solar neighborhood. That directly makes hwo's main
Speaker 3: job getting those twenty five biosignatures far more achievable within
Speaker 3: its likely mission lifetime and budget. It feels like perhaps
Speaker 3: the smartest way to leverage all that prior R and
Speaker 3: D investment from the CIA effort and frankly reduce the
Speaker 3: overall risk for hwo's core science.
Speaker 2: However, we should probably ground ourselves and you the listener,
Speaker 2: in the actual timeline here. HWO isn't launching next year
Speaker 2: or even this decade.
Speaker 3: Oh far from it. HWO development is still very much
Speaker 3: in the early study and planning phases. Serious hardware can
Speaker 3: instruction and detailed engineering work aren't really expected to kick
Speaker 3: off in earnest until sometime in the twenty thirties, and
Speaker 3: the most optimistic launch window for HWO itself is probably
Speaker 3: somewhere in the early to mid twenty forties. We're talking
Speaker 3: twenty years out, maybe more. But interestingly, that long lead
Speaker 3: time is actually a major advantage for this astrometry proposal.
Speaker 3: It means there's still plenty of time, well over a
Speaker 3: decade potentially to fully finalize the instrument design, build and
Speaker 3: thoroughly test prototypes of things like the detector calibration unit,
Speaker 3: and figure out how to integrate the whole astrometry package
Speaker 3: smoothly into the larger HWO observatory architecture without causing major
Speaker 3: delays or disruptions to the primary coronagraph instrument, which is
Speaker 3: still the centerpiece.
Speaker 2: So the underlying science case seems solid. The core technology
Speaker 2: is apparently quite mature thanks to the earlier THEO work,
Speaker 2: and the long HWO timeline actually provides a feasible window
Speaker 2: for implementation. So the final decision really comes down to
Speaker 2: the HWO project managers, the scientific advisory committees, and ultimately
Speaker 2: the funding aidies. Like Massa, it sounds like a classic
Speaker 2: strategic decision. Do you stick rigidly to the original highly
Speaker 2: focused mission plan for HWO centered on the coronograph, or
Speaker 2: do you allow the mission's scope its scientific ambition to
Speaker 2: grow a bit to incorporate this incredibly powerful dual purpose
Speaker 2: astrometry capability. Given the groundwork already laid, it.
Speaker 3: Really is a choice between perhaps maximizing the potential scientific
Speaker 3: discovery space versus maintaining programmatic simplicity and sticking to the
Speaker 3: original baseline. Integrating the astrometer undoubtedly adds complexity to the
Speaker 3: overall instrument package and the mission operations. There's no denying that,
Speaker 3: but the potential scientific payoff having hundreds of confirmed exo
Speaker 3: Earth masses to feed the chronograph, plus getting unique observational
Speaker 3: constraints on the nature of dark matter, that payoff is
Speaker 3: arguably multiplicatid it could be huge. It's definitely a major
Speaker 3: decision point that will likely shape hwo's ultimate scientific legacy
Speaker 3: long before it ever leaves the ground.
Speaker 2: It certainly seems to shift the perception of HWO, doesn't
Speaker 2: it from being primarily a specialized machine for analyzing atmospheres
Speaker 2: to becoming potentially a much more versatile foundational observatory for
Speaker 2: broad areas of space physics as well well. This has
Speaker 2: been a really fascinating look into the kind of high
Speaker 2: stakes planning and technological innovation that goes into shaping the
Speaker 2: next generation of big space science missions. We started with
Speaker 2: this fundamental need just finding a better and more efficient
Speaker 2: way to locate those small, rocky worlds that HBO is
Speaker 2: ultimately designed to study up close, and that let us
Speaker 2: down this path exploring an incredibly complex technological leap, combining
Speaker 2: that sophisticated detector calibration unit with the need for maybe
Speaker 2: over one hundred statistical measurements, all just to reach that
Speaker 2: almost unbelievable point five microarc second precision target, and.
Speaker 3: Then we discovered this amazing bonus that this hyper precision,
Speaker 3: initially conceived just for measuring planet masses accurately, it simultaneously
Speaker 3: gives us this completely new, powerful way to probe the
Speaker 3: universe on a much grander scale. It provides exactly the
Speaker 3: kind of leverage needed to observe vationally test competing theories
Speaker 3: about how cold dark matter behaves in the hearts of galaxies,
Speaker 3: potentially resolving that cusp versus core puzzle has been nagging
Speaker 3: cosmologists for years. So this proposed astrometer, it really isn't
Speaker 3: just some minor add on. It feels like it could
Speaker 3: fundamentally shift the scientific identity of the habital world's observatory.
Speaker 3: It potentially transforms it from being a highly specialized, though
Speaker 3: important coronagraph mission into more of a foundational, dual purpose
Speaker 3: powerhouse for both incredibly precise exoplanet characterization and fundamental deep
Speaker 3: space physics. It just seems to maximize the potential science
Speaker 3: you get out of one enormous public.
Speaker 2: Investment, and thinking about that dual use potential if one
Speaker 2: instrument developed primarily to measure a star moving just a
Speaker 2: tiny bit because of a planet sixty five light years away.
Speaker 2: If that same instrument could also potentially help resolve one
Speaker 2: of the deepest mysteries we have about the fundamental structure
Speaker 2: of the entire universe, it really prompts a final question
Speaker 2: for you, the listener, to maybe mull over. As we
Speaker 2: continue to pour billions into developing ever more sensitive, ever
Speaker 2: more precise scientific tools for space, what other profound, perhaps
Speaker 2: completely unintended discoveries might already be lurking, waiting to be
Speaker 2: made within the designs and development pipelines from missions that
Speaker 2: haven't even launched yet. Often the biggest scientific leaps seem
Speaker 2: to happen almost by accident, when instrument's built for one
Speaker 2: very specific purpose turn out to have an even grander
Speaker 2: application in a completely different scientific domain we hadn't anticipated.
Speaker 3: It's that kind of beautiful, unforeseen synergy that often drives
Speaker 3: scientific discovery forward in surprising ways.
Speaker 2: Absolutely well, thank you for joining us for this deep
Speaker 2: dive into the exciting future of space exploration and the
Speaker 2: potential of the habitable world's observatory. We'll catch you on
Speaker 2: the next one.
Speaker 3: Last DA