@sundogplanets@mastodon.social
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sundogplanets

@sundogplanets@mastodon.social

Professor of astronomy, farmer of goats. Asteroid (42910). She/her.

Has mostly lived in warmer places, now learning to live respectfully on Treaty 4 lands (Saskatchewan, Canada)

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astronomerritt, to random

So did anyone actually get time or was everyone rejected flat out?

(I have many, many sad astro friends right now.)

sundogplanets,
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@astronomerritt I talked to exactly one astronomer today who got time. (I didn't apply, I've got too much other telescope time! An excellent problem to have...)

cliff, to random

The boys are feasting on blackberry bushes today

image/jpeg

sundogplanets,
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@cliff NICE. Always satisfying to unleash your goats on thorny invasives (here it's just thistles, which haven't come up yet, but soon)

sundogplanets,
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@cliff Yeah, getting my herd around to different parts of my property is also a goal for me this year! Lots of weeds to eat all over the place.

sundogplanets, to random
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This morning has been CRAZY already. Got up extra early to take care of animals so that I could get back inside to watch talks while getting kids ready for school. Meanwhile, not 1, not 2, but THREE roll clouds went over!

Anyway...really neat talks this morning that I was able to half-watch while doing ALL THE THINGS.

5 white baby goats jumping all over a big round bale of hay, with a farmyard in the background.
3 nicely sunlit white baby goats jumping all over a big round hay bale, with farm fields and pretty clouds in the background
2 white baby goats drinking from bottles that I'm holding.

sundogplanets,
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First talk (by Sarah Millholland and Lauren Weiss) was about peas-in-a-pod systems: these are exoplanet systems that are very common, where there are multiple planets with very similar masses with nearly equal spacing between them. They have very circular orbits and very low mutual inclinations. This was a surprising discovery from Kepler/TESS, some estimates are a very large fraction of all stars should have systems like this.

sundogplanets,
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Next was Hilke Schlichting talking about how her simulations show that giant impacts are important for making peas-in-a-pod systems: you can't get them just through migration because you would expect to find lots of mean-motion resonances between planets, which we don't usually see. Having lots of impacts helps explain masses and orbital distributions. (We know giant impacts were important in our Solar System, makes sense they'd be important in exoplanet systems too)

sundogplanets,
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Talk just finishing now is Fred Adams, talking about how peas-in-a-pod systems are actually the lowest energy state you can get, so that's why they're common. During his talk he actually said "this is just calculus on steroids"

He does make a neat prediction: the peas-in-a-pod configuration should not continue to large semimajor axis - this is something astronomers will be able to test in the future as we get longer time baselines observing these systems

sundogplanets,
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Just ran outside to make sure all the new babies figured out to go inside the barn when it's raining (they did). And found the VERY BRAVE livestock guardian dog trembling at the barn door, trying to protect them from the very quiet distant thunder which he is deathly afraid of. He's such a good boy! (I put him in the bigger barn until the thunder passes so he can hide and hopefully be a little happier)

sundogplanets,
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Armaan Goyal uses Gini index (yes, like the economic thing that I don't really understand) to look at resonances in peas-in-a-pod systems.

Finds enhanced size uniformity in peas-in-a-pod systems is driven by near-resonant pairs and chains. So, the story is still complicated, but it looks like resonances are important for the evolution of these systems even if they're not currently in resonance.

sundogplanets,
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Next speaker apparently has COVID so is presenting virtually (COVID is not over...)

Talking about Kepler-90, an 8(!) planet system, adds in radial velocity data to transit timing data. Sounds like there weren't any firm conclusions from this study, just a neat system (and I found this graphic hilarious and also quite powerful to show the problem with exoplanet systems generally: we're only probing a tiny part of them with current techniques!)

sundogplanets,
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@pieist Oh I totally understand. I am very happy to keep attending these thing virtually.

sundogplanets,
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@colinburgess He's just a very good livestock guardian dog we bought from a local farm as a puppy. He's not perfect, he occasionally eats a chicken. But he's great with the goats (especially the babies)

sundogplanets, to random
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In light of the really impressive JWST observations of Fomalhaut that were released yesterday, I wanted to share my view of the Fomalhaut system. Story time!

Fomalhaut is a bright nearby star that has been known for decades to have a debris disk, a belt of dust caused by asteroids crashing into each other. Sounds very dramatic, but we see them all over the place! Our own Kuiper Belt and asteroid belt are extremely faint/low mass versions of debris disks we observe around other stars.

sundogplanets,
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And once they got the new observations, Fomalhaut b was totally not where it was supposed to be. Pretty much every possible orbit that connected the (now) 4 datapoints crossed right through the ring. This didn't make any sense at all. You can't have a planet crossing through an asteroid belt without completely destroying the asteroid belt.

https://esahubble.org/images/opo1301e/

sundogplanets,
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So, there's only really a couple of possible explanations at this point.

  1. We're seeing the planet just as it's going unstable. It's just been ejected and we're just happening to catch it at the right moment. Just happening to catch a once-in-a-solar-lifetime event is always a terrible explanation for anything in astronomy, so immediately sets of alarm bells.
sundogplanets,
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  1. Maybe it's on a newly eccentric orbit and the asteroid belt is just starting to get distorted by the planet? A little uncomfortable still, because only an (astronomically) short time windo to observe. But not totally implausible.

https://arxiv.org/abs/1312.7020

sundogplanets,
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  1. Or...here's a weird one: what if it's not actually a planet? What if it's a dust cloud? As I said back at the beginning, debris disks are made by lots of collisions between asteroids. What if there was a really big one and we saw it at the right moment? Again, has that "special moment" that sets of alarm bells, but if these collisions are happening all the time, that's not a big deal to see one just after it happens.

How often would collisions happen? This was something I could calculate!

sundogplanets,
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Several authors had suggested different versions of this idea before I started working on it.

The thing my team did a little differently was we used what we know about the orbital structure of the Kuiper belt to predict how often giant collisions could happen. We took our Kuiper Belt, multiplied it x100 (because that's about what you need to explain the dust we see), and basically whacked it with a stick to make it eccentric, like Fomalhaut's ring.

https://arxiv.org/abs/1412.1129

sundogplanets,
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Our simulations showed that if there's a high eccentricity "scattering" component, like in our Kuiper Belt, then collisions happen at higher speeds and higher frequencies right where Fomalhaut b was discovered. A 100km asteroid could make enough dust to be visible.

We estimated 1 potentially visible catastrophic collision per decade is reasonable given the timescales involved and the assumptions we made with our Kuiper Belt-turned-Fomalhaut model.

sundogplanets,
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2 predictions from this model:

  1. Fomalhaut b should expand and eventually become too faint to be visible as the dust cloud drifts apart

  2. There should be other dust clouds that become visible! (I even specifically wrote that JWST would be able to see this!)

We wrote: "While perhaps disappointing to think of Fom b as
merely a cloud of dust and not an actual planet, this scenario tells us about the structure of the Fomalhaut debris disk, and strongly implies the presence of multiple planets"

sundogplanets,
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Fast forward to 2020:

@andrasgaspar and collaborators re-imaged the Fomalhaut system with the Hubble Space Telescope

AND FOMALHAUT b was GONE!!!

https://arxiv.org/abs/2004.08736

https://hubblesite.org/contents/media/images/2020/09/4627-Image

sundogplanets,
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Fast forward to 2023: @andrasgaspar and collaborators got JWST data, and not only is Fomalhaut b still gone, but there's an extra belt in between the inner and outer debris belts! This perfectly explains where the Fomalhaut b collision could have come from!

AND THERE'S A NEW DUST CLOUD!

Andras's thread about the observations is here: https://mastodon.online/@andrasgaspar/110333666704386375

sundogplanets,
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So, I have to say at this point that it's pretty freaking cool to get to have your theoretical prediction confirmed in your lifetime in astronomy. (And others also independently had this prediction, it's not just me). But yeah, that feels pretty good.

Here's a Sky & Telescope article (where I got to be very excited about the new images): https://skyandtelescope.org/astronomy-news/the-james-webb-space-telescope-reveals-fomalhauts-disk-in-unprecedented-detail/

I think I'm also quoted in Nat Geo (but paywalled so I'll wait until I get get it from my library): https://www.nationalgeographic.com/premium/article/nasa-photo-of-planetary-debris-unlike-anything-seen-before

sundogplanets,
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In conclusion: Fomalhaut b is totally not an exoplanet. But personally, I think it's way cooler that we're seeing collision-produced dust clouds in real-time in another solar system! Don't think of it as losing an exoplanet, think of it as gaining a dynamically exciting Kuiper Belt!

(And boy, it's sure nice to write a big long thread about a super cool astronomy discovery instead of complaining about satellites ruining everything.)

sundogplanets,
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Hey cool! @andrasgaspar's JWST image of Fomalhaut is the Astronomy Picture of the Day today!

https://apod.nasa.gov/apod/ap230511.html

sundogplanets,
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@andrasgaspar Congrats!! That's a pretty big astronomy win there!

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