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Marshall

@captain-exoplanet.bsky.social
467 followers 466 following 207 posts

Astronomer, birder, TTRPG player and gluten-free cook. he/him.

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Marshall @captain-exoplanet.bsky.social · 10/10/2026
But Ohio came through, and I reached 242 species seen first in the state. I had thought I was pretty much done getting lifers in Ohio, but still managed 19 in 2026. I put in a lot of hours of birding this year and I'm elated that I've met my goal. And I still have another 12 weeks of the year...
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Marshall @captain-exoplanet.bsky.social · 10/10/2026
I figured that I could reach my goal if I found 200 species in Ohio and 200 on trips. Despite traveling to Canada, Arizona, and Spain, I fell short with "only" 158 species and with other trip plans falling through I wasn't sure if I would be able to reach my goal.
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Marshall @captain-exoplanet.bsky.social · 10/10/2026
At the start of 2026 I set an ambitious #birding 🪶 goal for the year of observing 400 species over the course of the year. Today, I reached that goal! The (lifer) Nelson's sparrow that had been hanging out in my county was good enough to stick around until the weekend when I could go find it.
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Marshall @captain-exoplanet.bsky.social · 13/09/2026
I've spent more than three months of my life observing on this telescope, searching for exoplanets. McDonald is a beautiful observatory site both day and night.
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Reposted by Marshall
CosmicRami 🏳️‍🌈🏳️‍⚧️ @rami.spaceaustralia.com · 11/09/2026
LFG, team #Calcite! It's such a neat mineral; it exhibits birefringence! Light has two propagation modes through the crystal structure, giving this effect. We see similar behaviour in the strongly magnetised plasma of pulsar magnetospheres: two modes of wave propagation! Vote Calcite in #MinCup26
Calcite crystal wth a line and the word "calcite' below it. The birefringence effects are causing the word and line to double up
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Marshall @captain-exoplanet.bsky.social · 30/08/2026
Go Roman! So exciting to watch the launch. I was lucky enough to see some of the spacecraft hardware in person a couple of years ago, amazing this is all now in space!
A photo of a smiling bearded white man leaning against a window. Behind the window is a giant clean room holding various pieces of spacecraft hardware. Decals on the windows read "Nancy Grace Roman Space Telescope."
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Reposted by Marshall
CosmicRami 🏳️‍🌈🏳️‍⚧️ @rami.spaceaustralia.com · 30/08/2026
T-60min to the scheduled launch time of the Nancy Grace Roman space telescope on the SpaceX Falcon Heavy. Watch live here: www.youtube.com/watch?v=9wq3...
youtube.com
Nancy Grace Roman Space Telescope Launch
YouTube video by NASA
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Marshall @captain-exoplanet.bsky.social · 27/08/2026
According to a colleague on the Roman team these are the typical Florida afternoon thunderstorms, which shouldn't have much impact since the launch is in the morning.
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Marshall @captain-exoplanet.bsky.social · 19/08/2026
100%. I hope the hats make a return for 4-HORSES in 2028.
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Marshall @captain-exoplanet.bsky.social · 19/08/2026
Someone decided that "high-resolution spectroscopy of stars and exoplanets" should acronym to HORSE and just ran with it. There were SO MANY horse puns and it's an ongoing conference series now (the 3rd edition #HoRS3S was this summer, though sadly they skipped the hats this time to keep costs down)
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Marshall @captain-exoplanet.bsky.social · 19/08/2026
Most useful? Tote bags or water bottles. Most fun? The straw cowboy hat from an inexplicably horse-themed spectroscopy conference.
A photograph of a straw cowboy hat sitting on a table in a classroom. The hat has a white cloth hatband with "Two HORSEs" printed on it.
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Marshall @captain-exoplanet.bsky.social · 08/08/2026
I also saw the pair of Mississippi kites that I'd originally gone out to find for a very nice, double-lifer, double-kite, double-RBA day.
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Marshall @captain-exoplanet.bsky.social · 08/08/2026
Had what I'm pretty sure was a big #birding 🪶moment this morning; I spotted a pair of swallow-tailed kites which, as far as I can tell from eBird, is the first time anyone has ever reported them in my county! A bunch of other birders showed up after I reported and eventually saw them too.
A low-quality photo of a bird flying past the viewer. It has a white body, dark wings, and a long, forked tail.A low-quality photo of a bird flying away from the viewer. It has a white body, dark wings, and a long, forked tail.
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Marshall @captain-exoplanet.bsky.social · 06/08/2026
* One great-great-grandfather was born in the Confederacy (🤮) ** My four 🇩🇪 great-great-grandparents were all born before the unification of Germany, in the states of Prussia, Saxony, Holstein, and Hease-Darmstadt.
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Marshall @captain-exoplanet.bsky.social · 06/08/2026
Live in: 🇺🇸 Born in: 🇺🇸 Parents: 🇺🇸🇺🇸 Grandparents: 🇺🇸🇺🇸🇺🇸🇺🇸 Great-grandparents: 🇺🇸🇺🇸🇺🇸🇺🇸🇺🇸🇺🇸🇺🇸🇺🇸 Great-great-grandparents: 🇺🇸x11* 🇩🇪x4** 🇬🇧 Been to: 🇨🇦🇬🇷🇹🇷🇩🇪🇧🇪🇨🇵🇬🇧🇪🇸🇦🇹🇨🇿🇮🇪🇮🇹🇻🇦🇮🇸🇸🇪🇯🇵🇨🇱🇳🇴🇵🇹
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
Absolutely! Glad you enjoyed following along.
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
And that's a wrap for #HoRS3S. Thanks to the organizers for putting together a great meeting, all of the presenters & attendees, and hope to see everyone again at #4-HORSES ( #4ORSES ?) in Nice in April 2028!
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
#HoRS3S rides off into the sunset with Maddalena Bugatti talking about instrumental profile characterization. Understanding the line spread function is important for precise measurements. Fit laser frequency comb with Gaussian process to get non-parametric LSF model, finely resolved on detector.
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
Katlyn Hobbs #HoRS3S: using HARPS-N, NEID, & KPF solar data to study impacts of spots and faculae & find lines susceptible to these effects, by comparing to spectra of quiet sun. Can also estimate facula filling factor directly from spectra.
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
I kicked off the final session @ #HoRS3S on the first light of iLocater, the new near-IR EPRV spectrograph for the LBT. Single-mode fiber fed for high spectral & spatial resolution (40 mas on sky). 4 nights 1st light run, nearly 150 spectra! Likely shared risk science 2027A, open to collaboration!
ilocater.nd.edu
iLocater records its first on-sky spectrum
The night of 27 June 2026 saw the culmination of over a decade of development for iLocater: the instrument spectrograph recording its first on-sky spect...
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
Thea Hood's big question #HoRS3S: do Doppler shifts measured during transit accurately trace the wind speed for hot Jupiters? Using GCM model grid, for orbital periods >2 days circulation is day-to-night wind dominated & winds recovered accurately; <1 day jet dominated & Doppler shift =/= wind speed
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
Krishna Kanumalla #HoRS3S: stellar contamination is a problem even for HRS emission observations of cool stars. Shows IGRINS observations successfully detecting a hot Neptune. Complementary to JWST observations but ground-based is much lower $ cost.
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
"Low resolution sees the forest. High resolution counts the trees. We need both." -Francesco Amadori presents high- and low-resolution transit observations of WASP-107 b, combining both gives fuller picture of atmosphere than either alone #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
Aline Novais: a few years ago JWST used to find water reservoir in inner system of PDS 70. Highly variable Na absorption now suggests presence of exocomets, and N-body simulations indicate it's plausible that the known #exoplanets scattered these inward from the outer disk. #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 10/07/2026
The last half day of #HoRS3S kicks off with Kevin Hoy (Ohio State Astro alumnus!) presenting the first evidence of radial velocity signals from satellite(s) around a substellar companion. CRIRES+ RVs give a nice orbital solution. Exciting system! Unclear what to call objects of this kind.
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
Valentin De Lia shows #HoRS3S MAROON-X transit data on KELT-20 b, presents new method to self-consistently model effects of vertical velocity gradient on transmission spectra. Using multiple methods, finds lower wind speeds at higher altitudes. Consistent with simple models of magnetic drag.
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
Ji Wang presents the work we've been with @toribonidie.bsky.social & others. Large survey of ultra hot Jupiters with LBT/PEPSI: UHJs have inverted atmospheres seen in Fe emission, strong Fe opacity could be source of inversions; best case to measure rock-to-ice ratios with optical+IR spectra #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
Luke Parker #HoRS3S: Si is important for understanding planet formation. In hot giant planets mostly in SiO, strong spectral features in M band (observations hard). Survey using CRIRES+ to observe several directly imaged objects; making detections, constrain ice-to-rock ratio of accreted material
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
Georgia Mraz #HoRS3S: high-res phase curve of #exoplanet WASP-33 b, covering full orbit; do 4 separate retrievals on pre/post eclipse/transit data to look @ both day and nightsides. Attempted to use best-fit dayside spectrum to pull out signal near quadrature, not clear why no solid detection.
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
Final keynote of #HoRS3S: Anish Amarsi on stellar spectra with 3D models. We need accurate stellar models to properly interpret spectra. Both direct (e.g. granulation) and indirect (e.g. temperature profile) results of 3D affect stellar spectra w.r.t. 1D models, change abundances on 0.1 dex level.
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
@tadkomacek.bsky.social : mineral clouds form in hot Jupiter atmospheres, directly detected by JWST & necessary to explain some JWST phase curves. TiO2 condensates nucleate silicate clouds, can explain Ti depletion reported in ultra hot Jupiters. Cloud microphysics is important! #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
#HoRS3S Day 4 starts with a keynote by Joost Wardenier on 3D effects in ultra hot Jupiters. High resolution observations often interpreted using Kp-vsys maps. The atmospheric dynamics affect the structure of these maps, but be careful of bad ephemerides, eccentricities. Lots of info in these data!
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Marshall @captain-exoplanet.bsky.social · 09/07/2026
I'll conclude the Day 3 thread from #HoRS3S by noting that the organizers made the good choice to make a memes channel on the conference Discord. This was my contribution (although I did make it some time ago, thought it was worth re-sharing) #exoplanets
A meme, of a three panel cartoon.

In the first panel, a child with wide, teary eyes asks, "NASA can you give me EPRV spectrographs"

In the second panel, a woman whose head is the NASA logo asks, "To find Earth-like planets?"

In the final panel, the enthusiastic child says, "Yeeees, Earth-like planets..." while looking at an artistic rendering of a very hot, massive planet (ultra hot Jupiter) and several plots showing the detections of gaseous iron in these planets' atmospheres.
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Khaled Al Moulla: most solar feeds on high-res spectrographs are disk integrated, but also want spatially resolved data to isolate active regions. PoET: solar feed for ESPRESSO, aperture sizes ranging from 1 to 55 arcsec. See substantial differences between spectra of spots, quiescent sun #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Romain Allart kicks off the last #HoRS3S Day 3 session summarizing atmospheric characterization with NIRPS; 225 night program through GTO for emission, transmission, He triplet, impressive number of forthcoming papers. Currently working to extend NIRPS to K band; lessons for ANDES development.
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
@astronemly.bsky.social: working 2 understand how spectra from individual regions of the planet combine into disk-integrated spectrum, using GCMs of hot Jupiters. Things change on a per-species basis due to different distributions, can back out surface velocity distribution from line profile #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Jens Hoeijmakers shows sobering simulations that HRS transmission observations of TRAPPIST-1-like planets w/ANDES will be limited by systematics due to the presence of spots, not photon noise. Results vary by species (H2O worse because present in spots) and by obliquity (aligned orbits best) #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Ah, I had not appreciated that history! This was from Mike Line's talk, he certainly may have mentioned this and I just missed it (or gave a caveat like "first use in exoplanets" that I misinterpreted).
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Benjamin Charnay shows a clever method to map the latitudinal distributions of different species on rapidly rotating brown dwarfs/massive planets: equator is hotter than poles, species more present @ equator will show more rotational broadening than those more concentrated at higher latitude #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
100%! It took me longer than I care to admit to figure out what the term actually meant, and I'm sure I'm not the only one.
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
We continue with today's keynote theme with Gloria Canocchi discussing NLTE in stars #HoRS3S This can have consequences for exoplanet studies: if ignore, measure inaccurate stellar abundances, get false transmission spectroscopy detections, can even change shape of Rossiter-McLaughlin curve.
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Jerry Xuan shows #HoRS3S JWST spectra of the 4 HR 8799 planets. Data such high quality that retrievals took 2 years to run. Many molecules detected including H2S, NH3. More metal rich than more massive distant companions, must have accreted solids. Planet b likely formed between CO & N2 snowlines.
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Jaume Orell-Miquel: survey of young planets in He triplet to look at atmospheric escape. HPF observations of one very young system show mysterious signal at planetary orbital period #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 08/07/2026
Day 3 of #HoRS3S is out of the gate with a gallop 🐎 w/ Luca Fossati discussing non local thermodynamic equilibrium in exoplanet atmospheres. "NLTE is horrible and fascinating at the same time" - every individual spectral line responds differently to NLTE, & is very important for He NIR triplet
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Marshall @captain-exoplanet.bsky.social · 07/07/2026
I was stressing about lectern vs podium and I guess I got the wrong one 🤣
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Marshall @captain-exoplanet.bsky.social · 07/07/2026
We end this session with Emily Deibert & Adam Langeveld on the SPECTRE-GHOST survey (great acronym!). One of several ongoing population surveys of UHJs, they have some nice results in both emission and transmission on several planets with more to come #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 07/07/2026
Stefan Pelletier points out that 🐎 love sodium (salt) #HoRS3S. Na abundances with D lines hard b/c formed very high in atmosphere, but can get other lines in hot planets, notably in K band, detected w/ IGRINS. Can also now probe rock/ice ratios for UHJs, more info on formation than just C/O.
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Marshall @captain-exoplanet.bsky.social · 07/07/2026
Julia Seidel talks about using atmospheric wind measurements of ultra hot Jupiters to constrain their magnetic fields. Wind speeds go down with increasing equilibrium temperature, which is the expected trend from magnetic drag affecting the circulation of the increasingly ionized atmospheres #HoRS3S
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Marshall @captain-exoplanet.bsky.social · 07/07/2026
We return after lunch #HoRS3S with a lively keynote by Mike "Retrievals" Line (per his title slide). TIL the term Retrieval comes from the title of a 2009 paper. Retrievals are key to enabling a wide range of high-res science: dynamics, spatially varying abundances, abundance ratios, &c.
A picture of a slide projected on a screen. Text at the top reads "Transformative Potential of Retrievals: A Temperature and Abundance Retrieval Method for Exoplanet Atmospheres" the latter is the title of a paper by Madhusudhan and Seager from 2009. Several colorful plots fill the remainder of the slide. At bottom left a man stands behind a podium and looks at the screen.
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