iiinova — where your digital self keeps evolving

Drew Weisserman @drewweisserman.bsky.social · 23/04/2026

seeing this on an in-class quiz today sent me into a rage

Note that in the real arrangement of the system, Kepler-80f is the innermost planet. For simplicity, we adopt here a list in which the planets are labelled from closest to farthest.

Drew Weisserman @drewweisserman.bsky.social · 10/04/2026

This!! It sure looks like our planets have less massive cores (and are thus less dense) than their host stars imply... (and we show that they do, statistically!) Earlier, we said if these planets are chronically underdense, that has to be because of something light making up part of the planet. 9/

$The core mass fractions of my planets, both as inferred from the planet's mass/radius and from their host stars' abundances. You can see that on a population level, the planets have consistently smaller core mass fractions (read: are less dense) than their host stars would imply, though due to the uncertainties involved it's hard to make that claim about any one planet.$

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Drew Weisserman @drewweisserman.bsky.social · 10/04/2026

We ALSO use these data to precisely measure abundances of these planets' host stars from near-infrared spectra, using a new routine developed by my friend and collaborator Nicole Gromek (paper coming pretty soon!) Getting abundances is REALLY difficult for these cool stars, but we do our best! 7/

A plot showing the fit to a single spectral line (an iron line of HD 260655), and our model fitting to it the best it can. (Sadly, most spectral lines are NOT nearly this clean!)

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Drew Weisserman @drewweisserman.bsky.social · 10/04/2026

them to their host stars! We got a WHOLE bunch of telescope time on the NIRPS spectrograph to precisely measure the masses of 3 hot rocky super-Earths (and take another 6 planet masses from other studies because we took up enough telescope time already 😭) Really, check out these RV curves! 6/

A plot of the RVs of GJ 1132 (b on top, c on bottom) as a function of orbital phase. Look at how precise our measurements are!

A plot of the RVs of GJ 1252 (b on top, (c) on bottom) as a function of orbital phase. Look at how precise our measurements are!

A plot of the RVs of LTT 3780 (b on top, c on bottom) as a function of orbital phase. Look at how precise our measurements are!

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Drew Weisserman @drewweisserman.bsky.social · 10/04/2026

form via something called "water-rich formation", where their planets form with, well, a lot of water vs. around bigger stars. This is what simulations predict, and on a demographics level we sort of see the signs of this. But how can we get more concrete observational evidence of this? 2/

A figure from Wanderley et al. (2025), showing that demographics of M dwarf exoplanets might be consistent with something called gas-poor formation (read: water-rich formation) rather than other formation theories. We want more evidence than this, though!

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Drew Weisserman @drewweisserman.bsky.social · 06/01/2026

My first attempt at sourdough turned out well!! (If you couldn’t tell by the fact that I ate the other half…)

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Drew Weisserman @drewweisserman.bsky.social · 28/08/2025

(example of what that looks like, for reference)

Histogram colored in matplotlib's default orange/blue/green/purple colors, at alpha = 0.8

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Drew Weisserman @drewweisserman.bsky.social · 19/08/2025

Finally, we make a little toy model to calculate the rate of HJMDs vs. hot Jupiters around Sun-like stars, too. We find that KL migration alone can fully account for the rate of HJMDs we see, if M dwarfs are better at damping the planets this migration excites (which is supported by theory.)

$Figure 5 from Weisserman & Gillis (2025). Left: A comparison of the various frequency terms featured in Eq. 5 obtained from the literature for early M dwarfs, FGK stars, and A stars. The terms fHJ, fCJ, fmult, and fmisaligned denote, respectively, the observed occurrence rates of hot Jupiters, cold Jupiters, the stellar multiplicity fractions, and the fraction of stellar binaries that are misaligned by ≥ 39◦ drawn from an isotropic distribution (i.e. 36.8%). The predicted frequency of HJs formed via KL migration is the distribution fHJ,pred = fCJSbinfmultfmisaligned (see Eq. 5). Right: cumulative distribution functions of the HJ formation efficiency by KL migration (fHJ/fHJ,pred) for each class of star considered herein.$

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Drew Weisserman @drewweisserman.bsky.social · 19/08/2025

So we check if that damping is feasible for these stars. Both have binary companions that could drive that high-eccentricity migration in the first place via Kozai-Lidov (KL) migration. Astrometric measurements from Gaia suggest these systems are aligned that KL migration is feasible, too.

Figure 4 from Weisserman & Gillis (2025). Results of orbital fits to Gaia DR3 astrometric data for the binary systems TOI-3714 (upper row) and TOI-5293 (lower row). Left column: a random selection of sky-projected binary orbit solutions from our astrometric fit posteriors. Right column: the distribution of minimum mutual inclinations between each system’s planet and binary companion. The vertical dashed line at arccos p 3/5 ≈ 39.2 ◦ corresponds to the minimum mutual inclination needed to drive KL migration. The percentiles of the mutual inclination distribution above and below 39.2 ◦ are depicted by different colors and are annotated for each system.

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Drew Weisserman @drewweisserman.bsky.social · 19/08/2025

This is not hugely unexpected: the 1st such measurement found the same result. But what does it mean? Well-aligned orbits COULD result from dynamically cold migration, or it could result from dynamically hotter high-eccentricity migration that was then damped away by the star's tides.

Figure 3 from Weisserman & Gillis (2025). The distribution of projected stellar obliquities |λ| for giant exoplanets (Rp ≥ 5 R⊕) as a function of host star effective temperature. All stellar obliquity measurements come from measurements of the Rossiter-McLaughlin effect and are retrieved
from the NASA Exoplanet Archive. Hot Jupiters around M dwarfs (HJMDs) occupy the shaded red region of parameter space with Teff < 3900 K, while host stars above the Kraft break (Teff ≥ 6100 K) occupy the shaded blue region. The HJMDs TOI-3714 b and TOI-5293 A b from this work, and TOI-4201 (T. Gan et al. 2024) are highlighted by red arrows.

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Drew Weisserman @drewweisserman.bsky.social · 19/08/2025

In this paper, we use the MAROON-X spectrograph to measure this effect for two HJMDs, TOI-3714 b and TOI-5293 A b. These are just the 2nd and 3rd ever measurements of this kind for HJMDs! And, spoilers... we find out these planets' orbits are well-aligned! 🎉

Figure 2 from Weisserman & Gillis (2025). The RM effect signatures for TOI-3714 b (left panel) and TOI-5293 A b (right panel). Each set of markers depicts the combined MAROON-X RV observations (i.e. blue plus red channels) for each transit sequence observed. The black curves
represent random draws from our RM model posteriors after removing the median detrending model for each transit and the planet-induced Keplerian orbital signals.

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Drew Weisserman @drewweisserman.bsky.social · 19/08/2025

We can get a good sense of how a planet formed by observing the Rossiter-McLaughlin effect. As a planet passes in front of its star, it blocks parts of the star moving towards/away from you (which are bluer/redder, respectively), making the star appear redder or bluer for a time.

Fig. 1 from Winn (2010), showing how the Rossiter-McLaughlin effect signals change as a function of the planet's obliquity.

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Drew Weisserman @drewweisserman.bsky.social · 19/08/2025

So, hot Jupiters are very close-in (P < 10d), big, gaseous planet. We see these sorts of planets around a lot of stars, and there's a lot of debate over how they form! Some evidence suggests they can form close-in, while more evidence finds that they form far away from their stars and migrate in.

Fig. 1 from Dawson & Johnson (2018), showing the methods of forming hot Jupiters.

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Drew Weisserman @drewweisserman.bsky.social · 18/07/2025

I assume this is a typo on page 145, but I'm glad to see the Juno spacecraft finally getting the 27 trillion dollars it deserves

"...sustained operations for high-performing missions in extended phases and provides not less than $27,200,000 million for Juno"

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Drew Weisserman @drewweisserman.bsky.social · 14/06/2025

Didn’t get great pics, but amazing turnout in Toronto!! 750-1000 people, half Americans and half Canadians.

A crowd protesting, many carrying American/Canadian flags or signs

A crowd protesting, many carrying American/Canadian flags or signs. A RESIST sign is prominent in frame.

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Drew Weisserman @drewweisserman.bsky.social · 03/06/2025

This isn’t someone trying to change the party, this is someone changing himself.

I’ve opened my eyes and listened to people who don’t think like me. And by doing so, I gained a greater understanding of and appreciation for LGBTQ issues, structural racism, the need for empathetic immigration reform, the dangers of climate change, and the role government must play to help care for the neediest and most vulnerable among us.

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Drew Weisserman @drewweisserman.bsky.social · 14/03/2025

I don't even LIKE poppy seed hamantaschens, why did I make so many of them

32 hamantaschens on a baking sheet, with black, orange, and red filling

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Drew Weisserman @drewweisserman.bsky.social · 19/02/2025

A second like has hit Phil Murphy’s post

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Drew Weisserman @drewweisserman.bsky.social · 07/02/2025

It wouldn't! If it hits the Earth, we know WHERE it would hit: somewhere on this red line. Big cities lie along this line (Dhaka, Bogota, and Lagos, for example), but a lot of empty space, too, and Yellowstone is nowhere near.