Will Misener

An illustration of a young planet with a surrounding disk of dust and gas potentially forming moons. The planet, which appears dark red, is shown at lower right, circled by a cloudy, clumpy reddish orange-colored disk. The host star appears at upper left, and glows yellow, with its own reddish disk of debris. The disk that surrounds the planet takes up about half the illustration. The black background of space is speckled with stars. At the bottom of the illustration, graphics of molecules are listed in the following order: Acetylene, Carbon Dioxide, Ethane, Benzene, Hydrogen cyanide. The words Artist’s Concept appear at upper right.

#NASAWebb has found the first direct evidence of potential moon formation around a giant exoplanet. The discovery is shedding light on how such systems evolve and why moons could be potentially habitable worlds: https://bit.ly/46xGodN 🔭 🧪

Three planeteers look through a mockup of a Curiosity rover wheel

The best part of my job is the people I get to work with 🪐💙

Tyler Rogers?

The advertisement for Carnegie EPL's 2026 postdoctoral fellowship is out! aas.org/jobregister/... We are also happy to host external fellowships like NHFP, NSF, and 51 Peg b (the latter is due Oct 3rd, one month away!). Please feel free to reach out if you have questions. (1/2)

I am a professional astronomy researcher

yes

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Don't miss our new NASA Science spending and economic impact resource at dashboards.planetary.org/nasa-science.html — see space science spending in every state and congressional district and custom reports for each region. A unique resource.

It looks like Rutgers is sorted into NJ-12 (I'm not local, but from a map it looks like the district boundary goes through campus)

Still obsessed with maps and waiting for the smallest opportunity to foist it on to others 🚇🗺️

Do #exoplanets evolve over time? ☄️

A thread 1/🧵

Lastly: this research, and in fact most of my PhD salary and tuition, was funded by federal NASA grants. I'm deeply grateful for the opportunity these funds have provided me to advance our knowledge of the universe. I hope dearly we will continue to give aspiring scientists that same chance. 10/10

I'm looking forward to thinking about what prospective compositions lead to what escape rates, and how this effect interacts with photoevaporation, the other mechanism thought to play a role in shaping sub-Neptunes. Thoughts welcome! 9/10

Three panel plot showing RCB radius, atmospheric mass, and mass loss rate as functions of time. Different color curves represent different values of gamma. High values of gamma lead to large escape rates. Therefore most of the initial atmosphere is stripped within 1 billion years. Conversely, if gamma is low, virtually no primordial atmosphere is lost. Adapted from Misener et al. (2025), Fig 4.

That means that sub-Neptunes will evolve differently depending on the exact upper atmosphere composition, even if they're always hydrogen-dominated. We find that the opacity ratios can make a difference between very little atmosphere being retained under core-powered mass loss, or nearly all. 8/10

A plot showing mass loss rate as a function of radiative-convective boundary (RCB) radius. Different colors show different values of the opacity ratio gamma. Mass loss rate increases as a function of radius for all gamma values. But lower values of gamma lead to escape rates lower by 10 orders of magnitude at small radii than do high values of gamma. The rates converge at larger radii. Adapted from Misener et al. (2025), Fig 3.

The difference in mass loss rates for different opacity ratios is biggest when the atmospheres are most contracted, with up to a factor of 10^10 in mass loss rate separating cold upper atmospheres from hot ones! We provide tabulated rates in case you'd like to use these numbers yourself. 7/10

A three panel plot: on the left are temperature and density as functions of radius. Different colors represent different opacity ratios, quantified by gamma. On the right are mass loss rates corresponding to each profile. For small gamma, the upper atmospheres are cool, leading to low escape rates. For large gamma, the upper atmospheres are hot, leading to high escape rates. Adapted from Misener et al. (2025), Figure 2.

What we found is that the opacities have big implications for escape from sub-Neptunes: hotter temperature profiles lead to more mass loss! The most important reason why is that the density falls off more slowly if the temperatures are higher, leading to higher escape rates. 6/10

To account for this, we implemented core-powered mass loss in aiolos, a 1D hydrodynamic radiative transfer code, for the first time. This allowed us to calculate the escape rates and profiles self-consistently, and in doing so test the analytic approximations previous work had used. 5/10

Model P-T profiles of hot Jupiters from Fortney et al. (2008), showing prominent thermal inversions due to the presence of efficient optical absorbers (i.e., high gamma values in the upper atmosphere).

If the ratio (termed gamma) is near 1, then the atmosphere is roughly isothermal, but if it's not, you can get cool stratospheres or thermal inversions. This won't come as news to a lot of exoplaneteers, as we've long seen evidence for the phenomenon in atmospheric spectra! 4/10

But whether the outer atmosphere actually is isothermal depends on the actual opacities. More specifically, it depends on whether the atmosphere is more opaque to incident stellar light or to outgoing thermal infrared. These in turn depend on the actual composition of the atmosphere. 3/10

A two-panel plot showing the predictions of a core-powered mass loss model (left) against the observed planet demographics (right), showing good agreement. The mass loss rates in the models were calculated assuming an isothermal outer atmosphere. Adapted from Gupta+Schlichting 2019, Fig 2.

Core-powered mass loss, one of the mechanisms that can explain the radius valley separating the super-Earths and sub-Neptunes, has always been modeled using an analytic escape rate calculation, called a Parker wind, that assumed the outer atmosphere was isothermal at the equilibrium temperature 2/10

Apparently, between the switch to Bluesky and my defense and move, I've neglected to post about the last paper of my PhD. Now that it's been published in ApJ, here's a thread on how upper atmospheric opacities can alter escape rates and whether sub-Neptunes can retain primordial H/He 🔭🧪 1/10

The Carnegie Science sign on a snowy campus

Calling all undergrads! Just one week left to apply for Carnegie’s 2025 summer internship and work with us on all kinds of interdisciplinary projects in Earth & planetary science! Campus won’t look quite like this in June, but it’ll still be a magical experience ✨ carnegiescience.edu/about/workin...

Selfie with a AAS logo backdrop at AAS 243 in New Orleans

Excited for my first-ever (!) AAS this week. Look out for my thesis talk, conveniently on Monday morning to ease you back into conferencing:
133.05D “Coupled chemistry and structure of sub-Neptune atmospheres: a window into the interior”
Mon, Jan 8 10:40-11:00am
Room R04 #AAS243

Makes sense! It seems like the numbers might get really big quickly if there are a lot of false positives though (which I suppose doesn't really matter except for aesthetics lol).

What's been confusing/bothering me is, how come when the planets get confirmed, they stay as TOIs and don't become TESS-1 b or whatever, like how KOI-157.01 -> Kepler-11 c? Was there a reason for this? I guess it's fewer numbers to keep track of...