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I'm excited about the potential this new model, named Rocky Raccoon because it has rocks, raccoons are cute, and the Beatles are good, has for exploring sub-Neptunes! The condensate sequence concept is an interesting space with lots still to work out. Paper submitted to ApJ, comments welcome!

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The structural changes, both in the locations of non-convective regions and in the mean molecular weights, lead to different planetary radii. The transitions between regimes are sudden for small changes in base abundance, indicating you can constrain interiors using atmospheric abundances.

$A three panel plot indicating the variation in atmospheric properties as function of base Mg/Si ratio. Variations in gas number fractions at the base, at the 1 bar level, and transit radii are shown by colored lines.$

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Different base abundances promote different condensates at equilibrium, which draw down Si and O at different rates and in different ratios. This feedback leads to entirely different atmospheric chemistry! We find Si-depleted envelopes rich in water and O-depleted endmembers with CH4 and SiH4.

Figure 2 from Misener et al. (2026), a six panel plot comparing the mixing ratios of gases, the condensate number densities, and temperatures as functions of pressure using colored lines for two base Mg:Si:O ratios.

Magnesium silicate condensation in sub-Neptune envelopes: the fundamental link between chemistry, structure, and observables

New paper on arxiv today! arxiv.org/abs/2608.24873. Taking a look at the great variety of Mg-Si-C condensates that can occur in sub-Neptunes. The sequence of condensates has a huge impact on envelope composition and structure: small differences in base composition completely change observables!

arxiv.org

Chemical interactions between the hydrogen-dominated envelopes and silicate-rich interiors of sub-Neptunes likely play a key role in shaping their atmospheric structure, mass-radius relations, and upp...

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Will Misener @willmisener.bsky.social · 06/08/2026

In the US (Mac, chrome), get a Bad Request error (“size of a request header field exceeds server limit”). Works on safari and mobile

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Jonathan Fortney @jjfplanet.bsky.social · 17/06/2026

Hello! We have a very-off-cycle postdoc fellowship at UC Santa Cruz. Open to any area of Astronomy and Astrophysics. Applications are due July 15th. It is funded by the Moore Foundation. Looking for someone to start Oct 1, 2026 (!, approx), see details below. aas.org/jobregister/...

aas.org

Postdoctoral Fellow in Astronomy & Astrophysics, UC Santa Cruz | American Astronomical Society

The Department of Astronomy and Astrophysics invites applications for a two-year Postdoctoral Fellowship position at the University of California, Santa Cruz, funded by the Moore Foundation. The searc...

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We also model planetary evolution using these self-consistent escape rates. We find that incorporating all relevant mechanisms is vital for capturing the evolution: any missing piece produces inaccurate results! Excited to see what people think!

Three panels showing atmospheric mass, transit radius, and mass loss rates as functions of time. A solid line shows PE+CPML, while dashed lines of various colors compare other models missing various components. The other models produce less escape and different radius evolution compared to the self-consistent one.

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We make easy-to-use scalings for the transition radius between CPML and PE as functions of planet mass and equilibrium temperature. We find that most sub-Neptunes transition into photoevaporation at late times, but core-powered escape is important early and dominates for low-mass, close-in planets.

Two panels plotting transition radius against planet mass and equilibrium temperature. Dots show the modeled transition radius, which increases with planet mass and decreases with temperature. Linear fit equations are shown.

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We find escape rates self-consistently over a range of planet radii, masses, temperatures, and UV fluxes. We find that outflows are core-powered early on, and transition to photoevaporation as they shrink! Funky physics happens at the transition, when UV just barely penetrates

Three panels showing mass loss rate as a function of radius for three planet masses. Dots show aiolos hydrodynamic outputs, which are overlain with lines showing analytic scalings. The dots follow the core-powered scaling at large radii and switch to the energy limit at small radii, with some dots in the middle dipping below both models

Three panels showing atmospheric escape rates against XUV luminosity for three planet masses. The lines are color coded by radius. Large radii in light-colors have large mass loss rates that are independent of XUV, while small radii in dark colorsare linearly dependent on XUV. Intermediate radii can decrease in mass loss rate with increasing XUV as they transition from bolometric to XUV dominated escape.

Characterizing the bolometric-photoevaporative transition in young sub-Neptunes with radiation-hydrodynamic simulations

Paper out on arxiv today! This one has been a longtime project so I'm happy to get it out there. We use the aiolos radiation-hydrodynamic code to map out the transition radius between core-powered/bolometrically-driven winds and photoevaporative/UV-driven winds arxiv.org/abs/2605.02766

arxiv.org

Hydrodynamic atmospheric escape plays a central role in shaping the demographics of small, close-in exoplanets. Two mechanisms have been proposed to drive mass loss: photoevaporation, powered by UV ir...

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Will Misener @willmisener.bsky.social · 20/04/2026

Three of the five shutdowns came in their game last Saturday against the Nats too haha fangraphs.com/scores/game-...

fangraphs.com

Game Stats | FanGraphs Baseball

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Chris Lintott @chrislintott.bsky.social · 28/01/2026

Research Notes is free to publish in and I think provides a very valuable service to the community. But I think we’re a month or two from being completely swamped.

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Carl T. Bergstrom @carlbergstrom.com · 27/01/2026

1. The thing about science that these jokers don't understand is that science cannot be vibe-coded. Whatever its flaws, the point with vibe coding is that you're trying to quickly make something that sorta works, where you can immediately sorta see if it sorta works and then sorta use it.

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The Onion @theonion.com · 06/01/2026

NASA Discovers Distant Planet With Conditions That Could Sustain Rocks theonion.com/nasa-discovers-distant…

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Reposted by Will Misener

Space Telescope Science Institute @stsci.edu · 29/09/2025

#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: bit.ly/46xGodN 🔭 🧪

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.

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Michael Wong @miquai.bsky.social · 21/09/2025

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

Three planeteers look through a mockup of a Curiosity rover wheel

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Johanna Teske @johannateske.bsky.social · 04/09/2025

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)

aas.org

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Will Misener @willmisener.bsky.social · 07/08/2025

I am a professional astronomy researcher

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Casey Dreier @caseydreier.bsky.social · 02/06/2025

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.

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Will Misener @willmisener.bsky.social · 02/06/2025

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)

Will Misener @willmisener.bsky.social · 26/03/2025

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

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Gijs D Mulders @gijsmulders.com · 17/03/2025

Do #exoplanets evolve over time? ☄️ A thread 1/🧵

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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

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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

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

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.

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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 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.

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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

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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

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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

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).

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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

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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

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.

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