Harrison Nicholls
@nichollsh.bsky.social
Astrophysicist and planetary scientist studying the atmospheres and interior interactions of rocky (exo)planets. Postdoc Research Associate @ Cambridge Institute of Astronomy. https://www.h-nicholls.space
The 30 July 2026 Astronomy Picture of the Day featured a remarkable shot of the Sun photographed through a wildfire smoke-filled sky that turned the star a deep red. So I tweaked it to look like we're orbiting an M-class red dwarf star with a close-in system of rocky planets, like TRAPPIST-1.
New paper from Lorenzo Cesario 🔭 His third first-author paper, and he only finished his MSc this year. "Characterizing the oxidation state of rocky exoplanets with the Large Interferometer for Exoplanets (LIFE)" Read the paper: https://arxiv.org/abs/2607.28121 #Exoplanets #PlanetaryScience
New paper on arXiv today! On the efficacy of using novel Bayesian machine learning to dispatch 'expensive' forward models of planetary evolution. This connects with #PLATO ageing and can help solve degeneracies in current static-retrieval approaches which treat #exoplanets as snapshots.
Constraining the lives and times of exoplanets through evolutionary Bayesian retrievals
Static retrieval frameworks are leading tools for interpreting exoplanet observations, yet time-independent modelling leaves them prone to degeneracy and unable to resolve exoplanets' histories. The c...
arxiv.org
🔭 Did you know that there is *silver* in the Sun? If yes: did you know we JUST found out there’s 55% more than previously thought?! +0.19 dex from ref values, which is a LOT! The culprit? (Scooby-Doo villain reveal) As always, those darn meddling 3D non-LTE effects!!! 👻 Press release & paper ⬇️
The Sun contains more silver than previously estimated – Uppsala University
uu.se
that uh… that sure is a lot of helium escape for a rocky planet, right?
When are #exoplanets in equilibrium? Sulfur photochemistry has the answer to this, and to inform about planets' deep interior redox conditions directly from #JWST data. Ioannis' paper is based on his MSc project, jointly supervised by @timlichtenberg.bsky.social, @exoshami.bsky.social, and myself.
Forming Worlds Lab@formingworlds.space · 3w agoNew paper led by Ioannis Panagiotou, his first as lead author, on arXiv ten days after he defended his MSc with us 🌋 "Sulfur photochemistry observationally traces mantle redox states of rocky planets" Read the paper: https://arxiv.org/abs/2607.15204 #Exoplanets #PlanetaryScience
New paper with @formingworlds.space colleagues. With planetary evolution models, we demonstrate that the combined physics of redox-sensitive degassing and escape can generate transient episodes of atmospheric re-inflation on super-Earths. "Reflation" is an observational marker of reducing interiors.
Forming Worlds Lab@formingworlds.space · 3w agoNew paper led by Lorenzo Cesario, his second first-author paper from his MSc 🌍 Some close-in super-Earths puff their atmospheres back up late in life instead of only shrinking. We call it reflation. Read the paper: https://arxiv.org/abs/2607.13793 #Exoplanets #PlanetaryScience
The small icy moon Mimas, floating in space above Saturn, the planet crossed by the shadows of its vast ring system. NASA Photojournal image PIA06176, taken by the Cassini spacecraft on 18 January 2005.
That's a wrap on #Exoplanets6 in Porto 🇵🇹 The Forming Worlds Lab brought four posters, all using our open PROTEUS model to link a rocky world's interior (magma ocean, redox, outgassing, escape) to what JWST can observe. Featuring @marianasastre.bsky.social, @nichollsh.bsky.social & team 👇
Delighted to share that I've been awarded two and complementary prizes for my PhD on magma ocean evolution and climate modelling. Firstly, Second Prize for computational physics by the Institute of Physics; secondly, part of the Early Career Medal by the UK Planetary Forum. Explainer below...
Harrison Nicholls and colleagues suggest that exoplanet L 98-59 d could be entirely composed of molten lava: a magma ocean covering a mushy core. http://dlvr.it/TRWtfm ☄️@nichollsh.bsky.social
Volatile-rich evolution of molten super-Earth L 98-59 d - Nature Astronomy
Planet-evolution models explain JWST data for L 98-59 d through a new scenario: while cooling and escape shrank this planet, a permanent magma ocean supplies sulfur to its atmosphere, in which SO2 is produced by photochemistry.
dlvr.it
Very pleased to share that I have been awarded a Pass, with no corrections, following my DPhil defence at Oxford AOPP (@oxoplanets.bsky.social). My thanks go to Paolo Sossi and @tadkomacek.bsky.social for their valuable input on my thesis, and their thoughtful suggestions for future directions.
It's happening!!! Pandora is going to space in just over 16 hours (if all goes well). Pandora is going to help us study exoplanet atmospheres, even when their host stars are misbehaving. I am headed up to Vandenberg to watch the launch shortly, and will make a thread about the mission/launch here!
TLDR; The PSF has made the decision to put our community and our shared diversity, equity, and inclusion values ahead of seeking $1.5M in new revenue. Please read and share. pyfound.blogspot.com/2025/10/NSF-... 🧵
The official home of the Python Programming Language
python.org
Success! @noaa.gov GOES-West full disk, without (left) the Rayleigh correction that 99% of the published imagery uses. I still need to tweak the settings, but I always thought the removal of atmospheric scattering makes Earth look too flat. Thanks to @stim3on.bsky.social & @simonsat.bsky.social
In our now-published paper we model the early history of three exoplanets to specifically study the role of tidal heating on their capacity to solidify. A physically robust feedback mechanism can keep them molten, even with relatively thin atmospheres, which may extend to lots of rocky exoplanets.
RAS Journals@rasjournals.bsky.social · last yr.Published in #MNRAS: "Self-limited tidal heating and prolonged magma oceans in the L 98-59 system", Nicholls et al. This is Fig. 1: for the caption & to read the paper please visit academic.oup.com/mnras/articl... @oxfordacademic.bsky.social @royalastrosoc.bsky.social
In our new paper we model the complete evolution of L 98-59 d from 'birth' up to the present day. We show that it cannot be a gas dwarf or a water world; it's a 'hybrid' planet with an H2-rich atmosphere containing H2S and SO2 (photochemistry!), and a deep magma ocean. @timlichtenberg.bsky.social
ClimateBook@climatebook.bsky.social · last yr.New paper on the molten Super-Earth L98-59d by @nichollsh.bsky.social in our group. arxiv.org/abs/2507.02656
New paper on arXiv today: "Absence of a Runaway Greenhouse Limit on Lava Planets" by Iris Boer, @nichollsh.bsky.social, and me (arxiv.org/abs/2505.11149). The runaway greenhouse limit is non-existent on molten planets (which is how planets form), questioning the general "habitable zone" concept.
Absence of a Runaway Greenhouse Limit on Lava Planets
Climate transitions on exoplanets offer valuable insights into the atmospheric processes governing planetary habitability. Previous pure-steam atmospheric models show a thermal limit in outgoing long-...
arxiv.org
A time-lapse of some images of asteroid (52246) Donaldjohanson during the encounter by Lucy! Images taken on April 20, 2025, from a distance of 1,600 to 1,100 km. Credit: NASA/Goddard/SwRI/Johns Hopkins APL science.nasa.gov/image-articl... #PlanetSci #SciComm 🧪
Our new paper on atmospheric convection on lava worlds is now on arXiv (accepted in MNRAS). We model the early time-evolution of two terrestrial-mass planets, and find that their atmospheres are not always convective. However, they can still have permanent magma oceans! arxiv.org/abs/2412.11987
Excited to share that our paper on atmospheres on lava planets has been accepted in JGR: Planets! You can find it on arXiv here: arxiv.org/abs/2411.19137
