iiinova — where your digital self keeps evolving

Reposted by Dr Ryan MacDonald

Royal Astronomical Society @royalastrosoc.bsky.social · 27/08/2026

🚨 Astronomy cuts update 🚨 Next Tuesday (1 September) a debate about the ongoing funding crisis will take place in Westminster Hall from 1-1.30pm. 🗣️🔭 The RAS welcomes the debate and is encouraging all Fellows to contact their MPs to urge them to attend. ✍️ Find out more 👉️ ras.ac.uk/news-and-pre...

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Astronomer Royal for Scotland | Catherine Heymans @astroroyalscot.bsky.social · 01/08/2026

"There are shades of the departed Starmer government in this saga: @ukri.org wants to tell a big story about science funding going up, but instead is mired in a row over a fairly minor sum.... One does not have to be an astronomer to know that optics matter." 👌🔭 www.theguardian.com/commentisfre...

theguardian.com

The Guardian view on the Lovell telescope: budget cuts to physics are bad science and worse politics | Editorial

Editorial: Funders have picked a damaging fight with scientists and the public. They should reconsider their plans

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ESA Space Science @science.esa.int · 01/07/2026

Can a planet survive the death of its star? ☠️ For WD 1856 b, the answer is yes, based on Webb observations. 🔭 🧪 ☄️ 1/2

Illustration of exoplanet WD 1856 b. An orange gas giant planet at left, taking up about one-third of the frame, facing a star, which appears at top right as a far smaller bright dot. The planet has subtle orange cloud bands. The star illuminates the right side of the planet like the crescent of a waxing moon. Both are on the black background of space. The words “artist’s concept” are in the bottom right corner. Credit: NASA, ESA, CSA, R. Crawford (STScI)

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

The high methane abundance is certainly a puzzle. We really need dedicated atmospheric models for post-main-sequence planets (especially for high metallicity atmospheres) to better understand what this is telling us about the planet's past.

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

The mass of the progenitor star (about 1.3 M_Sun) kept the orbit stable. Mass loss during the red giant and asymptotic giant branch phases expanded the original orbit of WD 1856b by a factor of 2, making it more susceptible to the influence of the M-dwarfs.

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

The original star in this system was similar to our Sun (about 30% more massive), so what is exciting here is having a case study for planets around a future version of our Sun. White dwarf planetary systems are a preview of our own future, so I for one find them incredibly interesting to study!

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

Our paper, 'Aerosols and hydrocarbons in the atmosphere of a white dwarf planet', is published today in Nature and is freely available: www.nature.com/articles/s41...

Screenshot of the paper 'Aerosols and hydrocarbons in the
atmosphere of a white dwarf planet', available in the journal Nature (https://www.nature.com/articles/s41586-026-10514-7).

Authors: Ryan J. MacDonald, Christopher E. O’Connor, Victoria A. Boehm, E. M. May, David K. Sing, Elijah Mullens, L. C. Mayorga, Trevor O. Foote, Simon Blouin, Logan A. Pearce, Nikole K. Lewis, Jeff Valenti, Natasha E. Batalha, Maura Lally, Joshua D. Lothringer, Mark S. Marley, Ishan Mishra & Susan E. Mullally

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

You can read more about our findings in the European Space Agency (@esa.int) and NASA press release: esawebb.org/news/weic2614/ I'd also like to thank the space art team at STScI (@stsci.edu), especially Ralf Crawford, for the incredible artist's concept of WD 1856b.

esawebb.org

Webb studies how a planet survived death of its star

An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to watch the Jupiter-sized exoplanet WD 1856 b transit its host star, measuring the planet’s mass and temper...

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

So our best explanation for how WD 1856b survived stellar death is that it was originally on a wide orbit, but gradually moved in closer due to the influence of two nearby M-dwarf stars (about 1,000 AU from the white dwarf). Close passes by with the white dwarf led to tidal heating and migration.

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

Perhaps our biggest surprise though is that the planet appears to be significantly warmer than we expected (effective temprature around 400 K). Using planet cooling models, we extrapolated back in time to find that planet must have been reheated billions of years after the star died.

Top: backwards extrapolation of WD 1856b's temperature using planetary cooling models. Bottom: the inferred time of reheating occured billions of years after the star became a white dwarf, pointing towards planetary migration long after the death of the star.

Plot from 'Aerosols and hydrocarbons in the atmosphere of a white dwarf planet', MacDonald et al. 2026, Nature 655, 76 (https://www.nature.com/articles/s41586-026-10514-7).

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

Our spectrum analysis finds that hydrocarbons (most likely methane) explains the absorption features (with an odds ratio of at least 167:1). The planet's atmosphere is also shrouded in aerosols (odds ratio at least 200,000:1). We also find the mass of the planet is about 7 Jupiter masses.

$Left: spectral contribution plot showing how different components of the atmospheric model for WD 1856b explain its JWST transit spectrum. The downwards slope above 3.5 microns is explained by thermal emission from the side of the planet facing the observer, while the absorption features at shorter wavelengths are explained by methane absorption and a scattering haze. Right: measured constraints on atmospheric properties for WD 1856b's atmosphere. Top row: the fraction of the atmosphere made of CH4, C2H6, and PH3. Bottom row: the planet's mass, cloud top pressure, and haze power-law slope. Plot from 'Aerosols and hydrocarbons in the atmosphere of a white dwarf planet', MacDonald et al. 2026, Nature 655, 76 (https://www.nature.com/articles/s41586-026-10514-7).$

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

The transit spectrum we measure shows multiple 'bumps' that are best explained by methane (CH4) in the planet's atmosphere, alongside a slope at short wavelengths caused by a haze in the upper atmosphere. This is the first time we've seen the atmosphere of a close-in planet orbiting a white dwarf!

NASA’s James Webb Space Telescope measured the constituents of exoplanet WD 1856 b as it passed in front of its star, finding signs of methane. WD 1856 b orbits a white dwarf star the size of Earth. As a result, the planet blocks more than half of the star’s light. The red bands indicate where bumps in the spectrum show that this planet’s atmosphere contains methane.

Credit:
NASA, ESA, CSA, Joseph Olmsted (STScI)

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

This planet is 7 times larger than its white dwarf star, so it blocks a record-breaking over 50% of the light from its white dwarf. One of our big surprises is that the planet appears to block *less* light at longer wavelength infrared light, which we explained by planetary thermal emission.

Transit light curve of the white dwarf planet WD 1856b as measured by the James Webb Space Telescope. The plant blocks 56% of the star's light at short wavelengths of light (blue curve), but only 52% of the light at longer infrared wavelengths (red curve).

Plot from 'Aerosols and hydrocarbons in the atmosphere of a white dwarf planet', MacDonald et al. 2026, Nature 655, 76 (https://www.nature.com/articles/s41586-026-10514-7).

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

We used the NASA/ESA/CSA James Webb Space Telescope to measure the spectrum of WD 1856b during a transit event. Our goal was to measure the atmosphere of this ancient planet (that formed around 10 billion years ago) to learn what planets like Jupiter may be like after the death of the Sun.

Artist concept of the James Webb Space Telescope floating in space, with a field of stars behind it.

Credit: NASA

Illustration of transmission spectroscopy. Light from a star passes through the atmosphere of a planet, with a PRISM splitting the light into its constitutent colours. Colours with less light indicate absorption from the planet's atmosphere.

Credit: Christine Daniloff/MIT, Julien de Wit

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

WD 1856b orbits a very old white dwarf, the leftover core of a star like our own Sun that died about 5.4 billion years ago. It was discovered in 2020 (Vanderburg+2020). The planet is a similar size to Jupiter, but orbits at 0.02 AU. A big mystery is how the planet survived the death of its star.

The white dwarf planet WD 1856b orbits 50x closer to its white dwarf than the Earth orbits the Sun.

Credit: NASA

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Dr Ryan MacDonald @distantworlds.space · 01/07/2026

🚨 New research alert 🚨 We have found an atmosphere on a planet orbiting a dead star 🔭✴️💀🪐 Our James Webb Space Telescope (JWST) observations of the white dwarf planet WD 1856b give us a preview into the fate of planets like Jupiter after the death of the Sun. 🧵⬇️ (1/10)

Artist concept of the white dwarf planet WD 1856b

Caption:
Exoplanet WD 1856 b, shown in this artist’s concept, is a gas giant that survived the death of its star. It now orbits a white dwarf at a distance 50 times closer than Earth orbits the Sun. Observations by NASA’s James Webb Space Telescope not only determined the planet’s temperature but also detected molecules in its atmosphere. The former measurement provides evidence that WD 1856 b migrated to its current location billions of years after its star became a white dwarf.

Credits:
NASA, ESA, CSA, Ralf Crawford (STScI)

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Dr Ryan MacDonald @distantworlds.space · 29/06/2026

Néstor telling us there are no CO2 planets, while we are all inside a CO2-rich environment 🫠

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Dr Ryan MacDonald @distantworlds.space · 28/06/2026

Hopefully the Exoplanets 6 conference swag includes some TiO2 suncream for Thursday and Friday 😎 ☀️

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Dr Ryan MacDonald @distantworlds.space · 09/06/2026

Kicking off #BPSC26 with a workshop on exoplanet atmosphere spectroscopy for planetary scientists. Be sure to follow @bpsc2026.bsky.social for updates over this 3 day conference! 🪐 🔭

Slide show 'Measuring Exoplanet Atmospheres with the James Webb Space Telescope' with Dr Ryan MacDonald (St Andrews) standing next to the screen.

Part of a Jupiter notebook for the BPSC 2026 Exoplanet Workshop showing a transiting exoplanet.

Part of a Jupiter notebook for the BPSC 2026 Exoplanet Workshop, showing a James Webb Space Telescope spectrum of the giant planet WASP-39b

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Reposted by Dr Ryan MacDonald

Astronomer Royal for Scotland | Catherine Heymans @astroroyalscot.bsky.social · 29/05/2026

"Someone, somewhere, has taken the decision to defund astrophysics research in the UK, but no-one seems quite sure who that was, or why." The latest on the impact of the catastrophic funding cuts to UK astrophysics, by me, in @natastron.nature.com 👩‍🔬🧪🔭 ✒️ www.nature.com/articles/s41...

World View: A change in UK policy jeopadizes the future of UK astrophysics - By Catherine Heymans

The latest budget proposal announced by the largest UK science funding agency threatens to severely affect UK astrophysics research. My colleagues and I are fighting back.

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Reposted by Dr Ryan MacDonald

Josh Lothringer @jlothringer.bsky.social · 18/05/2026

These are awesome positions where you'll play critical roles in STScI's missions (HST, JWST, Roman)! Definitely apply if interested! Feel free to reach out if you've any questions.

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Dr Ryan MacDonald @distantworlds.space · 20/05/2026

Do these STScI positions have any restrictions on citizenship?

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Reposted by Dr Ryan MacDonald

Emily Rauscher @astronemly.bsky.social · 05/05/2026

Woohoo! Robert Frazier, PhD student who did his pre-candidate project with me, had it accepted for publication today! An impressive comparison of a JWST spectroscopic phase curve to a set of 3-D models (of the ultra-hot Jupiter WASP-121b). Preprint here: arxiv.org/abs/2605.01589

arxiv.org

The Days Drag On on WASP-121 b: Interpreting its NIRISS Spectroscopic Phase Curve with General Circulation Models

Ultra-hot Jupiters present extreme atmospheric phenomena not found in the Solar System. These planets' daysides experience strong temperature inversions, molecular species (including H2) dissociate, a...

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Dr Ryan MacDonald @distantworlds.space · 04/05/2026

It is a holiday today here in the UK!

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Reposted by Dr Ryan MacDonald

British Planetary Science Conference 2026 @bpsc2026.bsky.social · 28/04/2026

Calling all planetary scientists: The #BPSC26 abstract and early-bird registration deadline of May 9th is soon approaching! Email us your abstracts following the instructions at tinyurl.com/4x8tm6bu, and register for the conference at tinyurl.com/yvnxf6jw. Come share your science with us in June!

tinyurl.com

Abstracts and Presenter Details – BPSC2026

You must be registered to have your contribution (oral/poster) included in the conference.

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Dr Ryan MacDonald @distantworlds.space · 01/04/2026

Incredible to see the #Artemis II mission finally launch! 🤩 For the first time in my life, humans are going back to the Moon 🌎🚀🌕

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Dr Ryan MacDonald @distantworlds.space · 21/03/2026

I had a great time chatting to Max Klymenko on the Career Ladder! Can he guess my job at @uniofstandrews.bsky.social within 2 minutes? 🤓 youtube.com/shorts/JaclY...

youtube.com

His job is BIZZARE and asks a question? 🏴󠁧󠁢󠁳󠁣󠁴󠁿 Ep. 531 🪜

YouTube video by Max Klymenko

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Reposted by Dr Ryan MacDonald

International Astronomical Youth Camp @iayc.bsky.social · 01/01/2026

✨ Applications for the 2026 International Astronomical Youth Camp are now open! ✨🚀 Join us in Spain for the 60th lAYC celebration and experience an unforgettable total solar eclipse! 🌘 Head to our First Info page via the link in our bio to apply! Clear skies 🌌 🔭🎢 #EduSky #scicomm #astroedu

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Dr Ryan MacDonald @distantworlds.space · 12/03/2026

🚨 Job vacancy! We are recruiting a Computing Officer for the School of Physics and Astronomy at St Andrews ⚛️🔭 High-Performance Computing is critical to our work on understanding the Universe, including the search for life on other planets. 🪐🧑‍💻🖥️ www.vacancies.st-andrews.ac.uk/Vacancies/W/...

vacancies.st-andrews.ac.uk

Computing Officer (Academic Computing) - AD2860

Computing Officer (Academic Computing) - AD2860, IT Services Salary: Grade 6 / £38,784-£46,049pa Start date: 1 June 2026 Full time Permanent, <p style="color: #212529; margin: 0px 0px 1rem; padding: 0...

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Dr Ryan MacDonald @distantworlds.space · 04/03/2026

Quite the crowd today in St Andrews for Max Klymenko filming the Career Ladder. I had a blast discussing our search for life of #exoplanets 🪐 🔭 Max asked many @uniofstandrews.bsky.social staff and students about their jobs - keep an eye out for the episode!

Max Klymenko and Ryan MacDonald standing on a ladder surrounded by a crowd of people.

In the background are the old stone buildings of St Salvator's quad in St Andrews, Scotland.

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Reposted by Dr Ryan MacDonald

Royal Astronomical Society @royalastrosoc.bsky.social · 16/02/2026

We have written to Science Minister Lord Patrick Vallance urging him to step him and help reverse the cuts to astronomy and space science proposed by the Science and Technology Facilities Council last month. Read the letter in full 👉️ ras.ac.uk/news-and-pre...

ras.ac.uk

'Reverse the cuts': RAS urges Vallance to avert scientific crisis

The Royal Astronomical Society (RAS) has called on science minister Patrick Vallance to step in and prevent the "catastrophic damage to astronomy and space science" ...

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British Planetary Science Conference 2026 @bpsc2026.bsky.social · 03/02/2026

BPSC2026 Registration and Abstract Submission is open! Information on rates, discounted accommodation and abstract format can be found here bpsc2026.wp.st-andrews.ac.uk/registration/ Early bird rates are available til 9th May 2026, which is the same day as the abstract deadline!

bpsc2026.wp.st-andrews.ac.uk

Registration – BPSC2026

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Dr Ryan MacDonald @distantworlds.space · 14/01/2026

We're excited to be hosting the British Planetary Society Conference in St Andrews this summer! One of our aims for BPSC 2026 is to connect the Solar System #planetaryscience and #Exoplanets communities. Be sure to follow the conference page for more details: ⬇️🪐🌍🧪⬇️

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Dr Ryan MacDonald @distantworlds.space · 11/12/2025

After the event, one of the other academics thanked me for speaking out, saying they feel like they're losing their mind being inundated by the push to use AI for everything. It really matters that we clearly say out loud the dangers of AI in education (and wider society).

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Dr Ryan MacDonald @distantworlds.space · 11/12/2025

I attended a welcome event for new academic staff recently. Two of the new faculty there were extremely pro-AI and said things like: "I require my students to use AI, telling them they will learn too slowly if they don't". I pushed back, citing the damage to learning from cognitive offloading.

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Royal Astronomical Society @royalastrosoc.bsky.social · 24/10/2025

Job vacancy 💻📝 Passionate about building vibrant professional communities? The RAS is seeking a dynamic Head of Membership to develop and deliver our membership strategy and play a pivotal role in growing our membership through retention and recruitment. Apply here👇 ras.ac.uk/news-and-pre...

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Dr Ryan MacDonald @distantworlds.space · 03/10/2025

The Norman Lockyer Fellowship is a great opportunity for postdoc research in #Exoplanets, and we'd love to host you at St Andrews! Feel free to reach out if you're interested in joining our exoplanet group in beautiful Scotland 🏴󠁧󠁢󠁳󠁣󠁴󠁿🪐

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Dr Ryan MacDonald @distantworlds.space · 01/10/2025

Trotta (2008) arxiv.org/abs/0803.4089

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Dr Ryan MacDonald @distantworlds.space · 27/09/2025

Many congratulations, Dr Boldt-Christmas! 🎉 Love the front cover transiting planet atmosphere graphic on your thesis!

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Dr Ryan MacDonald @distantworlds.space · 17/09/2025

Afraid not. Microlensing relies on a chance alignment between two distant stars, so you see the planet once and then it's gone forever.

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Dr Ryan MacDonald @distantworlds.space · 13/09/2025

The telescope that discovered this planetary system was named after the beer 😅

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

Finally, it's important to highlight that none of this would have been possible without the leadership of Nikole Lewis, who is the PI of this initial TRAPPIST-1e reconnaissance program. I was fortunate enough to be a postdoc at Cornell with Nikole, and she is a truly *fantastic* advisor and mentor!

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

We have follow-up observations of TRAPPIST-1e ongoing (led by Néstor Espinoza and Natalie Allen), which will provide 15 (!) more transits of TRAPPIST-1e. So if TRAPPIST-1e does indeed have an atmosphere, we will soon have the data to settle the enigma of this world.

Artist's impression of TRAPPIST-1e, showing a rocky world covered in scattered lakes and clouds.

Credit: NASA/JPL-Caltech.

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

Our constraints on potential atmospheres with molecules heavier than H2 and He (secondary atmospheres) are presented in our second TRAPPIST-1e paper, led by @ana-glidden.bsky.social at MIT. Be sure to check out the paper! iopscience.iop.org/article/10.3... So what comes next?

Screenshot of the title page of 'JWST-TST DREAMS: Secondary Atmosphere Constraints for the Habitable Zone Planet TRAPPIST-1 e'.

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

Technical point: retrievals of flat transmission spectra for rocky planets usually result in corner plots resembling the prior. For TRAPPIST-1e, we don't see this behaviour, with the CH4 posterior pushing to include this molecule. We haven't detected CH4, but future observations can assess this.

Posterior probability plots for the CH4 and CO2 abundances in TRAPPIST-1e's atmosphere. The CH4 abundance shows a spike near high atmospheric abundances (>~ 0.1-100 %), compatible with the CH4 abundance of Venus, Earth, or Titan. The CO2 abundance plot offers few constraints on the abundance of this molecule, though the authors note that the region allowing for 100% CO2 corresponds to an unphysically low temperature (~ 100 K) where CO2 would condense, and hence high-CO2 atmospheres like Venus or Mars are disfavoured.

Figure from Glidden et al. (2025).

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

Statistically, our current four-transit spectrum of TRAPPIST-1e can also be fit by a flat line (i.e. a featureless spectrum). So we can't rule out a bare rock with these data. There's also the important caveat that an incomplete stellar contamination correction could also imprint spectral features.

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

Intriguingly, forward models with N2 + CH4 provided a great fit to TRAPPIST-1e's transmission spectrum 😯 We found the same solution independently through atmospheric retrievals, which latched onto CH4 absorption as a potential explanation. 🔍 But this is not (yet!) an atmospheric detection.

Spectral fits to TRAPPIST-1 e’s stellar-contamination-corrected transmission spectrum. Top: best-fitting forward models for three different partial pressures of N2 and CH4 (solid, dotted, and dashed colored lines) compared to a flat line (dotted black line). Bottom: GP+atmosphere retrievals for the CLR (blue) and log-uniform priors with a “ghost” background gas (gray) compared to a flat line (dotted black line). All models are plotted binned to the same spectral resolution as the data. The wavelengths of potential CH4 absorption bands are annotated. The corresponding corner plot is in Appendix E. The best-fitting forward models and both retrieval approaches independently identify spectral features tentatively attributed to CH4 features in a potentially N2-rich atmosphere.

Figure from Glidden et al. (2025).

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

In Paper #2, we ran a grid of atmospheric models considering combinations of strong infrared absorbers (CO2 / CH4) and transparent background gases (N2 / H2). The figure below (from Glidden+2025) shows the range of excluded partial pressures. Big takeaway: large CO2 concentrations are unlikely.

Rejection significance for atmospheric forward models compared to TRAPPIST-1 e’s JWST transmission spectra. Each subplot represents a background gas (N2 or H2) together with an absorber (CO2 or CH4) over a range of surface partial pressures shown on the x- and y-axes. Gases are shown above each subplot. Grid boxes are labeled and colored with the significance of the difference between the data and the forward model. Black colored boxes represent “infinite” σ, meaning that the models are firmly inconsistent with the data and can be ruled out. The four boxes on the left side of the figure are for the combined visits 1 and 2, which were naturally less impacted by stellar contamination, while the four boxes on the right side are for the GP stellar-contamination-corrected spectrum from N. Espinoza et al. (2025), which includes all four visits. In both cases, our data are consistent across a range of N2 atmospheres, but we are able to place additional constraints on H2-rich atmospheres. In particular, we can rule out H2-rich atmospheres with a strong absorber until increasing the amount of the heavier absorber flattens out the spectrum so that any possible features are buried in the uncertainty. When all four transits are combined and stellar contamination is (partially) mitigated, we are able to place moderately tighter constraints on atmospheres with CH4 than we could with just visits 1 and 2 combined.

Figure from Glidden et al. (2025).

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Dr Ryan MacDonald @distantworlds.space · 10/09/2025

The observations, stellar contamination GP magic 🪄, and H2-upper limit we've discussed so far are covered in our first TRAPPIST-1e paper, led by Néstor Espinoza at STScI (not on Bluesky). Be sure to check out the paper! iopscience.iop.org/article/10.3... Next, we looked for secondary atmospheres.

Screenshot of the paper 'JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e'

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