Dr Ryan MacDonald

🚨 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)

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.

🚨 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)

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.

🚨 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)

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!

🚨 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)

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.

🚨 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)

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

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.

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

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.

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

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.

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

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.

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

Using GPs to account for the stellar contamination, we combined the time-independent spectral information from the four transits to produce the spectrum of TRAPPIST-1e shown in the press release. We then turned to atmospheric models to see if there were any signatures of atmospheric absorption.

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

When we modelled the stellar contamination (similar to previous studies on TRAPPIST-1b,c, d), the models couldn't simultaneously explain the entire wavelength range. Simply put, our stellar models for ultra-cool M-dwarf stars like TRAPPIST-1 don't work 😱 So we had to try something new...

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

TRAPPIST-1e is 92% Earth's size, 69% Earth's mass, and is illuminated by 66% of the integrated light that Earth receives. This means TRAPPIST-1e can potentially have liquid surface water *if* it has an atmosphere with a sufficient greenhouse effect. So TRAPPIST-1e was a priority target for JWST.

We observed the habitable zone planet TRAPPIST-1e with JWST to search for an atmosphere. You've seen the headlines, now let's dive into the science! 🧪 THREAD (1/N) #Exoplanets 🔭

We looked for an atmosphere on TRAPPIST-1d using JWST, but we didn't see any atmospheric absorption. So TRAPPIST-1d is quite different from Earth, despite lying just inside the habitable zone. The planet is either: ➡️ A bare rock. ➡️ Very cloudy. ➡️ Has a thin, Mars-like atmosphere. #Exoplanets 🔭

The JWST observations should have seen gases like CO2, H2O, or CH4 for relatively clear thick atmospheres. So the non-detections rule out many classes of rocky planet atmospheres, including: 🌍 Modern and Archean (early) Earth. ♀️ Venus (unless very cloudy). 🔱 Titan.

We looked for an atmosphere on TRAPPIST-1d using JWST, but we didn't see any atmospheric absorption. So TRAPPIST-1d is quite different from Earth, despite lying just inside the habitable zone. The planet is either: ➡️ A bare rock. ➡️ Very cloudy. ➡️ Has a thin, Mars-like atmosphere. #Exoplanets 🔭