Publications
Here you can find a list of all my publications: Astrophysics Data System (ADS) link
2026: Characterizing the surface of the hot, rocky exoplanet LHS 3844 b with JWST
My newest paper, published in Nature Astronomy, presents one of the first detailed studies of the surface of a rocky exoplanet outside the Solar System using the James Webb Space Telescope (JWST).
What makes this exciting is that we are beginning to move beyond simply asking whether rocky exoplanets have atmospheres. With JWST, we are now starting to directly study the geology and surface properties of worlds around other stars — something that was essentially impossible just a few years ago. This emerging field is sometimes called “exogeology.”
The planet LHS 3844 b is located about 49 light-years away and orbits its small red dwarf star every 11 hours. It is roughly 30% larger than Earth and reaches dayside temperatures of around 1000 K (~700°C). In short: not exactly a nice place to live.
Using JWST’s mid-infrared instrument (MIRI), we observed the planet disappearing behind its host star during so-called secondary eclipses. During those eclipses, the thermal emission from the planet temporarily vanishes, allowing us to isolate the planet’s own light. Even though the signal is tiny, JWST detected it extremely clearly.
In this animation, you can see the data we collected for the planet and how the flux drops when the planet temporarily disappears behind its star.
Credits: Sebastian Zieba (CfA)
Our observations suggest that the surface of LHS 3844 b is dark and likely basaltic, similar to volcanic rocks found on bodies like Mercury or the Moon. The surface may also be heavily altered by long-term space weathering from stellar radiation and micrometeorite impacts.
At the same time, we do not find evidence for a substantial atmosphere or volcanic gases such as CO₂ or SO₂. The data therefore point toward a mostly bare rocky surface rather than an atmosphere-dominated planet. We can also rule out granite-like surface compositions similar to Earth’s continental crust, suggesting a very different geological history from our own planet.
We are continuing this work with additional JWST observations to better understand whether the planet’s surface is relatively fresh volcanic rock or an older surface covered in space-weathered regolith.
📄 Nature Astronomy paper: The dark and featureless surface of rocky exoplanet LHS 3844 b from JWST mid-infrared spectroscopy
Below are some Press Releases on this publication, with each of those containing quotes from my brilliant co-authors.
And some other articles:
2024: Doctoral thesis: Pushing the characterization of exoplanet atmospheres down to temperate rocky planets in the era of JWST
Leiden University hosts my doctoral thesis on their website, which is openly accessible here.
A day after I defended my PhD, an interview with me was published on the Leiden University website. In it, I discuss my research achievements throughout my doctoral studies, along with comments from colleagues in the field. You can read the full article on the Leiden University website.
2023: No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c
This artist’s concept illustrates what the hot rocky exoplanet TRAPPIST-1 c could look like based on this work. 
Credits: NASA, ESA, CSA, Joseph Olmsted (STScI)
Check out the press releases to this work:
NASA press release
MPIA press release
astrobites article
My Twitter (X) thread on the paper:
🚨 Newly published JWST results from the TRAPPIST-1 system! 🚨
— Sebastian Zieba (@sebizieba) June 22, 2023
We measured the light emitted from TRAPPIST-1 c, the second world in the seven-planet system, to directly learn about the planet’s atmosphere (or lack thereof…). 🧵 pic.twitter.com/si8IW63yMC
2022: PACMAN: A pipeline to reduce and analyze Hubble Wide Field Camera 3 IR Grism data
If you want to reduce some HST observations taken with one of the WFC3 Grisms (G102 or G141), check out PACMAN! It is an end-to-end pipeline, beginning with a time series of 2D images and ending with a spectrum for the planet. PACMAN can easily fit multiple observations simultaneously and is completely open source, hosted on GitHub, and documented on ReadTheDocs. If you would like to use PACMAN for your observations and have questions, feel free to reach out.
2022: K2 and Spitzer phase curves of the rocky ultra-short-period planet K2-141 b hint at a tenuous rock vapor atmosphere
In this work, we analyzed Spitzer and Kepler observations to study the lava planet K2-141 b. Below you can see the K2 and Spitzer phase curves for the planet. We find no significant hotspot offset for the planet (no thick, low molecular weight atmosphere). However, highly irradiated rocky planets like K2-141 b will experience outgassing from their surfaces and the creation of a thin rock vapor atmosphere. Atmospheric modeling shows us that certain species in these rock vapor atmospheres, like sodium, can create a thermal inversion in the optical wavelengths. This scenario is consistent with our analysis of the observations, as we observed a significant emission in the Kepler bandpass.
My Twitter (X) thread on the paper:
Paper submission day! Today my 1st first-author PhD paper dropped! 🥳 🥳 🥳 We used observations collected by Kepler and Spitzer to characterize the lava planet K2-141 b. Here are some hot facts about the best-studied lava planet to this day. (1/12)
— Sebastian Zieba (@sebizieba) March 2, 2022
2019: Transiting exocomets detected in broadband light by TESS in the β Pictoris system
Best-fit comet model. Top panel: The binned photometry showing the largest transit event. The vertical dashes are the error bars on the photometry. The red line shows the best fit model for b = 0 (i.e., the median of the parameters shown in Fig. 4). The lower panel shows the residuals from the fit.
astronomy.com article (in English)
Der Standard article (in German)
University of Innsbruck press release (in German)
Poster summarizing this work (presented at TESSCon I)
(last revised May 14, 2026)