Josh Lothringer
@jlothringer.bsky.social
Assistant Astronomer at @spacetelescope.bsky.social researching exoplanet and brown dwarf atmospheres. Opinions expressed are my own.
https://jlothringer.github.io/
https://jlothringer.github.io/
Take a look at the paper, now accepted to AJ, for more info: arxiv.org/abs/2510.26785.
The code and calculations used in the paper are available at the GitHub linked above. The data used in the paper is available here: jlothringer.github.io/LExACoM_MRT_....
The code and calculations used in the paper are available at the GitHub linked above. The data used in the paper is available here: jlothringer.github.io/LExACoM_MRT_....
The Library of Exoplanet Atmospheric Composition Measurements: Population Level Trends in Exoplanet Composition with ExoComp
The present-day bulk elemental composition of an exoplanet can provide insight into a planet's formation and evolutionary history. Such information is now being measured for dozens of planets with sta...
arxiv.org
October 31, 2025 at 1:35 PM
Take a look at the paper, now accepted to AJ, for more info: arxiv.org/abs/2510.26785.
The code and calculations used in the paper are available at the GitHub linked above. The data used in the paper is available here: jlothringer.github.io/LExACoM_MRT_....
The code and calculations used in the paper are available at the GitHub linked above. The data used in the paper is available here: jlothringer.github.io/LExACoM_MRT_....
We hope this is just the start at looking at these population-level trends, now with more robust and reliable measurements. We'll continue to collect measurements as they become available and update the table. We plan to extend this to include free retrieval results (e.g., H2O, CO2 measurements).
October 31, 2025 at 1:35 PM
We hope this is just the start at looking at these population-level trends, now with more robust and reliable measurements. We'll continue to collect measurements as they become available and update the table. We plan to extend this to include free retrieval results (e.g., H2O, CO2 measurements).
Even though the trends are a bit offset, the transit and eclipse spectroscopy samples show very consistent mass-metallicity slopes! Both are steeper than the Solar System trend - perhaps interesting... All this is also consistent with interior bulk metallicity inferences.
October 31, 2025 at 1:35 PM
Even though the trends are a bit offset, the transit and eclipse spectroscopy samples show very consistent mass-metallicity slopes! Both are steeper than the Solar System trend - perhaps interesting... All this is also consistent with interior bulk metallicity inferences.
One of the highlights is the planet mass-(atmospheric) metallicity trend. While such a trend was somewhat controversial with HST measurements, this newer sample shows a much cleaner relationship. With ExoComp, we can break it down between O/H and C/H and compare directly to the Solar System.
October 31, 2025 at 1:35 PM
One of the highlights is the planet mass-(atmospheric) metallicity trend. While such a trend was somewhat controversial with HST measurements, this newer sample shows a much cleaner relationship. With ExoComp, we can break it down between O/H and C/H and compare directly to the Solar System.
There don't seem to be obvious trends or correlations between planet metallicity, C/O, temperature, stellar metallicity, or stellar mass. But carbon-dominated C/O > 1 planets appear to be rare, if any exist at all!
October 31, 2025 at 1:35 PM
There don't seem to be obvious trends or correlations between planet metallicity, C/O, temperature, stellar metallicity, or stellar mass. But carbon-dominated C/O > 1 planets appear to be rare, if any exist at all!
After we standardize the 65 atmosphere measurements from JWST and 8m-class telescopes, we can look for trends! And we see some surprises...
The first was that exoplanets measured by transit spectroscopy have low C/O compared to those measured in eclipse. It's not obvious why.
The first was that exoplanets measured by transit spectroscopy have low C/O compared to those measured in eclipse. It's not obvious why.
October 31, 2025 at 1:35 PM
After we standardize the 65 atmosphere measurements from JWST and 8m-class telescopes, we can look for trends! And we see some surprises...
The first was that exoplanets measured by transit spectroscopy have low C/O compared to those measured in eclipse. It's not obvious why.
The first was that exoplanets measured by transit spectroscopy have low C/O compared to those measured in eclipse. It's not obvious why.
ExoComp allows one to convert between different solar abundance references and different definitions of metallicity and C/O. Other tools include fitting metallicity, C/O, and refrac./vol. ratios to sets of atomic and molecular abundances (like from a free retrievals).
github.com/jlothringer/...
github.com/jlothringer/...
GitHub - jlothringer/exocomp: Exocomp is a toolkit with functions and utilities for normalizing measurements from different retrievals of exoplanets and brown dwarfs.
Exocomp is a toolkit with functions and utilities for normalizing measurements from different retrievals of exoplanets and brown dwarfs. - jlothringer/exocomp
github.com
October 31, 2025 at 1:35 PM
ExoComp allows one to convert between different solar abundance references and different definitions of metallicity and C/O. Other tools include fitting metallicity, C/O, and refrac./vol. ratios to sets of atomic and molecular abundances (like from a free retrievals).
github.com/jlothringer/...
github.com/jlothringer/...
Even back in 1850, the biomass of humans matched that of all wild land animals? Not what I would have thought!
October 30, 2025 at 2:49 PM
Even back in 1850, the biomass of humans matched that of all wild land animals? Not what I would have thought!
Now extended to Monday 10/20, FYI!
October 16, 2025 at 6:24 PM
Now extended to Monday 10/20, FYI!
Yeah! In the paper we estimated something a bit sub-solar for the heavy element abundance, but it gets tricky fast because lots of different things can absorb in the UV, while photochemistry, dissociation, and escape can all confound abundance measurements.
August 16, 2025 at 1:40 PM
Yeah! In the paper we estimated something a bit sub-solar for the heavy element abundance, but it gets tricky fast because lots of different things can absorb in the UV, while photochemistry, dissociation, and escape can all confound abundance measurements.
And a big shout-out to lead-author Yayaati for seeing this project through from proposal to paper and showing that HST still has lots to say about exoplanet atmospheres in the JWST-era!
Check out the paper here: arxiv.org/abs/2508.10092. Accepted for publication in AJ!
Check out the paper here: arxiv.org/abs/2508.10092. Accepted for publication in AJ!
Strong NUV Refractory Absorption and Dissociated Water in the Hubble Transmission Spectrum of the Ultra Hot Jupiter KELT-20 b
Ultra hot Jupiters (UHJs) present a promising pathway for drawing a link between a planet's composition and formation history. They retain both refractory and volatiles species in gas phase in their a...
arxiv.org
August 15, 2025 at 1:24 PM
And a big shout-out to lead-author Yayaati for seeing this project through from proposal to paper and showing that HST still has lots to say about exoplanet atmospheres in the JWST-era!
Check out the paper here: arxiv.org/abs/2508.10092. Accepted for publication in AJ!
Check out the paper here: arxiv.org/abs/2508.10092. Accepted for publication in AJ!
We find tentative evidence for a limb asymmetry in the huge NUV feature. 3D GCM models (with mag fields!) by @hayleybeltz.bsky.social to show that the data is (tentatively) more consistent with a model *with* a magnetic field than without!
More obs of, e.g., the hot spot offset, could help.
More obs of, e.g., the hot spot offset, could help.
August 15, 2025 at 1:24 PM
We find tentative evidence for a limb asymmetry in the huge NUV feature. 3D GCM models (with mag fields!) by @hayleybeltz.bsky.social to show that the data is (tentatively) more consistent with a model *with* a magnetic field than without!
More obs of, e.g., the hot spot offset, could help.
More obs of, e.g., the hot spot offset, could help.
KELT-20b is unique compared to other UHJs in that it appears to be well-aligned with the rotation of its host star, perhaps indicating something unique about its formation.
Our measurements suggest the accretion of volatile-rich solids or gas, though therm dissociation makes the measurement hard.
Our measurements suggest the accretion of volatile-rich solids or gas, though therm dissociation makes the measurement hard.
August 15, 2025 at 1:24 PM
KELT-20b is unique compared to other UHJs in that it appears to be well-aligned with the rotation of its host star, perhaps indicating something unique about its formation.
Our measurements suggest the accretion of volatile-rich solids or gas, though therm dissociation makes the measurement hard.
Our measurements suggest the accretion of volatile-rich solids or gas, though therm dissociation makes the measurement hard.
Free retrievals prefer fitting the NUV feature with Fe II rather than SiO, though SiO was preferred in chemical equilibrium. Either way, it appears that enormous NUV absorption may not be rare among ultra-hot planets.
August 15, 2025 at 1:24 PM
Free retrievals prefer fitting the NUV feature with Fe II rather than SiO, though SiO was preferred in chemical equilibrium. Either way, it appears that enormous NUV absorption may not be rare among ultra-hot planets.