Observational Work
Recent highlights
- ε Eridani b. One of the nearest Jupiter analogues, at 3.2 parsecs. By combining decades of radial velocities from eight instruments with Hipparcos, Hubble, and Gaia astrometry, we found that it has a mass of about one Jupiter mass on a near-circular orbit (Thompson et al. 2025). These orbit predictions help plan attempts to image it directly.
- Gliese 229 B. This famous brown dwarf turned out to be two brown dwarfs orbiting each other every 12 days, resolved with VLTI GRAVITY and VLT CRIRES+ spectroscopy (Xuan, Mérand, Thompson et al. 2024, Nature). I worked on the orbit modelling, and followed up with a joint fit of the inner and outer orbits.
- ε Indi Ab. A cold giant planet imaged by JWST. Orbit fits using only pre-JWST data correctly predicted where the planet was found, and the combined data give a precise dynamical mass (Sanghi, Thompson et al. 2026).
- JWST follow-up of Gaia planets. I am co-PI of JWST Cycle 5 program GO 11023 (PI J. Xuan, co-PIs D. Blakely and W. Thompson). It uses the NIRSpec integral field unit to search nine nearby young stars for giant planet candidates identified by astrometry, at solar-system-like separations.
HR 8799
One of my largest observational projects to date has been the Deep Orbital Search for Additional Planets in the HR 8799 system (Thompson et al. 2023). The image below combines four quarter-nights of Keck NIRC2 data to display the four known planets in the HR 8799 system (Marois et al. 2010).
These four planets were among the first planetary-mass objects outside our solar system to be directly imaged, and have been extensively studied.
My work on this system included observing and gathering 16 nights of NIRC2 observations, developing new ADI post-processing techniques (Thompson & Marois, 2021), and developing new orbit modelling techniques to search for faint companions in the presence of orbital motion.
This project led to the detection of a candidate fifth inner planet: a possible explanation for proper motion measurements that are in tension with atmosphere models. The orbital constraints from this program are also unique in that they come entirely from Keck L-band images, an instrument with exceptionally well-calibrated astrometry. Other instruments like GRAVITY can far exceed the precision of these measurements, but can't yet match the long time baseline.
Below is one of the highest SNR images recorded of the four confirmed planets:
And here is that same image, with orbits of the four confirmed and fifth candidate planet (with orbits derived exclusively from Keck images in this program):
I also used data from this project to create the first 100% uniformly reduced orbital animation of the system, see here:
This animation uses a Keplerian motion interpolation scheme to smoothly move between images.
Other projects
Current observational work includes:
- Efforts to directly image lower-mass and cooler companions around nearby stars, both at thermal wavelengths from the ground and from space.
- Following up Gaia-selected stars with JWST and large ground-based telescopes.
- Various observational programs with VLTI GRAVITY.
- Orbits of moving group binaries with Eric Nielsen.
- The Subaru/Keck accelerating stars program (OASIS) with Thayne Currie.
Last updated October 2026
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