UC San Diego Cool Star Lab
Welcome to the homepage of the UC San Diego Cool Star Lab! Feel free to use the links below to learn about our research, teaching, and community activities, and meet our present and past members.
In the News
(February 2025) The discovery of a potential fifth component to the Regulus system recently reported by Eric Mamajek and Adam Burgasser in the Astronomical Journal has been featured on AAS's Nova site! Nova curates the most interesting recent results published in AAS journals, providing astronomy researchers and enthusiasts summaries of recent research across a wide range of astronomical fields. (read the Nova article: https://aasnova.org/2025/02/05/a-new-groupie-in-regulus-entourage/)
(January 2025) Cool Star Lab undergraduate researchers Marylin Loritsch and Tianxing "Sky" Zhou have received the prestigious American Astronomical Society Chambliss Astronomy Achievement Student Awards! The Chambliss Awards recognize exemplary research by undergraduate and graduate students who present a poster session at the AAS national meeting. Awardees are honored with a Chambliss medal. Marylin received her award for her presentation "Characterizing the Optical Spectra of the Nearest Stellar Neighbors: The 20 Parsec Sample". Tianxing received his award for his presentation "Cool Stars, Hot Tech: Spectral Typing of M, L, and T Dwarfs with Machine Learning" Congratulations to our award-winning undergraduates! (see the press announcement from the AAS)
(August 2024) Our speedy little star was featured in the New York Times! NYT Science Reporter Katrina Miller highlighted the contributions of citizen scientists like Tom Bickle who was one of three amateur astronomers to identify the source as part of the Backyard Worlds: Planet 9 project.
(July 2024) Comic Con 2024 has come to San Diego! Cool Star Lab PI Adam Burgasser participated in a panel discussion on the TV series For All Mankind: Historic Fiction, Real Science with several experts in space science, engineering, biology, and sociology. The panel was hosted by the Fleet Center's Andrea Decker. Read how several UCSD folks contributed to Comic Con, and watch the For All Mankind panel discussion on YouTube.
(July 2024) The discovery of a hot Earth-sized planet orbiting the M-type star SPECULOOS-3, reported by Gillon et al. (2024), has been featured on the cover of Nature Astronomy! Read the paper by Gillon et al. (2024) and the press release by UCSD Physical Sciences.
(June 2024) Research led by Adam Burgasser and Roman Gerasimov were both featured in press conferences at the AAS 244 meeting in Madison, Wisconsin. Adam reported the discovery of a remarkably fast-moving, metal-poor L dwarf uncovered by citizen scientists that may be on its way to escaping the Milky Way. Roman reported the first discovery of brown dwarfs in JWST observations of the globular cluster NGC 6397. Learn more by watching the AAS 244 press conferences by Adam and Roman; you can also see some of the press images for the speedy L subdwarf in the UCSD Physical Science press release.
Research Highlights
Cool Star Lab Research at AAS 245
Cool Star Lab team members were out in force at the 245th American Astronomical Society meeting in Washington, DC. This was a big meeting for undergraduates to highlight their research results; Madison Fierro, Marylin Loritsch, Sara Morrissey, and Tianxing "Sky" Zhou all presented their current research projects, with Marylin and Sky both winning the prestigious Chambliss award for their posters. There were also plenty of CSL alumni at the conference, and a large contingent of UCSD undergraduate and graduate students, postdocs, and faculty in attendance. In addition to two posters, Adam Burgasser also led an Ethics Working Group listening session. Congratulations to all of the presenters!
Check out the CSL posters linked here:
Adam Burgasser: "STARTastro: A Transfer Receptive Culture Model for Community College Transfers into University of California Astronomy & Astrophysics Programs" (108.06)
Tianxing "Sky" Zhou: "Cool Stars, Hot Tech: Spectral Typing of M, L, and T Dwarfs with Machine Learning" (464.03)
Adam Burgasser: "Arcana of the Ancients: First Results from a JWST Spectral Survey of Metal-poor Ultracool Dwarfs" (464.06)
Marylin Loritsch: "Characterizing the Optical Spectra of the Nearest Stellar Neighbors: The 20 Parsec Sample" (464.17)
Madison Fierro: "Characterizing the Optical Spectra of the Nearest Stellar Neighbors: The Gaia UCD Sample" (464.18)
Sara Morrissey: "Spectral Model Fitting of Cold and Distant Brown Dwarfs Detected in a Deep Survey with the James Webb Space Telescope" (464.23)
(December 2024) NASA JPL's Eric Mamajek and CSL PI Adam Burgasser have potentially identified a fifth member of the Regulus star system. The discovery, a previously known L/T transition object 2MASS J10071185+1930563 was observed with Keck/NIRES, and the source's radial velocity, distance and proper motion all align with Regulus, suggesting a physical connection or a common origin. Remarkably, the brown dwarf is 7.5 degrees away from Regulus, about 3.9 parsecs (12.6 lightyears) in projected distance, almost 3 times the separation of the Sun and its nearest stellar companion Proxima Centauri. Regulus, or alpha Leonis, is the brightest star in the constellation Leo, and is a binary star composed of a B subgiant and a white dwarf that may have interacted. The other two stars in the system, Regulus BC (aka HD 87884), are a K dwarf/M dwarf pair, making this an extremely wide hierarchical quintuple (read the AJ article by Mamajek & Burgasser)
(November 2024) The North ecliptic pole EXtragalactic Unified Survey (NEXUS) project, a Multi-Cycle JWST Treasuary program, released its first set of data, including NIRCam images and wide-field slitless spectroscopy over a 100 square arcminute area near the North Ecliptic Pole. This area aligns with the Euclid North Deep Field, promising multi-epoch deep imaging and spectroscopy over the next 4 years. The final data will encompass deep, multi-epoch NIRCam imaging and NIRSpec PRISM spectroscopy over 400 square arcminutes down to imaging depths of 28-29 mag in 6 infrared filters. In addition to thousands of high redshift galaxies, this survey is expected to uncover dozens of brown dwarfs at kpc scales (read the preprint by Zuang et al. and access the data at https://ariel.astro.illinois.edu/nexus/edr/).
(November 2024) CSL PI Adam Burgasser and members of the Backyard Worlds: Planet 9 team have conducted a comprehensive study of metal-poor T dwarfs, including sources discovered by citizen scientists from multi-epoch WISE data. Selecting sources based on reduced proper motion, the team identified dozens of metal-poor objects, including three "extreme" cases. They also identified three metal-rich sources with thick disk kinematics, likely ejected from the inner Milky Way. 3D kinematics enabled by Keck/NIRES observations reveal that two sources may be part of the Thamnos population, and one source part of the Helmi stream. They study also made the first metallicity classification system for T (sub)dwarfs, and defined a metallicity index for near-infrared spectra. This work helps ongoing studies that are searching for thick-disk and halo brown dwarfs in deep JWST and Euclid fields (read the preprint by Burgasser et al.)
In the Community
UCSD Hosts CU*IP 2025
UCSD was one of 15 hosts sites for this year's Conferences for Undergraduate Women and Gender Minorities in Physics (CU*IP), organized nationally by the American Physical Society (APS). Co-organized by the Departments of Astronomy & Astrophysics and Physics, with co-Chairs Javier Duarte, Tongyan Lin, Adam Burgasser, and Robin Glefke, CU*IP@UCSD brought nearly 200 students from the southwest US, Hawaii, and (for the first time!) Mexico to a weekend of plenary talks (including one of UCSD's newest faculty members Floor Broekgaarden), workshops, and poster presentations. Cool Star Lab members Adam Burgasser and Sara Morrissey (who serves as Vice-President of UCSD's Society of Physics Students chapter) both helped to organize the meeting; Adam led two panels on Physics and Academia and served on an Education panel; and Sara, Madison Fierro, and Marylin Loritsch each presented posters at the conference. Marylin's poster received a conference prize for best poster on Stars and Stellar Populations! Congratulations to the conference team and the research presenters!
You can see all the conference posters, including those by Sara, Madison, and Marylin, at the conference poster webpage.
(December 2024) STARTastro scholars Annika Feng and Marylin Loritsch have been awarded the AAS FAMOUS Travel Grant for the upcoming AAS 245 meeting in Washington, DC. FAMOUS (Funds for Astronomical Meetings: Outreach to Underrepresented Scientists) grants award $1,000 for a single AAS meeting to present research, with priority given to members of historically underrepresented groups. Annika will be presenting her work on "Orbital Monitoring and Atmospheric Spectroscopy of the Directly Imaged Companion 1RXS J2351+3127 b" while Marylin will be presenting her work on "Characterizing the Optical Spectra of the Nearest Stellar Neighbors: The 20 Parsec Sample". Congratulations Annika & Marylin!
(November 2024) Emma Softich had the privilege of participating in the Girls Exploring Math and Science (GEMS), an outreach program associated with Keck Observatories. The November event included 16 workshops for over 150 5th-grade girls from the western part of the Big Island of Hawai'i. Emma helped present an exhibit on Infrared Astronomy which featured an interactive infrared camera, and shared the usefulness of infrared light when it comes to looking through dust - or trash bags! Emma really enjoyed the opportunity to interact with the students and help inspire the next generation of women in STEM.
(November 2024) CSL faculty Adam Burgasser and Chris Theissen organized a departmental table for UCSD's Native American Heritage Month (NAHM) annual luncheon. This is the kickoff event to a month of workshops, presentations, and celebrations on the continued contributions of indigenous people to the greater San Diego community. This year's speaker, Dr. Cutcha Risling Baldy (Hupa, Karuk, and Yurok) spoke on Indigenous feminism, Traditional Ecological Knowledge, and decolonization.
(November 2024) CSL undergraduates Madison Fierro & Marylin Loritsch, graduate student Emma Softich, and CSL Director Adam Burgasser visited Lick Observatory to conduct observations with the Kast spectrograph. Although the run was sadly weathered out, the team was treated to an in-depth look at the 65-year old Shane 3m telescope and the innards of the Kast spectrograph by telescope operator Paul Canton, explored the space under the telescope floor, and played with the PANOSETI optics. Even a cloudy night can be educational!
(August 2024) CSL undergraduates took the 2024 UCSD Summer Undergraduate Research Conference by storm, with 13 presentations, including eight by the first STARTastro scholar cohort. The presented work spanned cool stars near the Sun to the detection of the most explosive events in the gamma rays. The summer conference capped an exciting summer of research. Some of the presentations can be found at this video, this video, or this video. Congratulations to our undergraduates on their successful research presentations!
(August 2024) Members of the Cool Star Lab participated in the UCSD Astronomy & Astrophysics booth at the 4th Southeast Art & Science Expo at Malcolm X library in San Diego. This community event engages people of all ages in science, art, technology and exploration. Our booth featured demonstrations on optics, representations of the electromagnetic spectrum, tactile "images" of cosmic sources, and an opportunity to see the sunspots on our currently highly active Sun.