A collaborative team of astronomers led by The University of New Mexico has confirmed a rare gas giant exoplanet, TOI-4465 b, located about 400 light-years from Earth. The discovery was enabled by a worldwide network of citizen scientists and detailed in The Astronomical Journal, with UNM Postdoctoral Fellow Zahra Essack as lead author and Assistant Professor Diana Dragomir as co-author.
T by Dani Rae Wascher
Albuquerque, NM (SPX) Jun 26, 2025
A collaborative team of astronomers led by The University of New Mexico has confirmed a rare gas giant exoplanet, TOI-4465 b, located about 400 light-years from Earth. The discovery was enabled by a worldwide network of citizen scientists and detailed in The Astronomical Journal, with UNM Postdoctoral Fellow Zahra Essack as lead author and Assistant Professor Diana Dragomir as co-author.
TOI-4465 b was initially identified by NASA's Transiting Exoplanet Survey Satellite (TESS) during a single-transit event. Confirming its existence required detecting another transit, a challenge due to its 102-day orbital period and the need for long, uninterrupted observation windows.
"Each transit lasts about 12 hours, but it is incredibly rare to get 12 full hours of dark, clear skies in one location," said Essack. Weather, telescope availability, and the need for continuous observation further complicated the effort.
To meet these challenges, the team coordinated an international campaign involving 24 citizen scientists across 10 countries and support from professional observatories. These participants used personal telescopes to provide time-critical photometric data, capturing brightness dips as the planet passed in front of its star.
Essack emphasized the significance of their participation: "The discovery and confirmation of TOI-4465 b...shows how passionate astronomy enthusiasts can play a direct role in frontier scientific research."
The effort was bolstered by infrastructure from the TESS Follow-up Observing Program Sub Group 1 (TFOP SG1), the Unistellar Citizen Science Network, and the TESS Single Transit Planet Candidate (TSTPC) Working Group led by Dragomir. These platforms offered standardized tools, coordination frameworks, and expertise necessary for high-quality data collection and analysis.
TOI-4465 b is approximately 25% larger in radius than Jupiter, nearly six times more massive, and almost three times as dense. Its mildly elliptical orbit results in surface temperatures ranging from 375 to 478 K (200-400 F), placing it in a temperate regime not well-represented in known exoplanetary populations.
The discovery highlights the importance of studying long-period exoplanets-those with orbital periods over 100 days-which remain scarce due to observational limitations. Essack noted, "Studying these long-period planets gives us insights into how planetary systems form and evolve under more moderate conditions."
TOI-4465 b's unique properties make it an ideal candidate for future atmospheric studies using instruments like the James Webb Space Telescope (JWST), particularly via emission spectroscopy.
Research Report:Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. VI: Confirmation of a Long-Period Giant Planet Discovered with a Single TESS Transit
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