Three Thousand Motion-confirmed L and T Dwarf Candidates from the Backyard Worlds: Planet 9 Citizen Science Project
Authors:
- Adam C. SchneiderASAdam C. Schneider
- Marc J. KuchnerMKMarc J. Kuchner
- Jacqueline K. FahertyJFJacqueline K. Faherty
- Aaron M. MeisnerAMAaron M. Meisner
- J. Davy KirkpatrickJKJ. Davy Kirkpatrick
- Adam J. BurgasserABAdam J. Burgasser
- Daniella Bardalez GagliuffiDGDaniella Bardalez Gagliuffi
- Thomas P. BickleTBThomas P. Bickle
- Dan CaseldenDCDan Caselden
- Sarah L. CasewellSCSarah L. Casewell
- Jonathan GagnéJGJonathan Gagné
- Easton J. HonakerEHEaston J. Honaker
Open Access
- 11 May 2026
- journal article
- Published by American Astronomical Society in The Astronomical Journal
- Vol. 171 (6) , 341
Abstract
The Backyard Worlds: Planet 9 citizen science project uses data from the Wide-field Infrared Survey Explorer to detect infrared objects with significant motion. In this work, we present the majority of the L and T dwarf candidates discovered through this effort. For each candidate, we provide proper motion measurements as well as optical, near-infrared, and mid-infrared photometry (when available), photometric spectral types and distance estimates. 3006 new motion-confirmed discoveries are presented in this work, 2357 with L-type photometric spectral types and 649 with T-type photometric spectral types. We also present an additional 80 objects as likely L or T dwarfs based on available photometry, but for which a significant motion measurement could not be obtained. We identify 28 objects in this sample as new comoving companions to higher-mass stars, and an additional nine sources that are candidate binary systems made up of two ultracool dwarfs of L type or later. Follow-up spectroscopic observations will be necessary to confirm spectral types and further characterize the sources discovered through this project. This work presents the largest single sample of motion-confirmed L and T dwarf discoveries to date, which would more than double the number of known L and T dwarfs, if confirmed. We wish to sincerely thank our citizen scientist collaborators for their monumental efforts that have directly impacted this project’s success.Keywords
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