The coolest known brown dwarfs are our best analogs to extrasolar gas-giant planets. The prolific detections of such cold substellar objects in the past 2 years have spurred intensive follow-up, but the lack of accurate distances is a key gap in our understanding. We present a large sample of precise distances based on homogeneous mid-infrared astrometry that robustly establishes absolute fluxes, luminosities, and temperatures. The coolest brown dwarfs have temperatures of 400 to 450 kelvin and masses almost equal to 5 to 20 times that of Jupiter, showing they bridge the gap between hotter brown dwarfs and gas-giant planets. At these extremes, spectral energy distributions no longer follow a simple correspondence with temperature, suggesting an increasing role of other physical parameters, such as surface gravity, vertical mixing, clouds, and metallicity.
- Pub Date:
- September 2013
- ASTRONOMY Astronomy, Planetary-Science, Chemistry;
- Astrophysics - Solar and Stellar Astrophysics
- Accepted to Science, appears in Science Express. These parallax results will soon be added to the Database of Ultracool Parallaxes: https://www.cfa.harvard.edu/~tdupuy/plx/