The Extremely Red, Young L Dwarf PSO J318-22: A Free-Floating Planetary-Mass Analog to Directly Imaged Young Gas-Giant Planets

The Extremely Red, Young L Dwarf PSO J318-22: A Free-Floating Planetary-Mass Analog to Directly Imaged Young Gas-Giant Planets

Quote :

We have used Pan-STARRS1 to discover an extremely red late-L dwarf, which has (J-K)_MKO = 2.84 and (J-K)_2MASS = 2.78, making it the reddest known field dwarf and second only to 2MASS J1207-39b among substellar companions. Near-IR spectroscopy shows a spectral type of L7 and reveals a triangular H-band continuum and weak alkali (K I and Na I) lines, hallmarks of low surface gravity. Near-IR astrometry from the Hawaii Infrared Parallax Program gives a distance of 24.6+/-1.4 pc and indicates a much fainter J-band absolute magnitude than field L dwarfs. The position and kinematics of PSO J318-22 point to membership in the beta Pictoris moving group. Evolutionary models give a temperature of 1160 (-40,+30) K and a mass of 6.5 (-1.0, +1.3) Mjup, making PSO J318-22 one of the lowest mass free-floating objects in the solar neighborhood. This object adds to the growing list of low-gravity field L dwarfs and is the first to be strongly deficient in methane relative to its estimated temperature. Comparing their spectra suggests that young L dwarfs with similar ages and temperatures can have different spectral signatures of youth. For the two objects with well constrained ages (PSO J318-22 and 2MASS J0355+11), we find their temperatures are ~400 K cooler than field objects of similar spectral type but their luminosities are comparable, i.e., these young L dwarfs are very red and unusually cool but not "underluminous." Altogether, PSO J318-22 is the first free-floating object with the colors, magnitudes, spectrum, luminosity, and mass that overlap the young dusty planets around HR 8799 and 2MASS J1207-39.

http://arxiv.org/abs/1310.0457

News release:

SpaceRef: A Strange Lonely Planet Found Without a Star

As for calling it a planet rather than a (sub-)brown dwarf... hmmmm...

http://www.spacedaily.com/reports/Distant_worlds_weather_is_mixed_bag_of_hot_dust_and_molten_rain_999.html

"...A team led by the University of Edinburgh used a telescope in Chile to study the weather systems in the distant world - known as PSO J318.5-22 - which is estimated to be around 20 million-years-old.

Researchers captured hundreds of infra-red images of the object as it rotated over a 5-hour period. By comparing the brightness of PSO J318.5-22 with neighbouring bodies, the team discovered that it is covered in multiple layers of thick and thin cloud. These cause changes to the brightness of the distant world as it rotates, the team says..."

Paper on arXiv : http://arxiv.org/abs/1510.07625