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Large Gas Giant or Small Brown Dwarf Discovered Near the Galactic Bulge Using Microlensing

Accepted submission by takyon at 2017-11-09 09:23:52

Scientists have used the Spitzer Space Telescope [] to find a possible exoplanet or brown dwarf candidate, OGLE-2016-BLG-1190Lb, around 22,000 light years away near the center of the Milky Way galaxy. Spitzer is currently using transit photometry and gravitational microlensing [] to find exoplanets, a use the telescope wasn't originally designed for. Spitzer recently discovered five of the seven exoplanets around TRAPPIST-1 [] using the transit photometry method.

OGLE-2016-BLG-1190Lb is likely to be the first exoplanet Spitzer has found in the Milky Way's Galactic bulge [] using gravitational microlensing. At an estimated 13.4 ± 0.9 Jupiter masses, the object is right near the deuterium burning limit, the boundary dividing large gas giants from brown dwarfs [].

The paper explains the significance of the discovery:

The discovery of Spitzer microlensing planet OGLE-2016-BLG-1190Lb is remarkable in five different respects. First, it is the first planet in the Spitzer Galactic-distribution sample that likely lies in the Galactic bulge, which would break the trend from the three previous members of this sample. Second, it is precisely measured to be right at the edge of the brown dwarf desert. Since the existence of the brown dwarf desert is the signature of different formation mechanisms for stars and planets, the extremely close proximity of OGLE-2016-BLG-1190Lb to this desert raises the question of whether it is truly a "planet" (by formation mechanism) and therefore reacts back upon its role tracing the Galactic distribution of planets, just mentioned above. Third, it is the first planet to enter the Spitzer "blind" sample whose existence was recognized prior to its choice as a Spitzer target. This seeming contradiction was clearly anticipated by Yee et al. (2015b) when they established their protocols for the Galactic distribution experiment. The discovery therefore tests the well-defined, but intricate procedures devised by Yee et al. (2015b) to deal with this possibility. Fourth, it is the first planet (and indeed the first microlensing event) for which the well-known microlens-parallax degeneracy has been broken by observations from two satellites. Finally, it is the first microlensing planet for which a complete orbital solution has been attempted. While this attempt is not completely successful in that a one-dimensional degeneracy remains, it is an important benchmark on the road to such solutions.

Also at Newsweek [] and BGR [].

OGLE-2016-BLG-1190Lb: First Spitzer Bulge Planet Lies Near the Planet/Brown-Dwarf Boundary []

Related: Seven Earth-Sized Exoplanets, Including Three Potentially Habitable, Identified Around TRAPPIST-1 []
Scientists Improve Brown Dwarf Weather Forecasts []

Original Submission