Magnitude 5.8 Apparent magnitude (V) 5.8 | Constellation Sagitta | |
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15 Sagittae (15 Sge) is a 6th magnitude star in the constellation Sagitta. Considered a solar analog, it was the target of the first radial velocity survey from Lick Observatory, which found a drift due to a companion; In 2002, the cause of this was found to be brown dwarf companion B via direct imaging.
15 Sagittae B
15 Sagittae B is a high-mass substellar L dwarf of spectral class L4 ± 1.5, only a few Jupiter masses below the limit for stars, in a long-period orbit around the primary star. Imaged by the Keck telescope, was the first brown dwarf candidate orbiting a sun-like star detected via imaging and is currently the only known companion brown dwarf which both has a significant radial velocity trend on the primary that has also been imaged.
The brown dwarf was originally thought to have a semi-major axis of 14 AU and a circular orbit viewed from pole-on, but ten more years of observations found that the brown dwarf's orbit is viewed from nearly edge-on, is significantly eccentric and appeared to be moving in a circular orbit when first discovered, but is now approaching the primary as viewed from Earth.