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.
| Companion | Mass |
Radius |
Luminosity |
Temperature |
Orbital period |
Semimajor axis |
Orbital ecc. |
Inclination |
Discovery year |
|---|---|---|---|---|---|---|---|---|---|
| B | 68.7+2.4 −3.1 |
1.0 ± 0.4 | 0.000075 |
1510-1850 | 73.3+2.2 −3.9 |
18.3+0.4 −0.5 |
0.50 |
97.3 +0.4 −0.5 |
2002 |
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