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G-type main sequence star in the constellation Sagitta From Wikipedia, the free encyclopedia
15 Sagittae (15 Sge) is a star in the northern constellation Sagitta, located around 58 light years away from the Sun. It is visible to the naked eye as a faint, yellow-hued star with an apparent visual magnitude of 5.80.[2] 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.[6] In 2002, the cause of this was found to be brown dwarf companion B via direct imaging.[7]
Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Sagitta |
Right ascension | 20h 04m 06.22091s[1] |
Declination | +17° 04′ 12.6774″[1] |
Apparent magnitude (V) | 5.80[2] |
Characteristics | |
Evolutionary stage | main sequence |
Spectral type | G0V + L4[3] |
B−V color index | 0.600±0.005[2] |
Astrometry | |
Radial velocity (Rv) | 4.57±0.1[4] km/s |
Proper motion (μ) | RA: −387.590[1] mas/yr Dec.: −419.542[1] mas/yr |
Parallax (π) | 56.426 ± 0.069 mas[1] |
Distance | 57.80 ± 0.07 ly (17.72 ± 0.02 pc) |
Absolute magnitude (MV) | 4.55[2] |
Orbit[3] | |
Period (P) | 73.3+2.2 −3.9 yr |
Semi-major axis (a) | 18.3+0.4 −0.5 AU |
Eccentricity (e) | 0.50±0.01 |
Inclination (i) | 97.3+0.4 −0.5° |
Details[3] | |
15 Sge A | |
Mass | 1.08±0.04 M☉ |
Radius | 1.115±0.021 R☉ |
Luminosity | 1.338±0.032 L☉ |
Surface gravity (log g) | 4.42±0.06 cgs |
Temperature | 5,883±59 K |
Metallicity [Fe/H] | 0.05±0.07 dex |
Rotation | 17.5±2.3 |
Rotational velocity (v sin i) | 4.42±0.06 km/s |
Age | 2.5±1.8 Gyr |
15 Sge B | |
Mass | 68.7+2.4 −3.1 MJup |
Radius | 1.0±0.4 RJup |
Luminosity | 0.000075±0.000016 L☉ |
Temperature | 1,510–1,850 K |
Other designations | |
Database references | |
SIMBAD | data |
The companion is a high-mass substellar brown 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,[8] 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.[3]
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