Kapteyn's Star
Subdwarf star in the constellation Pictor / From Wikipedia, the free encyclopedia
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Kapteyn's Star is a class M1 red subdwarf about 12.83 light-years from Earth in the southern constellation Pictor; it is the closest halo star to the Solar System. With an apparent magnitude of nearly 9, it is visible through binoculars or a telescope.[9]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Pictor |
Right ascension | 05h 11m 40.58984s[1] |
Declination | −45° 01′ 06.3617″[1] |
Apparent magnitude (V) | 8.853±0.008[2] |
Characteristics | |
Spectral type | sdM1[3] or M1.5V[2][4] |
U−B color index | +1.21[5] |
B−V color index | 1.57±0.012[2] |
Variable type | BY Dra[6] |
Astrometry | |
Radial velocity (Rv) | 245.05±0.13[1] km/s |
Proper motion (μ) | RA: +6,491.223 mas/yr[1] Dec.: −5,708.614 mas/yr[1] |
Parallax (π) | 254.1986 ± 0.0168 mas[1] |
Distance | 12.8308 ± 0.0008 ly (3.9339 ± 0.0003 pc) |
Absolute magnitude (MV) | 10.89[3] |
Details[2] | |
Mass | 0.281±0.014 M☉ |
Radius | 0.291±0.025 R☉ |
Luminosity | 0.012 L☉ |
Surface gravity (log g) | 4.96±0.13 cgs |
Temperature | 3,570±80 K |
Metallicity [Fe/H] | −0.86±0.05 dex |
Rotation | 124.71±0.19 d[7] |
Rotational velocity (v sin i) | 9.15[8] km/s |
Age | 11.5+0.5 −1.5 Gyr |
Other designations | |
Database references | |
SIMBAD | The star |
planet b | |
planet c |
Its diameter is 30% of the Sun's, but its luminosity just 1.2% that of the Sun. It may have once been part of the globular cluster Omega Centauri, itself the likely core of a dwarf galaxy swallowed up by the Milky Way in the distant past. The discovery of two planets—Kapteyn b and Kapteyn c—was announced in 2014,[10] but had a mixed history of rejections and confirmations, until a 2021 study refuted both planets. The "planets" are in fact artifacts of the star's rotation and activity.[7]