Loading AI tools
Star in the constellation Gemini From Wikipedia, the free encyclopedia
81 Geminorum is a binary star[8] system in the northern constellation of Gemini. It has the Bayer designation g Geminorum, while 81 Geminorum is its Flamsteed designation. This system is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.89.[2] The pair are located approximately 360 light years away from the Sun, based on parallax,[1] and are moving further away with a radial velocity of +83 km/s, having come to within an estimated 164 light-years of the Earth nearly a million years ago.[2] 81 Geminorum lies close enough to the ecliptic to undergo lunar occultations.[4][9]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Gemini |
Right ascension | 07h 46m 07.45014s[1] |
Declination | +18° 30′ 36.0217″[1] |
Apparent magnitude (V) | 4.89[2] |
Characteristics | |
Spectral type | K4 III[3] |
B−V color index | 1.425±0.034[2] |
Astrometry | |
Radial velocity (Rv) | +83.13±0.08[2] km/s |
Proper motion (μ) | RA: −79.687[1] mas/yr Dec.: −53.551[1] mas/yr |
Parallax (π) | 9.1500 ± 0.2963 mas[1] |
Distance | 360 ± 10 ly (109 ± 4 pc) |
Absolute magnitude (MV) | −0.19[2] |
Orbit[4] | |
Period (P) | 1,519.7±1.7 d |
Semi-major axis (a) | ≥ 142±3 Gm |
Eccentricity (e) | 0.325±0.015 |
Periastron epoch (T) | 41,584±11 MJD |
Argument of periastron (ω) (secondary) | 73±3° |
Semi-amplitude (K1) (primary) | 7.21±0.13 km/s |
Details | |
81 Gem A | |
Mass | 1.22[5] M☉ |
Radius | 33.7+2.0 −1.7[1] R☉ |
Luminosity | 287.3±10.5[1] L☉ |
Surface gravity (log g) | 1.94[6] cgs |
Temperature | 4,095+109 −115[1] K |
Metallicity [Fe/H] | −0.18±0.06[2] dex |
Age | 6.32[5] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
The variable velocity of this system was first suspected at the Dominion Astrophysical Observatory in 1921, then confirmed by the Lick Observatory in 1922. It is a single-lined spectroscopic binary with an orbital period of 4.2 years and an eccentricity of 0.325.[4] The visible component is an aging giant star with a stellar classification of K4 III,[3] having exhausted the supply of hydrogen at its core then expanded to 34[1] times the Sun's radius. It is over six[5] billion years old with 1.22[5] times the mass of the Sun. This is a candidate alpha-enhanced star that displays a significant overabundance of silicon.[10] The star is radiating around 287[1] times the Sun's luminosity from its bloated photosphere at an effective temperature of 4,095 K.[1]
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.