81 Geminorum

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81 Geminorum
Gemini constellation map.svg
Red circle.svg
Location of 81 Geminorum (circled)
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
g Gem, 81 Gem, BD+18°1733, FK5  1200, GC  10456, HD  62721, HIP  37908, HR  3003, SAO  97221, WDS J07461+1831AB [7]
Database references
SIMBAD data

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]

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]

Related Research Articles

<span class="mw-page-title-main">Castor (star)</span> Sextuple star system in Gemini

Castor is the second-brightest object in the zodiac constellation of Gemini. It has the Bayer designation α Geminorum, which is Latinised to Alpha Geminorum and abbreviated Alpha Gem or α Gem. With an apparent visual magnitude of 1.93, it is one of the brightest stars in the night sky. Castor appears singular to the naked eye, but it is actually a sextuple star system organized into three binary pairs. Although it is the 'α' (alpha) member of the constellation, it is fainter than 'β' (beta) Geminorum, Pollux.

<span class="mw-page-title-main">Zeta Geminorum</span> Star in the constellation Gemini

Zeta Geminorum is a bright star with cluster components, distant optical components and a likely spectroscopic partner in the zodiac constellation of Gemini — in its south, on the left 'leg' of the twin Pollux. It is a classical Cepheid variable star, of which over 800 have been found in our galaxy. As such its regular pulsation and luminosity and its relative proximity means the star is a useful calibrator in computing the cosmic distance ladder. Based on parallax measurements, it is approximately 1,200 light-years from the Sun.

37 Geminorum is a solitary Sun-like star located at the northwest part of the northern constellation of Gemini, about three degrees to the east of the bright star Epsilon Geminorum. The apparent visual magnitude of 37 Geminorum is 5.74, which is just bright enough to be visible to the naked eye on a dark night. It is located at a distance of 57 light years from the Sun based on parallax. This star is drifting closer with a radial velocity of −15 km/s, and is predicted to come as near as 13.8 light-years in approximately a million years. It is positioned close enough to the ecliptic to be subject to lunar occultations, such as happened on April 8, 1984.

3 Cancri is a single star in the zodiac constellation of Cancer, located around 810 light years from the Sun. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.60. This object is moving further from the Earth with a heliocentric radial velocity of +39.5 km/s, and may be a member of the Hyades group. It is located near the ecliptic and thus is subject to lunar eclipses.

HD 142 is a wide binary star system in the southern constellation of Phoenix. The main component has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.7. The system is located at a distance of 85.5 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +6 km/s.

Lambda Geminorum, Latinized from λ Geminorum, is a candidate multiple star system in the constellation Gemini. It is visible to the naked eye at night with a combined apparent visual magnitude of 3.57. The distance to this system is 101 light years based on parallax, and it is drifting closer with a radial velocity of –7.4 km/s. It is a member of what is suspected to be a trailing tidal tail of the Hyades Stream.

5 Tauri is a binary star in the zodiac constellation of Taurus, located approximately 530 light years from the Sun. It is visible to the naked eye as a faint orange-hued star with an apparent visual magnitude of +4.14. It is moving further from the Earth with a heliocentric radial velocity of +14 km/s.

HD 222582 is a multiple star system in the equatorial constellation of Aquarius. It is invisible to the naked eye with an apparent visual magnitude of 7.7, but can be viewed with binoculars or a small telescope. The system is located at a distance of 138 light years from the Sun based on parallax, and it is drifting further away with a radial velocity of +12 km/s. It is located close enough to the ecliptic that it is subject to lunar occultations.

<span class="mw-page-title-main">30 Vulpeculae</span> Star in the constellation Vulpecula

30 Vulpeculae is a binary star system in the northern constellation of Vulpecula, located mid-way between Epsilon Cygni and a diamond-shaped asterism in Delphinus. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.91. The system is located approximately 350 light years away from the Sun based on parallax, and is drifting further away with a mean radial velocity of +30 km/s. The system has a relatively high proper motion, traversing the celestial sphere at the rate of 0.186 arc seconds per annum.

6 Persei is a binary star system in the northern constellation of Andromeda. It is faintly visible to the naked eye with an apparent visual magnitude of 5.29. The system is located 182 light years from Earth, as determined from its annual parallax shift of 17.9 mas. It is moving further away with a heliocentric radial velocity of +42 km/s. The system has a relatively high rate of proper motion, traversing the celestial sphere at the rate of 0.386 arcsecond/year.

Xi<sup>1</sup> Ceti Star in the constellation Cetus

Xi1 Ceti , Latinized from ξ1 Ceti, is a binary star system located in the equatorial constellation of Cetus. It is visible to the naked eye with a combined apparent visual magnitude of +4.36. The distance to this system is approximately 340 light years based on parallax measurements, and it is drifting closer to the Sun with a radial velocity of −4 km/s. The proximity of the star to the ecliptic means it is subject to lunar occultations.

HD 106760 is a single-lined spectroscopic binary star system in the northern constellation of Coma Berenices. It is faintly visible to the naked eye, having an apparent visual magnitude of 4.99. The system is located around 318 light years away, as determined from its annual parallax shift of 10.2417 mas. It is moving closer with a heliocentric radial velocity of −40 km/s, and is expected to come as close as 259 ly in about 772,000 years.

HD 175535 is a binary star system in the northern circumpolar constellation of Draco. It has an apparent visual magnitude of 4.92, which is bright enough to be faintly visible to the naked eye. The system is located about 302 light years away, as determined from its annual parallax shift of 10.8 mas. It is moving further from the Earth with a heliocentric radial velocity of +8.5 km/s.

<span class="mw-page-title-main">1 Geminorum</span> Triple star system in the constellation Gemini

1 Geminorum is a star in the constellation Gemini. Its apparent magnitude is 4.15.

38 Geminorum is a binary star system in the northern zodiac constellation of Gemini. It has the Bayer designation e Geminorum, while 38 Geminorum is the Flamsteed designation. This system is visible to the naked eye as a faint, white-hued point of light with an apparent visual magnitude of 4.71. The primary component is a magnitude 4.75 star, while the secondary is magnitude 7.80. The system is located about 98 light years away from the Sun based on parallax, and is drifting further away with a radial velocity of +16 km/s. It is a potential member of the Tucana–Horologium stellar kinematic group.

g Herculis Star in the constellation Hercules

g Herculis is a binary star system in the northern constellation of Hercules. It has the Flamsteed designation 30 Herculis, while g Herculis is the Bayer designation. This system is visible to the naked eye as a faint, red-hued point of light. Based upon a measured parallax of 9.2 mas, it is located around 354 light years away from the Sun. The system is moving further from the Earth with a heliocentric radial velocity of 1.5 km/s.

23 Orionis is a double star located around 1,200 light-years away from the Sun in the equatorial constellation of Orion. It is visible to the naked eye as a dim, blue-white-hued point of light with a combined apparent visual magnitude of 4.99. The pair are moving away from the Earth with a heliocentric radial velocity of +18 km/s, and they are members of the Orion OB1 association, subgroup 1a.

<span class="mw-page-title-main">RR Ursae Minoris</span> Star in the constellation Ursa Minor

RR Ursae Minoris, abbreviated RR UMi, is a binary star system in the northern circumpolar constellation of Ursa Minor. It can be viewed with the naked eye, typically having an apparent visual magnitude of around 4.710. Based upon an annual parallax shift of 10.0 mas as seen from Earth's orbit, it is located 330 light years away. The system is moving further from the Sun with a heliocentric radial velocity of +6 km/s.

4 Ursae Minoris is a binary star system in the northern circumpolar constellation Ursa Minor. It is faintly visible to the naked eye with an apparent visual magnitude of 4.80. Based upon an annual parallax shift of 7.14±0.42 mas as seen from Earth's orbit, it is located roughly 460 light years from the Sun. It is moving further away with a heliocentric radial velocity of +5.9 km/s.

16 Serpentis is a binary star system in the Serpens Caput portion of the equatorial constellation of Serpens, located 228 light years from the Sun. It is visible to the naked eye as a fain, orange-hued star with an apparent visual magnitude of 5.261. The system is moving further from the Earth with a heliocentric radial velocity of +3 km/s.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  2. 1 2 3 4 5 6 7 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv: 1108.4971 , Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID   119257644.
  3. 1 2 Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  4. 1 2 3 Griffin, R. F. (September 1982), "Photoelectric radial velocities. Paper IX. The orbits of the spectroscopic binaries 81 and chi Gem", Monthly Notices of the Royal Astronomical Society, 200: 1161–1168, Bibcode:1982MNRAS.200.1161G, doi: 10.1093/mnras/200.4.1161 .
  5. 1 2 3 4 Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, arXiv: 1507.01466 , Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID   118505114.
  6. ↑ Prugniel, Ph.; et al. (July 2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv: 1104.4952 , Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769, S2CID   54940439.
  7. ↑ "81 Gem". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 19 August 2017.
  8. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society , 389 (2): 869–879, arXiv: 0806.2878 , Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID   14878976.
  9. ↑ Cassar, L.; et al. (March 1989), "Lunar Occultations of IRAS Point Sources, 1991--2000", Astrophysical Journal Supplement, 69: 651, Bibcode:1989ApJS...69..651C, doi: 10.1086/191323 .
  10. ↑ Franchini, M.; et al. (2004). "Synthetic Lick Indices and Detection of α-enhanced Stars. II. F, G, and K Stars in the -1.0 < [Fe/H] < +0.50 Range". The Astrophysical Journal. 613 (1): 312. Bibcode:2004ApJ...613..312F. doi: 10.1086/422909 . S2CID   250877375.
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