Eta Geminorum

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Multiple star
η Geminorum
Left μ Geminorum, in the middle the supernova remnant IC 443, right η Geminorum
Left μ Geminorum , in the middle the supernova remnant IC 443 , right η Geminorum
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Twins
Right ascension 06 h 14 m 52.66 s
declination + 22 ° 30 ′ 24.5 ″
Apparent brightness 3.15 to 3.9 mag
Typing
B − V color index +1.61 
U − B color index +1.66 
R − I index +1.31 
Spectral class M3 IIIab
Variable star type SRA + EA 
Astrometry
Radial velocity (22.39 ± 0.36) km / s
parallax (8.48 ± 1.23)  mas
distance (380 ± 70)  ly
120  pc
Visual absolute brightness M vis −1.9 mag
Proper movement 
Rec. Share: (−62.46 ± 1.06)  mas / a
Dec. portion: (−12.12 ± 0.70)  mas / a
Physical Properties
Luminosity

Aa: 3200  L ☉

Effective temperature Aa: 3550  K
Other names
and catalog entries
Bayer name η Geminorum
Flamsteed name 7 Geminorum
Bonn survey BD + 22 ° 1241
Bright Star Catalog HR 2216 [1]
Henry Draper Catalog HD 42995 [2]
Hipparcos catalog HIP 29655 [3]
SAO catalog SAO 78135 [4]
Tycho catalog TYC 1877-1716-1 [5]
2MASS catalog 2MASS J06145266 + 2230244 [6]
Other names Propus

Eta Geminorum (short η Gem ; also: Propus , originally Greek for “front foot”) is a star system in the constellation Gemini, about 380 light years away . Its main component is a red giant of the spectral type M3. Eta Geminorum is also a semi-regularly variable star whose apparent magnitude fluctuates between 3.15 mag and 3.9 mag with a period of 233 days.

As a star near the ecliptic, Eta Geminorum can be covered by the moon and (very rarely) by planets . The last occultation by a planet was on July 27, 1910 by the planet Venus , the penultimate one on July 11, 1837 by Mercury .

The star also bears the historical proper name Tejat Prior .

properties

Eta Geminorum is a triple star system . The system is designed in such a way that component A itself is a spectroscopic double star , with component Aa being the red giant with a mass of 6.3  M ☉ . The companion Ab has a mass of about 2.1 M ☉ and the third star, component B, of 1.2 M ☉ . Little is known about the components Ab and B because they are outshone by the red giant Aa.

Individual evidence

  1. ↑ a b c d e f g h eta Gem. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed on August 2, 2018 .
  2. ↑ a b c d eta Gem. In: VSX. AAVSO, accessed August 2, 2018 .
  3. ↑ Jenna Ryon, Matthew D. Shetrone, Graeme H. Smith: Comparing the Ca ii H and K Emission Lines in Red Giant Stars . In: Publications of the Astronomical Society of the Pacific . 121, No. 882, August 2009, p. 842. arxiv : 0907.3346 . bibcode : 2009PASP..121..842R . doi : 10.1086 / 605456 .
  4. ^ A b A. Jorissen, A. Frankowski, B. Famaey, S. Van Eck: Spectroscopic binaries among Hipparcos M giants. III. The eccentricity - period diagram and mass-transfer signatures . In: Astronomy and Astrophysics . 498, No. 2, 2009, p. 489. arxiv : 0901.0938 . bibcode : 2009A & A ... 498..489J . doi : 10.1051 / 0004-6361 / 200810703 .
  5. ^ AA Tokovinin: MSC - a catalog of physical multiple stars . In: Astronomy and Astrophysics Supplement Series . 124, 1997, p. 75. bibcode : 1997A & AS..124 ... 75T . doi : 10.1051 / aas: 1997181 .
  6. ^ MSC in VizieR. Retrieved August 2, 2018 .