Eta Geminorum

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Eta Geminorum A/B
Observation data
Epoch J2000.0 (ICRS)
Constellation
(pronunciation)		 Gemini
Right ascension 06h 14m 52.657 / 52.567s
Declination +22° 30′ 24.48 / 24.51″
Apparent magnitude (V) 3.15 to 3.9 / 8.8
Absolute magnitude (V) -2.0 to -1.2 / 3.6
Distance 350±70 ly
(110±20 pc)
Spectral type M3IIIab / G0
Other designations
Propus, Praepes, Tejat Prior, η Geminorum, η Gem, 7 Geminorum, 7 Gem, HD 42995, HR 2216, BD+22°1241, HIP 29655, SAO 78135, CCDM J06149+2230A/B, ADS 4841A/B
Data sources:
Hipparcos Catalogue,
CCDM (2002),
GCVS (4.2)

Eta Geminorum (η Gem / η Geminorum) is a triple star system in the constellation Gemini. It also has the traditional names Tejat Prior, Propus and Praepes.

Eta Geminorum A is a spectroscopic binary. The primary is a semiregular variable star of type SRA whose brightness changes with a period of 234 days between magnitude +3.15 and +3.9. It is located 350 light years from the Sun and is a red giant of the spectral type M3. The secondary, probably a class B, orbits with a period of 8.2 years. Eta Geminorum B, a class G dwarf, orbits the pair with a period of at least 700 years.[1],[2]

Eta Geminorum is near the ecliptic, so it can be occulted by the Moon and very rarely by planets. The last occultation by a planet took place on July 27, 1910 by Venus, and the next to last on July 11, 1837 by Mercury.

[edit] References

  1. ^ The Spectrographic Orbit and Light-Variations of η Geminorum, Dean B. McLaughlin and Suzanne E. A. van Dijke, Astrophysical Journal 100 (July 1944), pp. 63–68.
  2. ^ Eta Geminorum at Jim Kaler's STARS.