| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
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|---|---|
| Constellation | 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 | |
| Data sources: | |
| Hipparcos Catalogue, CCDM (2002), GCVS (4.2) |
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Eta Geminorum (η Gem, η Geminorum) is a triple star system in the constellation Gemini. It has the traditional names Tejat Prior, Propus and Praepes and Pish Pai (from the Persian Pīshpāy, پیشپای, meaning foreleg).[1]
This star, along with γ Gem (Alhena), μ Gem (Tejat Posterior), ν Gem and ξ Gem (Alzirr) were Al Han'ah, "the brand" (on the neck of the camel). They also were associated in Al Nuḥātai, the dual form of Al Nuḥāt, "a Camel's Hump"[2]
In Chinese astronomy, Tejat Prior is called 钺, Pinyin: Yuè, meaning Battle Axe, because this star is marking itself and stand alone in Battle Axe asterism, Well mansion (see : Chinese constellation)[3][4]
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.[5],[6]
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.
USS Propus (AK-132) was a United States Navy Crater class cargo ship named after the star.
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