Gamma Hydrae
 Location of γ Hydrae (circled) |
|
| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Hydra |
| Right ascension | 13h 18m 55.29719s[1] |
| Declination | –23° 10′ 17.4514″[1] |
| Apparent magnitude (V) | +2.993[2] |
| Characteristics | |
| Spectral type | G8 III[3] |
| U−B color index | +0.645[2] |
| B−V color index | +0.920[2] |
| Astrometry | |
| Radial velocity (Rv) | –5.4[4] km/s |
| Proper motion (μ) | RA: +68.99[1] mas/yr Dec.: –41.85[1] mas/yr |
| Parallax (π) | 24.37 ± 0.15[1] mas |
| Distance | 133.8 ± 0.8 ly (41.0 ± 0.3 pc) |
| Absolute magnitude (MV) | –0.15[3] |
| Details | |
| Mass | 2.94[3] M☉ |
| Radius | 13[5] R☉ |
| Luminosity | 115[3] L☉ |
| Surface gravity (log g) | 3.02[6] cgs |
| Temperature | 5,087[6] K |
| Metallicity [Fe/H] | –0.06[6] dex |
| Rotational velocity (v sin i) | 8[7] km/s |
| Age | 372[3] Myr |
| Other designations | |
Gamma Hydrae (γ Hya, γ Hydrae) is a star in the equatorial constellation of Hydra. It has an apparent visual magnitude of 3.0,[2] placing it second in brightness among the members of this generally faint constellation. Based upon parallax measurements made during the Hipparcos mission, this star is at a distance of around 133.8 light-years (41.0 parsecs) from Earth.[1]
The spectrum matches a stellar classification of G8 III,[3] with the luminosity class of III indicating it has evolved into a giant star after exhausting the supply of hydrogen at its core. The interferometry-measured uniform disk angular diameter of this star is 2.96 ± 0.15 mas,[9] which, at its estimated distance, equates to a physical radius of roughly 13 times the radius of the Sun.[5] It has nearly three[3] times the mass of the Sun and is radiating 115[3] times the Sun's luminosity from its outer atmosphere at an effective temperature of 5,019 K.[3] This heat gives it the yellow glow of a K-type star.[10] Despite having reached an advanced stage in its evolution, it is considerably younger than the Sun with an age of around 372 million years. This is because higher mass stars consume their nuclear fuel at a more rapid rate.[3]
In culture
γ Hya appears on the flag of Brazil, symbolising the state of Acre.[11]
In the television show Star Trek: The Original Series, the starship Enterprise visits a planet named Gamma Hydrae IV in the episode "The Deadly Years". Within the same fictional setting, a region of space designated "Section 10" of Gamma Hydrae lies within a demilitarized area called the Klingon Neutral Zone. This comes into play during the Kobayashi Maru scenario depicted in the film Star Trek II: The Wrath of Khan.
References
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