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γ Hydri, Latinised as Gamma Hydri, is a solitary, red-hued star in the constellation Hydrus. It has an apparent visual magnitude of 3.26, making it easily visible to the naked eye at night. Based upon an annual parallax shift of 15.24 mas as measured from Earth, the system is located about 214 light-years from the Sun.

This is an evolved red giant star with a stellar classification of M1 III, and is most likely on the asymptotic giant branch of the HR diagram. It is a semiregular variable that pulsates between magnitudes 3.26 and 3.33, although its period is not known precisely. It has about the same mass as the Sun, but has expanded to around 62 times the Sun's radius. The star is radiating 513 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,499 K.

References

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2. ^ Ducati, J. R. (2002), "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system", CDS/ADC Collection of Electronic Catalogues, 2237, Bibcode:2002yCat.2237....0D.
3. ^ Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
4. ^ Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
6. Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics, 430: 303–311, arXiv:astro-ph/0409683, Bibcode:2005A&A...430..303C, doi:10.1051/0004-6361:20041440, S2CID 12136256.
7. ^ Cruzalèbes, P.; et al. (September 2013), "Fundamental parameters of 16 late-type stars derived from their angular diameter measured with VLTI/AMBER", Monthly Notices of the Royal Astronomical Society, 434 (1): 437–450, arXiv:1306.3288, Bibcode:2013MNRAS.434..437C, doi:10.1093/mnras/stt1037, S2CID 49573767.
8. "gam Hyi". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-08-18.{{cite web}}: CS1 maint: postscript (link)
9. 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.
10. Eggen, O. J. (1992), "Asymptotic giant branch stars near the sun", The Astronomical Journal, 104: 275, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
11. Tabur, V.; Bedding, T. R.; Kiss, L. L.; Moon, T. T.; Szeidl, B.; Kjeldsen, H. (2009), "Long-term Photometry and Periods for 261 Nearby Pulsating M Giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–61, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380.

v t e Constellation of Hydrus
List of stars in Hydrus Hydrus in Chinese astronomy
Stars	Bayer α β γ δ ε ζ η η θ ι κ λ μ ν π π σ τ τ Variable VW HD 1237 10180 20003 Other AB8 SMSS J0313−6708 WISEPC J014807.25−720258.7
Exoplanets η Hydri b GJ 3021 b HD 10180 c
Star clusters NGC 602 NGC 643 NGC 1466
Galaxies	NGC 646 802 813 Other KKs 3 PGC 6240 Small Magellanic Cloud (mostly in Tucana) Large Magellanic Cloud (mostly in Dorado, partly in Mensa)
Category

• M-type giants
• Semiregular variable stars
• Hydrus
• Bayer objects
• Durchmusterung objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects
• Asymptotic-giant-branch stars