Article · Wikipedia archive · Last revised Aug 1, 2026

Phi1 Hydrae

Phi1 Hydrae, Latinized from φ1 Hydrae, is a yellow-hued star in the constellation Hydra. Its apparent magnitude is 7.61, making it too faint to be seen with the naked eye. Based upon an annual parallax shift of 12.3 mas as seen from Earth, it is located about 264 light-years from the Sun. It forms a triangle with the brighter φ2 Hydrae and φ3 Hydrae, between μ Hydrae and ν Hydrae.

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Aug 1, 2026
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Phi1 Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra1
Right ascension 10h 32m 41.15960s2
Declination −16° 57′ 31.4112″2
Apparent magnitude (V) 7.613
Characteristics
Evolutionary stage subgiant2
Spectral type G2 V4
Astrometry
Radial velocity (Rv)+15.8±0.35 km/s
Proper motion (μ) RA: −20.9642 mas/yr
Dec.: −87.8702 mas/yr
Parallax (π)12.3313±0.0315 mas2
Distance264.5 ± 0.7 ly
(81.1 ± 0.2 pc)
Absolute magnitude (MV)+3.301
Details
Mass1.126 M☉
Radius2.16 R☉
Luminosity5.06 L☉
Surface gravity (log g)3.866 cgs
Temperature6,0236 K
Metallicity [Fe/H]+0.15±0.057 dex
Age4.17 Gyr
Other designations
φ1 Hya, 43 Hydrae, BD−16°3078, HD 91369, HIP 51614, SAO 1560478
Database references
SIMBADdata

Phi1 Hydrae, Latinized from φ1 Hydrae, is a yellow-hued star in the constellation Hydra. Its apparent magnitude is 7.61,3 making it too faint to be seen with the naked eye. Based upon an annual parallax shift of 12.3 mas as seen from Earth,2 it is located about 264 light-years from the Sun. It forms a triangle with the brighter φ2 Hydrae and φ3 Hydrae, between μ Hydrae and ν Hydrae.

Phi1 Hydrae is an ordinary G-type main-sequence star, having a Sun-like stellar classification of G2 V4 and a photospheric temperature only slightly higher than the sun.6 However, the mass is 34% greater than the Sun's, and it is radiating five times the Sun's luminosity.6 Phi1 Hydrae is moving further from the Sun with a radial velocity of +15.8 km/s.5

References

References

  1. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. Høg, E.; et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, 355: L27, Bibcode:2000A&A...355L..27H.
  4. Houk, N.; Smith-Moore, M. (1988), "Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars", Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, 4, Ann Arbor, MI, USA: Department of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  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. Stassun, Keivan G.; et al. (2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467.
  7. Bensby, T.; Feltzing, S.; Oey, M. S. (2014), "Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the solar neighbourhood", Astronomy & Astrophysics, 562 (A71): 28, arXiv:1309.2631, Bibcode:2014A&A...562A..71B, doi:10.1051/0004-6361/201322631, S2CID 118786105.
  8. "43 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-01-09.