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58 Hydrae is a single star in the equatorial constellation of Hydra, located around 290 light years away from the Sun based on parallax. It has the Bayer designation E Hydrae; 58 Hydrae is the Flamsteed designation − a later designation of 6 Librae. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.42. This object is moving closer to the Earth with a heliocentric radial velocity of −9 km/s.

This is an aging giant star with a stellar classification of K2.5 IIIb Fe-1:, most likely (98% chance) on the red giant branch. The suffix notation indicates an underabundance of iron in the spectrum, and some uncertainty about the classification. It is around 8.1 billion years old with 0.88 times the mass of the Sun. As a consequence of exhausting the hydrogen at its core, the star has expanded to 33.4 times the Sun's radius. It is radiating 310 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,210 K.

References

1. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. ^ 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, S2CID 119257644.
3. ^ Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
4. ^ Stock, S.; et al. (August 2018), "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search", Astronomy & Astrophysics, 616: 15, arXiv:1805.04094, Bibcode:2018A&A...616A..33S, doi:10.1051/0004-6361/201833111, S2CID 119361866, A33.
5. "E Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 4, 2019.
6. 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.
7. Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy, 18 (3): 218, Bibcode:1987JHA....18..209W, doi:10.1177/002182868701800305, S2CID 118445625

• K-type giants
• Hydra (constellation)
• Bayer objects
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects