Mu Hydrae

μ Hydrae

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	10^h 26^m 05.42630^s[1]
Declination	−14° 19′ 56.2675″[1]
Apparent magnitude (V)	3.83[2]
Characteristics
Spectral type	K4 III[3]
U−B color index	+1.83[2]
B−V color index	+1.47[2]
Variable type	Suspected[4]
Astrometry
Radial velocity (Rv)	+40.81±0.36[5] km/s
Proper motion (μ)	RA: −129.17[1] mas/yr Dec.: −79.76[1] mas/yr
Parallax (π)	13.93 ± 0.18 mas[1]
Distance	234 ± 3 ly (71.8 ± 0.9 pc)
Absolute magnitude (MV)	−0.45[6]
Details[5]
Radius	45 R☉
Luminosity	332[6] L☉
Surface gravity (log g)	1.5 cgs
Temperature	3,999±8 K
Metallicity [Fe/H]	−0.12 dex
Rotational velocity (v sin i)	6.0 km/s
Other designations
μ Hya, 42 Hydrae, BD−16° 3052, FK5 389, HD 90432, HIP 51069, HR 4094, SAO 155980.[7]
Database references
SIMBAD	data

μ Hydrae, Latinised as Mu Hydrae, is a solitary,^[8] orange-hued star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 3.83.^[2] Positioned just 1.8° to the south-southwest is the planetary nebula NGC 3242.^[9] Mu Hydrae has an annual parallax shift of 13.93 mas,^[1] which yields a distance estimate of 234 light years.

This is an evolved K-type giant star with a stellar classification of K4 III,^[3] having used up its core hydrogen and has expanded to around 45 times the radius of the Sun.^[5] It is a suspected variable star, with a brightness that varies about 0.03 in magnitude.^[4] The relatively cool outer atmosphere has an effective temperature of 3999 K.^[5]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
3. Houk, N.; Smith-Moore, M. (1988), University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Declinations -26°.0 to -12°.0, vol. 4, Department of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
4. Samus, N. N.; Durlevich, O. V.; et al. (2009), "General Catalogue of Variable Stars", Vizier Online Data Catalog, 1, Bibcode:2009yCat....102025S.
5. Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209, S2CID 121883397.
6. 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.
7. "* mu. Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-01-06.
8. 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.
9. O'Meara, Steve (2007), Herschel 400 Observing Guide, Cambridge University Press, p. 107, ISBN 978-0521858939.