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ρ² Eridani
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	03h 02m 42.28856s
Declination	−07° 41′ 07.7165″
Apparent magnitude (V)	5.32
Characteristics
Spectral type	K0 III
U−B color index	+0.73
B−V color index	+0.94
Astrometry
Radial velocity (Rv)	26.38±0.23 km/s
Proper motion (μ)	RA: +49.30 mas/yr ; Dec.: −5.42 mas/yr
Parallax (π)	12.32 ± 1.23 mas
Distance	260 ± 30 ly ; (81 ± 8 pc)
Absolute magnitude (MV)	0.830
Details
Mass	2.53 M☉
Radius	9 R☉
Luminosity	45.7 L☉
Surface gravity (log g)	2.6 cgs
Temperature	4,864 K
Metallicity [Fe/H]	0.19 dex
Rotational velocity (v sin i)	0.0 km/s
Other designations
	ρ2 Eridani, ρ2 Eri, 9 Eridani, BD−08°568, HD 18953, HIP 14168, HR 917, SAO 130254.
Database references
SIMBAD	data

Rho² Eridani is a star located in the constellation Eridanus. It forms an asterism with Rho¹ and Rho³ Eridani, south of Cetus, in the upper north east portion of Eridanus. The star has an apparent visual magnitude of 5.32,^[2] which indicates it is visible to the naked eye on a clear, dark night. Based upon parallax measurements made with the Hipparcos satellite, this star is roughly 260 light years away from the Sun.

This is an evolved K-type giant star with a stellar classification of K0 III.^[3] It is a red clump giant on the horizontal branch of the Hertzsprung–Russell diagram, indicating that is it now generating energy through the thermonuclear fusion of helium at its core.^[5] The star has 2.5 times the mass of the Sun and has expanded to 9 times the Sun's radius. As such, it is radiating nearly 46 times the solar luminosity from its outer atmosphere at an effective temperature of 4,864 K.^[4]

There is a magnitude 9.7 companion star at an angular separation of 1.8″. Most likely the pair form a binary star system.^[7] At least one of the stars appears to be a source of X-ray emission.^[8] The X-ray band flux is 3.65×10⁻¹⁵ W·m⁻².^[9]

References

^ ^a ^b ^c ^d ^e 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.
^ ^a ^b ^c ^d 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.
^ ^a ^b Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
^ ^a ^b ^c ^d ^e ^f ^g 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.
^ ^a ^b ^c ^d Zhao, G.; et al. (2001), "High-Resolution Spectroscopic Observations of Hipparcos Red Clump Giants: Metallicity and Mass Determinations", The Astrophysical Journal, 551 (1): L85, Bibcode:2001ApJ...551L..85Z, doi:10.1086/319832, S2CID 119700315.
^ "rho02 Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-12.
^ 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.
^ Haakonsen, Christian Bernt; Rutledge, Robert E. (September 2009), "XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources", The Astrophysical Journal Supplement, 184 (1): 138–151, arXiv:0910.3229, Bibcode:2009ApJS..184..138H, doi:10.1088/0067-0049/184/1/138, S2CID 119267456.
^ Schwope, A.; et al. (2000), "The ROSAT Bright Survey: II. Catalogue of all high-galactic latitude RASS sources with PSPC countrate CR > 0.2 s⁻¹", Astronomische Nachrichten, 321 (1): 1–52, arXiv:astro-ph/0003039, Bibcode:2000AN....321....1S, doi:10.1002/(SICI)1521-3994(200003)321:1<1::AID-ASNA1>3.0.CO;2-C.