Upsilon1 Eridani

From Wikipedia, the free encyclopedia
Jump to: navigation, search
υ1 Eridanian
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 04h 33m 30.55236s[1]
Declination −29° 45′ 59.3725″[1]
Apparent magnitude (V) 4.51[2]
Spectral type K0 III-IV[3]
U−B color index +0.70[2]
B−V color index +0.98[2]
Radial velocity (Rv) +20.89±0.69[4] km/s
Proper motion (μ) RA: −114.78[1] mas/yr
Dec.: −271.79[1] mas/yr
Parallax (π) 25.67 ± 0.24[1] mas
Distance 127 ± 1 ly
(39.0 ± 0.4 pc)
Absolute magnitude (MV) 1.60[4]
Mass 1.54[4] M
Radius 7.3[5] R
Luminosity 24[4] L
Surface gravity (log g) 3.09[4] cgs
Temperature 4,941[4] K
Metallicity [Fe/H] −0.16±0.08[4] dex
Rotational velocity (v sin i) 2.15[6] km/s
Other designations
υ1 Eridani, υ1 Eri, 50 Eridani, CD−30° 1883, HD 29085, HIP 21248, HR 1453, SAO 169570.[7]
Database references

Upsilon1 Eridani (υ1 Eri) is a single star in the constellation Eridanus. It has an apparent visual magnitude is 4.51,[2] which is bright enough to be faintly visible to the naked eye on a clear, dark night. The distance to this star, as determined using the parallax method,[1] is around 127 light years.

This is an evolved red clump[8] giant star with a stellar classification of K0III-IV.[3] The measured angular diameter, after correction for limb darkening, is 1.74±0.02 mas.[9] At an estimated distance of this star, this yields a physical size of about 7.3 times the radius of the Sun.[5] It has 154%[4] of the Sun's mass and radiates 24 times the solar luminosity from its outer atmosphere at an effective temperature of 4,941 K.[4]


  1. ^ a b c d e f van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752Freely accessible, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data, SIMBAD, Bibcode:1986EgUBV........0M. 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. ^ a b Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, Bibcode:2006AJ....132..161G, arXiv:astro-ph/0603770Freely accessible, doi:10.1086/504637. 
  4. ^ a b c d e f g h i Luck, R. Earle; Heiter, Ulrike (June 2007), "Giants in the Local Region", The Astronomical Journal, 133 (6): 2464–2486, Bibcode:2007AJ....133.2464L, doi:10.1086/513194. 
  5. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1 . The radius (R*) is given by:
  6. ^ Hekker, S.; Meléndez, J. (2007). "Precise radial velocities of giant stars. III. Spectroscopic stellar parameters". Astronomy and Astrophysics. 475 (3): 1003. Bibcode:2007A&A...475.1003H. doi:10.1051/0004-6361:20078233. 
  7. ^ "ups01 Eri -- Variable Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13. 
  8. ^ Alves, David R. (August 2000), "K-Band Calibration of the Red Clump Luminosity", The Astrophysical Journal, 539 (2): 732–741, Bibcode:2000ApJ...539..732A, arXiv:astro-ph/0003329Freely accessible, doi:10.1086/309278. 
  9. ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.