Pi Eridani

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π Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 03h 46m 08.53581s[1]
Declination −12° 06′ 05.7282″[1]
Apparent magnitude (V) 4.40[2] (4.38 - 4.44[3])
Spectral type M1 III[4]
U−B color index +1.96[2]
B−V color index +1.61[2]
Variable type Lb?[3]
Radial velocity (Rv) 45.2±0.1[5] km/s
Proper motion (μ) RA: +55.98[1] mas/yr
Dec.: +59.28[1] mas/yr
Parallax (π) 6.78 ± 0.53[1] mas
Distance 480 ± 40 ly
(150 ± 10 pc)
Radius 77[6] R
Luminosity 1,123[7] L
Temperature 3,841[7] K
Other designations
π Eridani, π Eri, 26 Eridani, BD-12° 707, HD 23614, HIP 17593, HR 1162, SAO 149158.[8]
Database references

Pi Eridani (π Eri) is a star in the constellation Eridanus. It has an apparent visual magnitude of 4.40,[2] which is bright enough to be seen on a dark, clear night. Based upon parallax measurements, it is located roughly 480 light years from the Sun.

This is an evolved red giant star with a stellar classification of M1 III,[4] and is currently on the asymptotic giant branch.[9] It is a slow irregular variable type LB that can increase in magnitude up to 4.38.[3][10] The measured angular diameter of this star is 4.8±0.5 mas.[11] At the estimated distance of Pi Eridani, this yields a physical size of about 77 times the radius of the Sun.[6] It shines with 1,123[7] times the luminosity of the Sun from an outer atmosphere at an effective temperature of 3,841 K.[7]


  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, 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 ^ a b c d Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b c Samus, N. N.; Durlevich, O. V.; et al. (2007), Combined General Catalogue of Variable Stars (GCVS4.2), retrieved 2016-09-30. VizieR On-line Data Catalog: B/gcvs. 
  4. ^ a b Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, 4, Bibcode:1988MSS...C04....0H. 
  5. ^ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065. 
  6. ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1.  The radius (R*) is given by:
  7. ^ a b c d McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037Freely accessible, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x. 
  8. ^ "pi. Eri -- Long Period Variable candidate", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-11. 
  9. ^ Eggen, O. J. (1992), "Asymptotic giant branch stars near the sun", The Astronomical Journal, 104: 275, Bibcode:1992AJ....104..275E, doi:10.1086/116239. 
  10. ^ Mennessier, M. O.; et al. (August 2001), "Long period variable stars: galactic populations and infrared luminosity calibrations", Astronomy and Astrophysics, 374: 968–979, arXiv:astro-ph/0105552Freely accessible, Bibcode:2001A&A...374..968M, doi:10.1051/0004-6361:20010764. 
  11. ^ Richichi, A.; Percheron, I. (May 2005), "First results from the ESO VLTI calibrators program", Astronomy and Astrophysics, 434 (3): 1201–1209, arXiv:astro-ph/0501532Freely accessible, Bibcode:2005A&A...434.1201R, doi:10.1051/0004-6361:20042257.