Astronomy:Epsilon Octantis

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Epsilon Octantis, Latinized from ε Octantis, is a star in the southern circumpolar constellation of Octans. It is a faintly visible to the naked eye with an apparent visual magnitude of 5.09.[1] The annual parallax shift of 11.22[2] mas yields a distance estimate of around 291 light years. It is moving further from the Sun with a radial velocity of +11.7 km/s.[3]

This is an evolved, cool red giant star with a stellar classification of class M5III.[4] It is a semiregular variable with a magnitude range of 4.58 to 5.3 and a (poorly defined) period around 55 days.[5] The star has 1.34[6] times the mass of the Sun and has expanded to around 112[7] times the Sun's radius. It is radiating 1,819[7] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,560 K.[7]


  1. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode2012AstL...38..331A.  Vizier catalog entry
  2. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode2007A&A...474..653V. 
  3. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759. doi:10.1134/S1063773706110065. Bibcode2006AstL...32..759G. 
  4. Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H 5050. Bibcode1995yCat.5050....0H. 
  5. Samus', N. N.; Goranskii, V. P.; Durlevich, O. V.; Zharova, A. V.; Kazarovets, E. V.; Kireeva, N. N.; Pastukhova, E. N.; Williams, D. B. et al. (2003). "An Electronic Version of the Second Volume of the General Catalogue of Variable Stars with Improved Coordinates". Astronomy Letters 29 (7): 468. doi:10.1134/1.1589864. Bibcode2003AstL...29..468S. 
  6. Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics 352: 555. Bibcode1999A&A...352..555A.  Vizier catalog entry
  7. 7.0 7.1 7.2 Arroyo-Torres, B. et al. (June 2014), "VLTI/AMBER observations of cold giant stars: atmospheric structures and fundamental parameters", Astronomy & Astrophysics 566: 11, doi:10.1051/0004-6361/201323264, A88, Bibcode2014A&A...566A..88A Octantis was the original source. Read more.