Alpha Octantis

Alpha Octantis
	Location of α Octantis (circled in red)
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	21h 04m 43.06347s
Declination	−77° 01′ 25.5735″
Apparent magnitude (V)	5.13
Characteristics
Evolutionary stage	Main sequence
Spectral type	F4III + F5III
U−B color index	+0.13
B−V color index	+0.490±0.008
Variable type	EB
Astrometry
Radial velocity (Rv)	85.9±1.5 km/s
Proper motion (μ)	RA: +22.5215 mas/yr ; Dec.: −369.325 mas/yr
Parallax (π)	22.5215±0.0955 mas
Distance	144.8 ± 0.6 ly ; (44.4 ± 0.2 pc)
Absolute magnitude (MV)	1.93±0.02
Orbit
Period (P)	9.073 d
Eccentricity (e)	0.39
Periastron epoch (T)	2,435,302.404
Argument of periastron (ω); (secondary)	276°
Semi-amplitude (K1); (primary)	47 km/s
Semi-amplitude (K2); (secondary)	47 km/s
Details
A
Mass	1.9 M☉
Radius	2.0 R☉
Luminosity	7 L☉
Temperature	6,700 K
Age	1.1 Gyr
B
Mass	2 M☉
Radius	2.0 R☉
Luminosity	7 L☉
Temperature	6,700 K
Age	1.1 Gyr
Other designations
	α Oct, CD−77°1053, CPD−77°1474, FK5 787, GC 29343, HD 199532, HIP 104043, HR 8021, SAO 257879, PPM 374864, LTT 8327, NLTT 50332
Database references
SIMBAD	data

Alpha Octantis is a binary star system in the constellation of Octans. The name is Latinized from α Octantis. Despite being labeled the "alpha" star by Lacaille, it is not the brightest star in the constellation—that title belongs to Nu Octantis. It is also the faintest "alpha" star overall, with Alpha Mensae a close second. It is visible to the naked eye as a faint, yellow-white-hued point of light with an overall apparent visual magnitude of approximately 5.13. The system is located approximately 148 light-years away from the Sun based on parallax.

This is a double-lined spectroscopic binary star which consists of two similar main sequence stars, each with spectral type F, orbiting each other with a period of just over 9 days and an eccentricity of 0.39. The pair form a Beta Lyrae-type eclipsing binary system, dropping by magnitude 0.04 during the primary eclipse. This system is a bright X-ray source with a luminosity of 22.78×10²⁹ ergs s⁻¹. The system displays an infrared excess suggesting the presence of a debris disk; with a temperature of 219 K and is orbiting at a distance of 9.8 AU from its host star.

References

1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
1 2 3 4 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.
1 2 3 4 5 6 7 8 9 "Alpha Octantis". stars.astro.illinois.edu. Retrieved 2025-07-13.
1 2 3 The double-lined binary alpha Octantis, William Buscombe and Pamela M. Morris, The Observatory 80 (February 1960), pp. 28–29, Bibcode:1960Obs....80...28B.
↑ HR 8021, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 4, 2008.
1 2 Samus', N. N; et al. (2017). "General catalogue of variable stars". Astronomy Reports. 5.1. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
↑ Nordström, B.; et al. (2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs". Astronomy and Astrophysics. 418: 989–1019. arXiv:astro-ph/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. S2CID 11027621.
1 2 3 Asensio-Torres, R.; Janson, M.; Bonavita, M.; Desidera, S.; Thalmann, C.; Kuzuhara, M.; Henning, Th; Marzari, F.; Meyer, M. R.; Calissendorff, P.; Uyama, T. (2018-11-01). "SPOTS: The Search for Planets Orbiting Two Stars - III. Complete sample and statistical analysis". Astronomy & Astrophysics. 619: A43. arXiv:1807.08687. doi:10.1051/0004-6361/201833349. ISSN 0004-6361.
↑ "* alf Oct". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 4, 2008.
↑ 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.
↑ Ridpath, Ian. "Star Tales – Octans". Retrieved 16 July 2025.
↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
↑ Makarov, Valeri V. (October 2003), "The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun", The Astronomical Journal, 126 (4): 1996–2008, Bibcode:2003AJ....126.1996M, doi:10.1086/378164.
↑ Trilling, D.E.; Stansberry, J.A.; Stapelfeldt, K.R.; Rieke, G.H.; Su, K.Y.L; Gray, R.O; Corbally, C.J; Bryden, G; Chen, C.H.; Boden, A; Beichman, C.A (2007). "DEBRIS DISKS IN MAIN-SEQUENCE BINARY SYSTEMS" (PDF). The Astrophysical Journal. 658 (2): 1289-1311. Bibcode:2007ApJ...658.1289T. doi:10.1086/511668.

[GaiaDR2-1] 1 2 3 4 5 Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.

[Anderson2012-2] 1 2 3 4 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.

[kaler-3] 1 2 3 4 5 6 7 8 9 "Alpha Octantis". stars.astro.illinois.edu. Retrieved 2025-07-13.

[obs-4] 1 2 3 The double-lined binary alpha Octantis, William Buscombe and Pamela M. Morris, The Observatory 80 (February 1960), pp. 28–29, Bibcode:1960Obs....80...28B.

[bsc1-5] HR 8021, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line September 4, 2008.

[Samus2017-6] 1 2 Samus', N. N; et al. (2017). "General catalogue of variable stars". Astronomy Reports. 5.1. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.

[Geneva-7] Nordström, B.; et al. (2004). "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs". Astronomy and Astrophysics. 418: 989–1019. arXiv:astro-ph/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. S2CID 11027621.

[SPOTS-8] 1 2 3 Asensio-Torres, R.; Janson, M.; Bonavita, M.; Desidera, S.; Thalmann, C.; Kuzuhara, M.; Henning, Th; Marzari, F.; Meyer, M. R.; Calissendorff, P.; Uyama, T. (2018-11-01). "SPOTS: The Search for Planets Orbiting Two Stars - III. Complete sample and statistical analysis". Astronomy & Astrophysics. 619: A43. arXiv:1807.08687. doi:10.1051/0004-6361/201833349. ISSN 0004-6361.

[sb0-9] "* alf Oct". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved September 4, 2008.

[Eggleton2008-10] 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.

[Ridpath-11] Ridpath, Ian. "Star Tales – Octans". Retrieved 16 July 2025.

[MAST-12] "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.

[Makarov2003-13] Makarov, Valeri V. (October 2003), "The 100 Brightest X-Ray Stars within 50 Parsecs of the Sun", The Astronomical Journal, 126 (4): 1996–2008, Bibcode:2003AJ....126.1996M, doi:10.1086/378164.

[14] Trilling, D.E.; Stansberry, J.A.; Stapelfeldt, K.R.; Rieke, G.H.; Su, K.Y.L; Gray, R.O; Corbally, C.J; Bryden, G; Chen, C.H.; Boden, A; Beichman, C.A (2007). "DEBRIS DISKS IN MAIN-SEQUENCE BINARY SYSTEMS" (PDF). The Astrophysical Journal. 658 (2): 1289-1311. Bibcode:2007ApJ...658.1289T. doi:10.1086/511668.