Beta Reticuli

Beta Reticuli (Beta Ret, β Reticuli, β Ret) is binary star[6] system in southern constellation of Reticulum. It is visible to the naked eye with an apparent visual magnitude of +3.84.[2] Based upon an annual parallax shift of 33.49 mas,[1] it is located some 97 light years from the Sun.

Beta Reticuli
Location of β Reticuli (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Reticulum
Right ascension 03h 44m 11.97587s[1]
Declination −64° 48′ 24.8610″[1]
Apparent magnitude (V) +3.84[2]
Characteristics
Spectral type K0IV SB[3]
U−B color index +1.11[2]
B−V color index +1.13[2]
Astrometry
Radial velocity (Rv)51.1±4.1[4] km/s
Proper motion (μ) RA: +307.13[1] mas/yr
Dec.: +77.50[1] mas/yr
Parallax (π)33.49 ± 0.53[1] mas
Distance97 ± 2 ly
(29.9 ± 0.5 pc)
Absolute magnitude (MV)+1.46±0.03[3]
Orbit[3]
Period (P)1,918.31±0.73 d
Semi-major axis (a)27.8±0.46 mas
Eccentricity (e)0.33461±0.00035
Inclination (i)82.85±3.0°
Longitude of the node (Ω)16±4.4°
Periastron epoch (T)2452806.14 ± 0.33
Argument of periastron (ω)
(secondary)		42.023±0.084°
Semi-amplitude (K1)
(primary)		5.1235±0.0025 km/s
Details
β Ret A
Mass1.2±0.2[3] M☉
Radius9.3±0.4[3] R☉
Temperature4,580±80[3] K
Age5–6[3] Gyr
β Ret B
Mass0.4±0.1[3] M☉
Other designations
β Ret, CPD−65° 263, FK5 141, HD 23817, HIP 17440, HR 1175, SAO 248877, WDS J03442-6448A.[5]
Database references
SIMBADdata

This is a single-lined spectroscopic binary with an orbital period of 5.25 years and an eccentricity of 0.33. The primary, component A, is an evolved K-type giant star with a stellar classification of K0 IVSB:. It is between 5 and 6 billion years old, with 1.2 times the mass of the Sun and 9.3 times the Sun's radius. The companion, component B, is most likely a red dwarf with a classification in the range M0–M4.[3]

During the mid-20th century, the Dutch-American astronomer Willem Jacob Luyten proposed that the G3V star HD 24293 formed a third component of this system, based upon similar proper motions. However, this was subsequently ruled out based on more accurate measurements, since their actual distances, radial velocities, and proper motions do not match.[7]

Beta Reticuli is moving through the Galaxy at a speed of 69.2 km/s relative to the Sun. Its projected Galactic orbit carries it between 10,100 and 24,200 light years from the center of the Galaxy.[8] Beta Reticuli came closest to the Sun 319,000 years ago when it had brightened to magnitude 2.98 from a distance of 67 light years.[8]

Naming

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 蛇首 (Shé Shǒu), meaning Snake's Head, refers to an asterism consisting of β Reticuli and α Hydri. Consequently, β Reticuli itself is known as 蛇首二 (Shé Shǒu èr, English: the Second Star of Snake's Head.)[9]

References
  1. 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.
  2. 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. Ramm, D. J.; et al. (April 2009), "Spectroscopic orbits for K giants β Reticuli and ν Octantis: what is causing a low-amplitude radial velocity resonant perturbation in ν Oct?", Monthly Notices of the Royal Astronomical Society, 394 (3): 1695–1710, Bibcode:2009MNRAS.394.1695R, doi:10.1111/j.1365-2966.2009.14459.x.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  5. "* bet Ret". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-13.
  6. 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.
  7. Caballero, J. A. (November 2009), "Reaching the boundary between stellar kinematic groups and very wide binaries. The Washington double stars with the widest angular separations", Astronomy and Astrophysics, 507 (1): 251–259, arXiv:0908.2761, Bibcode:2009A&A...507..251C, doi:10.1051/0004-6361/200912596, S2CID 118194112.
  8. Beta Reticuli (HIP 17440) Archived January 2, 2013, at the Wayback Machine
  9. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 27 日
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