2 Centauri

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title: "2 Centauri" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["m-type-giants", "asymptotic-giant-branch-stars", "semiregular-variable-stars", "centaurus", "bayer-objects", "durchmusterung-objects", "flamsteed-objects", "henry-draper-catalogue-objects", "hipparcos-objects", "bright-star-catalogue-objects", "objects-with-variable-star-designations"] description: "Star in the constellation Centaurus" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/2_Centauri" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Star in the constellation Centaurus ::

| image = |image=Centaurus constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=2 Centauri |x=435|y=268 | caption = Location of 2 Centauri (circled in red) | epoch= J2000.0 | constell = Centaurus | ra = | dec = | appmag_v = 4.16–4.26 | type = AGB | class = M5 III | b-v = +1.49 | u-b = +1.44 | variable = SRb | radial_v = | prop_mo_ra = | prop_mo_dec = | parallax = 17.82 | p_error = 0.21 | parallax_footnote = | absmag_v = +0.51 | source = | mass = 1.0 | radius = 82.4 | luminosity = 767 | temperature = 3,438 | metal_fe = | gravity = 0.65 | rotational_velocity = | age_gyr = | names = | Simbad = HD+120323

2 Centauri is a single star in the southern constellation of Centaurus, located approximately 183 light-years from Earth. It has the Bayer designation g Centauri; 2 Centauri is the Flamsteed designation. This object is visible to the naked eye as faint, red-hued star with an apparent visual magnitude of about 4.2. It is moving away from the Earth with a heliocentric radial velocity of +41 km/s. The star is a member of the HR 1614 supercluster.

::figure[src="https://upload.wikimedia.org/wikipedia/commons/2/2f/V806CenLightCurve.png" caption="A [[light curve]] for V806 Centauri. The main plot shows the long term variability from ''[[Hipparcos]]'' data, and the inset plot shows the variability over the 26.5 day period, using data from Tabur ''et al.'' (2009). The green curve shows the best-fit sine wave, which has an amplitude of 18 millimagnitudes."] ::

This is an evolved red giant star with a stellar classification of M5 III. In 1951, Alan William James Cousins announced that the star, then called g Centauri, is a variable star. It was given its variable star designation, V806 Centauri, in 1978. It is classified as a semiregular variable star and its brightness varies from magnitude +4.16 to +4.26 with a period of 12.57 days. The star has around 82 times the Sun's radius and is radiating 767 times the Sun's luminosity from its enlarged photosphere at an effective temperature of .

References

References

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6. Gontcharov, G. A.. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters.
7. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data.
8. (June 1998). "The HR 1614 Group and HIPPARCOS Astrometry". The Astronomical Journal.
9. (September 2008). "A catalogue of multiplicity among bright stellar systems". [[Monthly Notices of the Royal Astronomical Society]].
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11. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey.
12. (October 1951). "Photographic magnitudes of the brightest stars". The Observatory.
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15. (2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society.
16. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S.

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