Epoch J2000.0 Equinox J2000.0
|Apparent magnitude (V)||6.1 - 7.5|
|Spectral type||K0 0-Ia|
|B−V color index||+1.98|
|Radial velocity (Rv)||−38.20 km/s|
|Proper motion (μ)||RA: −2.94 mas/yr
Dec.: −-2.54 mas/yr
|Parallax (π)||1.35 ± 1.59 mas|
|Mass||39 (combined) M☉|
|Surface gravity (log g)||0 cgs|
V766 Centauri (V766 Cen; also known HD 119796 and HR 5171) is a yellow hypergiant star in the constellation Centaurus. Its spectral type is variable around G8Ia+ - K3Ia+ and its brightness varies in an irregular fashion. It has a distant B-type companion and is in close contact with a cool companion. It is around 3,600 parsecs (12,000 ly) from Earth and is the largest known yellow hypergiant, most likely due to interactions with the close companion.
This type of star has evolved from an initial mass of around 40 times the sun to a red hypergiant and is now shedding its remaining outer layers in a series of dramatic explosions, progressively increasing in temperature. It may become a blue supergiant or luminous blue variable before declining in luminosity as a late type Wolf–Rayet star, but is expected to explode as a supernova before that point.
The very high luminosity, extreme size, and mass exchange with the lower mass companion make this an unusual star within a very rare class of stars, but it has been relatively poorly studied until recently.
The Star was observed by the European Southern Observatory’s (ESO) Very Large Telescope Interferometer (VLTI) and has been revealed to be the largest yellow star. This star has been determined to be more than 1,300 times the diameter of the Sun and part of a double star system, with the second component so close that it is in contact with the main star. If V766 Centauri were to be put in the center of the Solar System, it would stretch to a distance of 912,584,500 kilometres (567,053,700 mi), between the orbits of Jupiter and Saturn. It has a volume approximately 2.274 billion times bigger than the Sun.
Using ESO’s VLTI, an international team of observers led by Olivier Chesneau from the Observatory de la Côte d’Azur in Nice, France, have found that V766 Centauri is much larger than was expected, making it the largest yellow star known. The star is 50 percent larger than the red supergiant Betelgeuse and about 1 million times brighter than the Sun.
The star has also been found to be getting larger in size over the time of its examination and is one of the very few stars that have been found to be changing their temperature with difference in size: V766 Centauri is getting cooler as it grows.
The astronomers concluded that the star is in a binary system by studying the data contributed by several observatories and determined the system as an eclipsing binary star system with the smaller companion star orbiting the larger V766 Centauri once every 1300 days.
- Chesneau, O.; Meilland, A.; Chapellier, E.; Millour, F.; Van Genderen, A. M.; Nazé, Y.; Smith, N.; Spang, A. et al. (2014). "The yellow hypergiant HR 5171 A: Resolving a massive interacting binary in the common envelope phase". arXiv:1401.2628v2 [astro-ph.SR].
- Keenan, P. C.; McNeil, R. C. (1989). "The Perkins catalog of revised MK types for the cooler stars". The Astrophysical Journal Supplement Series 71: 245. doi:10.1086/191373.
- ESO, Garching, Germany (2014-03-12). "ESO's Very Large Telescope spots largest yellow hypergiant star". Astronomy.com. Archived from the original on 2014-03-13.