Epoch J2000 Equinox J2000
|Right ascension||05h 38m 42.45s|
|Declination||−69° 06′ 02.2″|
|Apparent magnitude (V)||13.38|
|Evolutionary stage||Wolf-Rayet star|
|Luminosity (bolometric)||6,000,000 L☉|
|Age||≥ 2 Myr|
RMC 136a2, NGC 2070 MH 511, BAT99 109
R136a2 (RMC 136a2) is a Wolf-Rayet star located near the center of the R136 super star cluster, which is located near the center of the Caldwell 103 complex (also known as Tarantula Nebula), near the upper left corner of the neighboring galaxy Large Magellanic Cloud. It is one of the most massive stars known, at almost 200 solar masses, and one of the most luminous, at some six million times the luminosity of the Sun. It is located near R136a1, an even more massive and more luminous star. They are the two largest, most massive, and also most luminous stars of R136, which produces most of the light that makes the entire C103 complex visible.
The star was discovered by a team of British astronomers led by Paul Crowther, a professor of astrophysics at the University of Sheffield, at the Very Large Telescope in the Atacama Desert in Chile, with additional data from the Hubble Space Telescope. The team were studying two star clusters, namely NGC 3603 and R136. In their study, they spotted three stars in R136 with masses exceeding 150 solar masses, including R136a1 and R136a2, the other being R136c.
Like all Wolf-Rayet stars, R136a2 is undergoing severe mass loss by a fast stellar wind. The high mass of the star compresses the core and ignites fusion at a high rate using the CNO process, leading to an extremely high luminosity. The fusion rate is so great that in 12 seconds R136a2 produces as much energy as the Sun does in a year. It may have been a 220 solar mass star at the time it was born and lost as much as 30 solar masses in the past 1 to 2 million years, but since current theories suggest that no stars can be born above 150 solar masses, it may be a merger of two or more stars.
The future of R136a2 depends on its mass loss. If the star is above 150 solar masses at the time of its core collapse, it may explode as a pair-instability supernova, a very luminous stellar explosion caused by the runaway production of positron pairs, leaving no remnant behind, similar to the luminous supernovae SN 2006gy, SN 2005ap and SN 2006tf. It is possible that the star may explode as a hypernova, or even produce a gamma-ray burst. If the star loses mass down to 130 solar masses, it may explode as an ordinary supernova, leaving either a neutron star or a black hole.
- Crowther, P. A.; Schnurr, O.; Hirschi, R.; Yusof, N.; Parker, R. J.; Goodwin, S. P.; Kassim, H. A. (2010). "The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 M⊙ stellar mass limit". Monthly Notices of the Royal Astronomical Society 408 (2): 731. arXiv:1007.3284. Bibcode:2010MNRAS.408..731C. doi:10.1111/j.1365-2966.2010.17167.x.
- Banerjee, Sambaran; Kroupa, Pavel; Oh, Seungkyung (2012). "The emergence of super-canonical stars in R136-type star-burst clusters". arXiv:1208.0826v1 [astro-ph.SR].