R136a1

R136a1

R136a1 resolved at the center, with R136a2 close by, R136a3 below right, and R136b to the left.
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Dorado
Right ascension	5h 38m 42.43s
Declination	−69° 06′ 02.2″
Apparent magnitude (V)	12.77
Characteristics
Spectral type	WN5h
B−V color index	+0.01
Astrometry
Distance	165,000 ly
Details
Mass	265+80 −35 M☉
Radius	35.4+4.0 −3.6 R☉
Luminosity	≈ (8.7)×106 L☉
Temperature	53,000 ± 3,000 K
Age	unknown years
Other designations
BAT99 108, RMC 136a1, [HSH95] 3, [WO84] 1b, Cl* NGC 2070 MH 498, [CHH92] 1, [P93] 954.
Database references
SIMBAD	data

R136a1 is a Wolf–Rayet star and the most massive star known. It is an estimated 265 solar masses. It is also the most luminous star known at 8,700,000 times the luminosity of the Sun. It is a member of R136, a super star cluster near the center of the 30 Doradus complex (also known as the Tarantula Nebula), in the Large Magellanic Cloud. The mass of the star was determined by Paul Crowther et al. (2010).

Discovery

Zooming in from the Tarantula Nebula to the R136 cluster, with R136a1/2/3 visible as the barely resolved knot at bottom right. The brightest star just to the left of the cluster core is R136c, another extreme massive WN5h star.

News of the star's discovery was published in July 2010. A team of British astronomers led by Paul Crowther, professor of astrophysics at the University of Sheffield, used European Southern Observatory's Very Large Telescope (VLT) in Chile, as well as data from the Hubble Space Telescope, to study two star clusters, NGC 3603 and R136a. R136a was once thought to be a supermassive object with 1000–3000 solar masses. R136a's nature was resolved by holographic speckle interferometry and found to be a dense star cluster. The team found several stars with surface temperatures exceeding 40,000–56,000 K, more than seven times that of the Sun, and which are several million times brighter. At least three of the stars weigh in at about 150 solar masses.

Physical characteristics

Left to right: a red dwarf, the Sun, a blue dwarf, and R136a1. R136a1 is not the largest known star in terms of volume; this distinction belongs to NML Cygni.

R136a1 is a Wolf–Rayet star with surface temperature over 50,000 K . Like other stars that are close to the Eddington limit, R136a1 has been shedding a large fraction of its initial mass through a continuous stellar wind. It is estimated that, at its birth, the star held 320 solar masses and has lost 50 solar masses over the past million years. However, current theories suggest that no stars can be born above 150 solar masses but instead supermassive stars like this one formed through mergers of multiple stars.

Stars between about 8 and 150 solar masses explode at the end of their lives as supernovae, leaving behind neutron stars or black holes. Having established the existence of stars between 150 and 300 solar masses, astronomers suspect that such an enormous star will perish as a hypernova, a stellar explosion with an energy of over 100 supernovae (10⁴⁶ joules). The star may also die prematurely long before its core could collapse naturally from lack of fuel as a "pair-instability supernova". Hydrogen-fusing cores should create large numbers of electron–positron pairs, which drop the thermal pressure present within the star to the point a partial collapse occurs. If R136a1 underwent such an explosion it would fail to leave behind a black hole and instead the dozen solar masses of iron within its core would be blown out into the interstellar medium as a supernova remnant.

See also

• List of most massive stars
• List of most luminous stars
• Orders of magnitude (length)
• List of largest known stars
• Lynx Arc