R136a1

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R136a1
The young cluster R136.jpg
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) 12.28[1]
Characteristics
Spectral type WN5h[2]
B−V color index +0.01
Astrometry
Distance 165,000 ly
Details
Mass 265+80
−35
[2] M
Radius 35.4+4.0
−3.6
[2] R
Luminosity ≈ (8.7)×106[2] L
Temperature 53,000 ± 3,000[2] K
Age ≤ 2,000,000 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.[2] It is also the most luminous star known at 8,700,000 times the luminosity of the Sun.[2] 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.[2]

Discovery[edit]

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.[2][3] 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.[4] 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[edit]

Left to right: a red dwarf, the Sun, a blue dwarf, and R136a1. R136a1 is not the largest known star in terms of radius or volume, only in mass and luminosity.

R136a1 is a Wolf–Rayet star with surface temperature over 50,000 K .[2] 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.[2] 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.[5][6]

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 electronpositron 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.[3] If R136a1 managed to survive to the end of its life without exploding as a pair-instability supernova, it would be so massive that it would explode as a hypernova as mentioned above, but then collapse directly into a black hole.

See also[edit]

References[edit]

  1. ^ Doran, E. I.; Crowther, P. A.; de Koter, A.; Evans, C. J.; McEvoy, C.; Walborn, N. R.; Bastian, N.; Bestenlehner, J. M. et al. (2013). "The VLT-FLAMES Tarantula Survey - XI. A census of the hot luminous stars and their feedback in 30 Doradus". arXiv:1308.3412v1 [astro-ph.SR].
  2. ^ a b c d e f g h i j k Crowther, Paul A.; Schnurr, Olivier; Hirschi, Raphael; Yusof, Norhasliza; Parker, Richard J.; Goodwin, Simon P.; Kassim, Hasan Abu (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): 731–751. arXiv:1007.3284. Bibcode:2010MNRAS.408..731C. doi:10.1111/j.1365-2966.2010.17167.x. 
  3. ^ a b "A 300 Solar Mass Star Uncovered". ESO Press Release. 2010-07-21. 
  4. ^ http://www.eso.org/sci/publications/messenger/archive/no.40-jun85/messenger-no40-4-6.pdf PDF (R136a and the Central Object in the Giant HII Region NGC 3603 Resolved by Holographic Speckle Interferometry).
  5. ^ http://www.newscientist.com/article/dn22161-astrophile-monster-stars-are-just-misunderstood.html
  6. ^ Oh, Sambaran; Kroupa, Pavel; Oh, Seungkyung (2012). The emergence of super-canonical stars in R136-type star-burst clusters 1208. p. 826. arXiv:1208.0826. Bibcode:2012arXiv1208.0826B. 

Coordinates: Sky map 05h 38m 42.43s, −69° 06′ 02.2″