Westerlund 2

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Open star cluster
Westerlund 2
Image of the Hubble Space Telescope of the star cluster Westerlund 2 and its surroundings
Image of the Hubble Space Telescope of the star cluster Westerlund 2 and its surroundings
AladinLite
Constellation Keel of the ship
Position
equinox : J2000.0
Right ascension 10 h 24 m 02 s
declination -57 ° 46 ′ 00 ″
Appearance
Physical data

Affiliation Gum 29
distance  20,000 ly
(6,000 pc )
Dimensions 7.400 M ☉
history
Discovered by Bengt Westerlund
Discovery time 1961
Catalog names
 C 1022-575 • OCl 807 •  ESO  127-18 • Westerlund 2

Westerlund 2 is a covert compact young star cluster (possibly a super star cluster ) in the Milky Way , believed to be a million or two million years old. It includes some of the hottest, brightest, and heaviest stars known. The star cluster lies in the star formation region Gum 29 and is 20,000 light years away in the constellation Kiel of the ship .

particularities

The star cluster includes at least a dozen young O stars that are hotter than 38,000 K and have a luminosity of more than 230,000 times the luminosity of the sun. The other 20 O-stars of the star cluster, which belong to the main sequence , indicate that the star cluster is very old.

Several Wolf-Rayet stars are located in the vicinity of Westerlund 2, although not in the center. These include WR20a, a binary system made up of two WR stars, and the stars WR20aa, WR20b, and WR20c. These five WR stars are extremely young and massive objects of the OIf * / WN spectral class, and are among the most luminous stars in the galaxy: the composite spectral class identifies young and extremely massive, hydrogen-burning stars that have started to surface nitrogen and helium convert and develop a strong stellar wind so that they have the emission lines of a Wolf-Rayet star. Only the double star WR21a, which lies in approximately the same line of sight, is probably not a member of Westerlund 2.

Westerlund 2 also includes many stars that have not yet reached the main sequence and have a mass of less than 2.5 solar masses. These stars limit the age of the star cluster to about two million years.

discovery

The star cluster was discovered by Bengt Westerlund in the early 1960s and named after him; the star population was determined later.

Web links

Commons : Westerlund 2  - Collection of images, videos and audio files

Individual evidence

  1. ^ WS Dias, BS Alessi, A. Moitinho, JRD Lépine: New catalog of optically visible open clusters and candidates . In: Astronomy and Astrophysics . 389, 2002, pp. 871-873. bibcode : 2002A & A ... 389..871D .
  2. ↑ a b c Hyeonoh Hur, Byeong-Gon Park, Hwankyung Sung, Michael S. Bessell, Beomdu Lim, Moo-Young Chun, Sangmo Tony Sohn: Reddening, distance, and stellar content of the young open cluster Westerlund 2 . In: Monthly Notices of the Royal Astronomical Society . 446, No. 4, 2015, p. 3797. arxiv : 1411.0879 . bibcode : 2015MNRAS.446.3797H . doi : 10.1093 / mnras / stu2329 .
  3. ↑ Y. Fukui et al .: Cloud-cloud collision which triggered formation of the super star cluster RCW38 . In: Astrophysical Journal . 1504, 2015. arxiv : 1504.05391 . bibcode : 2015arXiv150405391F .
  4. ^ Hubble Space Telescope Celebrates 25 Years of Unveiling the Universe . NASA. April 23, 2015.
  5. ^ Rauw: Early-type stars in the core of the young open cluster Westerlund 2 . In: Astronomy & Astrophysics . 463, No. 3, March 1, 2007, pp. 981-991. arxiv : astro-ph / 0612622 . bibcode : 2007A & A ... 463..981R . doi : 10.1051 / 0004-6361: 20066495 .
  6. ^ G. Carraro, D. Turner, D. Majaess, G. Baume: The distance to the young open cluster Westerlund 2 . In: Astronomy . 555, 2013, p. A50. arxiv : 1305.4309 . bibcode : 2013A & A ... 555A..50C . doi : 10.1051 / 0004-6361 / 201321421 .
  7. ^ J. Ascenso, J. Alves, Y. Beletsky, MTVT Lago: Near-IR imaging of Galactic massive clusters: Westerlund 2 . In: Astronomy and Astrophysics . 466, 2007, pp. 137-149. bibcode : 2007A & A ... 466..137A . doi : 10.1051 / 0004-6361: 20066433 .
  8. ↑ Bengt Westerlund: A Heavily Reddened Cluster in Ara. . In: Astronomical Journal . 70, March 1, 1961. bibcode : 1961AJ ..... 66T..57W . doi : 10.1086 / 108585 .
  9. ↑ Moffat: New Wolf-Rayet stars in Galactic open clusters - Sher 1 and the giant H II region core Westerlund 2 . In: Astronomical Journal . 102, Aug 1, 1991, pp. 642-653. bibcode : 1991AJ .... 102..642M . doi : 10.1086 / 115897 .