1806−20 cluster

1806−20 cluster
Observation data (J2000 epoch)
Right ascension	18^h 08^m 39.33^s[1]
Declination	−20° 24′ 40.0″[1]
Distance	~28000 ly (~8700 pc[2])
Physical characteristics
Contains SGR 1806−20 and LBV 1806−20.
Other designations	G10.0-0.3, W31
Associations
Constellation	Sagittarius

H-band infrared image of 1806−20 cluster

1806−20 (originally named the SGR 1806−20 cluster) is a heavily obscured star cluster on the far side of the Milky Way, approximately 28,000 light-years distant.[3] Some sources claim as far as 50,000. It contains the soft gamma repeater SGR 1806−20 and the luminous blue variable hypergiant LBV 1806−20, a candidate for the most luminous star in the Milky Way. LBV 1806−20 and many of the other massive stars in the cluster are thought likely to end as supernovas in a few million years, leaving only neutron stars or black holes as remnants.

The cluster is heavily obscured by intervening dust, and mostly visible in the infrared. It is part of the larger W31 H II region and giant molecular cloud. It has a compact core of ~0.2 pc in diameter with a more extended halo of ~2 pc in diameter containing the LBV[1] and at least three Wolf–Rayet stars (of types WC8, WN6, and WN7) and an OB supergiant, plus other young massive stars.[4]

See also

• Wolf–Rayet star
• LBV 1806−20
• SGR 1806−20
• Hypergiant
• Star cluster
• Luminous blue variable
• Charles Wolf
• Georges Rayet

References

1. SIMBAD/Aladin plot, of r=30 asec region around SGR B18054117-20251165
2. H. E. S. S. Collaboration; et al. (2018). "Extended VHE γ-ray emission towards SGR1806-20, LBV 1806-20, and stellar cluster Cl* 1806-20". Astronomy and Astrophysics. 612: 612. arXiv:1606.05404. Bibcode:2018A&A...612A..11H. doi:10.1051/0004-6361/201628695. S2CID 118345803.
3. Bibby, J.; Crowther, P.; Furness, J.; Clark, J. (2008). "A downward revision to the distance of the 1806-20 cluster and associated magnetar from Gemini Near-Infrared Spectroscopy". Monthly Notices of the Royal Astronomical Society. 386 (1). arXiv:0802.0815. Bibcode:2008MNRAS.386L..23B. doi:10.1111/j.1745-3933.2008.00453.x. S2CID 14466990.
4. Figer, Donald F.; Najarro, Francisco; Geballe, T. R.; Blum, R. D.; Kudritzki, Rolf P. (2005). "Massive Stars in the SGR 1806-20 Cluster". The Astrophysical Journal. 622 (1): L49 – L52. arXiv:astro-ph/0501560. Bibcode:2005ApJ...622L..49F. doi:10.1086/429159. S2CID 14696048.

External links

• The Unusual High-Mass Star Cluster 1806−20