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.

1806−20 cluster
Observation data (J2000 epoch)
Right ascension	18h 08m 39.33s[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
See also: Open cluster, List of open clusters

H-band infrared image of 1806−20 cluster

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