| Emission nebula | |
|---|---|
| H II region | |
 Artist's impression ofSGR 1806-20, a magnetar located in1806-20 cluster | |
| Observation data:J2000epoch | |
| Right ascension | 18h 10m 28.6s[1] |
| Declination | −19° 55′ 51″[1] |
| Distance | 11,000–15,000 ly (3,300[2]–4,500[3] pc) |
| Constellation | Sagittarius |
| Notable features | massiveH II region Star-forming regions |
| Designations | GRS G010.47 +00.03[1] |
| See also:Lists of nebulae | |
Westerhout 31, also known asW31, is a complex ofstar formation regions of theMilky Way located in the constellation ofSagittarius.
As happens with other similar star-forming regions, Westerhout 31's location in the Milky Wayobscures it so much due to theinterstellar dust located between it and theSolar System that it cannot be studied withopticaltelescopes and for its observationinfrared telescopes such asSpitzer,radiotelescopes, or instruments able to detectX-Rays andgamma rays are needed.
Westerhout 31 seems to be actually formed of several star-forming regions at very different distances that from our line of sight appear together: one (formed by the radio-emittingnebulaeG10.2-0.3 andG10.6-0.4) at a distance of 3.3[2] or 4.5[3]kiloparsecs from theSun and other (the radio-emitting nebulaG10.3-0.1) much farther away, at a distance between 11.8[4] and 14.5[3] kiloparsecs (in the other side of the galaxy respect to the Sun, with the former distance more likely due to its stellar content).
G10.3-0.1 is the most notable as it contains thestar cluster1806-20 that includes the famousluminous blue variable starLBV 1806-20, themagnetarSGR 1806-20, twoblue hypergiant stars, asupergiantO star, threeWolf-Rayet stars, two of them carbon-rich, and other young, massive stars.
The closest complex, formed byG10.2-0.3 andG10.6-0.4, includes a very young (0.6Myr) star cluster with at least four O stars and five massiveYSOs.[2]