NGC 206
OB association in the Andromeda Galaxy
From Wikipedia, the free encyclopedia
NGC 206 is a bright star cloud in the Andromeda Galaxy, and the brightest star cloud in Andromeda when viewed from Earth. It was discovered by German-born English astronomer William Herschel in 1786[2] and possibly even two years earlier when he observed "a streak of milky nebulosity, horizontal, or part of the 31st Nebula."
| NGC 206 | |
|---|---|
NGC 206 | |
| Observation data (J2000 epoch) | |
| Right ascension | 00h 40m 31.3s[1] |
| Declination | +40° 44′ 21″[1] |
| Absolute magnitude (V) | Unknown |
| Apparent dimensions (V) | 4.2′ (arcmin) |
| Physical characteristics | |
| Radius | Ca. 400 ly |
| Associations | |
| Constellation | Andromeda |
Features
NGC 206 is the richest and most conspicuous star cloud in the Andromeda Galaxy, and is one of the largest and brightest star-forming regions in the Local Group.[3] It contains more than 300 stars brighter than Mb=−3.6.[4] It was originally identified by Edwin Hubble as a star cluster but today, due to its size, it is classified as an OB association.[5]
NGC 206 is located in a spiral arm of the Andromeda Galaxy, in a zone free of neutral hydrogen. It contains hundreds of stars of spectral types O and B. The star cloud has a double structure: one region has an age of around 10 million years and includes several H II regions in its border; the other region has an age of 40 to 50 million years and includes a number of cepheids. The two regions are separated by a band of interstellar dust.[6]
