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. It contains more than 300 stars brighter than Mb=−3.6. It was originally identified by
Edwin Hubble as a star cluster but today, due to its size, it is classified as an
OB association. 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. ==See also==