Messier 107, NGC 6171

Messier 107 is a very loose globular cluster in the constellation Ophiuchus.

This 9th magnitude cluster was discovered by Pierre Mechain in April of 1782, and independently by William Herschel in 1793. However, M 107 wasn't formally added to the Messier list until 1947, by Helen Sawyer Hogg.

Visually, M 107 is about 3' across, while in photos it extends to a diameter of about 13'. M 107 has a very open, loose star distribution; it also apparently contains some dark, obscured regions, which is unusual for a globular cluster.

M 107 has a diameter of about 80 light-years, and approximately 21,000 light-years away. It contains at least 50,000 stars, of which 25 are known variables. M 107 is approaching us at 147 km/sec.