M 3
M 3
M3 is one of the most outstanding globular clusters, containing an estimated half million stars! It is extremely rich in variable stars: According to B. Madore (in Hanes/Madore, Globular Clusters, 1978), 212 variables have been found, 186 periods determined, more than in every other globular cluster in our Milky Way galaxy (and thus the most ever observed); at least 170 RR Lyrae variables were discovered.
This cluster was the first `original' discovery by Charles Messier when he logged it on May 3rd, 1764. At that time it was the 63rd or 64th deep sky object ever observed by human eyes (and apparatus), according to my sources and current knowledge [- hf]. It was also apparently the discovery of this object which eventually caused Charles Messier to start a systematical search for these comet resembling objects, and not just catalog chance findings as in the previous cases M1 and M2, as is demonstrated by the fact that in 1764, he found and measured all the objects M3-M40.
When the final object of the catalog, M107, a globular cluster in Ophiuchus, was discovered by Messier's friend Pierre Mechain in 1782, 16 years later, a total of at least 140 objects were known, more than double the number, and 110 of them described by Messier (who discovered 42 or 43) and Mechain (27 or 28) -- the doubty counting being a result of the dubious circumstances concerning the discovery of M102.
| Right ascension | 13 : 39.9 (hours : minutes) |
|---|---|
| Declination | +28 : 38 (degrees : minutes) |
| Distance | 30.0 (light-years*10^3) |
| Visual magnitude | 6.3 |
