Globular Cluster in Canes Venatici
More variable stars (over 270) have been found in Messier 3 than in any other globular cluster. More than half of these are categorized as RR Lyrae variables, which change in brightness over periods of just a few hours. This makes it possible to take a series of pictures in a single night and record these stars brightening and dimming.
More than 20 of these short-period variables can be seen in this sequence of four images taken roughly 1 hour apart. If you look carefully both around the periphery of the cluster and also closer to the center, you can see them blinking as they increase and decrease in brightness.
Messier 3:
| Magnitude | 6.4 |
| Apparent Size | 16' |
| Distance (light yrs) | 32,000 |
| Right Ascension | 13:42.2 |
| Declination | +28 32 |
Image details: Each of the four images is based on exposure times of 5 minutes luminance and 4 minutes each of red, green, and blue, taken with an SBIG ST-8300M imager and a 14" Meade LX850 telescope at f/6.
April 2017