by Bob Franke
North is to the top
Charles Messier discovered M48 in 1771. Charles mistakenly cataloged the cluster's location. This led to later independent discoveries by Johann Elert Bode in 1782 and William Herschel's sister, Caroline Herschel, in 1783. Herschel published his sister's discovery in his catalog as H VI.22 on February 1, 1786.
The cluster spans roughly 23 light-years and lies about 1,500 to 2,000 light-years away, toward the constellation of Hydra. M48 is about 300 million years old, still young enough to have many young bright blue stars. Clusters, like this, are loosely bound by gravity. As they age, the clusters spread out and the member stars slowly escape.