Messier 37- Open star cluster in the Constellation Auriga

Messier 37 - Combined image - stack of 10 x 30sec lights with the Altair 66mm Doublet wide-field scope  from the Jodrell Plank Observatory (Credit: Archie Mendes) and  1x 180sec light with the PIRATE robotic telescope (Credit: telescope.org - Open University) - combined using Registar Software -(Credit: Pip Stakkert)

"Open star clusters are collections of up to a few thousand stars loosely bound by mutual gravitational attraction. The stars in an open cluster form from the same giant molecular cloud of gas and dust. More than 1100 open clusters have been found in the Milky Way. Open clusters are  found  only in spiral and irregular galaxies where active star formation is occurring. They generally survive for a few hundred million years before the stars disperse as the result of galactic migration and disturbance in close encounters with other clusters. Massive clusters may stay together longer surviving for a few billion years.
Messier 37 is the richest open star cluster in the constellation Auriga and is approximately 4500 light years distant. So the light we collected the other night from M37 set off from the cluster when on Earth the Pyramids were being constructed. The cluster has an estimated combined mass of 1500 suns and angular diameter of 24 arc minutes which corresponds to a dimension of 20 to 25 light years. Messier 37 is somewhere between 350 and 550 million years old - in cosmic terms quite young - younger than the Hyades but older than the Pleiades". - Kurt Thrust - acting CEO and current Director of the Jodrell Plank Observatory.