Melotte 15: Within ‘The Heart’ Nebula

7500 light years away from Earth, The Heart Nebula is located in the Perseus Arm of the Galaxy in the constellation Cassiopeia. The nebula is formed by plasma of ionized hydrogen and free electrons, and this open cluster of stars  contains a few bright stars nearly 50 times the mass of our Sun, and many more dim stars that are only a fraction of our Sun’s mass. The cluster used to contain a microquasar that was expelled millions of years ago. [image via]