Black holes Relation of Black Hole Mass to Cluster Mass September 17, 2002 · NASA · M15, M31 G1 Zoom to full resolution Share Original on NASA ↗ More Hubble images of M15, M31 G1Using Spectroscopy to Measure Velocity DispersionSeptember 17, 2002Relative Location of M15 and M31 G1September 17, 2002Evidence for Existence of a Black HoleSeptember 17, 2002Location of M15 and M31 G1 in the Northern Autumn SkySeptember 17, 2002Black Holes Unexpectedly Discovered in Globular Clusters M15 and G1September 17, 2002Globular Cluster M15September 17, 2002Globular Cluster M31 G1September 17, 2002Location of Globular Cluster G1 in Galaxy M31September 17, 2002 ← Newer: Using Spectroscopy to Measure Velocity DispersionOlder: Relative Location of M15 and M31 G1 →