Hyper-Velocity Globular Cluster 1, HVGC-1.


The overwhelming majority of globular clusters are in orbit around a galaxy. HVGC-1 is a very rare exception. Some billions of years ago it must have approached very close to a super-massive black hole and the gravitational sling-shot effect ejected it from Messier 87 at high velocity. Its speed is so high that it will escape not only from M87 but from the entire Virgo cluster of galaxies. The galaxy is far enough away from us that it is receding from us because of the overall expansion of the universe. HVGC-1, on the other hand, is approaching at 1026 km s-1 and leaving M87 at 2200 km s-1 or 0.7% of the speed of light.

M87 is 16.4 megaparsec away. At that distance the Sun would be a 36th magnitude star and far too faint to be seen with any telescope yet built. Even M2, a bright globular cluster in our galaxy and visible in binoculars, would look like a 22nd magnitude star at that distance. HVGC-1 shines at magnitude 20.61, meaning it would be an easy naked eye object if it were as close as M2.

Image information
Date and time of observation  2019-06-25 00:10 UT
Telescope 0.4m f/6.5 Dilworth-Relay
Filter None
Exposure 137×30s (4110s total)
Centre of image RA 12h30m54.9s  Dec +12°40'45"
Image dimensions 12.7 arcmin × 7.0 arcmin