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About this observation
Paul Leyland
Time of observation
25/06/2019 - 22:30
Observing location
Tacande Observatory, MPC J22
0.4m Dilworth-Relay
No filter
137x 30 second subs median filtered = 4110 seconds total
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M87 is renowned for having an enormous entourage of globular clusters.  There are at least 12,000 known and some are very bright considering their distance of 16.4 Mpc, which corresponds to a distance modulus of 31.0.  At that distance M13, which has an absolute magnitude of -8.5, would appear as a star of magnitude 22.5. The imaged globular cluster "Hyper-Velocity Globular Cluster 1" shines with a Gaia G magnitude of 20.61.  It would be an easy naked eye object at the distance of M13, comparable in brightness to ⍵ Centauri.

HVGC-1 doesn't technically belong to M87 any more.  It was ejected from the galaxy a long time ago, presumably by a gravitational sling shot from a black hole binary.  It is now travelling at 1026 km/s towards us (i.e. it is blue shifted) and moving at a speed of 2200 km/s away from M87, faster than the escape velocity of the entire Virgo cluster of galaxies!

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