For this week's APOD, I chose the picture called Globular Cluster M15 From Hubble, uploaded on May 3. It was taken by the earth-orbiting Hubble Space Telescope, and captures an object that is 35,000 light years away.
Many stars are around the center of the cluster, about 100,000 to be more exact. This is an old group of stars, that still orbits the center of the Milky Way. The whole thing spans close to 120 light years, and is located toward the constellation Pegasus. Globular clusters are gravitationally bound concentrations of stars, spread out over a long diameter. These types of clusters can usually be found near the halo of The Milky Way Galaxy. This is only one of the 150 globular clusters remaining, but is a very visible one at that. One can examine it with only a pair of binoculars, as its center is known for having one of the densest groups of stars, which contains many variable stars and pulsars. Variable stars are those that swarm the center and often fluctuate in brightness. Pulsars are spinning neutron stars that blink on and off at a consistent frequency. There is an easily seen increased density of stars in the center, and it is rumored that the center of M15 might in fact become a black hole someday.
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