Deep Sky

Constellation: Pegasus
Maraldi discovered this globular cluster in 1746, and Messier thought it was good enough to include it in his catalogue at M15 in 1764.  Cant blame him, I think its beautiful. It is one of the most densely packed globulars known in the Mikly Way, home to over 100,000 stars.   Of course, Lil Bill, our biologist, says one cluster looks like another.
Astronomers think this globular is one of the oldest at 12 billion years old.  It is approx 33,600 light-years from us, and some 175 light-years in diameter.  Its magnitude of -9.2.  Also, something I found interesting, it has undergone what they call a contraction known as a 'core collapse' , a central density cusp with a huge number of stars surrounding a black hole?  Not sure.  M15 contains some 112 + variable stars and at least 8  pulsars, including one double neutron star system. (take that Bill!)  Additionally, a fun fact, this cluster contains Pease 1, the first planetary nebula discovered within a globular cluster.  Only three others have been discovered in globulars since then.

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date: 9-15-12