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Messier 15 or
M15 (also designated
NGC 7078) is a
globular cluster in the
constellationPegasus. It was discovered by
Jean-Dominique Maraldi in 1746 and included in
Charles Messier's catalogue of
comet-like objects in 1764.[
citation needed] At an estimated 12.5±1.3 billion years old, it is one of the oldest known globular clusters.
[10]M 15 is about 35,700
light-years from
Earth,
[3] and 175 light-years in diameter.
[11] It has an
absolute magnitude of −9.2, which translates to a total
luminosity of 360,000 times that of the
Sun. Messier 15 is one of the most densely packed globulars known in the
Milky Way galaxy. Its core has undergone a contraction known as "
core collapse" and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole.
[12]Home to over 100,000 stars,
[11] the cluster is notable for containing a large number of
variable stars (112) and
pulsars (8), including one double
neutron star system, M15-C. It also contains
Pease 1, the first
planetary nebula discovered within a globular cluster in 1928.
[13] Just three others have been found in globular clusters since then.
[14]https://en.wikipedia.org/wiki/Messier_15
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