Astronomers think that our own Star, the Sun, was born long ago in an open cluster inhabited by its long-since-lost fiery sister stars. In fact, almost all stars are born in groups. Most stars, like our own Sun in its infancy, form in benign environments, that are relatively peaceful--small clusters that rapidly fall apart, with their individual members going their own stellar ways. Others, alas, are doomed to inhabit older, dense clusters, where sister-stars bump into each other and jostle one another for precious space--while stormy stellar winds and powerful radiation, tearing through the space between stars, strip planet-birthing material from sister stars.prada handbags sale
Globular clusters are so named because their constituent stars are closely packed together into a symmetrical, almost spherical shape. These spherical clusters are the largest and most massive of all stellar clusters. Several globular clusters in our Milky Way are visible to the unaided eye as blurry patches of light, but sufficient attention was paid to them only after the telescope was invented. The first record of a globular cluster, located in the constellation Sagittarius, dates back to 1665--and it was ultimately named Messier 22, or M22. The second globular was spotted by the English astronomer and mathematician Edmond Halley in 1677. Studies of globulars have proven valuable because they have greatly aided astronomers in their understanding of our Milky Way Galaxy. In 1917, as a result of observations of the distributions and distances of globular clusters, the American astronomer Harlow Shapley, then of the Mount Wilson Observatory in California, was able to determine that the Milky Way's center is located in the Sagittarius region.低息
Messier 15--or M15, for short--was discovered in 1746 by Jean-Dominique Maraldi, and it was listed in Charles Messier's detailed catalogue of comet-like bodies in 1764.
M15 is approximately 33,600 light-years from our Solar System, and it is about 175 light-years in diameter. At approximately 12 billion years of age, it is certainly one of the oldest globular clusters bouncing around in our Galaxy. With a total luminosity of about 360,000 times that of our Sun, M15 is easily one of the most densely packed globular clusters in our Milky Way. Its heart--or core--has experienced core collapse, which is a form of contraction, and it has a central density cusp inhabited by a vast number of brilliant stars that circle around it.
This remarkable, mysterious, starlit bauble in the sky, is home to more than 100,000 fiery stars, and is also notable for harboring about 112 variable stars (a large number for this particular class of stars), and pulsars, including one double neutron star system.Finally, is to leave