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| Globular Clusters in NGC 4490 - Photo: Flickr |
Globular clusters are defined as a dense grouping of thousands to millions of stars. They are comprised of young stars at millions of years old to older stars at billions of years old. The stars in these clusters are usually very tightly bound together.
They are considered deep sky objects. They are easily found in the night sky in the hours before midnight in the months of April through September. They appear in your telescope as concentrated patches of gray mist. The amazing part is the average distance between any of the given stars is between ¾ to 1 ½ light years.
The most spectacular of all is the NGC 5139. You can see it with your naked eye because it is three times the moon's diameter. There are millions of stars that take up your viewfinder. It is truly a wondrous sight to behold. If you live in or around North Carolina close to the latitude of +36 degrees, you will be able to spot it easily in the night sky.
Clusters such as these are very common. In the Milky Way, there are 150 known clusters. The Andromeda galaxy could have upwards of 500. The giant elliptical galaxies, such as M87, have as many as 10,000. The neat thing is the globular clusters contain some of the first stars that were created when time began. Their origins are still unclear.
The major part of these clusters is found near the galactic core. And another large majority lie on the celestial sky side. Clusters contain a high density of older stars but they are not great locations for planetary systems. The orbits of the planets become unstable in the dense clusters. These clusters can be dated by viewing the temperature the coolest white dwarf stars are in the group. Common results say some of these stars are 12.7 billion years old or older.
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