Celestial Splendors

Among the most magnificent celestial splendors are globular star clusters. These are spherical in shape, and each contains from ten thousand to hundreds of thousands of stars. There are about 100 known globular clusters in our Milky Way galaxy.

In our neighborhood of the Milky Way, stars are spaced an average of four to five light-years apart.a In a globular cluster, the stars are packed tightly, about one tenth of a light-year apart.

The cluster in the photograph is Omega Centauri. To the naked eye, it appears to be a single star. However, through a large telescope, it becomes a dazzling cluster of many stars, some one million in all. Omega Centauri can be seen best in the Southern Hemisphere, though on spring and summer evenings up to the middle northern latitudes, it can be observed low in the southern sky.

The diameter of Omega Centauri is about 150 light-years; it would take approximately 150 years for light to travel from the bottom of the photograph to the top! The distance from the earth to Omega Centauri is an estimated 17,000 light-years.

For ages, Omega was known as a single star. In the 17th century, German amateur astronomer Johann Bayer labeled it with the Greek letter Omega (ω). However, it was first observed as a globular cluster by English astronomer Edmond Halley in 1677.

In the Northern Hemisphere, one of the best clusters to observe is M13, in the Hercules constellation. It contains about one million stars and is 4,000 light-years farther away from us than Omega Centauri. So it appears smaller.

If you have an opportunity to observe a globular cluster through a moderately large telescope, by all means do so. It is one of the most impressive creations you can see in the night sky.

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Omega Centauri

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National Optical Astronomy Observatories

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M13

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Milky Way galaxy and M13: Courtesy United States Naval Observatory