GLOBULAR CLUSTERS…What are they?

You may have heard the term “Globular Clusters” before, but exactly what are they?  According to the Planetary Society: “Like stellar time capsules adorning the periphery of galaxies, globular clusters contain some of the oldest stars in the universe.” Some of these star clusters may seem to have the appearance of galaxies. This is because they are a symmetrical system of stars with the highest concentration of stars near their own center and bound together by gravity. Imagine yourself on a world where the sky is always ablaze with the sight of hundreds of thousands of stars as bright as the full Moon. Most likely these stars would be the older, fainter, red and yellow stars.

The more dense globular clusters can be found in the halo of a galaxy, whereas the less dense galactic, or open, clusters are located in the disk of a galaxy. The clusters in the halo contain considerably more stars than the open clusters. Globular clusters are fairly common; there are about 157 of them currently known in the Milky Way Galaxy. Larger galaxies, such as our neighbor Andromeda, may have as many as 500. Moreover, the giant elliptical galaxies may have as many as 13,000 globular clusters.

The first globular cluster discovered was M22 in 1665 by Abraham Ihle, a German amateur astronomer. However, given the poor aperture ability of early telescopes, individual stars within a globular cluster were not resolved until Charles Messier observed M4, discovered in 1746. The designation before a number refers to the catalog where the discovery is listed. The letter “M” tells us it is listed in the Messier catalog, whereas “NGC” tell us it could be found in the New General Catalog by John Dreyer. The designation letter is something that I’ve wondered about and just learned more details in this research.

We have 157 cataloged globular clusters right in our own galactic neighborhood, the Milky Way. There are too many to list here, but our largest cluster is Omega Centauri (NGC5139) and second is 47 Tucanae, both of which can be observed with the naked eye under the right conditions., M4 and NGC6397 are both 7200 light years away. Some other noteworthy clusters are NCG104, NGC4833, M55, M69, and M13. There are so many of these beautiful star clusters - out there, waiting for you to discover.

Stunning images and more info at: http://www.astro.keele.ac.uk/workx/globulars/globulars.html

My sources: NASA.gov, en.wikipedia.org, spider.seds.org, astrosociety.org, hyperphysicis.phy-astr.gsu.edu, astro.keele.ac.uk, Britannica.com, The Planetary Society, ned.ipac,caltech.edu, and astronomy.com.