A globular cluster is a spherical collection of stars that orbits a galaxy core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shape, and relatively high stellar density towards their core. Globular clusters contain considerably more stars than the less dense galactic, or open clusters. Globular clusters are fairly numerous; there are about 150 currently known globular clusters in the Milky Way, with perhaps 10– 20 more undiscovered. Large galaxies can have more: Andromeda, for instance, may have as many as 500. Some giant elliptical galaxies, such as M87, may have as many as 10,000 globular clusters. These globular clusters orbit the galaxy out to large radii, 40 kiloparsecs or more. Every galaxy of sufficient mass in the local group has an associated group of globular clusters, and almost every large galaxy has been found to possess a system of globular clusters. The Sagittarius Dwarf and Canis Major Dwarf galaxies appear to be in the process of donating their associated globular clusters to the Milky Way, such as Palomar 12.

Read the rest of this article: http://en.wikipedia.org/wiki/Globular_cluster

_______________________________ Today's selected anniversaries:

1459: Yorkist forces led by Richard Neville won the Battle of Blore Heath in Staffordshire, England, the first major battle of the Wars of the Roses. (http://en.wikipedia.org/wiki/Battle_of_Blore_Heath)

1845: Origins of baseball: Alexander Cartwright organized the first "base ball" team, the New York Knickerbockers. (http://en.wikipedia.org/wiki/New_York_Knickerbockers)

1846: The planet Neptune was discovered by astronomers Urbain Le Verrier, Johann Gottfried Galle and John Couch Adams. (http://en.wikipedia.org/wiki/Neptune)

1868: Ramón Emeterio Betances led the Grito de Lares, a revolt against Spanish rule in Puerto Rico. (http://en.wikipedia.org/wiki/Grito_de_Lares_(The_Cry_of_Lares))

1932: Hejaz and Nejd were merged and renamed the Kingdom of Saudi Arabia, with Ibn Saud as the first monarch and Riyadh as the capital city. (http://en.wikipedia.org/wiki/Saudi_Arabia)

_____________________ Wikiquote of the day:

"There is in the worst of fortune the best of chances for a happy change." -- Euripides (http://en.wikiquote.org/wiki/Euripides)