open cluster

description

An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age.

distribution

Open clusters are not seen in elliptical galaxies: Star formation ceased many millions of years ago in ellipticals, and so the open clusters which were originally present have long since dispersed.
In spiral galaxies, open clusters are largely found in the spiral arms where gas densities are highest and so most star formation occurs, and clusters usually disperse before they have had time to travel beyond their spiral arm.
In irregular galaxies, open clusters may be found throughout the galaxy, although their concentration is highest where the gas density is highest.

plural

open clusters

random

Osama bin Laden (Wikipedia) Osama bin Mohammed bin Awad bin Laden (Arabic: أسامة بن محمد بن عوض بن لادن, romanized: Usāma bin Muḥammad bin ʿAwaḍ bin Lādin; 10 March 1957 – 2 May 2011) was a Saudi Arabian-born Islamist dissident and militant leader who was the founder and first general emir of al-Qaeda from 1988 until his death in 2011. Ideologically a pan-Islamist, he participated in the Afghan jihad against the Soviet Union and supported the activities of the Bosnian mujahideen during the Yugoslav Wars. Bin Laden is most widely known as the mastermind behind the September 11 attacks in the United States.

tags

star cluster

Wikipedia

Open cluster (Wikipedia)