The Oort cloud (artist's rendering pictured) is a hypothesized spherical cloud of comets that may lie nearly a light-year from the Sun. It is thought to comprise two separate regions: a spherical outer Oort cloud and a disc-shaped inner Oort cloud, or Hills cloud; the outer extent of the cloud defines the boundary of the Solar System. Objects in the Oort cloud are largely composed of ices, such as water, ammonia, and methane and are thought to have formed close to the Sun, later being scattered into space by the gravitational effects of the giant planets early in the Solar System's evolution. Although no confirmed direct observations of the Oort cloud have been made, astronomers believe that it is the source of all long-period and Halley-type comets entering the inner Solar System, as well as many of the Centaurs and Jupiter-family comets.

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

_______________________________ Today's selected anniversaries:

1786:

Michel-Gabriel Paccard and Jacques Balmat completed the first recorded ascent of Mont Blanc in the Alps, an act considered to be the birth of modern mountaineering. http://en.wikipedia.org/wiki/Mont_Blanc

1918:

The Battle of Amiens began in Amiens, France, marking the start of the Allied Powers' Hundred Days Offensive through the German front lines that ultimately led to the end of World War I. http://en.wikipedia.org/wiki/Battle_of_Amiens_%281918%29

1929:

German airship LZ 127 Graf Zeppelin embarked on a flight to circumnavigate the world. http://en.wikipedia.org/wiki/LZ_127_Graf_Zeppelin

1967:

Indonesia, Malaysia, the Philippines, Singapore and Thailand founded the Association of Southeast Asian Nations. http://en.wikipedia.org/wiki/ASEAN

1988:

The 8888 Uprising, a series of marches, demonstrations, protests, and riots against the one-party state of the Burma Socialist Programme Party in Burma, began. http://en.wikipedia.org/wiki/8888_Uprising

_____________________________ Wiktionary's word of the day:

obesogenic (adj): That causes obesity http://en.wiktionary.org/wiki/obesogenic

___________________________ Wikiquote quote of the day:

No live organism can continue for long to exist sanely under conditions of absolute reality; even larks and katydids are supposed, by some, to dream. --Shirley Jackson http://en.wikiquote.org/wiki/Shirley_Jackson