Wikipedia:Main Page history/2011 May 21

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Today's featured article
The asteroid belt is a region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. More than half the mass of the belt is contained in the four largest objects: Ceres, 4 Vesta, 2 Pallas, and 10 Hygiea. These have mean diameters of more than 400 km, while the remaining bodies range down to the size of a dust particle. Individual asteroids within the main belt are categorized by their spectra, with most falling into three basic groups: carbonaceous (C-type), silicate (S-type), and metal-rich (M-type). The asteroid belt formed from the primordial solar nebula as a group of planetesimals, which in turn formed protoplanets. Between Mars and Jupiter, gravitational perturbations from the giant planet imbued the protoplanets with too much orbital energy for them to accrete into a planet. Collisions became too violent and, instead of sticking together, the planetesimals and most of the protoplanets shattered. Asteroid orbits continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter. Other regions of small solar system bodies include the centaurs, the Kuiper belt and scattered disk, and the Oort cloud. (more...) Recently featured: 1906 French Grand Prix – Netley Abbey – Taare Zameen Par Archive – By email – More featured articles...
Did you know...
From Wikipedia's newest articles: ... that Gidleigh Park, a hotel-restaurant in Chagford, Devon, England, is located in a Tudor-style country house (pictured) set in 54 acres of gardens and woodlands? ... that Montenegrin nationality law first recognised the right of renunciation of citizenship in 1905 during the reign of Nicholas I? ... that the Malagasy rodent Eliurus petteri is the only tufted-tailed rat with completely white underparts? ... that Lauren Beukes wore a fake sloth draped over her shoulders to the ceremony in which she won the 2011 Arthur C. Clarke Award for her novel Zoo City? ... that, as president of the College of St. Scholastica, Jesuit educator Francis X. Shea started a campus tradition by holding a fish fry at his home during the spring smelt run? ... that the Belgian Entertainment Association, established in February 2008, represents the interests of the music, video and video game industries in Belgium? ... that the 15.5-metre (51 ft) floodgate that protected Fudai, Iwate, Japan, from the recent tsunami was derided as a waste of public funds when it was built in the 1970s? Archive – Start a new article – Nominate an article

In the news
Boeing and Airbus both claim victory as the WTO rules on the world's largest trade dispute. Dominique Strauss-Kahn (pictured) resigns his position as head of the International Monetary Fund in the wake of sexual assault charges. The Eurozone financial leaders approve a €78-billion bailout package for Portugal, making it the third country, after Ireland and Greece, to receive a bailout in the Eurozone sovereign debt crisis. Queen Elizabeth II makes the first state visit by a British monarch to the Republic of Ireland. Space Shuttle Endeavour launches on its final mission, delivering the Alpha Magnetic Spectrometer for installation on the International Space Station. At least 12 Arab protesters are killed during Nakba Day protests and marches on Israel's borders. Wikinews – Recent deaths – More current events...
On this day...
May 21: Armed Forces Day in the United States (2011); Navy Day in Chile 879 – Pope John VIII became the first to officially recognise Croatia as a nation-state, and Branimir as its Duke. 1674 – John III Sobieski (pictured), elected by the szlachta, became the King of the Polish–Lithuanian Commonwealth. 1881 – Clara Barton founded the American Red Cross. 1911 – Mexican President Porfirio Díaz and the revolutionary Francisco Madero signed the Treaty of Ciudad Juárez to put an end to the fighting between the forces of both men, and thus concluding the initial phase of the Mexican Revolution. 1946 – Manhattan Project physicist Louis Slotin accidentally triggered a fission reaction at the Los Alamos National Laboratory and gave himself a lethal dose of hard radiation, making him the second victim of a criticality accident in history. 1998 – Indonesian President Suharto resigned following the collapse of support for his three-decade-long reign. More anniversaries: May 20 – May 21 – May 22 Archive – By email – List of historical anniversaries It is now May 21, 2011 (UTC) – Refresh this page

Today's featured picture

With almost 450 described species, Pergidae (Perga sp. larva pictured) is the third-largest family of sawflies. The members follow a Gondwanan distribution, occurring in the Americas and Australasia, with their greatest diversity in the Neotropics.

Photo: JJ Harrison

Recently featured: Chien-Ming Wang – Antigenic shift – "Salvage Scrap to Blast the Jap"

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