Main Page

The main sequence is a continuous and distinctive band of stars that appear on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung-Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell. After a star has formed, it generates energy at the hot, dense core region through the nuclear fusion of hydrogen atoms into helium. During this stage of the star's lifetime, it is located along the main sequence at a position determined primarily by its mass, but also based upon its chemical composition and other factors. All main sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward gravitational pressure from the overlying layers. The main sequence is sometimes divided into upper and lower parts, based on the dominant process that a star uses to generate energy. Stars below about 1.5 times the mass of the Sun primarily fuse hydrogen atoms together in a series of stages to form helium, a sequence called the proton-proton chain. Above this mass, in the upper main sequence, the nuclear fusion process mainly uses atoms of carbon, nitrogen and oxygen as intermediaries in the production of helium from hydrogen atoms. Main sequence stars below 0.4 solar masses undergo convection throughout their mass. In general, the more massive the star the shorter its lifespan on the main sequence. (more...)

Recently featured: Red River Trails – Barthélemy Boganda – Germanium

From Wikipedia's newest articles:

• ... that the Chattri (pictured) in Brighton, England, stands on the site of the ghat where Hindu and Sikh soldiers of the First World War were cremated after dying while being treated at the Royal Pavilion?
• ... that ballerina Jocelyn Vollmar danced as the Snow Queen in the first American production of The Nutcracker?
• ... that the original Sinhalese Sports Club Ground was situated on land of Victoria Park with sandy soil and covered with cinnamon trees?
• ... that future A.B.A. president Loyd Wright represented Mary Pickford in her divorce of Douglas Fairbanks and Jane Wyman against Ronald Reagan?
• ... that the property of Sjøholmen in Bærum, Norway, started out as a farm, was suburbanized and is now, in part, an alternative school where children are taught to be mariners?
• ... that during his study of the palm family, Harold E. Moore collected all but 18 of the approximately 200 genera of palms, and earned membership in The Explorers Club?
• ... that the Galápagos hotspot, located in the east Pacific Ocean, is responsible for the creation of the Galápagos Islands?
• ... that association footballer Mikkel Diskerud played both for and against the United States national youth team in the spring of 2008?
  
  Archive – Start a new article – Nominate an article

• The Pakistan Rangers and Elite Police retake a police academy in Lahore which had been seized by gunmen.
• Coalition for a European Montenegro wins an absolute majority in the parliamentary election, securing Milo Đukanović (pictured) a sixth term as the Prime Minister of Montenegro.
• Researchers from the University of Toronto report the discovery of GhostNet, a China-based electronic spying operation which has infiltrated at least 1,295 computers in 103 countries.
• In a referendum, Mayotte chooses to become an overseas department of France.
• A stampede kills at least 22 people and injures at least 130 more during a 2010 FIFA World Cup qualifying match in Abidjan, Côte d'Ivoire.
• Flooding in the Red River causes evacuations in Manitoba, Canada, and in North Dakota and Minnesota, USA.
  Wikinews – Recent deaths – More current events...

March 31: César Chávez Day in various U.S. states; Freedom Day in Malta

• 1778 – English explorer James Cook landed on Vancouver Island and claimed it for Great Britain.
• 1854 – Commodore Matthew C. Perry of the U.S. Navy signed the Treaty of Kanagawa, forcing the opening of Japanese ports to American trade.
• 1903 – New Zealand inventor Richard Pearse reportedly flew in one of the first powered flying machines (replica pictured) for a distance of several hundred metres, about nine months before the Wright brothers flew their Wright Flyer.
• 1917 – The Danish West Indies became the U.S. Virgin Islands after the United States paid Denmark US$25 million for the Caribbean islands.
• 1995 – American singer Selena, known as "The Queen of Tejano music", was shot and killed in Corpus Christi, Texas, by the president of her fan club, Yolanda Saldívar.
• 2004 – Iraq War: Iraqi insurgents in Fallujah ambushed a convoy containing four American contractors from the private security company Blackwater USA.

• More events: March 30 – March 31 – April 1

  Archive – By email – More anniversaries...
  It is now March 31, 2009 (UTC) – Refresh this page