Wikipedia:Main Page history/2011 June 18

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Artist's illustration showing the life of a massive star as nuclear fusion converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses to form a black hole. Theoretically, energy may be released during the collapse along the axis of rotation to form a gamma-ray burst.

Gamma-ray bursts (GRBs) are flashes of gamma rays associated with extremely energetic explosions in distant galaxies. GRBs are the most luminous electromagnetic events known to occur in the universe. A burst typically lasts 20–40 seconds, but can last from ten milliseconds to several minutes. The initial burst is usually followed by a longer-lived "afterglow" emitted at longer wavelengths. Most observed GRBs are believed to be a narrow beam of intense radiation released during a supernova event, as a rapidly rotating, high-mass star collapses to form a neutron star or black hole. The sources of most GRBs are billions of light years from Earth, implying that the explosions are both extremely energetic and extremely rare. GRBs were first detected in 1967 by the Vela satellites, but it was not until 1997 that they were better understood, with the use of optical spectroscopy to detect the first X-ray and optical afterglows and to directly measure their redshifts. (more...)

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Did you know...

From Wikipedia's newest content:

A small bird with green back, brown belly and blue wings with black-and-white feathers

  • ... that the diet of Mangrove Pitta and Blue-winged Pitta (pictured) includes hard-shelled snails?
  • ... the Ionian University of Smyrna, established in Turkey by Greece during the occupation of Smyrna, was never opened due to latter's defeat in the Greco-Turkish War?
  • ... that it was during Operation Fustian in 1943, that artillery was first flown into combat?
  • ... that after publishing bestsellers Father Goose and The Wonderful Wizard of Oz, the George M. Hill Company was compelled in 1902 to declare bankruptcy?
  • ... that Indonesian politician Mohammad Roem moved to Pekalongan as a child to escape an outbreak of cholera?
  • ... that the Harvard Institute for International Development co-developed the Harvard Analytical Framework, which showed the importance of channeling foreign aid to women?
  • ... that Somerset County Cricket Club named three official captains for the 1948 season?
  • In the news

  • Let the Great World Spin, by Irish writer Colum McCann (pictured), wins the International IMPAC Dublin Literary Award.
  • Ayman al-Zawahiri succeeds Osama bin Laden as al-Qaeda's leader.
  • In ice hockey, the Boston Bruins defeat the Vancouver Canucks in game seven to win the Stanley Cup for the first time since 1972.
  • Amid protests and deepening economic crisis, Greek Prime Minister George Papandreou submits a new cabinet for a vote of confidence.
  • In basketball, the Dallas Mavericks defeat the Miami Heat to win their first NBA championship.
  • A Gay Girl In Damascus, a popular opposition blog about the 2011 Syrian uprising, is revealed to be a hoax.
  • On this day...

    June 18: International Sushi Day

    Emperor Gaozu of the Tang Dynasty

  • 618 – Lǐ Yuān became Emperor Gaozu of Tang (pictured), initiating three centuries of the Tang Dynasty in China.
  • 1815War of the Seventh Coalition: Napoléon Bonaparte fought and lost his final battle, the Battle of Waterloo in Belgium.
  • 1908 – The University of the Philippines, the national university of the Philippines, was established.
  • 1979 – The United States and the Soviet Union signed the SALT II treaty, placing specific limits on each side's stock of nuclear weapons.
  • 1994The Troubles: Members of the loyalist Ulster Volunteer Force attacked a crowded bar in Loughinisland, Northern Ireland, with assault rifles, killing six.
  • More anniversaries: June 17June 18June 19

    Today's featured picture

    Machu Picchu

    Machu Picchu, with the peak Huayna Picchu behind it. Perhaps the most famous Inca site, Machu Picchu is situated on a mountain ridge above the Urubamba Valley in Peru. It was probably built as an estate for the Inca emperor Pachacuti in the 15th century, but abandoned soon after during the Spanish conquest of the Inca Empire. Although known locally, it was unknown to the outside world before being brought to international attention in 1911 by the American historian Hiram Bingham, and is now an important tourist attraction.

    Photo: Martin St-Amant

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