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On October 4, 1957, Sputnik 1 became the first artificial satellite to orbit the Earth after being launched by the Soviet Union.
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On 3 November, 1957 Laika the dog (Soviet Union) became the first animal in space and also the first animal to die in space, after overheating several hours after launch.
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On April 12, 1961, Yuri Gagarin (Soviet Union) became the first human to orbit the Earth, doing so in the spaceship Vostok 1. He returned to Earth as an international celebrity, and was also crowned 'Hero of the Soviet Union,' the nations highest honour. He died in 1968 when a MiG 15 training jet he was flying crashed.
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On 16 June, 1963, in the Vostok 6, Valentina Tereshkova became the first woman to go into space. She was selected out of over 400 applicants, and then from 5 finalists. She spent 2 days, 22 hours and 50 minutes in space before returning to Earth for a safe touchdown.
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Neil Armstrong and Buzz Aldrin become the first people to walk on the moon after a four day journey through space.
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On March 11, 1986, Halley's comet passed through the inner solar system. Named after Edmund Halley, who determined it's periodicity in 1705, Halley's comet it the best known of the short period comets , and it is visible from Earth every 75-76 years.
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On 5 January, 2005, Eris was discovered by a Palomar Observatory team. Led by Mike Brown, the team calculated that it was 2300-2400km in diameter, or about 23% larger than pluto, or about 0.27% of Earth's mass. It was classified a planet until the IAU defined what it meant to be a planet, therefore classifying Eris as a dwarf planet.
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On 24 August, 2006 scientists at the International Astronomical Union (IAU) classified Pluto as a dwarf planet, after the IAU defined what it meant to be a planet. This definition excluded Pluto as a planet and added it as a member of the new category of a 'dwarf planet.'
