Rigel is a blue supergiant star in the constellation of Orion, approximately 860 light-years (260 pc) from Earth. It is the brightest and most massive component of a star system of at least four stars that appear as a single blue-white point of light to the naked eye. A star of spectral type B8Ia, Rigel is calculated to be anywhere from 61,500 to 363,000 times as luminous as the Sun, and 18 to 24 times as massive. Its radius is over 70 times that of the Sun, and its surface temperature is 12,100 K. Rigel varies slightly in brightness, its apparent magnitude ranging from 0.05 to 0.18. It is classified as an Alpha Cygni variable. It is generally the seventh-brightest star in the night sky and is usually the brightest star in Orion, though it is occasionally outshone by Betelgeuse. With an estimated age of 7 to 9 million years, Rigel has exhausted its core hydrogen fuel, expanded and cooled to become a supergiant. It will end its life as a type II supernova. (Full article...)
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Source: Wikimedia Commons.
- 1542 – Explorer Juan Rodríguez Cabrillo (pictured), the first European to travel along the coast of California, landed at what is now the city of San Diego.
- 1912 – Over 470,000 people from Ulster, Ireland, signed the Ulster Covenant in protest against the Third Home Rule Bill.
- 1963 – Whaam!, now considered one of Roy Lichtenstein's most important works, debuted at an exhibition held at the Leo Castelli Gallery, New York City.
- 2014 – Hong Kong protests: Unhappy with the direction of electoral reform, Occupy Central with Love and Peace began a civil disobedience campaign to fight for equal suffrage.
- Age of Earth: ~ 4.568 billion years
- World Population: 7.3 billion (July 2015)
- Continents: 7 (Asia, Africa, North America, South America, Antarctica, Europe, and Australia)
- Mean Radius: 6371.0 km
- Axial Tilt: 23,44°
Image Source: Wikipedia - License: Public Domain (thanks to NASA)
Our solar system consists of
1 star (Sun) and 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune).
- 1 AU (astronomical unit) is roughly the distance between Earth and the Sun (about 150 million kilometres).
- The space probe Voyager 1 was launched by the NASA in 1977 and is meanwhile (autumn 2015) about 133 AU away from Earth.