One of the biggest viral news stories of 2011 was the discovery of Comet Elenin (C/2010 X1). For a wide variety of reasons, people began to think the comet posed a threat to Earth. Articles were written that examined Elenin. People were intrigued by the comet and its close approach to the Earth in October, 2011. Some predicted Comet Elenin was a sign that the Maya prophecy was valid. In response to the attention, NASA was forced to give a collection of statements. They said the comet posed no threat to the Earth. On August 19, 2011, the story burst into flames and quickly disappeared. Here are ten interesting facts about Comet Elenin.
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What is a Comet?
In ancient history, comets were traditionally considered to be bad omens. They are small Solar System bodies (SSSB) that will display a visible coma (a thin, fuzzy, temporary atmosphere) when close to the Sun. The main difference between an asteroid and a comet is that a comet shows a coma. Asteroids are also thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System. This gives the orbital history of comets more importance.
The coma of a comet is formed when it passes by the Sun. The coma is generally made of ice and dust, and can grow to be incredibly large. In October 2007, comet 17P/Holmes briefly had a tenuous dust atmosphere larger than the Sun. It has been estimated that roughly one comet is discovered each year that is visible to the human eye. In some rare cases, a Great Comet can form which is brighter than any star in the sky. It has been estimated that one Great Comet will appear every decade.
The requirements for a Great Comet include a large and active nucleus, a close approach to the Sun, and a close approach to the Earth. In 1996, Comet Hyakutake, which had a similar sized nucleus as Comet Elenin, made an extremely close approach to Earth. The Ulysses spacecraft crossed the Hyakutake’s tail at a distance of more than 500 million kilometers (3.3 AU or 3×108 mi) from the nucleus, showing that Hyakutake had the longest tail known for a comet.
