Halley's Comet
Comet Halley
Orbital period : 75 years
Discovered : 1705
Last perihelion : February 9, 1986
Orbits : Sun
Discoverer : Edmond Halley
Meteor shower spawned: Orionids, Eta Aquarids
British astronomer Edmond Halley(1656-1742) was the first to prove that comets travel in orbits, making it possible to calculate when they will next be seen from Earth. He predicted that the comet he saw in1682 would return in1759. It did and was named in his honour.
- Halley's Comet is classed as a short period comet, a classification given to any comet that takes less than 200 years to orbit the Sun. It is believed that it was once a long period comet, but at some point the gravity of one of the Gas Giants (Jupiter, Saturn, Uranus or Neptune) attracted the comet. It didn't collide with any of these planets, but instead was flung into the inner Solar System towards the Sun. After orbiting the Sun, it is flung back outwards before being drawn back. This is kind of like a sling shot effect.
- Halley's Comet is darker than coal, and reflects only 4% of the sunlight it receives. It only shines brightly when it is close enough to the Sun for its dust and vapours to be burnt off.
- Halley's Comet is shaped like a peanut and is about 15 kilometres (9 miles) long, and 8 kilometres (5 miles) wide and thick.
- Halley's Comet is estimated to be 4.5 billion years old.
- Halley's Comet made of composition is comprised of water, hydrocarbons, iron, carbon monoxide, methane, ammonia, and sodium.
- The first up-close observation of the comet took place on March 4, 1986 when the Soviet Vega 1 probe started sending back images of Halley.
- Records of humans observing Halley’s Comet go back thousands of years, with appearances noted by Babylonian, Chinese and European star gazers.
- It last appeared in the inner Solar System in 1986 and will return again sometime in 2061.
-
American
writer Mark Twain was born on November 30th 1835, two weeks after an appearance
of Halley's Comet's. In his biography, he stated that he was born with Halley's
Comet, and is likely to die with it. Mark Twain died on April 21st 1910 - the
day after Halley's Comet reappeared.
(photograph of Halley's Comet was taken January 13,1986, by James W. Young, resident astronomer of JPL's Table Mountain Observatory
Date closest to Sun and Observations
25 May 240 BC : Seen in China.
10 October 12 BC : Belived to mark the deth of Roman general Agrippa.
28 June AD 451 : Belived to mark the defeat of Attila the Hun.
20 March 1066 : William believed the comet was the sign of imminent victory over king Harold at the battle of Hastings.
9 June 1456 : The defeat of the Turkish army by papal forces was thought to be linked to the comet.
15 September 1682 : Observed by Edmond Halley, who predicted its return.
13 March 1759 : The comet's first return, as predicted by Halley, proving his calculations correct.
16 November 1835 : American writer Mark Twain was born on November 30th 1835, two weeks after
an appearance of Halley's Comet's. In his biography, he stated that he was
born with Halley's Comet, and is likely to die with it. Mark Twain died on
April 21st 1910 - the day after Halley's Comet reappeared.
10 April 1910 : There was a panic as many believed the world would come to an end.
9 February 1986 : The Soviet Union
sent Vega 1 and Vega 2 to visit Halley's Comet, and the European Space
Agency sent Giotto. They recorded data and sent back images of the comet.
28 July
2061 :
Next due to appear.
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