Halley's Comet
The appearance in the sky of this beautiful comet is listed for centuries. But it is only since his last visit in 1986 that knows more about this exotic solar system.
Halley's Comet is one of the known comets of the public. His spectacular pass in 1910 has long marked the spirits.
History of comet
In 1705, the English astronomer Edmond Halley announced that comets that had appeared in 1531, 1607 and 1682 were in fact one and the same comet. He predicted, thanks to the laws of Newton, his return in 1759. The comet actually came back in 1758 with a few months in advance, 16 years after his death. The comet was named in his honor, even if now, comets are baptized in the name of their discoverer.
This triumph of the late astronomer allowed to permanently sit laws of Newtonian mechanics.
famous passages
The most famous appearance of Halley's comet was undoubtedly at the Battle of Hastings in 1066, which marked the invasion of England by the Normans. This famous event is represented on the 32nd stage of the famous Bayeux Tapestry. This appearance on the eve of the battle was interpreted as a bad omen. The English defeat that ensued gave them ample reason.
More recently, last appearances dating from 1910, which was an impressive sight and winter 1986 when several probes went visits to the comet. The Giotto probe afforded some impressive photos of the comet nucleus and learn more about these strange bodies of the solar system.
The accurate prediction of the next passage of the comet is difficult because it undergoes gravitational influence of the giant of the solar system that may cause it to radically change its trajectory. However, with the data collected, astronomers estimate that the comet will return in 2061 near the Earth.
Specifications
Orbit of the comet: The comet's orbital period varies around 76 years. With perihelion located 88 million kilometers from the Sun and an aphelion located 5240 million kilometers, its orbit is highly elongated. The comet orbits in retrograde direction (east to west) and is inclined 18 ° to the plane of the ecliptic. Only when the comet is less than 200 million kilometers that we can begin to see on Earth.
With all these features, astronomers think it would come from the large tank, located in the outer solar system called the Oort Cloud. However, comets coming from this reservoir has a period greater than 200 years. Now Halley's Comet to a period of 76 years. This anomaly could be explained by the gravitational perturbations of the giant that would have shortened its orbit.
A dark core: With an albedo of only 3%, Comet Halley is even darker than coal. With the Giotto probe, astronomers have seen surprised by the darkness of the sun so bright when it first appeared. This albedo because of Comet Halley one of the darkest planets of the solar system.
Low density: The density of the comet nucleus of Halley's comet is much lower than previously thought: 0.1 mg / cm3. We must therefore imagine a porous foam made of water ice, dry ice and hydrocarbons rather than a block of ice. Astronomers have in fact estimated the mass of this star range only between 20 and 100 billion tons. The comet, with each pass, losing about 0.1% of its mass which represents some 100 billion kilos! It was estimated that the icy geysers of Halley's Comet expelled at their maximum activity around 30 000 liters of water per second!
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