Observation of Comet

In the past, except very far away from the sun, the comet's long, bright sparse tail, this gives people the impression that the comet is very close to the earth, even in our atmosphere. 1577 Tycho pointed to different locations when viewed from the Earth, the comet does not show the orientation is different: his right to come they must be very far from the conclusion. Comet belongs to the small bodies of the solar system. Whenever comet close to the sun, its brightness rapidly enhanced. The observations of the comet far from the sun along highly elongated elliptical motion, and the sun is a focus of the ellipse, Kepler's first law. The comet most of the time running in a place far from the sun, where they are invisible. Only when they are close to the sun to see. About of 40 comet orbital period is relatively short (less than 100 years), so they have emerged as one day experience.
A first observed appeared one after another of the same celestial Halley's Comet in 1705, Newton's friends and donors Harley (1656, 1742) recognize that it is cyclical. Its period is 76 years. The historical record shows that since 240 BC may also come from 466 years BC, through the sun each time it is observed in the. It last passed in 1986. The brightness of the comet far from the sun is low, and its spectrum is simply reflected the sun's spectrum. Comets entering less than astronomical units from the sun eight, its brightness began to grow rapidly, and the spectrum is changing dramatically. Scientists see several bright lines are known molecular. This change occurs because the composition of the comet's solid material (nucleus) suddenly becomes hot enough to evaporation and nucleus surrounded by a cloud of gas called the coma. Caused by the sun's UV luminous gas. Coma diameter is usually about 105 kilometers, but the tail is often very long, up to 108 km or 1 astronomical unit.
Scientists estimate that generally only a few astronomical units of the comet close to the sun distance in thousands of years

The comet strikes (20) to collapse. In 1066, the Norman invasion of Britain on the eve of regression coincided with Halley's Comet. At that time, people had a complex mood, watching the night sky Fengyun strange celestial dragging a long tail, considered to be a war warning given by God and foreshadowing. Later, the Normans conquered Britain, Norman commander's wife when Halley's Comet regression scene embroidered on a tapestry to commemorate. Chinese folk banished the comet known as the "jinx", "bane". The comet appeared and the world of war, famine, flood, pestilence and other disasters linked things like this, there are many Chinese and foreign history. Comet in prolate track (a handful around the sun in a nearly circular orbit) on a quality smaller cloudy Small Bodies