Because of what English astronomer Edmond Halley deduced about it. It duly did, though he was dead by then and it was actually the last few days of before it was observed.
The Great Comet of , which turned out to be Halley's Comet. This is a BETA experience. You may opt-out by clicking here. More From Forbes. Nov 12, , am EST. Nov 11, , pm EST. Halley's nucleus, which is about 16 x 8 x 8 km, has a low density, indicating that it is probably porous. In summary, Halley is a large, active comet with a well-defined, regular orbit. This marks it as being rather unusual among comets.
Halley will next be visible as it approaches the Sun in Instead, it is named in honour of the 17th century English astronomer Edmond Halley Using Isaac Newton's newly published theory of gravitation, Halley calculated the orbits of several comets and made the revolutionary suggestion that the bright comet seen in was the same object previously recorded in and His theory was proved to be correct when, as he predicted, the comet duly returned once more in ESA uses cookies to track visits to our website only, no personal information is collected.
By continuing to use the site you are agreeing to our use of cookies. OK Find out more about our cookie policy. It is one of the darkest, or least reflective, objects in the solar system. It has an albedo of 0. Comet Halley moves backward opposite to Earth's motion around the Sun in a plane tilted 18 degrees to that of the Earth's orbit.
Halley's backward, or retrograde, motion is unusual among short-period comets, as is its greatest distance from the Sun aphelion is beyond the orbit of Neptune. Halley's orbit period is, on average, 76 Earth years. This corresponds to an orbital circumference around the Sun of about 7. The period varies from appearance to appearance because of the gravitational effects of the planets. Measured from one perihelion passage to the next, Halley's period has been as short as The comet's closest approach to Earth occurred in , at a distance of 0.
At that time, April 10, , Halley reached a total apparent brightness of about magnitude The light of Halley was spread over an extended area, however, so its surface brightness was less than that of Venus. During its appearance, Halley's nearest approach to Earth occured on the outbound leg of the trip at a distance of 0. It was slightly brighter than the north star Polaris, but again spread over a much larger area than a point-like star.
At aphelion in , Halley was The comet was moving 0. At perihelion on February 9, , Halley was only 0. Halley was moving at , mph With each orbit around the Sun, a comet the size of Halley loses an estimated 3 to 10 feet 1 to 3 meters of material from the surface of its nucleus.
Thus, as a comet ages, it eventually dims in appearance and may lose all the ices in its nucleus. The tails disappear at that stage, and the comet finally evolves into a dark mass of rocky material or perhaps dissipates into dust.
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