Comets……. What are they???. Comets are small bodies made out of dust and ices ("dirty snowballs"). The term "comet" derives from the Greek aster kometes , which means "long-haired star. What do meteors and comets have in common???. Comet West (1976). Comet Hyakutake (1996) .
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Comet Hyakutake (1996)
Comet Halley (1984)
The nucleus of Comet Halley is approximately
Comet Halley (1984) nucleus as it is heated by the Sun. The coma is bright both because it reflects sunlight and because its gases are excited by sunlight and emit electromagnetic radiation.The Tail…
In 1705 Edmond Halley predicted, using Newton's newly formulated laws of motion, that the comet seen in 1531, 1607, and 1682 would return in 1758 (which was, alas, after his death). The comet did indeed return as predicted and was later named in his honor.
Discovery: Edmond Halley was the first person to recognize that this comet was periodic. He computed parabolic orbits for 24 comets observed from 1337 to 1698. His analysis of the list revealed the comets of 1531, 1607, and 1682 moved in almost identical orbits and were separated by intervals of roughly 75 years. From this information, he predicted the comet that now bears his name. It was rediscovered on December 25, 1758 by Johann Georg Palitzsch), a German farmer and amateur astronomer
The density of Halley's nucleus is very low: about 0.1 gm/cm3 indicating that it isprobably porous,perhaps because it is largely dust remaining afterthe ices have sublimed away.
The average period of Halley's orbit is 76 years but you cannot calculate the dates of its reappearances by simply subtracting multiples of 76 years from 1986. The gravitational pull of the major planets alters the orbital period from revolution to revolution. Nongravitational effects (such as the reaction from gasses boiled off during its passage near the Sun) also play an important, but smaller, role in altering the orbit.
Comet Halley was visible in 1910 and again in 1986. It's next perihelion passage will be about 2061.
Between 16 July 1994 and 22 July 1994 the fragments impacted the upper atmosphere of Jupiter. This was the first time that scientists had an opportunity to witness the collision of two extraterrestrialbodies.
Comet Shoemaker-Levy 9 was discovered by Eugene and Carolyn Shoemaker and David Levy in 1993. Shortly after its discovery it was determined to be in a highly elliptical path near Jupiter and on a collision course. It was difficult to calculate its orbit prior to its 1992 pass near the giant planet.
Earth Closest Approach: March 22, 1997 (1.315 AU)
Sun Closest Approach: April 1, 1997 03:14 UT (0.914 AU)
1 AU = 93 Million Miles = 150 Million
Experiments on-board the interplanetary Ulysses probe, which lasted for several hours on May 1, 1996,indicate the probepassed throughcomet Hyakutake'stail.