Halley’s Comet

Nathan Reeves Geo 105 prof Kerr 12-13-11 Halleys Comet Astronomers first observed Halleys Comet as far back as 200 BCE. The comets periodicity was first determined in 1705 by English astronomer Edmond Halley, who it was eventually named after. Halleys Comet last appeared in the inner(a) Solar System in 1986 and wont appear again until mid-2061. Although the nucleus of the comet itself is not that large, the swooning can extend to a very large size.As the gas molecules in the coma are ionized by the solar ultraviolet radiation pressure from the solar wind, a stream of particles emitted by the Sun, pulls the comas ions issue into a long tail, which may extend more than 100millionkilometers into space. The nucleus itself is only 15kilometers long, 8kilometers wide and 8kilometers thick. In comparison, the earth has a diameter of 12,756 km and the sun has a diameter of 1,392,000 km.This means that Halleys Comet is only about 4% the size of earth but because of its coma, it appears mu ch larger to the naked eye. While the planets orbit around the sun, Halleys Comet orbits towards and a representation from the sun, all the way out to Jupiter, perpendicular to the planets orbits. Halley is classified as a periodic or short-period comet, star with an orbit lasting 200 years or less. This contrasts it with long-period comets, whose orbits last for thousands of years.Most short-period comets, those with orbital periods shorter than 20 years and inclinations of 2030 degrees or less, are called Jupiter family comets. Those like Halley, with orbital periods of between 20 and 200 years and inclinations extending from postcode to more than 90 degrees, are called Halley type comets. Only 54 Halley-type comets have been observed, compared with almost 400 place Jupiter family comets. The orbits of the Halley-type comets uggest that they were originally long-period comets whose orbits were altered by the gravity of the giant planets and directed into the inner Solar System. If Halley was once a long-period comet, it is likely to have uprised in the Oort cloud a sphere of bodies that has an inner edge of 50,000AU. Also, the Jupiter family comets are believed to originate from the Kuiper belt, a flat disc of icy masses between 30AU and 50AU, from the Sun. some other point of origin for the Halley type comets has been proposed.In 2008, a new object with a retrograde orbit uniform to Halleys was discovered. Named Drac, its orbit takes it from average outside that of Uranus to twice the distance of Pluto. It may be a member of a new population of small Solar System bodies that serves as the source of Halley type comets. A hardly a(prenominal) things make Halleys Comet popular and unique. The obvious thing is that it is fairly easy to see when it does orbit, more so than most other orbiting comets. Also, it orbits every 70 years or so.This makes it unique because it means that most multitude have a chance to see it at least once. Every generation of p eople gets an decent opportunity to see it ,which makes it special because now everybody can have a part in it. A lot of other comets only orbit every hundred years or so, so you just have to be lucky to be able to see them. References 1. ) http//csep10. phys. utk. edu/astr161/lect/comets/halley. html 2. ) http//nineplanets. org/halley. html 3. ) http//en. wikipedia. org/wiki/Halley%27s_Comet