";s:4:"text";s:2763:" They are thought to originate in the Oort cloud. The short-period comets are thought to originate in the Kuiper Belt, an area outside Neptune's orbit (from about 30 to 50 AU) that has many icy comet-like objects. Exploration of Comets. Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud. The following list is of comets with very long orbital periods, defined as between 200 and 1000 years.These comets come from the Kuiper belt and scattered disk, beyond the orbit of Pluto, with possible origins in the Oort cloud for many. As comets travel close to the Sun, the Sun's heat begins to vaporize the ices and causes them to form a fuzzy, luminous area of vaporized gas around the nucleus of the comet known as a coma. Re believed to have two sources. One tail is called the ion tail and is made up of gases which have been broken apart into charged molecules and ions by the radiation from the Sun. Comets are small, irregularly shaped bodies in the solar system composed mainly of ice and dust that typically measure a few kilometers across. Long period comets are comets that have orbits of high eccentricity, usually resembling the shape of a parabola. StarChild Question of the Month for December 2001 Question: Where do comets come from? Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud. Outside the coma is a layer of hydrogen gas called a hydrogen halo which extends up to 1010 meters in diameter.The solar wind then blows these gases and dust particles away from the direction of the Sun causing two tails to form. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. However, some comets, called sungrazers, crash straight into the Sun or get so close that they break up and evaporate. Unlike the Earth and other celestial bodies that take circular or elliptical orbits, these comets that have periods over two hundred years seem to make parabolic paths. Both tails can be seen in the image of Comet Hale-Bopp to the right, taken by Malcom Ellis in England. Short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt. A comet’s nucleus is comprised of ice, dust and rock. The long-period comets tend to have orbits that are randomly oriented, and not necessarily anywhere near the ecliptic.