Canada>Canada <a href=" http://www.vdb.nl/where-to-buy-xenical-orlistat-120mg.pdf#marched ">orlistat tablets for sale</a> Most observed comets have highly elliptical orbits, meaning that they only rarely approach the Sun. Some of these so-called long period comets take thousands of years to complete each orbit around our nearest star. There is also a population of about 500 short period comets, created when long period comets pass near Jupiter and are deflected in orbits that last anything between 3 and 200 years. Although uncommon events, comets also collide with the Earth from time to time and may have helped bring water to our planet.