Where do comets originate?

The most commonly accepted theory about where comets (celestial bodies that have tails and follow an orbit around the sun) originate was developed by Dutch astronomer (a scientist specializing in the study of matter in outer space) Jan Oort in 1950. According to Oort, trillions of inactive comets lie on the outskirts of the solar system, between 50,000 and 150,000 AUs from the sun. (An AU is an astronomical unit, the distance between the Earth and sun, about 92 million miles.) They remain there in a large cloud of gas and dust, called an Oort cloud, until a passing star or gas cloud jolts a comet into orbit around the sun. In 1951, another Dutch astronomer, Gerard Kuiper, suggested that a second cometary reservoir exists just beyond the orbit of Pluto, around 1,000 times closer to the sun than the Oort cloud. His proposed Kuiper belt is located somewhere between 35 and 1,000 AUs from the sun....  more