Comet

Earth mostly regarded the comets as messengers of destruction and rarely as bringers of good or prosperity, while the scientists today think they might have played a key role in the formation of our planet and view them as carriers of possible information about the galaxy. Comets have been the most feared and admired sky spectacles of all. But while astronomers have been able to predict eclipses for thousands of years, only in the 1700s was a comet's return correctly predicted, by Edmond Halley. The comets that pass close to the Sun originally came from one of two places that either the Oort cloud or the Kuiper Belt. You can think of the Oort cloud as a giant spherical shell surrounding the Sun that's filled with about 1 million comets. In the early 1930 an Estonian astronomer proposed a structure formed of billions of comets which lie beyond the Kuiper belt. However, the theoretical structure one light year in radius equivalent to a quarter of the distance to the nearest star to the Sun, Proxima Centauri, has not been detected yet.