Oort cloud
Comets are observed to come into the Solar System from all directions[Citation Needed], and on each orbit as they pass near the sun they lose material, which forms the comet's "tail". This loss of material means that they must have relatively short lives (calculated to be 11 million years at the most[1]), which means that they could not have been travelling past the sun for the supposed 4,600-million-year age of the Solar System.
Most cosmologists therefore believe that there must be a source supplying fresh comets, and this is believed to be a giant sphere surrounding the solar system. This sphere is called the Oort cloud after Jan Oort who postulated its existence in 1945. Thus most comets are said to come from the Oort cloud, with the rest coming to the solar system from the nearer Kuiper Belt, which is located past the orbit of Pluto. Kuiper belt objects are suspected by those who believe the universe to be billions of years old to be the source of the Jupiter family, a group of comets whose orbits take them between Jupiter and the sun in a short period of time (3-5 years). Comet Shoemaker-Levy 9 may have been one of those.
Young-Earth creation scientists point out that there is no hard evidence for the existence of the Oort comet cloud, and that it is nothing more than an ad hoc explanation for the existence of "young" comets in an "old" Solar System, and that the actual evidence is more consistent with a biblical age of the universe.[2]
Sources
- Faulkner, Danny, Comets and the age of the solar system, Journal of Creation 11(3):264â273, December 1997.
- Faulkner, Danny, More problems for the âOort comet cloudâ, Journal of Creation, 15(2):11, August 2001.