Обсуждение:Облако Оорта
Перевод для статьи Облако Оорта
Пояснение
Кометы делятся на 2 группы, с длинным и коротким периодом. Комета имеющая период более 200 лет считается кометой с длинным периодом обращения.[1][2] Эти 2 группы имеют следующие характеристики, with редкими исключениями:
- Кометы короткого периода обращаются около Солнца и с небольшим, или даже отсутствующим уклоном относительно эклиптики.
- Кометы с длинным периодом are as likely to be in retrograde as in prograde (обращающийся на орбите в том же направлении, что и небесное тело) orbits, and have been observed to have any inclination with respect to the ecliptic.[1]
Weisstein observes that the aphelia of long-period comets are distributed about two modes: 10,000 AU and 50,000 AU.[1]
Faulkner observes that Comet Halley, a short-period comet, is highly inclined and in a retrograde orbit. Comet Halley is, therefore, an important exception to the distinction. Faulkner also observes that short-period comets do not differ from long-period comets in composition.[2]
Cometary orbits are highly elliptical[2], and some of these orbits are almost parabolic.[1] Hyperbolic cometary orbits have never been observed.[2] This last observation is credited to Jan Oort himself.[3]
The more important point is that comets have a limited life span. After a few hundred perihelion passes at the Sun, a comet loses all of its tail-forming substance.[4] In addition, comets often destroy themselves in collision with planets and other bodies, or are ejected from the solar system entirely after making close flybys of Jupiter and other gas giants.[4][2][5]
For these reasons, astronomers realized that the supply of comets would require replenishment over the supposed great age of the solar system. Comets cannot be interstellar, else they would have hyperbolic orbits. Some astronomers have proposed cryovulcanism as the source of comets, but comets are not sufficiently dissimilar in composition to support this.[2]
In 1950, astronomer Jan Oort first proposed the existence of a "cloud of comets" in the outer fringes of the solar system.[6][7] Oort calculated that this cloud might contain a trillion comets.[3] Short-period comets are supposed to come from the Kuiper belt.[1][2][3][8] Oort originally speculated that the total mass of the Oort cloud would be as much as the mass of Jupiter ({{#show:Jupiter|?Planet mass#M⊕}}). More recent studies have suggested that the total mass might be forty times the mass of the earth.[5]
- ↑ 1,0 1,1 1,2 1,3 1,4 Ошибка цитирования Неверный тег
<ref>; для сносокWeissteinне указан текст - ↑ 2,0 2,1 2,2 2,3 2,4 2,5 2,6 Faulkner, Danny. "Comets and the Age of the Solar System." TJ, 11(3):264-273, December 1997. Accessed June 2, 2008.
- ↑ 3,0 3,1 3,2 Arnett, Bill. "The Kuiper Belt and the Oort Cloud." The
Nine8 Planets, March 18, 2007. Accessed June 2, 2008. - ↑ 4,0 4,1 Arnett, Bill. "Comets." The
Nine8 Planets, May 1, 2003. Accessed June 2, 2008. - ↑ 5,0 5,1 Faulkner, Danny. "More problems for the 'Oort comet cloud'." Journal of Creation 15(2):11, August 2001. Accessed June 2, 2008.
- ↑ Tenn, Joseph S. "The Bruce Medalists: Jan Hendrik Oort." Department of Physics and Astronomy, Sonoma State University, October 11, 2006. Accessed June 2, 2008.
- ↑ Oort, J.H., 1950. The structure of the cometary cloud surrounding the solar system and a hypothesis concerning its origin. Bulletin of Astronomy of the Netherlands, 11:91–110.
- ↑ Harvey, Samantha. "Solar System Exploration: Oort Cloud." NASA, March 29, 2006. Accessed June 2, 2008.
