Do Comets Turn Into Asteroids After Many Orbits?
Most people do not know the difference between meteorites, meteors, asteroids, or comets - and if you fall into this camp as most do, you are not alone, in fact most astronomers don't either, and there are various definitions of each - many of which conflict.
Hey, no wonder Pluto didn't get a fair shake and got demoted from its former planet status - I guess Pluto might say; "with friends like human astronomers, who needs enemies?" Good point.
It appears that even these space rocks like comets and asteroids have trouble with straddling definitions, as an asteroid can have an orbit, much like a comet, although generally much smaller, but there are comets with small orbits or periods too. And some say size matters, I know most women would agree, but when it comes to space rocks, that's generally not it either, you see.
Worse, as asteroids and comets move through the solar system, they bump into each other, thus making them bigger or smaller depending on what they hit, or what hits them. Often we find comets losing their velocity or energy after they bump into something and thus with that momentum loss they end up back in the main asteroid belt, "evolving back into comets," astronomers say. Okay so, this definitional stuff seems rather hard to grasp and now you can see why.
We used to think that comets just keep going forever until they collide with the Sun or a planet, but no so, say scientists now. Nevertheless, since this is the case one has to ask; "should we bother to shoot one down if it looks as if it crosses the Earth's orbit, thus, save our planet from future impact?" Or should we watch it for a while to see if its orbit decays or it hits something and takes itself out of our danger zone?
The orbits of comets are not constant, and can appear to be unpredictable according to this research paper by E Belbruno and BG Marsden entitled "Resonance Hopping in Comets," which I found in the online version of The Astronomical Journal v.113, p.1433 (BC:1997AJ....113.1433B). So, just because a comet passes close to Earth and we see it's trajectory will bring it closer on another subsequent pass sometime well off into the future, doesn't mean a thing. Please consider all this.
Additional References:
1.-Research Paper; "Evolution of Comets Into Asteroids?" by BG Marsden, published in the Journal of Physical Studies of Minor Planets, and also presented at the Proceedings of IAU, Tucson, AZ, March, 1971. This paper was edited by T. Gehrels of NASA, SP 267, 1971., p.413 (1971NASSP.267..413M).
2.-A Book Review of "The origin of comets / Pergamon, 1990" by Clube and Genuth, which can be found in the Journal for the history of astronomy vol. 23, pt. 3, pp. 215 (1992); (1992JHA....23..215C).
3.-Research Paper, "Lessons from Shoemaker-Levy 9 about Jupiter and Planetary Impacts," by J. Harrington, I. de Pater, SH. Brecht, D. Deming, V. Meadows, K. Zahnle, Philip D. Nicholson.
About The Author:Lance Winslow is a retired Founder of a Nationwide Franchise Chain, and now runs the Online Think Tank. Lance Winslow believes it's hard work to write 21,200 articles; http://www.bloggingcontent.net/
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