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Do comets orbit the Sun in an anti-clockwise direction?
Last night, at SMASHfestUK, during a period of cloud cover this question was posed. It had been bugging me since so I thought I'd look it up. Here's what I found:
"Comets whose orbits take them very far from the Sun tend to have especially eccentric and inclined orbits.
Many of those comets also orbit in a different direction than most other objects in the Solar System... The comets with large orbits and the icy bodies of the Oort cloud are thought to be distributed randomly in all directions of the sky. Many of these objects orbit the Sun in retrograde motion…"
New Views of the Solar System by Encyclopaedia Britannica.
Apparently Halley's comet is in retrograde orbit too. So there you go. I didn't know that!
Posted : 19/02/2015 10:21 pm
Makes a lot of sense, though it's interesting that the majority of comets from the Oort cloud have retrograde orbital motion. I wonder why? Can't see any obvious explanation in the article... just that it happens to be the case.
More research needed, I think.
Posted : 20/02/2015 11:41 am
Interesting, thanks for following up the question Christina.
I simply assumed that if comets were formed from the same proto-planetary disc as the planets then they would have acquired the same rotational direction. Perhaps the Oort cloud was formed from material sufficiently far away from the early Sun's gravitational influence that it did not acquire any angular momentum as the disc collapsed to form the planets? Is the retrograde orbital motion of comets from the Oort cloud a real or apparent motion.
Now where can we find an expert on comets?
Posted : 20/02/2015 2:05 pm
Topic starter
Now where can we find an expert on comets?
Oh bugger! We had a comet expert at our February Flamsteed lecture! Let's bring him back 🙂
From my understanding of extracts that I've read online, they imply that the retrograde orbital motion of comets originating from the Oort cloud is real as they infer to the vantage point being above the plane of the Solar System:
"Most bodies, including comets, orbit the Sun ANTI-clockwise. That is, viewing from above the North Poles of the Sun and planets. "
http://www.newton.dep.anl.gov/askasci/ast99/ast99683.htm
it’s interesting that the majority of comets from the Oort cloud have retrograde orbital motion. I wonder why? Can’t see any obvious explanation in the article…
I'm not able to find any succinct, ratified articles online that explain why this might be. Just this short abstract from 1991 (so quite old) within a NASA reports server saying the following:
"Cometary orbits in the cloud evolve under the complex interaction of stellar, galactic, and giant molecular cloud perturbations, as well as planetary and nongravitational perturbations when the orbits reenter the planetary region."
http://ntrs.nasa.gov/search.jsp?R=19930029573
To me the above excerpt suggests that the Oort cloud might be, or has been a chaotic place. I'm imagining comets being flung out from the Oort cloud into the long eccentric orbits around our Sun characteristic of long period comets... This is all stuff I've just learnt so please forgive my naivety!
Posted : 21/02/2015 12:31 am
