Solar system objects

Re: Is Lulin orbiting around sun or is it just passing through?

Centaur — Sat, 04 Jul 2009 16:19:12 GMT

second sight:

How close would a neighboring star have to be to affect a comet like this one to head towards the sun? Wouldn't the odds of it being hurled with such accuracy into our solar system be extremely small? I read recently that some kind of gravitational anomoly had been detected beyond the solar system. The article was not very precise but seemed to imply that the source might be relatively close beyond the edge of the Ort cloud. Have you heard of this? If true, could this be a possible candidate for fed-exing comets our direction?

There is an immense number of comets in the Oort cloud. Any gravitational disturbance from an external object that might have affected Comet Lulin would have occurred eons ago. It could have affected a great many comets scattering them in differing directions. Apparently at least one of them was deflected toward the inner solar system.

Re: Is Lulin orbiting around sun or is it just passing through?

second sight — Sat, 04 Jul 2009 15:39:36 GMT

How close would a neighboring star have to be to affect a comet like this one to head towards the sun? Wouldn't the odds of it being hurled with such accuracy into our solar system be extremely small? I read recently that some kind of gravitational anomoly had been detected beyond the solar system. The article was not very precise but seemed to imply that the source might be relatively close beyond the edge of the Ort cloud. Have you heard of this? If true, could this be a possible candidate for fed-exing comets our direction?

Re: Is Lulin orbiting around sun or is it just passing through?

Centaur — Sat, 04 Jul 2009 01:52:19 GMT

second sight:

i read that comet lulin is on a parabolic orbit and that this may be the first time it has entered the inner portion of the solar system. is it orbitng the sun or is it passing through our solar system just once?

A perfectly parabolic orbit is statistically impossible. Its eccentricity would have to be precisely 1. A nearly parabolic orbit would actually have an eccentricity a little less than 1 (elliptical and closed, thus orbiting the Sun) or a little more than 1 (hyperbolic and open, thus a temporary visitor). Although that just considers the simplified two-body problem of Sun and comet. Perturbations due to planets complicate the situation and cause comets’ orbits to differ slightly from perfect conic sections. Those perturbations can also cause a comet’s orbit to switch either way between an ellipse and a hyperbola.

If Comet Lulin originated from beyond the solar system, I suspect it would have been detected that its orbit is slightly hyperbolic. Since that is not the case, it probably has orbited the Sun in the very deep reaches of the solar system for eons before being gravitationally disturbed by a star or other object. That could have it sent it hurtling toward the Sun in a new orbit. If that new orbit is still elliptical, the comet will remain in the solar system. If it has become hyperbolic, then bye bye.

Re: Is Lulin orbiting around sun or is it just passing through?

chipdatajeffB — Wed, 01 Jul 2009 16:13:55 GMT

Yes, that's possible. However, its orbit would more likely be hyperbolic (open).

A lot depends on its passage through the outer Solar System and how near it comes to any of the gas giants. They could change its orbit and/or period, or eject it from the Solar System altogether.

If it is in a captive orbit, its period is quite likely to be very long ... longer than a human lifespan.

Re: Is Lulin orbiting around sun or is it just passing through?

second sight — Wed, 01 Jul 2009 16:11:15 GMT

so is it possible that this comet came from outside the solar system and is literally just passing through one time enroute to who knows where?

Re: Is Lulin orbiting around sun or is it just passing through?

chipdatajeffB — Wed, 01 Jul 2009 13:01:34 GMT

According to Brian Marsden of the Minor Planet Center at Harvard, its parabolic orbital parameters indicate this might be its first passage through the inner Solar System.

It is also in an unusual retrograde orbit (opposite the orbital direction of the planets). Until it is observed interacting with the more massive outer planets it will be impossible to accurately calculate its orbital period. I haven't seen a period listed yet in any of the ephemerides I've seen on the Web.

Is Lulin orbiting around sun or is it just passing through?

second sight — Wed, 01 Jul 2009 12:11:43 GMT

i read that comet lulin is on a parabolic orbit and that this may be the first time it has entered the inner portion of the solar system. is it orbitng the sun or is it passing through our solar system just once?