Talk:Comet Lulin

Orbital elements
There are far too many digits in the orbital elements. They need to be rounded off according to their accuracy. Bubba73 (talk), 22:19, 13 February 2009 (UTC)


 * It's all sort of wacky, eccentricity>1, causes negative distances? And another source has e<1?
 * C/2007 N3 (Lulin) Orbital Elements
 * SockPuppetForTomruen (talk) 23:28, 13 February 2009 (UTC)


 * Please read the articles Orbital eccentricity and Oort cloud. — Chesnok (talk) 21:07, 25 February 2009 (UTC)


 * The stat table is inconsistent, giving an orbital period while says e>1, but two different sources. SockPuppetForTomruen (talk) 21:31, 25 February 2009 (UTC)
 * I see, the source claims e slightly below 1. Probably its useless to give a period or semimajor axis when e is anywhere near 1. SockPuppetForTomruen (talk) 21:33, 25 February 2009 (UTC)


 * Please note that on different epochs orbital elements are different because of gravitational perturbations. At one epoch e can be > 1, and at another epoch it can be < 1 for the same object. — Chesnok (talk) 08:40, 26 February 2009 (UTC)


 * So perhaps it was hyperbolic (first entry into the solar system), and has changed to a long long long ellipse. SockPuppetForTomruen (talk)


 * I removed the aphelion and period from different data. Can anyone explain the negative apogee? It must be some sort of convention for hyperbolic "orbits", but doesn't make any sense without explanation. I'd say it should just be removed. SockPuppetForTomruen (talk) 18:25, 26 February 2009 (UTC)

Composition
Apparently contains cyanogen and diatomic carbon (link). Should be added to the article. -- Natural  R X 23:29, 23 February 2009 (UTC)

Non-periodic
How do we know it's non-periodic? Is it coming back in more than 200 years? Or is it never coming back? Is it moving faster than the sun's escape velocity, or what? --Uncle Ed (talk) 17:18, 24 February 2009 (UTC)

It's the eccentricity. If e<1, it's periodic, e=1 parabolic (never to return slowly), e=2 hyperbolic (never to return faster!). Since e is somewhere very close to 1, very close to escape velocity, it's very close to parabolic, so won't return unless in many thousands of years. SockPuppetForTomruen (talk) 19:10, 24 February 2009 (UTC)

Peak magnitude
The article says that it peaked between +4 and +6 magnitude, but this was written some time ago. The peak is supposed to be about now, and it is 6.2, so shouldn't this +4 peak be taken out? Bubba73 (talk), 19:14, 24 February 2009 (UTC)

Aphelion
The aphelion distance given in the orbital characteristics is greater than the distance to the nearest star (other than the sun.) If this number were correct, Lulin would be a wanderer from interstellar space. The eccentricity given is that of a hyperbolic trajectory ( >1 ). And, as another poster has pointed out, the precision of the figures are completely ridiculous.

68.166.16.207 (talk) 19:54, 25 February 2009 (UTC)


 * This great value of eccentricity is because of gravity perturbations from Giant planets and possibly nearby stars. Read the article Oort cloud. — Chesnok (talk) 21:04, 25 February 2009 (UTC)

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