Talk:Halley's Comet

Reached Escape Velocity?

Yesterday and today, there are facebook posts by Yann LeCun (here) and Andy Borowitz (here) that seem to say JWST has observed Halley's Comet now traveling at solar escape velocity. This should be an interesting rumor to follow. If officially confirmed, this page will need significant updating. Pulu (talk) 15:18, 24 July 2022 (UTC)

Ellipticity

I may be dumb, but how about this statement about ellipticity: "(with 0 being a circle and 1 being a parabolic trajectory)" at the start of the Origin section. It seems to me that the orbit with ellipticity 1 is a straight line to the barycenter. Is that considered a parabolic trajectory? I've always believed that ellipticity doesn't exist for parabolas, since the definition involves the semi-major and -minor axes. SkoreKeep (talk) 23:37, 10 August 2020 (UTC)

Hold one vertex and one focus of an ellipse in the same place, and start increasing the ellipticity subject to that constraint. As the ellipticity approaches 1, any fixed portion of the curve near the vertex will approach a parabola. If you have further questions about this (which I think is sort of an interesting topic) the right place to ask would be the mathematics reference desk. --Trovatore (talk) 03:18, 11 August 2020 (UTC)

That's eccentricity, not ellipticity. 89.168.85.237 (talk) 14:37, 1 July 2021 (UTC)

Oops, my bad. --Trovatore (talk) 02:33, 19 November 2021 (UTC)

Is apparition the correct word?

Apparition appears 41 times in the article, but I wonder if appearance is a better word. According to Oxford dictionary, an apparition is 1) "a ghost or ghostlike image of a person", or 2) "the appearance of something remarkable or unexpected, typically an image of this type". Is the word apparition common among astronomers and Oxford is missing that definition? If not, consider replacing with the simpler, clearer word "appearance". –Novem Linguae (talk) 12:06, 7 March 2021 (UTC)

Apparition is the correct word. Also see here, if you want a reference. 89.168.85.237 (talk) 14:55, 1 July 2021 (UTC)

Star of Bethlehem

How does this article fit into the Star of Bethlehem category? --Whiteguru (talk) 09:43, 29 July 2021 (UTC)

BC/AD change to BCE/CE

Would it be appropriate to change this article to the non-Christian year denominators CE/BCE? From https://en.wikipedia.org/wiki/MOS:ERA, I conclude it suggests that there should be a change to CE/BCE when there is no specific reference to Christian/European historical topics (although this is not clearly stated in the text). Also, the wiki states "more neutral and inclusive of non-Christian people is to call this the Current or Common Era (abbreviated as CE)" In this case, an article about Halley's comet, which was also observed in the far east for examples, I would deem it appropriate. Fsikkema (talk) 01:57, 19 November 2021 (UTC)

You've misunderstood MOS:ERA. The key sentence is An article's established era style should not be changed without reasons specific to its content -- just "not specifically Christian" doesn't count; you need a specific reason not to use BC/AD, if that's the established era format.

It's in the spirit of WP:RETAIN, which is about English variety rather than date style, but it's basically the same concept. --Trovatore (talk) 02:22, 19 November 2021 (UTC)

Could it hit the earth?

I see that the "minimum orbit intersection distance" (MOID) is given as about 0.06 AU, which seems to say that it can't hit the earth. But in AD 837 it may have passed as close as 0.03 AU, according to our article. Which means that the orbit gets perturbed enough to change the MOID from 0.03 to 0.06. So it seems obvious to me that it could equally well go back to 0.03 or to 0.00! And that means it could hit the earth. Rather unlikely, but it came pretty close in AD 837. Has anything been published about this possibility? Eric Kvaalen (talk) 15:26, 3 January 2022 (UTC)

Thinking about it a bit more, it seems to be very unlikely. First of all, the MOID would have to be considerably less than 0.0001. And secondly, the timing would have to be just right as well. If it cut through the earth's orbit a few minutes before the earth gets to the crossing point, or a few minutes later, there would be no collision. The chance that the earth would be right at the crossing point within the time window of a few minutes is very small. So I suppose Halley will disappear or fly off into interstellar space before it hits the earth. But it would still be worth putting something into the article about this. Eric Kvaalen (talk) 15:43, 3 January 2022 (UTC)