metz@troll.DEC (02/28/86)
I am somewhat confused on Halley's reappearance. I watched as it became lower in the evening sky and eventually disappeared behind the sun. I also understand that it will now be a morning object. What I need help with is how it will again become an evening object without circling to the other side of the sun again. Is this due to it orbit crossing earth's to the other side or what? Please clearify. Thanks.
anita@utastro.UUCP (Anita Cochran) (03/04/86)
In article <1428@decwrl.DEC.COM>, metz@troll.DEC writes: > > I am somewhat confused on Halley's reappearance. I watched as it became > lower in the evening sky and eventually disappeared behind the sun. I > also understand that it will now be a morning object. What I need help > with is how it will again become an evening object without circling to > the other side of the sun again. Is this due to it orbit crossing earth's > to the other side or what? Please clearify. > Thanks. Comet Halley is in an elliptical orbit around the sun but travels in the reverse direction around the sun that the earth does. Thus, as the comet recedes from the sun it passes us as we are heading back where it came from (except that our orbit is nearly circular so we don't get in as close to the sun as Halley does). It is also closer to the sun than the earth until the end of march. When it comes closest to the earth in early April, it will actual be up in the middle of the night but because it is so far south, most people in the Northern hemisphere won't see it well, if at all. Halley will switch from a morning object to an evening object by being a night time object. This is actually true of most stars, etc due to the revolution of the earth around the sun. Halley just does it faster since it too is moving. -- Anita Cochran uucp: {noao, ut-sally, ut-ngp}!utastro!anita arpa: anita@astro.UTEXAS.EDU snail: Astronomy Dept., The Univ. of Texas, Austin, TX, 78712 at&t: (512) 471-1471