Comet Leneos Question

[misterp]

Hi Guy,

According to http://www.ast.cam.ac.uk/~jds/07f1.uk comet Leneos will shortly be visible in the evening for a few minutes (after sunset) and also in the morning for a few minutes (before sunrise), how can this be? If it is visible after the sun sets then surely it will rise after the sun in the morning (or am I missing something).

Thanks for any explanations

Ian

[maroon bells]

I remember the big comet last year was similar and I also wondered exactly the same thing, hopefully someone here can explain why. It does seem to defy logic.

Matthew

[James]

If the comet is to the north of the sun (or south of it in the southern hemisphere) to a sufficient degree then it may be visible both in the morning and the evening. An object many degrees to the north will rise before the sun and set after it. I can't really explain it properly but an exaggerated example might be a constellation like Lyra, visible in the early evening in winter to the north west then visible to the north east by the early morning. I'm sorry thats not a particularly clear explanation but I'm going to have a play with Stellarium to try and see if I can explain it better...

James

[barkis]

If an objects declination is due North of the sun in the west after sunset, then it is feasable that the same object will be visible in the pre dawn sky too. I would say a comet is one of the best examples of this, due to it's tail being away from the sun. I guess that the said comet, would be an object from the OORT cloud, rather than from the Kuiper belt region whereby they tend to stay in the plane of the ecliptic.

Oort cloud members can approach from any direction. This is my understanding of the mechanics of it. I stand to be corrected by superior knowledge of course.

Ron.

[misterp]

Thanks for that guys, that makes sense

Ian