Re: [Phys-L] Comet ISON

[Paul Nord <paul.nord@valpo.edu>]

Consider only that the North Star is in the sky ALL the time.  For someone in the northern hemisphere, it never sets.  That should help to explain how something may be seen both before and after sunset.

Here at about 40º N, there is a big chunk of the sky around the pole star which is always above the horizon.  Around that circle I can draw other circles which are in the sky "most" of the time and only set briefly at some point every 24 hours.  Some parts of the sky are above the horizon for 12 hours.  And some parts of the sky (e.g. southern constellations) never rise above the horizon.

Paul


On Nov 14, 2013, at 4:03 PM, Bruce Sherwood <Bruce_Sherwood@ncsu.edu> wrote:

> Good point, but judging from the images shown in Sky & Telescope, as ISON
> approaches the Sun it's near Mercury and Saturn in the sky, a bit below but
> near the ecliptic plane, so not visible after sunset. Then, something I'd
> missed in the article, the closest approach to the Sun is about Nov. 28, so
> close that it may disintegrate due to extreme heating and tidal effects. If
> it does emerge, the images shown for the first few days in December show it
> moving nearly vertical, so definitely not visible after sunset.
>
> Bruce