Re: Jupiter, seen from Vesta

Dorothy J Heydt wrote:
I'm sure the answer to this is all over the Web, but my
google-fu is weak and I haven't been able to find it.

Question: If you were standing on the surface of 4 Vesta, and
Jupiter happened to be in your sky, what would you see? A
bright untwinkling "star"? A small or large disc? Would it
be visibly red or orange in color? (Would any of the
Galileans be visible?)

The solid angle subtended by Jupiter from Vesta (at closest approach) would be about 8.5 x 10^-8 sr; solid angle you can think of as the "area" of Jupiter's disk, for very small angles, which that is). That's only about 26% bigger than the solid angle subtended by Venus from Earth (at closest approach). If you want to put it in terms of angular radius or distance -- i.e., measure it's apparent width, not its area), then it's only about 12% bigger. Certainly an untwinkling star, but it wouldn't visibly look like a disk to the untrained eye.

I'm not sure whether it would appear orange or red; perhaps it would, but Jupiter is still pretty pale. The tendency, like with the other actually _really_ red stars, would be brought out more with comparison when Jupiter-from-Vesta happens to be a near a bright white or blue star. That's if it's detectable at all, which I'm not sure.

As for the magnitudes, I'll let someone else handle that for now (mostly since BOTEC doesn't do that and I'm too lazy to add the functionality right this second :-).

--
Erik Max Francis && max@xxxxxxxxxxx && http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M, Skype erikmaxfrancis
Silence is the most perfect expression of scorn.
-- George Bernard Shaw
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