How large is Jupiter in the sky from its moons?

Question

I've always wondered about this. And how large is the sun in Mercury's sky?

Answer 1

very large! :) much larger than is earth as viewed from moon

Answer 2

They are both the exact size they are. Size does not vary with distance, only perception of the size.

Answer 3

Jupiter is 143,000 km across.  The distances of the big four Galilean satellites, from the center of Jupiter, are Io at about 420,000 km; Europa at about 670,000 km; Ganymede at about 1,070,000 km; and Callisto at about 1,880,000 km.

As a ballpark estimate, then, Jupiter covers about 20° as seen from Io, about 12° as seen from Europa, about 8° as seen from Ganymede, and about 4° as seen from Callisto.  For reference, your fist at arm's length covers about 10°; 20° is almost as wide across as a basketball at arm's length.

Mercury is about 60,000,000 km from the Sun, about 2/5 the Earth's distance.  Since the Sun appears about 0.5° from the Earth, it must appear 5/2 times larger from Mercury, about 1.25°.  That's about as big as your index fingertip at arm's length (probably smaller than you thought).

EDIT: To figure these out for yourself, take the diameter of the object you're "observing," divide by its distance from you (make sure you use the same units), and multiply by about 57.  This last number is about equal to 180/pi.  This formula becomes less accurate as the object becomes closer/larger, but it should be all right for most astronomical objects.

Answer 4

work both of these out yourself from published information. figure jupiter is 140,000 km across. ganymede is 1 million km from jupiter. io is about half that; callisto is just under twice that.

find and use the numbers for the sun.

Answer 5

Not nearly as big as Uranus.

Answer 6

If you were standing on the moon Europa (Jupiter's moon with the greatest chance of having life on it), Jupiter would appear to be 28.57 times the diameter of our moon from Earth.

Its apparent surface area would be 816.32 times larger than our view of our moon. Instead of 0.42 degrees of arc in the sky, it would fill 12 degrees.

Answer 7

Watch the film 2010 - that's pretty accurate.