size of Jupiter from Io's surface?

[Dead_Moroz]

I've used the search tool at this forum, but didn't find an answer to a question: how large a share of Io's sky Jupiter should occupy? A google image search gives (quite predictably) different results.

If (a) the distances between Io and Jupiter, on the one hand, and the Earth and Moon, on the other, is comparable, (b) the diameter of Jupiter is ca. 40 times larger than that of the Moon (142,984 km vs. 3,475 km) and (c) the Moon occupies 0.001% of the Earth's celestial hemisphere, does it mean that Jupiter's apparent size from the surface of Io should be ca. 0.04% of its celestial hemisphere?

[grapes]

The moon at apogee gets almost as far from the earth as Io is from Jupiter, and using a half-degree as the moon diameter I get that the moon is about .0008%, which is close to your figure. However, Jupiter would be 40x wider as well as 40x higher (not ambiguous?), so it would be 40x40x.001%, using your figures. About 1.6%.

With a radius of 69173 km and a distance of 420K km, it would subtend an angle of 2x tan^-1(69/420), or 18.5 degrees, which would put it close to 1%

[Rhaedas]

I think someone asked a similar question about Titan and Saturn not too long ago. You're looking for a numerical answer, which I think grapes fulfilled, but if you want a visual you can either use Celestia to go to Io and look up, or even easier, Stellarium, which lets you change the observation location to other bodies, including Io, and see their skies.

[Dead_Moroz]

Thanks to grapes and Rhaedas! The "40x40x.001%" thing is because we deal with the area, not linear distance -- I should have guessed than myself :\
The question was inspired with today's featured photo at NASA's Astronomy picture of the day.

[Ara Pacis]

Thanks to grapes and Rhaedas! The "40x40x.001%" thing is because we deal with the area, not linear distance -- I should have guessed than myself :\
The question was inspired with today's featured photo at NASA's Astronomy picture of the day.

Don't forget that how big it looks will depend on your optics.

[noncryptic]

I was surprised to find that (according to Celestia) Jupiter viewed from the surface of Io takes up about 18 arc degrees of the sky, versus the Sun viewed from Earth only ~30 arc minutes. That difference in apparent size is much larger than i had intuited.

[Ara Pacis]

I was surprised to find that (according to Celestia) Jupiter viewed from the surface of Io takes up about 18 arc degrees of the sky, versus the Sun viewed from Earth only ~30 arc minutes. That difference in apparent size is much larger than i had intuited.

Really? The oribital radius for Earth-Moon and Jupiter-Io aren't different and the moon is much smaller than Jupiter, and the moon is about the same angular diameter as the sun, or else we wouldn't get annular eclipses.

[grapes]

Yes, it would be impressive. 1% of the sky means it extends one tenth of the way from horizon to horizon, in both directions.

[Saluki]

The mathmatical side of the question has been answered quite well, but a quick Google Image search on "view of jupiter from io" will give you several artistic and computerized renderings of the view. It is quite impressive.