The Half-Astrophysicist Blog

Hubble Does it Again: Jupiter and Ganymede

The Hubble Space Telescope has again given us a spectacular video.  This time it is a two hour sequence of Jupiter’s largest Moon, Ganymede, disappearing behind the giant planet.

Jupiter rotates on its axis about once every 10 hours so you can see significant rotation during this time.  Ganymede orbits the planet once every 7 days (as opposed to our Moon’s 29 day period).  Ganymede is also the largest moon in the solar system with a diameter of about 3200 miles, slightly larger than Mercury.  Jupiter is about 88,000 miles in diameter!

That is what struck me about this movie…it gives a good sense of just how large Jupiter is.  Ganymede might be considered a planet if it didn’t orbit Jupiter.  They are both the same distance away, so the difference in sizes is to scale (well, Ganymede it technically a LITTLE farther away, but only a small fraction of a percent…not enough to matter).  Ganymede is large and bright enough that it would be visible to the naked eye…if it weren’t so close to the much larger, brighter Jupiter.

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December 19, 2008 - Posted by | Uncategorized

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