Explanation:
This false-color
image of banded gas giant Jupiter
shows a triple eclipse in progress on March 28 - a relatively
rare
event, even for a large planet with many moons.
Captured by the Hubble Space Telescope's near-infrared camera are
shadows of
Jupiter's moons Ganymede (left edge), Callisto (right
edge) and Io, three black spots crossing the sunlit Jovian cloud tops.
In fact, Io itself is
visible as a white spot
near picture center with a bluish Ganymede above and to the right,
but Callisto is off the right hand edge of the scene.
Viewed from Jupiter's perspective, these
shadow crossings would be
seen as solar eclipses, analogous to the
Moon's shadow crossing
the sunlit face of planet Earth.
Historically,
timing the eclipses of Jupiter's moons allowed
astronomer Ole Roemer
to make the first accurate
measurement of
the speed of light in 1676.
