This shot from the Hubble Telescope shows Uranus' moon Ariel crossing the gas giant planet's face. You can see Ariel as the white dot and its corresponding shadow as the black dot on the cloudy surface. If you were on the planet below, the moon would be eclipsing the sun. The event is rare because Uranus' moons have orbits that carry above the equator, and the moons' paths align with the sun only once every 42 years. The moon Ariel is about 1/3 the size of our moon, and orbits Uranus closer than any of its other large moons. Uranus is now approaching its 2007 equinox where the sun will be shining over the planet's equator.

Image Credit: NASA / ESA / L. Sromovsky, U.Wisconsin / H. Hammel, SSI / K. Rages, SETI

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