Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

October 16, 1998
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Io Aurora
Credit: Galileo Project, University Of Arizona (PIRL), JPL, NASA

Explanation: Alluring aurora surrounding Io (eye-oh) appear as a ghostly glow while the volcanic moon orbits within Jupiter's dark shadow. Gas giant Jupiter is off to the right of this image, recorded in May by the robot Galileo spacecraft's solid state imaging camera from a distance of about 1.3 million kilometers. Energetic charged particles colliding with Io's atmospheric gases create the vivid colors and produce the red and green glow analogous to the aurora of Earth. The striking blue light is caused by dense volcanic plumes and may indicate regions electrically connected to Jupiter itself.

Tomorrow's picture: Giant Globular Star Cluster

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U.