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 21, 1998
See Explanation. Clicking on the picture will download the highest resolution version available.

The Case of the Missing Aurora
Credit: J. P. Dwyer

Explanation: Sometimes, near midnight, auroras suddenly stop. Nobody knows why. This nightside gap in aurora was confirmed recently by D. Chua (U. Washington) and colleagues in data from the Ultraviolet Imager onboard the Polar spacecraft. The gap appears from space as a slight break in a more full auroral arc surrounding a magnetic pole of the Earth. Pictured above are clouds and auroras occurring last August near Wildcat Mountain in Wisconsin.

Tomorrow's picture: A New Storm In The Solar System

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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.