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.

March 30, 1999
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An Anomalous SETI Signal
Credit & Copyright: SETI League

Explanation: No one knows for sure what caused this signal. The bright colors on the blue background indicate that an anomalous signal was received here on Earth by a radio telescope involved in a Search for Extraterrestrial Intelligence (SETI). A search for these signals is ongoing by several groups including volunteer members of the SETI League. Time labels the vertical axis of the above plot, and frequency marks the horizontal axis. Although this strong signal was never positively identified, astronomers have identified in it many attributes characteristic of a man-made satellite in low Earth orbit. Many unusual signals from space remain unidentified. No signal has yet been strong enough or run long enough to be unambiguously identified as originating from an extraterrestrial intelligence.

Tomorrow's picture: A Gravitational Cloverleaf

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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.