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The Question
(Submitted May 07, 1997)
When were all of the planets discovered?
The Answer
Mercury, Venus, Mars, Jupiter, and Saturn have been known for a very
long time...but no one knows when they were first seen. Being such
bright objects in the sky, they have been known and observed by ancient
civilizations.
Uranus was first recorded in 1690, but thought to be a star. William
Herschel discovered it as a planet in 1781.
Neptune was discovered in 1846....by James Challis (who recorded it
first, but did not realize what it was) and Johann Galle (who knew exactly what
he was observing).
Pluto was discovered by Clyde Tombaugh in 1930.
Laura Whitlock and Tim Kallman
for the Ask an Astrophysicist team
Questions on this topic are no longer responded to by the "Ask an Astrophysicist" service. See http://imagine.gsfc.nasa.gov/docs/ask_astro/ask_an_astronomer.html
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