Changes

== Discovery ==

== Discovery ==

In 1930, [[Clyde W. Tombaugh]] at the Lowell Observatory surveyed the sky, looking for a planet beyond [[Neptune]] (called "Planet X") that other astronomers had predicted from calculations based on an erroneous value for Neptune's mass. Tombaugh knew nothing of the error, but found an object anyway, and named it Pluto.

In 1930, [[Clyde W. Tombaugh]] at the Lowell Observatory surveyed the sky, looking for a planet beyond [[Neptune]] (called "Planet X") that other astronomers had predicted from calculations based on an erroneous value for Neptune's mass and its orbital patterns. Tombaugh knew nothing of the error, but found an object anyway; the object was soon named Pluto.

But even he realized that Pluto was not large enough to be the predicted Planet X. Astronomers continued to search in vain for it, until [[Voyager 2]] made its flyby of [[Neptune]], and the [[Jet Propulsion Laboratory]] scientists determined from this flyby that Neptune was significantly heavier than previously supposed. Current theory predicts no more planets other than the eight now known, but still allows for many other objects, both in the classic [[asteroid]] belt and in the [[Kuiper Belt]], essentially a second belt of asteroids and [[comet]]s.

But even he realized that Pluto was not large enough to be the predicted Planet X. Astronomers continued to search in vain for it, until [[Voyager 2]] made its flyby of [[Neptune]], and the [[Jet Propulsion Laboratory]] scientists determined from this flyby that Neptune was significantly heavier than previously supposed. Current theory predicts no more planets other than the eight now known, but still allows for many other objects, both in the classic [[asteroid]] belt and in the [[Kuiper Belt]], essentially a second belt of asteroids and [[comet]]s.