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== 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 and its orbital patterns. Tombaugh knew nothing of the error, but found an object anyway; the object was soon named Pluto.

On February 18, 1930, [[Clyde W. Tombaugh]] at the Lowell Observatory surveyed the sky, looking for a planet beyond [[Neptune]] (called "Planet X"). Other astronomers had inferred such an object 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. Tombaugh's daughter Annette proposed the name of that object: 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.

Even Tombaugh 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.

== The dwarf planet controversy ==

== The dwarf planet controversy ==

== Observation and Exploration ==

== Observation and Exploration ==

On January 19, 2006, the [[New Horizons mission]] was launched. Pluto is its prime target, but mission planners are considering plans to study at least one other [[Kuiper belt]] object.<ref name=Jenner>Jenner, Lynn. "[http://www.nasa.gov/mission_pages/newhorizons/main/index.html NASA - New Horizons]." [[National Aeronautics and Space Administration|NASA]], October 9, 2007. Accessed July 3, 2008.</ref><ref name=Talbert>[http://www.nasa.gov/mission_pages/newhorizons/main/index.html New Horizons official site], ed. Tricia Talbert/NASA. First accessed 10 July 2015.</ref>

On January 19, 2006, the [[New Horizons mission]] was launched. Lead investigator Alan Stern and his team collected one U.S. Customary [[ounce]] of the ashes of the discoverer, sealed them in a canister, and installed this on the upper deck of the New Horizons probe. Alan Stern inscribed it thus:{{cquote|Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system's "third zone." Adelle and Muron's boy, Patricia's husband, Annette and Alden's father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906-1997).<ref name=CNN>Mullen J, "[http://www.cnn.com/2015/07/13/us/nasa-pluto-new-horizons-clyde-tombaugh-ashes/ Pluto discoverer's ashes are aboard New Horizons probe]," [[Cable News Network]]. Published 14 July 2015. Retrieved 5 August 2015.</ref>}}

On 15 January 2015, New Horizons began its final approach to Pluto. In July of 2015, New Horizons passed directly through the Plutonian system and took the best photographs of it to date. Mission controllers expect New Horizons to transmit its thousands of high-resolution photographs and other data by the end of 2016.

 

On 15 January 2015, New Horizons began its final approach to Pluto. On 14 July of 2015, New Horizons passed directly through the Plutonian system and took the best photographs of it to date. Mission controllers expect New Horizons to transmit its thousands of high-resolution photographs and other data by the end of 2016.

 

New Horizons now awaits further orders to alter its course to reconnoiter any other Kuiper Belt object it might be able to reach.

== In popular fiction ==

== In popular fiction ==

[[Science fiction]] author Larry Niven once speculated on an "earlier generation" race of [[extraterrestrial life|extraterrestrial beings]] that controlled the [[galaxy]] until it suffered mutual annihilation in a war with a revolting slave race. As part of that scenario, a member of that "slaver race" once had to make an emergency "landing" in a crippled spacecraft that could no longer brake to a safe approach speed. He then set a course for the [[earth]], bailed out of his ship, and left the ship's autopilot with orders to crash-land on Neptune. Instead of that happening, the ship struck a moon of Neptune hard enough to knock it out of orbit; that moon became known as Pluto.

[[Science fiction]] author Larry Niven once speculated on an "earlier generation" race of [[extraterrestrial life|extraterrestrial beings]] that controlled the [[galaxy]] until it suffered mutual annihilation in a war with a revolting slave race. As part of that scenario, a member of that "slaver race" once had to make an emergency "landing" in a crippled spacecraft that could no longer brake to a safe approach speed. He then set a course for the [[earth]], bailed out of his ship, and left the ship's autopilot with orders to crash-land on Neptune. Instead of that happening, the ship struck a moon of Neptune hard enough to knock it out of orbit; that moon became known as Pluto.