Cosmic Date

On Tuesday, NASA's New Horizon arrived at Pluto after a nine year journey. The small space probe was launched on January 19, 2006 when Pluto was still classified as a planet. The mysterious body at the edge of our universe was discovered in 1930 by American astronomer Clyde Tombaugh. In 1929, Tombaugh was hired by Lowell Observatory where he was tasked with searching for "Planet X," a planet that was thought to be beyond Neptune because of its gravitational effect on Uranus and Neptune. On February 18, 1930, the planet was ruled as having been discovered and was named Pluto, for the Roman underworld god who could turn himself invisible. 

Photo: NASA, New Horizons

The Pluto flyby occurred on the 50th anniversary of the Mars flyby. A flyby is classified as a spacecraft passing by an object in space without landing or going into orbit. Mariner 4 was launched on November 28, 1964 and performed its Mars flyby on July 14, 1965. On that date, Earth saw the first images of the surface of Mars and confirmed that Mars was not inhabited by lifeforms like humans.

Photo: NASA, Mariner 4, Martian surface

As New Horizons leaves Pluto, it will continue into the Kuiper Belt and will observe Kuiper Belt objects, if they are within the vicinity of the satellite. As the spacecraft travels farther and farther from Earth, its flight trajectory will no longer be able to be altered, limiting what it can observe. When it was discovered that Pluto is actually a Kuiper Belt Object, it was declassified from a planet down to Dwarf Planet status. Within the Kuiper Belt, Pluto is the largest object. 

Photo: nature.com