The Prodigal Planet: 5 Interesting Things You Need To Know About Pluto

A team of NASA scientists led by Alan Stern is redefining the makings of a planet, potentially ending Pluto's 11-year exile.

Before Pluto makes its big comeback into planethood, check out five of the most interesting facts about this controversial dwarf planet.

Pluto Was Discovered By A Research Assistant

Pluto was first discovered on Feb. 18, 1930 by Clyde William Tombaugh, an American astronomer who was then working as a 24-year-old research assistant at the Lowell Observatory in Arizona.

Using the observatory's telescope (which produced two photographs of the sky on different days) and a blink compactor (a device that flipped back and forth between the two photographs to detect movement), Tombaugh began his effort to look for the elusive Planet X. He spent at least a week examining each pair of photographs, which had anywhere from a 150,000 stars to a million.

Pluto Was Named After The Greek God Of The Underworld By An 11-Year-Old Girl

The Lowell Observatory officially announced the discovery of a ninth planet on March 13, 1930 and sent out a worldwide invitation to suggest a fitting name for the new planet.

Venetia Burney, and 11-year-old schoolgirl from Oxford, England thought of the name Pluto, after a deity in the classical Greek mythology. Burney's grandfather told a friend, who interestingly is an astronomy professor at the esteemed Oxford University.

Pluto was also highly favored over other entries because its first two letters could stand for Percival Lowell's initials. Lowell devoted his life's work to Planet X, completing a three-stage search of the hypothetical ninth planet, which paved the way to Clyde Tombaugh's sighting of Pluto.

Why Pluto Was Demoted To A Dwarf Planet

Back in August 2006, the International Astronomical Union demoted Pluto's status from a planet to a dwarf planet.

According to the IAU, there are three criteria for a full-sized planet: it has to be in orbit around the sun, it should have sufficient mass to assume hydrostatic equilibrium or a circular shape, and it has "cleared the neighborhood" around its orbit. This means that planet is gravitationally dominant, without anything of comparable size near it other than its own satellites.

This is where Pluto falls short, and why experts have concluded that it is merely the brightest member of the Kuiper Belt, a mass of objects that orbit the sun beyond Neptune. But as mentioned above, the tides have changed.

Pluto Was First Probed By The New Horizons, A Spacecraft The Size Of A Grand Piano

In 2006, NASA launched New Horizons to fly by Pluto and its moons. Costing approximately $700 million and weighing in at 1,000 pounds, the camera-fitted rocket is reportedly only as big as a grand piano. Clyde Tombaugh's ashes also joined the probe aboard the NASA spacecraft.

In the summer of 2015, New Horizons did a six-month-long reconnaissance flyby study of Pluto and its moons, producing a series of the most stunning and by far the closest photos of the faraway planet.

Pluto Has Ice Volcanoes And Pluto Has Floating Mountains

On the far western edge of Pluto's iconic heart-shaped surface, dubbed the Tombaugh Basin after its discoverer, are massive mountains of solid ice that go as high as 3.1 miles above the ground. With a bedrock of nitrogen and carbon monoxide ice, which are denser than water, the ice mountains float atop ice water.

NASA's New Horizons spacecraft observed that two of Pluto's prominent peaks - the 13,000-foot-high Wright Mons and the roughly 18,000-foot-high Piccard Mons — appear to be ice volcanoes or cryovolcanoes. Instead of erupting and spewing molten rocks and lava from its crater, Pluto's ice volcanoes explode with water ice and frozen nitrogen, ammonia, or methane.

"Cryovolcanism could provide an important clue in understanding Pluto's geologic and atmospheric evolution," Amy Shira Teitel, shared.