Pluto, once considered the ninth and most distant planet from the sun, is now the largest known dwarf planet in the solar system.
Pluto is one of the largest known members of the Kuiper Belt, a shadowy zone that exists beyond the orbit of Neptune, thought to be populated by hundreds of thousands of icy, rocky bodies each larger than 62 miles (100 kilometers) across, along with 1 trillion or more comets. With discoveries about Pluto from NASA’s New Horizons mission, here are some of the most interesting facts about the former planet.
Formation and origins of Pluto
The leading hypothesis for the formation of Pluto is that in its nascent stage it was struck with a glancing blow by another Pluto-sized object. Most of the combined matter became Pluto, while the rest spun off to become Charon (Pluto’s largest moon).
Pluto was first discovered by a young research assistant in 1930
Photographic evidence of the former ninth planet was first sighted by a 24-year-old research assistant named Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona. Astronomer Percival Lowell predicted Pluto’s existence 15 years prior to Tombaugh’s discovery, even charting its approximate location based on the irregularity of Neptune’s orbit.
Pluto was named by an 11-year-old girl
When Venetia Burney’s grandfather told her the news of the newly discovered planet, she proposed the name Pluto, after the Roman god of the Underworld. It seemed fitting, as Pluto the planet, like God, sat at the far reaches of the solar system. Her grandfather was taken by the name and suggested it to a friend, conveniently an astronomy professor at Oxford University. Astronomers were particularly keen on Pluto because the first two letters of the word are Percival Lowell’s initials.
Pluto is smaller than Earth’s moon
Pluto is 1,473 miles in diameter, according to recent measurements obtained from New Horizons, while Earth’s moon has a diameter of 2,160 miles. Pluto is 18.5% the size of Earth but is larger than it was anticipated earlier.
Orbit and rotation
Pluto's rotation is retrograde compared to the other planets of the solar system; it spins backward, from east to west. Pluto's highly elliptical orbit can take it more than 49 times as far out from the sun as Earth. Since the dwarf planet's orbit is so eccentric, or far from circular, Pluto's distance from the sun varies considerably. The dwarf planet actually gets closer to the sun than Neptune is for 20 years out of Pluto's 248-Earth-years-long orbit, providing astronomers a rare chance to study this small, cold, distant world.
Pluto was demoted to dwarf planet status in 2006
The news of Pluto’s larger than expected size was particularly exciting to Pluto partisans because many believe the outsider was stripped of its planetary status because it was too small. However, Pluto was actually downgraded to dwarf planet because it’s simply not unique. Pluto is merely the brightest member of the Kuiper Belt, a mass of objects that orbit the sun beyond Neptune.
The question of Pluto's planet status has attracted controversy and stirred numerous debates in the scientific community, and among the general public, since 2006 and continues to date.
