The most distant planet in the solar system, Pluto’s exact nature is a mystery. Is it a planet? Or a large asteroid? Though we’ve known of Pluto’s existence since 1930, there are a lot of questions we haven’t answered. And because no spacecraft has visited the tiny planet, an in-depth understanding of Pluto may be light-years away.
As is so common in science, Pluto was discovered by accident. It was noted that there were irregularities in the orbits of some of the outer planets. Astronomers theorized there must be another, unidentified, planet disrupting their movements. Astronomer Percival Lowell made new calculations, and though he didn’t find the planet, his work led to its discovery by Claude Tombaugh, 16 years after Lowell’s death. However, Pluto is too small to have an effect on such large planets, so there may be yet another unidentified planet at the outskirts of the solar system.
Pluto has the most eccentric orbit of all the planets (in other words, its orbit departs from a circle more than any other planet), coming as close as 2.7 billion miles to the Sun and as far away as 4.3 billion miles. Every 248 years, Pluto crosses into Neptune’s orbit for 20 years, replacing Neptune as the eighth planet from the Sun.
Pluto is a tiny, frozen planet, with a surface temperature of -233 degrees Fahrenheit. It is believed to have a rocky core and icy mantle, and its surface consists mainly of nitrogen, with traces of carbon monoxide and methane. Pluto has one satellite, Charon, which is over half the diameter of its parent planet. Because the two bodies are so close in size, Pluto and Charon are often called a double planet system. Astronomers believe Charon formed from a collision on Pluto’s surface, much as the Earth’s moon is believed to have formed.
Pluto’s origin and classification have long been disputed. Some astronomers believe Pluto would more accurately be classified as an asteroid, and in 1999 some attempted to have the planet renamed asteroid No. 10,000. While some say Pluto is merely the largest member of the Kuiper Belt, others argue that, unlike most asteroids, which are irregularly shaped, Pluto is round like the planets.
Pluto
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