Poor, poor Pluto. The heavenly object that once stood tall with the eight planets that orbit our sun is now just another anomalous piece of rock, demoted, soon to be left off those colorful solar system diagrams that filled the walls of our grade school classrooms. Pluto may not be a planet, but it is still interesting.
Sort of Like a Planet, but not Really
Pluto was discovered in 1930, and named after the Roman god of the underworld for its expected cold, dark nature so far from the sun. The name also referenced the initials of Percival Lowell, who spent the final 20 years of his life searching, unsuccessfully, for a planet outside Neptune. Pluto orbits at 40 times the Earth's distance from the Sun, orbiting every 248 Earth years. There the sunlight is less than one thousandth as strong as on Earth. Pluto is so cold its surface is covered in frozen nitrogen. For about 20 year of every orbit, it crosses Neptune's path and is closer to the Sun than the eighth planet, though they cannot collide. This last happened between 1979 and 1999.
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| Sizes to scale (NASA) |
