The Hunt. Before or after bagging Them! head down the east ridge to the cache, a small metal butter container; be sure it is sealed properly before rehiding.
Name. Pluto was the god of the underworld in both Roman and Greek mythology. His name meant riches or wealth. Pluto and Hades (the Greek name for the god of the underworld) are the same being, though they differ in character. While Hades is seen as violent, Pluto is venerated and seen as a positive god who welcomes souls to the afterlife.
Factoids. Pluto has long been an elusive object. It was originally know as Planet X, an unseen body that subtly influenced the orbit of Neptune. Astronomer Percival Lowell (1855-1916) spent the later part of his life searching for it without success. It was finally discovered in 1930 at the Lowell Observatory in Flagstaff, Arizona where Lowell had worked. After much debate, the 9th planet was eventually named Pluto at the suggestion of an 11-year-old schoolgirl in England. It remained a planet for 76 years until it was demoted to a "dwarf planet" to be more consistent with recent discoveries of other small, planet-like bodies in the Solar System.
Pluto is tiny, about half the size of Mercury, and its rocky core is covered with a thick layer of water ice and frozen methane, pitted with craters. It is so cold that only a few basic elements would not freeze. Its strange orbit is inclined to the other planets and is highly elliptical, so that at times Pluto goes inside the orbit of Neptune. In sunlight, its surface appears pinkish, indicating the presence of carbon. There are white polar caps, probably made of frozen methane. When closest to the Sun, a thin atmosphere of methane and nitrogen may boil off the surface.
Pluto has four known moons, the largest being Charon discovered in 1978. Charon is over half Pluto's diameter and is only 12,200 miles away (20 times closer than Earth's moon). Charon and Pluto are so close that tidal force has locked their spins and orbits. They spin in opposite directions and the same sides always face each other. Seen from Pluto's surface, Charon hangs motionless in the sky, never rising nor setting. This pairing looks very much like a binary planet, although it is not officially designated as such. Charon is named for the mythological figure who ferried the dead across the River Aceron into the underworld.
- Distance from Sun = 30-49 AU (2.7-4.6 billion miles)
- Diameter = 0.18 Earths (1440 miles)
- Year in Earth years = 248
- Satellites = 4
- Mean surface temperature = 44 K (-380 F)
- Weight of 100 pounds on surface = 7
Exploration. For many of us, Pluto will always be the 9th planet. We will learn more about it in 2015 when the New Horizons mission pays a visit. Ironically, when the spacecraft was launched in 2006, Pluto was still classified as a regular planet. Some ashes of Clyde Tombaugh, Pluto's discoverer, are aboard the spacecraft.