Pluto: Planet Lost

Pluto was once considered a planet on its own, but sadly, it is now classified as a dwarf planet.  Pluto was discovered in 1930 by Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona.  It took Tombaugh over a year to find Pluto.  It was named by an 11 year old girl from Oxford, England, who had submitted the name to her father, who had it sent to the astronomers at Lowell Observatory.  Pluto is the name of the mythological figure that was the god of the underworld.  In 2006, the International Astronomical Union (IAU) redefined the meaning of a planet, which bumped Pluto into the dwarf planet category.

There are five other icy planets at the edge of our solar system in the same category as Pluto, but there are likely hundreds more still waiting to be discovered.  Pluto is currently the second largest known dwarf planet coming in at about 2,302 kilometers (1,430 miles) in diameter.  Eris, the largest known dwarf planet, isn't much larger, measuring 2,326 kilometers (1,445 miles).

A dwarf planet is a solid (typically ice and rock) planet-like body that orbits the Sun, but has not cleared its orbital path around the Sun of other orbital debris, such as asteroids.  The five known dwarf planets in our solar system are in an area known as the Kuiper Belt. The Kuiper Belt is a ring of objects, like comets, asteroids, and dwarf planets, that orbit the Sun at a distance of 30-55 AU (remember: AU stands for Astronomical Unit and is the average distance between the Earth and Sun; 93 million miles).   The comets that live in this area are usually seen more frequently.  These comets usually orbit the sun every 200 years or so. Halley's Comet is an example of this type.

Beyond the Kuiper Belt lies the Oort Cloud.  It occupies an area of our solar system between 5,000 and 100,000 AU. This area houses the comets that take hundreds to thousands of years to orbit the Sun.  Comet Hale-Bopp is a good example of this type.

Most, if not all of the objects in these 2 regions of our solar system are smaller than Earths Moon, including Pluto and Eris.  The Moon measures about 3,475 kilometers (2,160 miles) in diameter, which is about a quarter the size of the Earth.  Pluto is about 33% smaller than the Moon.

If you wanted to view Pluto at night, forget it!  Unless you have a 10 inch telescope or larger, you won't be able see it.  Even then, it will just look like a regular star.  It would have to be viewed continuously over a long period of time to see it move against the background stars.