On August 24, 2006, the heavenly sphere known as Pluto was reclassified from being one of the nine planets in the Solar System to a classification of dwarf planet. Have you ever wondered why? Well, for an extensive explanation, check out Pluto - on Wikipedia. For a simpler explanation, watch this video in which Dr. Robert Hurt explains, or read my post below.
In the late 1800's, through astronomical observations, astronomers speculated that Uranus' orbit was being disturbed by another planet besides Neptune. From Wikipedia we read, "In 1906, Percival Lowell, a wealthy Bostonian who had founded the Lowell Observatory in Flagstaff, Arizona in 1894, started an extensive project in search of a possible ninth planet, which he termed, "Planet X". Lowell and his observatory conducted his search until his death in 1916, but to no avail."
Thirteen years after Lowell's death, the project was given to 23 year old astronomer, Clyde Tombaugh from Kansas. Again from Wikipedia we read, "Tombaugh's task was to systematically image the night sky in pairs of photographs taken two weeks apart, then examine each pair and determine whether any objects had shifted position. Using a machine called a blink comparator, he rapidly shifted back and forth between views of each of the plates to create the illusion of movement of any objects that had changed position or appearance between photographs. On February 18, 1930, after nearly a year of searching, Tombaugh discovered a possible moving object on photographic plates taken on January 23 and January 29 of that year. A lesser quality photograph taken on January 21 helped confirm the movement. After the observatory obtained further confirmatory photographs, news of the discovery was telegraphed to the Harvard College Observatory on March 13, 1930."
Naming the New Planet
News of the discovery of a ninth planet in the Solar System quickly spread throughout the world, and, of course, this new planet needed a name. Thousands of suggestions poured in from people all around the world. Percival Lowell's widow, Constance, suggested three names: Zeus, Percival, and Constance. All were rejected.
Finally, the name of Tombaugh's newly discovered planet came from a nine year old girl from Oxford, England. Venetia Burney, who was interested in mythology as well as astronomy, thought that Pluto, the name of the Greek god of the Underworld, would be a perfectly suitable name for a "presumably dark and cold world". After a unanimous vote from the members of the Lowell Observatory, the planet was officially named "Pluto" on May 1, 1930.
Interestingly, rumor is that in 1930, in honor of the planet Pluto, Walt Disney introduced a canine pal for Mickey Mouse whose name was, of course, Pluto. Also, following with the tradition of naming elements after planets (uranium after Uranus, neptunium after Neptune) in 1941, Glen T. Seaborg named the newly created element plutonium after Pluto.
Characteristics of Pluto
Because Pluto is so far away from the Earth, it has been difficult for astronomers to make an in-depth investigation of it. They do, however, know many things (please refer to Wiki), a small part of which are: that Pluto is relatively small. It is approximately one sixth the mass of the Earth's Moon and one third it's volume, and it is composed primarily of ice and rock.
A spacecraft is at this very moment heading towards Pluto to gather further information. The New Horizons spacecraft was launched on January 19, 2006 (interestingly just months before Pluto's classification was changed). It's closest approach to Pluto will be on July 14, 2015. It will make scientific observations of Pluto for six months prior to that date and one month after. Aboard the spacecraft are some of the ashes of Pluto's discoverer, Clyde Tombaugh, who died in 1997. Cool!
In 1992, a discovery was made of the Kuiper Belt (pronounced Kiper). This is a region in the Solar System containing small (relatively speaking), icy objects which are remnants of the formation of the Solar System. Pluto is among the objects in the Kuiper Belt.
There are three components which classify a planet: (from Wikipedia)
- The object must be in orbit around the sun. (Pluto is).
- The object must be massive enough to be a sphere by it's own gravitational force. More specifically, it's own gravity should pull it into a shape of hydrostatic equalibrium. (Pluto's does).
- It must have cleared the neighbourhood around it's orbit. (This is where the question with Pluto lies).
With the discovery of the Kuiper Belt and Pluto's place within it, controversy arose among astronomers and scientists as to whether Pluto was a separate planet or simply a large piece belonging to the mass of objects in the Kuiper Belt.
On August 24, 2006, after a vote between 424 astronomers belonging to the International Astronomical Union, Pluto was designated, by them, as no longer being a "full-fledged" planet but rather a dwarf planet. This decision, while upheld by hundreds of astronomers, is still opposed by hundreds more and by many people around the world.
My mind may tell me Pluto is a dwarf planet, but my heart tells me it's a planet.