Pluto

From its discovery in 1930 up until 2006, Pluto was considered to be the ninth planet and the farthest from the sun. It is so faint that it can only be seen with an extremely powerful telescope. It is unknown whether or not this planetary body has any satellites.

Pluto rotates on its axis once every 6 days, but it takes it 248 years to complete a full revolution around the sun. The tilt of the axis is about 17º, which is unique because none of the planets have atilt more than 7º. Its orbit around the sun follows an elliptical path os that from 1979 to 1999, it was actually closer to the sun than Neptune.

It is made up mostly of nitrogen ice and there are traces of carbon monoxide and methane. In the images captured by the Hubble Space Telescope, there do not appear to be any marks of any kind on the surface. The concentrations of ice on the surface make it one of the most concentrated celestial bodies in the solar system. Through these images, scientists estimate that Pluto is composed of about 30-50 % rock and the rest ice.

In 1976, it was determined that due to the amount of ice on the surface, Pluto was only about 1% percent the size of the Earth and showed up because it was so luminous. A satellite, named Charon, was discovered in 1978 and because of the gravitational pull this satellite exerted, it was determined that Pluto was even smaller than this.

The atmosphere consists mainly of gases that freeze and fall to the surface when the body is farther from the sun. As it nears the sun, these gases then evaporate once more, only to repeat the cycle. The distance of Pluto from the earth presents many challenges to scientists in their studies. Astronomers have always been puzzled by its existence, believing that instead of being a planet, it could be an escaped moon of Neptune. In 1992, they discovered a belt of small icy objects, just beyond Neptune, which they named the Kuiper belt. Pluto has similar characteristics to these objects and is somewhat like a comet without a tail.

In 2006, there was much discussion about the status of Pluto as a planet. In order for a body to be designated as a planet, it has to meet three conditions:

• It has to revolve around the sun
• It must have its own gravitational force
• It must clear the neighborhood around its orbit.

In their studies, scientists realized that Pluto met the first two conditions, but not the third. Therefore, Pluto has been reclassified as a minor planet and not one of the major planets in the solar system.