Pluto

The second largest dwarf planet is called Pluto. It is also the 10th largest body observed which orbits the Sun It was first classified as a planet in 1930 when it was first discovered. However, later on in year 2006, the International Astronomical Union had the planet to change its status to dwarf planet instead.

This dwarf planet is situated furthest from the sun than the other eight planets. However, it is closer to the Sun than Neptune for 20 years from 249 year orbit due to its high eccentricity of the orbit.

It has a 6.387 of rotation period, which is the same as Charon, one of its satellites. It is normal that a satellite travels in a synchronous orbit together with its planet. However for Pluto, it rotates synchronously with the satellite’s orbit instead.

It shares a similarity with planet Uranus where it rotates with its pole which is approximately in its orbital plane. When this dwarf planet was first discovered, the view that was seen from the Earth was a bright south polar area. It grew dimmer as the viewpoint from Earth shifted from nearly pole-on to nearly equator-on.

Pluto has an average density which ranges from 1.8 to 2.1 grams per cubic centimetre. And it was concluded that it has about 50% to 75% of rock and ices mixture. Charon’s density of 1.2 to 1.3g/cm3 shows that it contains a little rock substance. The difference between the dwarf planet and Charon shows that both are formed independently from each other.

Besides that, the dwarf planet’s icy surface is of 98%. It was observed that methane and carbon monoxide do exist in the planet as well. There is a layer of thin atmosphere that will freeze and fall off as the planet travels away from the Sun.

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