As stated in an earlier article, Pluto has been relegated to the status of a dwarf planet. But many people still think of it as an object of importance which deserves its own section. I tend to agree with them so I have included it as part of this series of blog articles.
Having said this, Pluto is not a very inviting dwarf planet. It has a large rocky core surrounded by a mantle made up mainly of water ice but also containing methane, nitrogen and carbon monoxide, all in ice form. This is covered by a thin icy crust. Pluto is relatively small at only 1,485 miles in diameter.
It is approximately 3.7 billion miles from the Sun which means that it takes nearly 248 years to make one orbit which is the longest in the solar system. Pluto’s orbit is a little strange because unlike all the other planets whose orbits are close to being circular and on the same plane, Pluto’s is more elliptical and is also inclined to the planetary plane. In fact its orbit is so elliptical that it takes it within the orbit of Neptune for up to 20 years. The last time this occurred was from 1979-1999. Being so far out from the Sun also means its surface temperature is very cold at minus 230º Celsius.
Pluto’s rotational period lasts for 6.4 Earth days. There is also something a bit different here as well because Pluto spins in the opposite direction to most of the planets including the Earth. This means that on Pluto the Sun rises in the west and sets in the east.
Although Pluto is no longer considered a full planet, it does have its own moon. It’s called Charon and it is about half the size of Pluto. This means that it is the largest moon in relation to its parent planet. However, our own Moon still holds the record because Earth is a full planet and Pluto is not. There is a strange connection between the orbit of Charon and the rotation period of Pluto. They are both the same at 6.4 days. This means that Pluto and Charon always present the same side to face each other.
Pluto is marks where most people believe the solar system comes to an end. But they would be wrong. There are other “things” further out. And we shall explore what they are in a coming article.
John Pullen 