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Laboratory for Atmospheric and Space Physics
New Horizons: Student Dust Counter

Fun Facts

The Amazing, Vanishing Atmosphere

Pluto's orbit

Pluto's orbit is more eccentric than those of the other planets.
(Courtesy LASP)

"Pluto is just a big, boring rock floating out there in space. There's nothing interesting about it."

Or is there?

Being as far from the sun as it is, there are some pretty interesting things about Pluto.

Pluto has a very eccentric orbit. This means that at some points in its orbit, it's closer to the sun than at other times. This makes for an interesting situation.

Pluto has a thin atmosphere. When Pluto is closer in its orbit to the sun, everything is fine. But when Pluto starts to get farther from the Sun, something interesting occurs. The atmosphere begins to freeze and snow down onto the surface of Pluto.

By the time Pluto has moved near its farthest point from the sun, it has no atmosphere at all! All of it has snowed onto the surface! How's that for a disappearing trick?

I See!

The sun from Pluto

In this artist's rendering, the Sun appears dim from Pluto.
(Courtesy NASA)

At its current location, it takes light from the sun about 4.5 hours to reach Pluto. In comparison, it takes light from the sun 8 minutes to get to the Earth.

Just to make this interesting, consider the following. You live on Pluto in a sealed environment. Life is good and you couldn't really ask for more. All of a sudden, you see the small, dim sun explode in the sky! The sun has just exploded!

But wait! It took light 4.5 hours to reach you. That means that the sun actually exploded 4.5 hours ago and you are just now seeing it! It's almost like looking into the past and seeing something that happened a little while ago!

Hi Neighbor!

Pluto's orbit

The oort cloud, compared to the rest of the solar system.
(Courtesy Calvin J. Hamilton & NASA)

The Kuiper Belt is big and far away. It's out beyond Pluto! But there are things that are farther away than the Kuiper Belt.

Out past the Kuiper Belt is something known as the Oort Cloud. It is hypothesized that this is where a lot of comets are born. But that's not the interesting part. The interesting part is that the Oort Cloud is divided into two regions: the Inner Oort Cloud and the Outer Oort Cloud. Scientists think that the Outer Oort Cloud stretches out so far that it actually touches the edge of the Outer Oort Cloud of our nearest stellar neighbor, Alpha Centauri!

This would mean that there is a part of our solar system that stretches out two light years!