The Solar System

Most of us have studied in our science classes that the solar system starts with the sun and then goes on with the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto (even though Pluto isn't thought of as an official planet anymore). That's usually all we think of. But is that all? Is there more? There sure is!

The first collection of bodies other than the main planets is the asteroid belt. This sits conveniently between Mars and Jupiter. Within the asteroid belt sits the dwarf planet known as Ceres, which is slightly under 1000 km in diameter and large enough to be spherical in shape.

The area beyond Neptune is called the "Trans-Neptunian Region" and it remains mostly unexplored; however, there are many interesting things out there. The second collection of bodies other than the main planets is the Kuiper Belt. This collection of debris is similar to the asteroid belt, but differs in one important area: the asteroid belt is mainly made up of rock and metallic substances, whereas the Kuiper Belt is mostly ice. It's in this Kuiper Belt that you'll find Pluto and its "moon" Charon (although it's more agreed upon now that Pluto and Charon are more of a binary planet system, meaning they revolve around each other). Other dwarf planets in the Kuiper Belt include Eris (which is actually more massive than Pluto), Haumea, and Makemake. Past the Kuiper Belt, there is also Sedna. Not much is known about Sedna. Many speculate that it's a dwarf planet, but it hasn't been officially categorized yet.

But is that it? Not quite. Out past the Kuiper Belt is a hypothetical (which translates into scientists believe it to be there, but haven't proven it yet) area called the Oort Cloud. It is estimated to be between 1 to 1.87 light years from the sun. It is supposedly made up mostly of ice like the Kuiper Belt, but much farther out. The Oort Cloud is thought to be where long range comets come from.

Is there anything else? The short answer is that we really don't know. There are still vast amounts of the solar system that haven't been mapped yet. Believe it or not, astronomers are still looking at the area between the sun and Mercury for objects. If we haven't found all the objects that are that close, who knows what wonders lie a light year away.

So what exactly is the boundary of the solar system? That depends on who you talk to. Some say it's just the distance of the planets, and others say it's the distance of the Oort Cloud, and others say it's the distance that the sun's gravity can affect, and still others say it's as far as the solar wind (charged particles from the sun) can reach. Either way, it's a very long way from earth (from the billions to the trillions of miles).

Bet you didn't know that!