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Parts of Solar Systems

Most of what we know about solar systems comes from knowledge of our own system. The recent discovery of another solar system with many similarities to our own has scientists wondering whether solar systems like ours are a common occurrence. In an article appearing on Space.com on February 14, 2008, researchers note several commonalities between our solar system and the new discovery, including the presence of multiple planets, common orbiting ratios, and similar size ratios for planets. These findings suggest that the parts of our solar system may be found in other solar systems, too.

Central Star
- By their very nature solar systems have at least one central star. In our solar system, there is one star--the Sun. In the nearby solar system found by astronomers, there is also a single star. It's much smaller than the sun. The size and heat given off by different stars varies greatly, so different solar systems will haven different types of stars. Some may have a binary star system at their center.
Planets
- In our local solar system, the planets fall into two groups. The inner planets are small, rocky, and close to the sun. They don't have rings and have from zero to two moons. The outer planets, by contrast, are large, gaseous, and distant from the Sun. These planets are commonly called gas giants. They each have rings, although some are very faint. Each of the gas giants also has many moons.
  
  Even with powerful telescopes, it is difficult to see the planets in a neighboring solar system. So far, astronomers have only been able to identify gas giants in other solar systems. The gas giants appear to follow the same orbiting patterns as gas giants in this solar system.
Other Elements
- Our solar system also contains a number of other elements, such as asteroids, comets, the Kuiper belt, and the distant Oort cloud. Asteroids are chunks of rock floating in space. Some have irregular orbits, but in our system they exist mostly between Mars and Jupiter. Comets have irregular orbits that bring them close to the Sun at periodic intervals and then carry them out to the distant reaches of the system. The Kuiper belt stretches from Neptune to the outer reaches of the solar system. It's three billion km wide and contains a number of large objects, including the "dwarf planet" Pluto. The Oort cloud is beyond the Kuiper belt and is believed to be the source of most comets.

Astronomy