This strange place called Earth

Scientists are finding that our planet and solar system are oddities in the universe.

Scientists are discovering that Earth and our solar system may be unusual places in the universe, reports the BBC.

Up until 20 years ago, we were only aware of the nine planets in our solar system. But in 1995, astronomers discovered the first planet orbiting another star — 51 Pegasi B. Since then, thousands of other extra-solar planets have been identified. "The solar system, we now know, is far from alone," says the BBC.

The discoveries made in the past few years so far tend to highlight just how "odd" our planet is. In some solar systems, planets orbit two stars at the same time. In others, they orbit at large angles compared to their star's axis of rotation. And planets the size of Earth seem very rare, but this may be because they are beyond the reach of current telescopes.

The biggest anomaly is probably Jupiter. To have such a large planet orbiting in such a position is most unusual. And contrary to what astronomers used to think, our planets did not necessarily form in the orbital spot where they are positioned today. In some systems, large gassy Jupiter-like planets orbit very close to their star, in conditions normally too adverse for their formation. Scientists now think some planets "migrated" to their spots.

The migration theory would apply to Jupiter. Some think it slowly zigzagged its way into its present orbit. On the way, it likely created conditions allowing for Mars and Earth to form and hurtled countless ice-carrying asteroids in the direction of the future Earth.

That would explain why Earth has water, and in just the right proportion to form a single large ocean that does not flood the continents — even though Earth grew up in an interplanetary desert where the Sun's heat creates conditions that make it extremely unlikely for water to form. Very odd indeed.