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Physical Environment > Planets |
This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Note: Many facts have been simplified to make them easier to understand. |
 Figure 1 |
Planets are lumps of gas and rock held close to a star by the force of gravity. We live on planet Earth going round star Sun, along with eight other planets. Together these are called the solar system.
Because stars form in dark clouds of dust and molecules in open star clusters, it is difficult to watch them form. So the story of how planets formed which we have just given has not been confirmed by observation. About 20 planets have been discovered near Sun-like stars, although they are hard to see. Looking for planets near a star is a bit like trying to watch a moth flying around a spotlight which is pointing at you -- you get dazzled by the light. See the article Giant Planets Orbiting Faraway Stars for an explanation of how they are found. Since discs of gas and dust have been detected around some young stars, we guess that planets might be common. But none of the planets so far discovered are like our Solar System. Indeed these discoveries are challenging current theories of the origin of planets. If planets like ours are common, then life too could be common in the Galaxy. |
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Figure 1 Credit
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Physical Environment > Planets |
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Basic Information |
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