An Exoplanet or Extra Solar Planet is a planet orbiting another sun or star outside the Solar System. Astronomers are searching for exoplanets because it is possible that some, perhaps many of them of them may sustain alien life.  SETI is seriously looking for alien signals. In late 2009 over 400 exoplanets are known.  Most are Gas giants at least as big as Jupiter, Saturn, Uranus and Neptune. Some are many times heavier than Jupiter. Smaller exoplanets may be very common but are harder to find with present intsruments.
Others are smaller and could sustain life like the Earth. COROT-Exo-7b is the smallest yet discovered and has a diameter less than twice that of Earth. Scientists expected such planets before it was found and were not surprised to find it. COROT-Exo-7b orbits close to its sun and must be too hot for our kind of life but others like COROT-Exo-7b may be at the best distance for life. Scientists plan to look for water and oceans on exoplanets as life possible on such planets. 
- Planetary systems
- Gliese 581 and its Planets There may be life in this system.
- Carbon Planet
- Chthonian Planet
- Circumbinary Planet
- Eccentric Jupiter
- Hot Jupiter
- Ocean Planet
- Extrasolar planet Wikipedia article
- COROT discovers smallest exoplanet yet, with a surface to walk on
- New method to seek life on exoplanets
- Scientists announce planet bounty
- First Time Photos of Extrasolar Planets! Well worth watching
- First Image of an Alien Planet
- First "Earth-like" planet found (April 2007) Video about a planet where there may be flattened bugs.
- Do Other Solar Systems Exist? Explaining how other planets are discovered.
- Life in the Universe, Just on Earth, or Everywhere? Life and exoplanets.
- Can a Planet Have Two Suns?
- ↑ http://news.bbc.co.uk/1/hi/sci/tech/7891132.stm
- ↑ http://www.esa.int/esaCP/SEM7G6XPXPF_index_0.html
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