How to Detect Extrasolar Planets

Since planets only reflect light from their central star they are extremely difficult to 

The fact that 1995 marked the discovery of the first extrasolar planet can be compared with the Copernican Revolution that not the Earth but the Sun is the center of our planetary system and the discovery of Hubble, that the universe is expanding. Since 1995 it became evident that planetary systems are common in the universe and this has certainly big impact on the question whether there are other habitable planets or not. 

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