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Written by spacetravel.org
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Wednesday, 18 May 2005 12:47 |
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An international team of astronomers, led by Dr. Bruno Lopez of the Observatoire de la Cote dAzur says that the search for life should not be limited to stars similar to the Sun. Life depends on liquid water; for a planet to contain liquid water, it cannot be so close to its star that water boils, or so far away that water freezes. Dr. Lopez team argues that as a star ages, it becomes brighter, and the habitable zone around it is pushed further out. As the star ages, it will warm outer worlds that were previously too cold for life to exist.
Dr. Lopez and his colleagues calculated the evolution of habitable zones for stars of 1, 1.5 and 2 solar masses in the red giant and sub-giant phases, and found that for planets between 2-9 AU from a solar mass star, the transit of the habitable zone will last from a few million to around two billion years. This resembles the timescale on which life on Earth is thought to have evolved. The team estimates that about 150 red giant or sub-giant stars are close enough for future missions to detect signs of life in any orbiting planets.
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