Suitable Star1 - Any life forms will need to use some of...

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Suitable Stars On the other hand, if the planet has a thick carbon-dioxide atmosphere, the atmosphere could circulate enough heat between the day and night sides to keep the surface temperatures uniform (like Venus that has a very slow rotation rate). Most small, cool M stars have frequent stellar flares with more energy than our Sun's flares that could kill off any complex life. Perhaps a planet with thick enough atmosphere to keep the surface temperatures uniform could also provide enough of a shield from the flares. The very narrow habitable zone of the small, cool stars would mean a small chance of finding a nice planet in the habitable zone. On the other hand, the sheer number of M stars in the Galaxy (recall that the M stars make up the greatest proportion of stars ) means that there could be many habitable worlds around M stars.
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Unformatted text preview: Any life forms will need to use some of the elements heavier than helium (e.g., carbon, nitrogen, oxygen, phosphorus, sulfur, chromium, iron, and nickel) for biochemical reactions. This means that the gas cloud which forms the star and its planets will have to be enriched with these heavy elements from previous generations of stars. If the star has a metal-rich spectrum, then any planets forming around it will be enriched as well. This narrows the stars to the ones of Population I---in the disk of the Galaxy. Most searches are focusing on the stars more like the Sun that are not too hot nor too cool---those with masses between 0.5 and 1.4 solar masses. Some searches are including the M stars but they will need to look at a large number of M stars to improve their chances of finding the ones with habitable planets....
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