Habitable zones about main sequence stars |
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Authors: | Michael H Hart |
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Institution: | Systems and Applied Sciences Corporation, 6811 Kenilworth Avenue, Suite 606, Riverdale, Maryland 20840, USA |
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Abstract: | Calculations show that a main sequence star which is less massive than the Sun has a continuously habitable zone about it which is not only closer in than the corresponding zone about the Sun, but is also relatively narrower. Let L(t) represent the luminosity after t billion years of a main sequence star of mass M, and let rinner and router represent the boundaries of the continuously habitable zone about such a star—that is, the zone in which an Earthlike planet will undergo neither a runaway greenhouse effect in the early stages of its history nor runaway glaciation after it develops an oxidizing atmosphere. Then our computer results indicate that is roughly proportional to . This ratio is smaller for stars less massive than the Sun (because they evolve more slowly), and the width of the continuously habitable zone about a main sequence star is therefore a strong function of the initial stellar mass. Our calculations show that rinner = router for (i.e., K1 stars), and it therefore appears that there is no continuously habitable zone about most K stars, nor any about M stars. |
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