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This second term in the equation, the percent of stars that are appropriate, is a way of getting at the question: What percent of the stars in the Milky Way Galaxy are of types believed appropriate in terms of size, stability, and emissions? Thus, with this term, we reduce the number of stars we are considering to just those that are appropriate for (ultimately) supporting life.
We don't know what is actually required to make a star appropriate, but many scientists believe that a star has to be a Main Sequence star in order to be appropriate. (Main Sequence stars are stars whose luminosity is directly related to their temperature.) Other scientists believe that a star has to be very much like the Sun, which is a Main Sequence star and more specifically a G-type star. Only about 5% of the stars in our galaxy are G-type stars, though about 10% more are F- and K-type stars-the types of stars closest to G-type (Sunlike) and about 90% of stars are Main Sequence stars. Also, about half of stars exist in binary or multiple systems, which may make those stars inappropriate.
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Star Types and Implications for Life
G-type
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F,G,K-type
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Main Sequence
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All Types
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Star Arrangements and Implications for Life
Singular Star Systems
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Multiple Star Systems
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Your current choice for this term:
To update this value, return to the full equation page and change the value in the form.
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