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Planets for Man
Recipe for Habitable Worlds
In the mid-1960's, Stephen H. Dole, of the RAND Corporation (a world famous think tank), collaborated with the late renowned author, Isaac Asimov, to create a popular version of Dole's study, "Habitable Planets for Man." The title may not be politically correct in today's world, but the focus was on an incredible concept: What would it take for nature to create a world like our own Earth? Which stars in our night sky are likely to harbor a world suitable for human habitation?
The Ingredients
The authors first approached the problem by listing what we humans need in order to survive. They followed this with the human-friendly properties of planets, and the elements of a star system well-suited to habitability.
Human Requirements
- Temperature between
- Light
- Gravity
- Atmosphere (ingredients and pressure)
- Water
- Other Requirements like, indigenous plant life (source of free oxygen), modest winds, low levels of silica dust, etc.
Planets
- Limits of Planetary Mass
- Gas Capture and Retention
- The Thickness of Atmospheres
- Oblateness of Rotating Planets
- Rate of Rotation
- Spacing of Planets
- Inclination
- Satellite Relationships
- Age
Star Systems
- Distance from Primary
- Special Properties of Binary Star Systems
Though they talk of the upper limit of star ages based on spectral type, when the book was written there was no way to determine the approximate age of individual stars. Only the members of star clusters had ages known to a modest degree of accuracy. Now, forty years later, we know a great deal more about ages of individual stars and the need for rich and ancient star systems to fulfill the desire for habitable worlds beyond the Solar system.
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