Question

What exactly is a habitable zone? What would you recommend I read to find out more?

A habitable zone is the thin band of space around any given star that a planet may reside and still maintain liquid water. In our solar system, Venus and Mars seem to mark the outer boundaries of our sun's habitable zone-these planets are either far too hot or far too cold to maintain liquid water. Venus retains a little water vapor in its atmosphere while Mars retains most of its water trapped in polar ice caps. However, the calculation of a habitable zone does not depend solely on the distance from a planet to its sun. Scientists must also take into account the different sizes and types of stars, as well as the fact that stars burn brighter and hotter as they age. Thus, as a star grows older, its habitable zone is pushed further out into space. The zone in which a planet may reside and maintain liquid water throughout most of a star's life is called the continuous habitable zone. Since one of the fundamental requirements of life as we know it is the presence of liquid water, the calculation of a habitable zone is critical to our search for life in other star systems. For more information as well as some great animation concerning habitable zones, check out the following website: http://library.thinkquest.org/C003763/index.php?page=planet07&tqskip=1
December 11, 2001