AST 248 Chapter 10 HW Problems
Ryan Richards
What is a habitable zone , and how is the idea useful? Is a planet in the habitable zone necessarily habitable? Explain.
As defined by the text, a habitable zone refers to the range of distances around a star where a planet can have surface temperatures that are suitable for liquid water. However, a planet in the habitable zone is not necessarily habitable. There are other factors that a planet needs to harbor life. Some of these include a suitable atmosphere and energy.
Describe several ways in which it may be possible to have habitability outside the habitable zone.
Some of these answers were already mentioned in the previous assignment. For example, Mars and Jupiter’s moon Europa has been recorded to have liquid water underneath the surface. Also,
Saturn’s moon Titan has a thick atmosphere (which is thicker than the Earth as mentioned in the text).
Venus is not in the habitable zone now, but it may have been in the past.
This statement is plausible. Over time the Sun has brightened. One should know that the Sun’s increase in luminosity moves the habitable zone farther out, which would support the idea that
Venus was once inside the Sun’s habitable zone.
While the habitable zone of the Sun migrates outward over time, the habitable zones of the other Sun-like stars might migrate inward over time.
This does not make any sense. A Sun-like star undergoes the same processes that the Sun goes.
Also a Sun-like star’s luminosity should increase.
Earth has been warmer in the past than it is today, so there is nothing to worry about with global warming.
This does not make sense. There is still a large concern with global warming. There is a higher concentration of greenhouse gases that have been emitted in the atmosphere due to human activity. If this activity is not regulated, the increase in greenhouse gases will continue to rise.
The habitable zone refers to (c) the range of distances from a star within which water could exist in liquid form on a suitably sized planet.
A planet that is not within a habitable zone cannot have (c) abundant liquid water on the surface.
As the sun ages, the habitable zone will (a) move outward and grow wider.

Global Warming means that (a) Earth’s average temperature is increasing.
The current concentration of atmospheric carbon dioxide on Earth is (a) higher than the concentration at any time during the past million years.