stevestory
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Quote | Home » Exoplanets, Extraterrestrial life, News » Earth is outside habitable zone? Earth is outside habitable zone? August 20, 2015 Posted by News under Exoplanets, Extraterrestrial life, News
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Kepler has been looking for rocky worlds that could possibly retain liquid water on their surface Well, first, the BBC asks: What makes a planet habitable?
Here:
Quote | Water in liquid form is thought to be a necessity for life on Earth. |
Based on this, let’s look at the classical definition for the habitable zone as the region around a star, such as our own Sun, where the temperature of any orbiting planet permits water in liquid form. Quote | But, as it happens, there are difficulties.
What if the planet sports a blanket of white clouds? Clouds are reflective and therefore will cool the planet, acting to push the habitable zone closer to the star.
Amusingly, if we calculate this “equilibrium temperature” for the Earth, taking into account its beautifully reflective clouds, then it turns out that we live outside the classical habitable zone!
The same calculation for Venus gives an expected equilibrium temperature of about -10̊C, but in reality it is more like 450̊C.What happened? |
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and then she skips to some other quotes. let's see what she cut off from the BBC hmmmm?
Quote | What if the planet sports a blanket of white clouds? Clouds are reflective and therefore will cool the planet, acting to push the habitable zone closer to the star. Amusingly, if we calculate this "equilibrium temperature" for the Earth, taking into account its beautifully reflective clouds, then it turns out that we live outside the classical habitable zone! The same calculation for Venus gives an expected equilibrium temperature of about -10°C, but in reality it is more like 450°C. What happened?
Clouds' reflective qualities cool the planet and mean the habitable zone can be closer to a star Both these planets have greenhouse gases present in their atmospheres, warming the planet up and driving the outer boundary of the habitable zone further away from the star (while clouds drive the inner boundary closer to the star). The very latest habitable zone definitions use simulations of these cloud and greenhouse effects - widening and blurring the crude classical definition. |
UD linky
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