Gliece 581c is a planet orbiting Gliece 581, a red dwarf star in the constellation Libra. Gliese 581c first gained prominence when it was found to be within its star’s habitable zone – the first low mass extrasolar (outside our Solar System) planet found in such a region.
A star’s habitable zone, as the name implies, is a region around a star in which the conditions are right for water to exist and subsequently, for life to flourish. Another term commonly used for such a region is the Goldilocks zone.
More recent studies, however, led scientists to suspect that Gliese 581c’s atmosphere has the runaway greenhouse effect and hence cannot be habitable. The runaway greenhouse effect is a phenomena wherein too much greenhouse gas in the atmosphere forces the surface to overheat.
This in turn promotes very rapid evaporation and an accumulation of water vapor in the atmosphere. Incidentally, water vapor is an identified greenhouse gas. Thus, the accumulation of water vapor further enhances the greenhouse effect in the planet. And this is what is known as the runaway greenhouse effect.
Because of this, some scientists believe that while water may exist in the planet, it would not be in liquid form. Rather, it would be in vapor form.
The mass of Gliese 581c is estimated to be within 5.36 to 10.4 Earth masses. Scientists are not yet sure what the radius of the planet is.
Since Gliese 581 has a bolometric luminosity of only 1.3% of our Sun’s total luminosity, it is expected that its habitable zone should be much closer than our Sun’s, e.g., where our Earth is. As a matter of fact, Gliese 581c is only about 11 km from Gliese 581. By comparison, the Earth is 150 km from the Sun.
This extrasolar planet is so close to its sun, that it only takes 13 Earth days for it to complete one revolution. That essentially means “one year” there is only equivalent to 13 days. Whereas here, we roughly have 365 days.
Just like many moons in our Solar System, our Moon included, Gliese 581c experiences what is known as tidal locking. Meaning, only one of its hemispheres keep on facing its sun. This is because of Gliese 581c’s closeness to it. The result of this behavior is that only one side will experience day. The other side will be constantly dark.
Universe Today has an article that talks about Gliese 581 and its planets within the habitable zone.
For those who are into Twitter, you might want to check out the article entitled: Send a Tweet to Our Alien Friends on Gliese 581 D.
Of course, there’s more information from NASA. Check out
Habitable World Around Gliese 581? How about an astronomy picture of the day on it instead?
Alternatively, you can also listen to an interesting episode about craters in Astronomy Cast.
Source: Wikipedia
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