Earth is similar to Gliese 581 c, in that they both are the third planet from their sun. See related links for information about Gliese 581 c.
Impossible to tell given current technology.
3-6. The 3 planet model would have gliese 581 b too hot, gliese 581 c in the habitable zone, and gliese 581 d too cold. The 6 planet model would have gliese 581 e, b, and c too hot, gliese 581 g and d in the habitable zone, and gliese 581 f too cold.
12,000 miles in diameter
Otherwise known as Zarmina's world, Gliese 581 G is apparently of the condition to sustain life. It is an estimated 20.3 light years away. It orbits around a red dwarf called Gliese 581. For more info check out the related link
The most likely candidates are (in no order): Gliese 581 g, HD 40307 g, Gliese 163 c, Gliese 581 d, Tau Ceti e, Gliese 667C c, Kepler 22 b, HD 85512 b and Tau Ceti f
Because Gliese 581 g, if it exists, is located near the middle of the habitable zone (or Goldilocks zone - [See related question]) of its parent star.
3-6. The 3 planet model would have gliese 581 b too hot, gliese 581 c in the habitable zone, and gliese 581 d too cold. The 6 planet model would have gliese 581 e, b, and c too hot, gliese 581 g and d in the habitable zone, and gliese 581 f too cold.
The temperature is not precisely known. If you read the Wikipedia article on Gliese 581 c, you'll find various estimates, based on different methods.
Gliese 581 c is too hot for life because it is closer to its star. This planet is similar to venus. This planet traps too much heat that causes a strong greenhouse effect. The temperature is too high and the atmosphere is nearly all carbon dioxide. Gliese 581 d is at the right distance for liquid water to exist. It is at the Goldilocks zone just like the earth. That means life could exist on Gliese d. This planet have the right temperature. It has a magnetic field and a rich oxygen and nitrogen atmosphere.
Gliese is a new planet discovered in April 27, 2007 but told in 2010.
12,000 miles in diameter
The planet Gliece does not exist. Are you thinking of the Gliese 581 system?
There are planets that are good candidates. There called Gliese 581 c and Gliese 581 d, they orbit a red dwarf 20.3 light years away. And they are thought to have an atmosphere and a temperature in which water may exist, and may also be in the "Goldilocks Zone."
Gliese 581 g was discovered on September 29, 2010.
Gliese itself does not exist, but Gliese 581 is a red star.
Otherwise known as Zarmina's world, Gliese 581 G is apparently of the condition to sustain life. It is an estimated 20.3 light years away. It orbits around a red dwarf called Gliese 581. For more info check out the related link
The most likely candidates are (in no order): Gliese 581 g, HD 40307 g, Gliese 163 c, Gliese 581 d, Tau Ceti e, Gliese 667C c, Kepler 22 b, HD 85512 b and Tau Ceti f
Gliese 581 IS the system, D is the planet.