"Gliese is considered the most exciting planetary system astronomers have discovered to date outside our own solar system. A total of six planets orbit the red sun in the Libra constellation. Only last week, US scientists announced that they had discovered another planet in the system that's even more similar to Earth. The smaller, rocky planet Gliese 581 g also appears to orbit its sun in the 'habitable zone.' Kaltenegger has already begun calculating the climate for this satellite. The most important requirement to allow for the development of life as we know it is that a planet is heated by its sun to a sufficiently moderate degree that liquid water can form there."