Gliese 581g is part of an exoplanet system located “just” 20 light years from Earth. What makes it rank so high in its Earth Similarity Index rating is the fact that the planet is located just far enough from its dwarf red sun, in what is known as the “habitable zone,” to support the existence of liquid water and possibly life.
Scientists say the planet could have a radius up to 1.5 times that of Earth. Also, The planet’s mass suggests that the surface may be solid and that it could have enough gravity to sustain an atmosphere.
Exoplanet habitability research is finding more possibly habitable planets, so many that we now have a top five list. But the science is still a working theory considering it is only backed up by telescope data and theories of life sustaining conditions based on our own planet. We won’t know if these worlds are real and habitable until we actually get there.