The planet lies in what they describe as a "habitable zone", neither too near its sun to dry out or too far away, which freezes it.
And the discovery could help answer the question of whether we are alone in the universe, which has puzzled astronomers and alien fanatics for years.
Scientists found the planet, Gliese 667Cc, orbiting a red dwarf star, 22 light years away from the Earth.
Red dwarf stars are the most common stars in the neighbourhood of the Sun, usually hosting planets called gas giants, which are not composed of rock matter.
Re-analysing data from the European Southern Observatory, the astronomers found Gliese 667Cc is a solid planet with roughly four and a half times the mass of Earth.
The University Göttingen and University of California scientists have calculated the planet receives about 10% less light from its star than the Earth gets from the Sun.
The planet also receives nearly the same amount of energy as the Earth, meaning water could be liquid and surface temperatures could be similar to ours.
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