There's still much that is unknown about the new planet, which could be deemed inhospitable to life, once more is known about it. And it's worth noting that scientists' requirements for habitability count Mars in that category: a size relatively similar to Earth's, with temperatures that would permit liquid water. However, this is the first planet outside our solar system that meets those standards.

"It's a significant step on the way to finding possible life in the universe," said University of Geneva astronomer Michel Mayor, one of 11 European scientists on the team that found the planet. "It's a nice discovery. We still have a lot of questions."

The new planet is about five times heavier than Earth. Its discoverers aren't certain whether it is rocky like Earth or a frozen ice ball with liquid water on the surface. If it is rocky like Earth, which is what the prevailing theory proposes, it has a diameter about 1.5 times bigger than our planet. If it is an ice ball, as Mayor suggests, it would be even bigger.