For the first time, astronomers have discovered a planet outside our solar system that is potentially habitable with Earth-like temperatures - a find researchers described Tuesday as a big step in the search for life in the universe. The planet is just the right size, might have water in liquid form, and in galactic terms is relatively nearby at 120 trillion miles away. But the star it closely orbits, known as a "red dwarf," is much smaller, dimmer and cooler than our sun. There is still a lot that is unknown about the new planet, which could be deemed inhospitable to life once more is known about it. And it is 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 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."