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 (193 trillion km) away. But the star it closely orbits, known as a ''red dwarf,'' is much smaller, dimmer and cooler than our sun.