Astronomers have discovered the most Earth-like planet ever detected.

Scientists have discovered a distant, rocky world that is similar in size to Earth, and exists in the "Goldilocks Zone," in which it's not too cold or too hot to host human life, the Associated Press reports.

Lead researcher Elisa Quintana of NASA's Ames Research Center said at a news conference that the find "is special because we already know that a planet of this size and in the habitable zone is capable of supporting life as we know it."

"This is the best case for a habitable planet yet found. The results are absolutely rock solid," said University of California, Berkeley astronomer Geoff Marcy.

The planet was discovered by NASA's orbiting Kepler telescope, which studies space to detect subtle changes in brightness that could indicate when an orbiting planet is passing in front of a star. Scientists can calculate a planet's size and determine facts about its makeup from the changes.

The object, which is being called Kepler-186f, circles a red dwarf star 500-light years away from Earth. It orbits the star in the constellation Cygnus.

The planet is roughly 10 percent larger than Earth, and may have water on its surface. It lies at the outer edge of the temperature zone around its star, meaning rivers and/or oceans can exist without freezing or completely boiling into nothing.

The discovery, which was released in Friday's issue of the journal Science, is based on observations made before the Kepler telescope had a mechanical malfunction last year.

Marcy said that the planet is most likely cooler than Earth, with an average temperature slightly above freezing, "similar to dawn or dusk on a spring day."

The planet is believed to be more like an "Earth cousin," because while Earth revolves around the sun in 365 days, the planet completes an orbit of its star every 130 days.

Scientists say that if the planet has an atmosphere, it probably contains a great deal of carbon dioxide.

"Don't take off your breathing mask if you ever land there," said Lisa Kaltenegger, a Harvard and Max Planck Institute astronomer.

If the planet is habitable, scientists believe photosynthesis may be possible.

Since Kepler's launch in 2009, it has confirmed 961 planets, but only a couple dozen are in the habitable zone.

The latest discovery is the closest in size to Earth, more than any other planet that is known to exist in the habitable region.