Astronomers announced on Thursday they have discovered a planet that is both similar in size to Earth as well orbiting its star within the habitable zone.

They named the planet Kepler-186f after it was discovered by the Kepler space telescope orbiting a red star about 490 light-years away. According to Space.com, the newly found exoplanet lies within the habitable zone - where liquid water is possible - of the star.

The planet is slightly larger than Earth and the red star isn't as bright as the Sun, but scientists believe the planet could possibly contain water on its surface. NASA Kepler scientist and co-author of the new exoplanet research Tom Barclay said, "One of the things we've been looking for is maybe an Earth twin, which is an Earth-size planet in the habitable zone of a sunlike star."

Barclay added that Kepler-186f isn't exactly a twin, but closer to "an Earth cousin. It has similar characteristics, but a different parent."

Still, little is actually known about the planet, reports the Los Angeles Times. The scientists who published their discovery in the journal Science, note that it isn't guaranteed there is actually water on Kepler-186f. They also aren't sure of the planet's mass.

The unknowns, however, don't diminish the excitement over the exoplanet.

UC Berkeley astronomer Geoffrey Marcy said in an email, "This is an historic discovery of the first Earth-size planet found in the habitable zone around its star." Marcy added, "This is the best case for a habitable planet yet found. The results are absolutely rock solid."