Astronomers, with the help of NASA's Kepler Space Telescope, have discovered a planet that closely resembles Earth's size and orbits a red dwarf star in the habitable zone about 493 light-years away, National Geographic reported.

The discovery of the planet, which was announced Thursday at a NASA press conference and published in the journal Science, marks the first discovery of a planet that closely resembles Earth, said Elisa Quintana of SETI Institute and NASA's Ames Research Center in Mountain View, Calif.

"This is the first, validated Earth-size planet in the habitable zone of another star," Quintana said

Since NASA launched the $600-million spacecraft in 2009 it has already found nearly 1,000 planets although only a half a dozen of them are terrestrial and orbit their star in the habitable zone, also known as the "Goldilocks" distance, according to Nat Geo.

The red dwarf star, dubbed Kepler 186, has five planets orbiting around it, one of them being Kepler-186f. Scientists have found that it is 1.1 times wider than Earth and estimate that is has a mass of 1.5 times that of our own planet.

Because Kepler 186 is a red dwarf star that is only about half the size of our sun, the star is much cooler and dimmer and requires Kepler-186f to conduct a tighter orbit that lasts 130 days.

The research team argues that the planet should be cooler than Earth's but still be warm enough to sustain liquid water without it freezing as long as it has an atmosphere proving a substantial greenhouse effect, according to Nat Geo.

The habitable zone implies that a planet could have water on it surface, which is essential for life, as it's not too close to its star, causing the water to boil and evaporate nor is it too far from the star where the planet could freeze over.

Geoff Marcy, a pioneering planet hunter of the University of California, Berkeley, wrote in an email to Nat Geo that the planet would likely have a sky that resembles Earth's sunset because of its red dwarf star.

"This planet basks in an orange-red glow from that star, much as we enjoy at sunset," Marcy said. "The temperature on the planet is likely cool, similar to dawn or dusk on a spring day."