According to research published in the Science journal in the US , the planet, dubbed Kepler-186f, was detected by scientists using NASA's Kepler telescope.

It is roughly 10 percent larger than Earth and was located some 500 light years away in the constellation Cyprus.

Speculation that it could have liquid water, a crucial component to life, marks a significant step forward in the search for habitable spots outside our solar system.

Researchers said Kepler-186f resides at the outer edge of the habitable temperature around its star, the so-called sweet spot, meaning lakes, rivers or oceans could exist without freezing solid or boiling away.

"What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form," said lead researcher Elisa Quintana at NASA's Ames Research Center.

However she said she considers the planet more of an "Earth cousin" rather than a twin because it orbits a star that is dimmer and smaller than our sun meaning it is likely to be much cooler.

Kepler-186f's size is also said to be a significant aspect of the discovery as a planet's size is key to predicting the composition of the surface and its atmosphere.

Planets that are more than 1.5 times the size of Earth or larger, often attract a thick hydrogen layer that makes them start to resemble gas giants like Jupiter or Saturn. Those that are smaller have a greater chance of being rocky.

Kepler-186f is one of five planets orbiting the Keplar-186 star. All are roughly Earth's size, however the others are too close to the star to support life.

The Kepler space telescope has found 961 planets since its launch in March 2009.

Only a few are in the habitable zone and all appear to be larger than earth.

ccp/jm (AFP, AP)