Astronomers have discovered a system of seven Earth-sized planets orbiting a single star.

According to scientists three of the newly discovered planets are in the so-called habitable zone, an area where there is potential for liquid water and possibly life.

Nasa said that the 7 planets are circling around a small dwarf star called TRAPPIST-1 which is cooler than the sun meaning that there is a possibility liquid water could survive on the planets orbiting close by.