NASA has just announced the discovery of seven Earth-sized planets that orbit a star other than our sun. And they're relatively close, just 40 light years away.

Three of them are in what is described as the "habitable zone" where scientists say liquid water, and therefore life, could possibly exist.

This is a 3d artists impression of what the surface of what the surface of one of those planets,  TRAPPIST-1d, could look like. Use your mouse or smart phone to explore the panorama.

Planet hunter, Associate Professor Michael Albrow, is a Senior Lecturer in Astronomy at the University of Canterbury – he explains how significant this discovery is and what these planets might be like.