Astronomers discover system of seven Earth-sized planets just 40 light-years away

An international team of astronomers, including space scientists from our University, has found a system of seven Earth-sized planets just 40 light-years away.

Using ground and space telescopes, including NASA's Spitzer Space Telescope and ESO’s Very Large Telescope, the planets were all detected as they passed in front of their parent star, the ultracool dwarf star known as TRAPPIST-1.

According to the paper, appearing in the journal Nature, three of the planets lie in the habitable zone and could harbour oceans of water on their surfaces, increasing the possibility that the star system could play host to life.

This system has both the largest number of Earth-sized planets yet found and the largest number of worlds in the habitable zone, where liquid water is most likely to be detected on the surface.

Dr Matt Burleigh from the Department of Physics and Astronomy, working with PhD student Alex Chaushev, observed TRAPPIST-1 in early July of last year using a telescope at the South African Astronomical Observatory in Sutherland, South Africa.

Dr Burleigh explained: “At the time there were thought to be perhaps four planets orbiting the star, and our aim was to observe one of the planets ‘transiting’ the star. A transit is when a planet passes directly in front of a star as seen by us on Earth, blocking some of the star’s light.

“By measuring the dip in the star’s brightness, we can infer the size of the planet. By observing successive transits, we can also constrain the orbit of the planet, and that was the primary aim of our observations.

“Puzzlingly, we didn’t see a transit at the expected time. This was actually a vital clue, since it indicated there was more going on in the TRAPPIST-1 solar system than we were previously aware.

“Thanks to a whole programme of observations with different telescopes and the NASA Spitzer satellite over the last few months, we now know that there are at least 7 planets in the system, all roughly the size of Earth.”

PhD student Alexander Chaushev from the Department of Physics and Astronomy, who assisted in the telescope observations in South Africa and helped to analyse the data in good time for the rest of the team, added: “Being involved in this project has been very exciting. It's not often you get to be part of such a fascinating discovery as a PhD student!”