Earth: Four Earth-sized planets have been discovered orbiting the nearest Sun-like star, Tau Ceti which is about 12 light years away and is visible to the naked eye.
Two of the planets are super-Earths located in the habitable zone of the star, tau Ceti, meaning they could support liquid surface water, said researchers at University of California (UC), Santa Cruz in the US.
The planets have masses as low as 1.7 Earth mass, making them among the smallest planets ever detected around nearby Sun-like stars, they said.
They were detected by observing the wobbles in the movement of tau Ceti. This required techniques sensitive enough to detect variations in the movement of the star as small as 30 centimetres per second.
“Our detection of such weak wobbles is a milestone in the search for Earth analogs and the understanding of the Earths habitability through comparison with these analogs,” said Fabo Feng from the University of Hertfordshire in the UK.
“We have introduced new methods to remove the noise in the data in order to reveal the weak planetary signals,” said Feng, lead author of the study published in the Astrophysical Journal.
The outer two planets around tau Ceti are likely to be candidate habitable worlds, although a massive debris disc around the star probably reduces their habitability due to intensive bombardment by asteroids and comets.
Sun-like stars are thought to be the best targets in the search for habitable Earth-like planets due to their similarity to the Sun, researchers said.
Tau Ceti is a star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun’s mass. At a distance of just under 12 light-years from the Solar System, it is a relatively nearby star.