WASHINGTON - Scientists from U.S. and Britain have found four planets, slightly larger than Earth, orbiting a star visible with a naked eye.
Using a technique so sensitive that it can measure tiny changes in the light emitted by stars, scientists at University of California Santa Cruz and the University of Hertfordshire detected the planets orbiting the star Tau Ceti, which is 12 light-years from Earth. Two of the planets orbit in the so-called habitable zone, meaning the surface water could possibly exist.
The changes in light are caused by gravitational pull of the planets orbiting the star.
Tau Ceti, in the south of the constellation Cetus, emits light spectrum similar to our sun but is about 25 percent smaller.
The two planets in its habitable zone are larger than Earth, but frequent bombardment by asteroids and comets from the star's massive debris ring make them improbable candidates to sustain life.
Observations were done from the Keck Observatory in Hawaii and the European Southern Observatory's Very Large Telescope in Chile.