Researchers from the University of Hertfordshire in the UK have detected four Earth-sized exoplanets orbiting the closest Sun-like star outside our solar system, and think that two of them could be habitable. The star, called Tau Ceti, is located around 12 light-years away, and the scientists believe it has the potential to support alien life. The exoplanets were discovered using a technique called Doppler spectroscopy, also referred to as radial velocity or 'the wobble method', which detects extremely slight wobbles in Tau Ceti's movement, due to the gravitational pull of smaller astronomical bodies. Two of the exoplanets are located within the boundaries of Tau Ceti's habitable zone, where the conditions could support liquid water on their surface, and could possibly support life. This is not the first time Tau Ceti has been found to host potentially habitable worlds; a few years back the same team discovered five worlds orbiting the star, and the latest research is an amendment to their previous work, the findings from which will appear in an upcoming edition of The Astrophysical Journal. To find out more check out Color difference makes a difference: four planet candidates around tau Ceti.