One of the closest stars to our own, Tau Ceti, appears to have five planets, including one that's in the so-called habitable zone and could be suitable for life.
Not only is Tau Ceti a near neighbor, at 12 light years away, it has the same spectral classification as our sun. Previously, the nearest planet believed to be capable of supporting life - found just last month - was 42 light years away.
The new-found planets are estimated to have masses between two and six times the mass of the Earth, making this the lowest-mass planetary system yet detected. The planet that lies in its habitable zone has a mass around five times that of Earth, making it the smallest planet found in the habitable zone of any sun-like star.
"This discovery is in keeping with our emerging view that virtually every star has planets, and that the galaxy must have many such potentially habitable Earth-sized planets," says Steve Vogt, a professor of astronomy and astrophysics at UC Santa Cruz.
"We are now beginning to understand that nature seems to overwhelmingly prefer systems that have multiple planets with orbits of less than 100 days. This is quite unlike our own solar system, where there is nothing with an orbit inside that of Mercury. So our solar system is, in some sense, a bit of a freak and not the most typical kind of system that Nature cooks up."
The international team made the discovery using a new method that, they say, can detect signals half the size previously thought possible.
"We pioneered new data modeling techniques by adding artificial signals to the data and testing our recovery of the signals with a variety of different approaches," says first author Mikko Tuomi of the University of Hertfordshire.
"This significantly improved our noise modeling techniques and increased our ability to find low-mass planets."
While over 800 exoplanets have been discovered so far, most couldn't possibly host Earthlike life, and most are at very great distances. Discovering planets - and particularly one that might be suitable for life - so close to home will open up a vast range of new research possibilities.
"Tau Ceti is one of our nearest cosmic neighbors and so bright that we may be able to study the atmospheres of these planets in the not-too-distant future," says James Jenkins of Universidad de Chile, a visiting fellow at the University of Hertfordshire.