Tau Ceti, one of the closest Sun-like stars to our own solar system, may support five planets, says a team of astronomers. The team also believes that one of those planets may be within the star's habitable zone, meaning it's at the right distance to allow liquid water and therefore more likely to be able to support life. While these findings are still preliminary, the researchers say they could be extremely valuable to astronomy. "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 the Universidad de Chile.
The news was reported by the University of California Santa Cruz yesterday, and the resulting paper has been accepted for publication in the journal Astronomy & Astrophysics. The discovery was made by modeling thousands of data points from three different spectrographs in Chile, Hawaii, and Australia, looking for orbital "wobbles" that could indicate a planet's gravitational pull. While previous searches hadn't found planets, these researchers say their methods can detect smaller-massed bodies that wouldn't have been picked up otherwise. Indeed, the theoretically habitable planet is only about five times as big as Earth, making it the smallest alien planet yet to be found in a habitable zone. It's not, however, likely to be rocky like Earth, lead author Mikko Tuomi tells Space.com. "It might be a 'water world,' but at the moment it's anybody's guess."
Besides being exciting in its own right, USCS astronomer Steve Vogt says this discovery is another data point suggesting that stars with planets in tight orbits are relatively common. "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." That, he says, makes our own solar system "a bit of a freak." However, Tuomi also notes that it's too early to be certain that it's planets that have been discovered. "I cannot be that sure whether [the signals] are of planetary origin or some artifacts of insufficient noise modelling or stellar activity and/or magnetic cycles at this stage," he says.