Could they be a future target for interstellar colonization?

Maybe so, according to astronomers working at Mauna Kea’s W.M. Keck Observatory, who have confirmed the discovery of a couple of Earth-sized planets in the hospitable zone of the nearest sunlike star, a mere 12 light years away from sun.

The exoplanets capable of supporting a liquid surface are two of four planets with girth similar to the Earth confirmed by an international team of astronomers, according to a new study published in Astrophysical Journal.

The other two Earth-sized planets are too close to their host star, described as our sun’s closest twin and known as Tau Ceti, a star visible with the naked eye in the evening sky.

With masses as low as 1.7 times the mass of the Earth, they are among the smallest planets ever detected around the nearest stars similar in size to the sun.

The study’s data was obtained from the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph at the European Southern Observatory in Chile and the High Resolution Echelle Spectrometer (HIRES) at the W.M. Keck Observatory in Hawaii.

The same international team produced a 2012 study that suggested that five planets were orbiting Tau Ceti.

That study also used Keck’s HIRES spectrometer, which detects planets by measuring the wobbles in the movement of stars. The wobbling occurs when a planet’s gravity pulls at its host star as it moves in orbit.

The scientists over the years have improved their planet-detecting ability, now measuring variations in movement as small as 30 centimeters, in part using a technique that allows the scientists to differentiate the star’s normal activity from motion created by the tugging of the planets, according to the study.

“We have painstakingly improved the sensitivity of our techniques and could rule out two of the signals our team identified in 2012 as planets. But no matter how we look at the star, there seems to be at least four rocky planets orbiting it,” lead author Mikko Tuomi of the United Kingdom’s University of Hertfordshire said in a press release.

According to the same news release, Tau Ceti could be an optimal target for interstellar colonization, as depicted in science fiction, if the outer two planets are found to be habitable.

But it could be an interesting place. Earlier observations have detected more than 10 times as much dust surrounding Tau Ceti as within our own solar system. And with its busy debris disk, any planet in Tau Ceti’s orbit would experience many more space impacts than Earth.

With its relative close proximity, Tau Ceti has been a popular location in science fiction, featured in novels, television, movies and more. For example, the USS Enterprise, under the command of Capt. James T. Kirk, engaged and defeated a Romulan vessel near Tau Ceti.

Earlier this year Keck astronomers made public two decades of data, including the coordinates of more than 100 exoplanets, in a collection described as the largest-ever compilation of exoplanet-detecting observations.