The closest unary type-G solar or star system to earth is thought to be the Tau Ceti system. Dustier than our solar system, the ‘inhabitable zone’ of this system would seem to be more prone to collision, and lacks a rocky, metallic planet of a mass capable of generating Earth’s gravity and holding an atmosphere such as ours. Tau Ceti is in the constellation Cetus.
Tau Ceti is a star similar to the Sun, 20% smaller. 12 light-years from Earth, it is the closest star similar to the sun. A multitude of types of stars have been discovered from brown dwarfs to red giants, and many stars form binary and tertiary star systems, which would seem not to allow a planet to orbit in the habitable zone with earth type gravity. So we have become more interested, in 2014, to stars like our Sun in unary star systems and of an age between two and six billion years. In travel time, at the speed of light, with a rapid acceleration and deceleration, it would take at least two decades to reach the Tau Ceti system.
The Tau Ceti system is more gaseous and less rocky and metallic than our solar system. Evidence of five planets orbiting Tau Ceti with one in the habitable zone has been recently found. Tau Ceti can be seen without a telescope. Tau Ceti is only about half as bright as our sun, so the habitable zone would be closer to the star than in our solar system. Scientific calculations put the optimal habitable orbit for the Tau Ceti system to be roughly equal to the orbit of Venus in our solar system. The magnetic field of Tau Ceti also seems to be weaker than our sun. The magnetic field of the sun shields the inner planets from high levels of cosmic rays. The level of asteroids, comets and general debris in the Tau Ceti system is much higher, even ten times higher than our solar system.
It is exciting for us to learn so much about a class G unary solar system just 12 light years from Earth, but difficult to imagine life as we know it evolving there. Nonetheless, in the search for Extra-Terrestrial intelligence, or SETI, Tau Ceti is a fascinating aiming point for listening. Even Frank Drake chose Tau Ceti for research. Drake pioneered the Drake Equation, an infamous postulate for the likelihood of life elsewhere in the universe. Other SETI scientist, notably Turnbull and Tarter, have listed more than 17,000 theoretically habitable nearby star systems. Plans are in the works to search more carefully five candidates like Tau Ceti, all within 100 light years of Earth.