Earth 2.0 within grasp with potential candidates just 12 lightyears away
Christmas gift for mankind: A second earth! The discovery of 5 planets, one of them having the right size and orbit to be habitable like Earth, orbiting the star Tau Ceti, which happens to be the closest sun-like star near our own solar system, is like a heavenly gift for Christmas.
An international team of astronomers led by Mikko Toumi from the University of Hertfordshire made the discovery while testing a new method to find small, low-mass exo-planets. "One of the planets lies in the habitable zone of the star and has a mass around five times that of Earth, making it the smallest planet found to be orbiting in the habitable zone of any Sun-like star," the astronomers' team said in a release.
Tau Ceti, located at a distance of twelve light years and visible with the naked eye in the evening sky, is the closest single star that has the same spectral classification as sun.
The next step will be to confirm and refine the new discovery, which should involve a powerful space-based observatory to gain insights into parameters like the exact orbits or the kind of atmospheres.
"Tau Ceti is one of our nearest cosmic neighbours and so bright that we may be able to study the atmospheres of these planets in the not too distant future. Planetary systems found around nearby stars close to our Sun indicate that these systems are common in our Milky Way galaxy," a team member James Jenkins said.
Over 800 planets have been discovered so far orbiting other stars. After qualifying those exo-planets, especially those close by, the focus could shift to exploring them with fully autonomous robotic probes, and later possibly manned spaceships. First concepts of the propulsion technologies needed to bridge several lightyears of interstellar empty space already exist, but alot of research efforts and funding will be necessary to advance mankinds ability to actually construct and send even just a robotic probe with a fraction of the speed of light.
One popular propulsion concept, as explored by foundations like Tau Zero or Icarus Interstellar, is the use of a sail which is pushed by a very powerful laser from our solar system. This system could deliver theoretical speeds of about ten percent of the speed of light. A fusion powered spaceship could even reach speeds of about 20 percent of the speed of light, and thus reach Tau Ceti in less than one hundred years, but it would consume huge amounts of energy (just like the laser would also). So besides developing those interstellar propulsion technologies, a prerequisite for accessing neighbouring planets, which are now proven to exist, will be to develop the kind of abundant energy sources that can power mankinds growing civilization both on earth and in space.
The potential list of targets is ever growing, meanwhile. A new study suggests that there are not just one but at least three planets within the habitable zone around the star Gliese 667C (Gregory (2012) "Evidence for Multiple Planets in the Habitable Zone of Gliese 667C: A Bayesian Re-analysis of the HARPS data").
And according to the Planetary Habitability Laboratory, based at Arecibo, there could be even two habitable planets among the 5 discovered, with the outermost planet "Tau Ceti f" still in the habitably zone, although it would be a rather cold planet.
"As we stare at the night sky, it is worth contemplating that there may well be more planets out there than there are stars ... some fraction of which may well be habitable," said Chris Tinney from the University of New South Wales.