We may have discovered most Earth-like planet beyond our solar system

The Guardian reports that the planet, Kepler 438b, which orbits a distant star in the constellation of Lyra, may be slightly larger than the Earth. It circles an orange dwarf star that bathes it in 40 % more heat than we receive from our sun. The small size of Kepler 438b makes it likely to be a rocky world, while its proximity to its star puts it in the so-called ‘Goldilocks’ or habitable zone where the temperature is just right for liquid water to flow, according to the Guardian.

The newly-discovered world, which is 470 light years away, completes an orbit around its star every 35 days, making a year pass 10 times as fast as on Earth. And Kepler 438b is not alone. It is one among eight new potentially habitable planets, including some close to Earth in size and situation, which were announced at the recent meeting of meeting of the American Astronomical Society. Speaking of the announcement, Douglas Caldwell of the SETI Institute in Mountain View, California noted to Science magazine, ‘We’ve significantly increased the list of verified small planets in the habitable zone’.

One of the other planets on the new list also looks promising. Kepler 442b lies in the same constellation 1 100 light years away. The Guardian reports that it is about a third larger than Earth, receives about two thirds as much starlight, and has a 60 % chance of being rocky. According to Scientific American, both Kepler 438b and Kepler 442b may be somewhat warmer than Kepler's two previous premier rocky worlds, Kepler 186 f and Kepler 62 f, each of which gets significantly less starlight—similar to that received by Mars.

The research team used a statistical technique known as Blender to confirm that the planets originally spotted by NASA’s ‘planet hunting’ Kepler space telescope were real. Science magazine elaborates, ‘[Blender] calculates what various false-positive objects would look like and then compares them with the brightness curves of the Kepler candidates, also incorporating any follow up data from other observations. Starting with 12 Kepler candidates believed to be small rocky worlds, the Blender analysis whittled them down to eight new exoplanets with radiuses smaller than 2.7 times Earth’s, all believed to be in the habitable zone.’

Although the newly-discovered planets show positive indicators for habitability, study co-author David Kipping, an astronomer at the Harvard–Smithsonian Center for Astrophysics, sounded a word of caution in Scientific Amercian: ‘We can't say for sure whether these planets are truly habitable—only that they are promising candidates for habitability.’ He also noted to the Guardian that Kepler 438b and 442b were ‘as close to Earth analogues as we’re going to find in the Kepler data’.

So what’s next in the quest to find life beyond our world? The Guardian believes that planet hunters’ hopes are now likely pinned on the next generation of telescopes, including Hubble’s replacement, the James Webb Space Telescope, and the European Extremely Large Telescope. Scientific American meanwhile looks stateside to NASA's upcoming Transiting Exoplanet Survey Satellite, or TESS, expected to launch in 2017. TESS would perform an all-sky survey focused on finding transiting rocky planets around nearby stars.

The study will be published in The Astrophysical Journal.