Nearest ‘Earth-like’ planet may be closer than we think

Scott Sutherland
February 8, 2013

Astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) announced yesterday that, based on data provided by the Kepler Space Telescope, Earth-sized planets are far more common than previously thought, and there could be an Earth-like planet — with an atmosphere and possibly life — as close as 13 light years away.

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"The information we presented today will excite the general public because we now know that the nearest potentially Earth-like world is likely within 13 light years of the sun," CfA astronomer Courtney Dressing told The Huffington Post.

"Astronomically speaking, 13 light years is practically next door."

Using the Kepler data, Dressing and her co-authors examined the light collected from various stars and found that, while stellar atmosphere models worked quite well for stars that are the size and temperature of our Sun, they did not work as well for smaller, cooler stars, such as red dwarfs.

Refining these models to better estimate the size and temperature of red dwarfs, they looked at 95 planet candidates from the Kepler data that orbit red dwarf stars and discovered that 6o% of these candidates are smaller than Neptune. Also, six percent of them are potentially Earth-like planets — planets that are roughly the same size as Earth and are the right temperature to have liquid water on their surface.

"The reason why we decided to focus on these small red dwarfs is because, contrary to what you probably learned in school, our Sun is not a typical star," Dressing said in a press conference yesterday. "In fact, most stars are red dwarfs."

According to Dressing, 75 per cent of the stars in our galaxy are red dwarfs, and "this means that if we want to understand how many Earth-sized planets there are in the galaxy, it's very important to the study the fraction of red dwarfs that host small planets."

Another benefit of studying red dwarf stars is that because they are smaller and dimmer and cooler, their habitable zone will be much closer to the star than the habitable zone of a larger star, and thus any planet orbiting in a red dwarf's habitable zone will have a fairly short orbital period. Since the Kepler telescope looks for transits — when the light we see from a star dims because a planet passes in front of it — it is far easier to identify a planet when it transits its star several times during Kepler's viewing period, as opposed to one that only transits once (or has yet to transit).

[ More from Geekquinox: Astronomers redefine habitable zone around stars ]

Applying their results across our galaxy, the team determined with 95% confidence that that the nearest transiting Earth-like planet is within 29 light years of us, and the nearest non-transiting Earth-like planet is as close as 13 light years away.

Even with our fastest spacecraft (currently Voyager 1) it would take over 225 thousand years to travel that kind of distance. So, we wouldn't be going to visit such a planet anytime soon, unless one of our scientific breakthroughs pulls faster-than-light travel out of science fiction and into reality. However, both the James Webb space telescope and the proposed Earth-based Giant Magellan Telescope will have the capability to examine the atmospheres of distant planets for conditions that will support life, thus finally providing an answer to the question, "Are we alone in the universe?"

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