Is Discovery of Earth’s Twin Imminent? Kepler Mission Finds Numerous Small, Rocky Planets (Sound Familiar).

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"It could happen almost any time now. We now have the technological capability to identify Earth-like planets around the smallest stars."
             David Latham — Harvard-Smithsonian Center for Astrophysics


One of the most intriguing results of the Kepler Mission is the discovery of the small size of the planetary candidates. For years the list of known extrasolar planets had been dominated by massive "Hot Jupiters," comparable to the biggest planet in our solar system.

Such massive worlds are the easiest to find, whereas Earth-sized planets are much more  elusive. But Kepler was designed to be sensitive to those smaller worlds, even the temperate, rocky worlds that might be more life friendly. The spacecraft is showing that smaller planets are common — more common, in fact, than their larger brethren. At least that is how things look in the inner regions of planetary systems, where Kepler's data is currently the strongest.

"There are some Jupiters, there are some Saturns," University of California, Berkeley, astronomer Geoff Marcy said at a meeting of the American Astronomical Society (AAS). "But there are far more of the smaller and smaller planets going down to about two Earth diameters."

Marcy and his colleagues have used Kepler's data set to extrapolate how often planets of different sizes appear around stars, taking into account the biases that make Kepler spot some planets while missing others. (For every planet that orbits its star in just such a way that it crosses Kepler's line of sight, there might be five to 20 other planets that are not so favorably aligned.) The team found that planets of just a few times Earth's diameter are quite common around stars of the sun's spectral type. "If you take a sample of G-type main sequence stars, 8 percent of them will have two- to 2.8-Earth-radii planets with orbital periods of less than 50 days," Marcy said.

Kepler's potential for spotting relatively small worlds was highlighted by the announcement at the AAS meeting of a newfound planet from the mission.

Francois Fressin of the Harvard–Smithsonian Center for Astrophysics said that he and his colleagues have vetted a candidate planet, now known as Kepler 10 c, which has a diameter 2.2 times that of Earth. Kepler 10 c resides in a planetary system with the even smaller Kepler 10 b, which was announced in January. At the time of that announcement Kepler 10 c was an intriguing hint that could not be validated.

But Fressin and his colleagues used complementary observations from NASA's Spitzer Space Telescope as well as a supercomputer program that simulates confounding astronomical phenomena that might mimic the signal of a planet to conclude that there is only a 1 in 60,000 chance that Kepler 10 c is not a planet.

Astronomers may be on the brink of discovering a second Earth-like planet, a find that would add fresh impetus to the search for extraterrestrial life. Astronomers interpreting the Kepler data hint that now that we are able to detect the presence of small, rocky planets, much like our own, around distant stars for the first time that the discovery of a Twin Earth may not be too far off — planets that are considered the most likely habitats for extraterrestrial life.

The majority of the atoms in our bodies were created in the Big Bang 15 billion years ago. Most of the mass in our bodies are oxygen atoms that were created by generations of stars that preceded the formation of our Sun. We are a subset of the physical universe. And through astronomy this negligible subset is slowly acquiring — however limited — an awareness of the total Universe that created it.

The Daily Galaxy via scientificamerican.com and Harvard Smithsonian Center for Astrophysics

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