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1. The Earthiest Kepler-78b is most similar to Earth in mass, diameter and composition; it could be made of rock with an iron core. But it’s no Earth analog, whizzing around its star in 8.5 hours, with temperatures exceeding 2,000° Celsius (SN Online: 10/30/13). 2. The wettest HR 8799c’s atmosphere lacks methane, which could signal life, but does have water and carbon monoxide (SN: 4/6/13, p. 5). Water has also been found in the atmospheres of WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b. 3. The rogue Planetary candidate PSO J318.5-22 has no parent star. The object is roughly six times the...

While astronomers didn't bag that elusive first "alien Earth" in 2013, they made plenty of exciting exoplanet discoveries during the past year. Here's a list of the top exoplanet finds of 2013, from a tiny world about the size of Earth's moon to a blue gas giant on which it rains molten glass: The most Earthlike world yet Also this year, researchers found the closest thing to an Earth twin in size and composition, though it's far too hot to support life as we know it. Kepler-78b is just 20 percent wider and about 80 percent more massive than our...

Explanation: Even though Kepler-78b is only slightly larger than the Earth, it should not exist. Its size is extraordinary only in the sense that it is the most similar in size to the Earth of any exoplanet yet directly discovered. Its orbit, however, is extraordinary in the sense that it circles a Sun-like star 40 times closer than planet Mercury. At such a scathing distance, even rock is liquid. Models of planet formation predict that no planet can form in such a close orbit, and models of planet evolution predict that Kepler-78b's orbit should decay -- dooming the planet to...

Molten sphere could give clues to planetary mass Researchers at the Massachusetts Institute of Technology have discovered a new, Earth-sized exoplanet for which orbiting its star is literally all in a day's work.The newly discovered planet, dubbed Kepler 78b, completes one full revolution around its star in just 8.5 hours – fast enough that by the time you clock in at the office and clock out again, another solar year will have passed for Kepler 78b. To achieve this rapid orbital period, the planet revolves around its star at a distance 40 times closer than Mercury is to our sun.As...