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...extraordinary may be too understated a descriptor for the discovery reported on Wednesday in the journal Nature: an international team led by Harvard astronomer David Charbonneau has spotted a "super-Earth," a planet 2.7 times bigger than Earth, circling a dim red star called GJ 1214, just 40 light-years away in the constellation Ophiuchus. "It's spectacular," says Geoffrey Marcy of the University of California, Berkeley, who is the world's most prolific planet hunter and is credited with discovering 70 of the first 100 exoplanets. "It's a top-of-the-top discovery in the quest for Earth...
While the new planet, dubbed GJ 1214b, is too big to be considered Earth-like, it comes pretty close. But GJ 1214b's relatively compact size - smaller than the vast majority of planets identified so far - is only one reason for astronomers' enthusiasm. Another is GJ 1214b's likelihood of bearing the stuff of life: water...
...Goldilocks" location that allows a planet to be neither too hot nor too cold. In that respect, GJ 1214b is again a near miss. Its surface temperature hovers at a sweltering 190°C (374°F), which is well above the boiling point of water, at least in Earth's atmospheric pressure. Fortunately, GJ 1214b's atmosphere makes the pressure a lot higher than on Earth - "crushing," as Charbonneau describes it - and increases the odds of liquid water. (Under pressure, water can remain liquid above...
Astronomers were further able to estimate the planet's makeup by calculating its size, based on the amount of light that GJ 1214b blocked when it passed in front of its star, as well as its mass (6.6 times Earth's mass), based on the wobble in the wavelength of starlight caused by GJ 1214b's gravitational pull on its star. That analysis revealed the new planet's density: about one-third of Earth's. Because water has a much lower density than rock, astronomers figured that the "most plausible scenario is a planet made mostly of water, with...
...like stars - that is, large and hot - on the assumption that if you're looking for life, you should look in a place that is as similar to our solar system as possible. Charbonneau, however, focused on about 2,000 small, dim, red stars known as M-dwarfs, nearby Earth. M-dwarfs are much more numerous than Sun-like stars; of the 300 stars closest to Earth, says Charbonneau, 220 or so are M-dwarfs. They're also much cooler than Sun-like stars, so their habitable zones are close-in. A planet in the Goldilocks position around...