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Most Earth-Like Extrasolar Planet Found "Right Next Door"

Discussion in 'Tech, Gadgets & Science Forum' started by Bluray, Dec 17, 2009.

  1. Bluray

    Bluray JF-Expert Member

    Dec 17, 2009
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    Most Earth-Like Extrasolar Planet Found Right Next Door


    An artists rendition of the extrasolar planet GJ 1214b

    Meet GJ 1214b, the most Earth-like planet ever found outside our solar system.

    It’s not exactly Earth’s twin: It’s about six times bigger, a whole lot hotter and made mostly of water. But compared to the giant gas balls that account for nearly every other extrasolar planet ever found, it’s pretty darn close. And through a fortunate happenstance of cosmic geometry, astronomers will be able to study GJ 1214b in great detail.

    “If you want to describe in one sentence what this planet is, it’s a big, hot ocean,” said Harvard University astronomer David Charbonneau. “We can even study its atmosphere. This planet will occupy us for years. That’s part of what’s so exciting about it.”

    Described by Charbonneau and 17 other astronomers in a paper published Wednesday in Nature, GJ 1214b is the latest of roughly 400 planets detected by earthly telescopes. Of these, 28 are considered “super-Earths” — planets with a mass roughly comparable to our own.

    The super-Earths themselves are too distant to be seen. Instead, astronomers infer their presence from subtle distortions in starlight, caused when photons travel through the super-Earths’ gravitational fields. Depending on the degree of distortion, astronomers can even calculate a planet’s mass.

    That’s how Corot-7b, a rocky planet with roughly twice the heft of Earth, was spotted in February. Ditto Gliese 581c, identified two months later, and orbiting its star at a distance consistent with human notions of habitability.

    Unfortunately, not much more will ever be known about those planets. Corot-7b is 500 light-years away, too distant for our telescopes to discern more detail. And from our viewing angle, Gliese 581c never quite crosses directly in front of its sun, causing photons to warp in ways that would reveal its atmospheric character.

    GJ 1214b does pass in front of its sun. Separated from Earth by a distance of just 42 light years, it’s close enough to be studied. Scientists will finally get to look at another Earth-like world.

    “Only rarely does a long-sought scientific frontier loom so prominently just beyond the horizon, that the next generation of instruments seems sure to reach it,” wrote Geoffrey Marcey, a University of California, Berkeley astronomer, in a commentary accompanying the findings. “They provide the most-watertight evidence so far for a planet that is something like our own Earth, outside our solar system.”

    Based on its radius and mass — about 2.7 and 6.6 times that of Earth’s — Charbonneau and the other astronomers have calculated GJ 1214b’s density. It appears to be composed of extraordinarily deep oceans, surrounding a rocky core.

    The planet’s atmosphere and precise composition remain a mystery, but it’s likely composed of many of the same elements found elsewhere at sites of planetary formation, in swirling disks of dust and gas that have yet to accrete: hydrogen, helium, nitrogen, magnesium, oxygen, carbon.

    That list of ingredients raises at least the possibility of life. With an estimated temperature of 370 degrees Fahrenheit, GJ 1214b is an unlikely incubator (Earth’s toughest extremophile, a microbe that lives in deep-sea volcanic vents, maxes out at 284 degrees) but it’s not impossible.

    “I don’t want to imply that there’s any indication of life as we know it. It might have life, but it would have to be a strange kind of life,” said Charbonneau.

    The telescopes sure to be trained on GJ 1214b in the near future will try to answer that question. But even if it proves barren, other planets await. The telescopes that spotted GJ 1214b were custom designed to find Earth-like planets around nearby stars, and had only operated for a few months before striking water.

    “We only look at a handful of stars before finding this planet, said Charbonneau. “Either we got lucky, or the planets are very common.”

    Image: Nature
  2. MziziMkavu

    MziziMkavu JF-Expert Member

    Dec 18, 2009
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    Alien 'water world' found

    Posted: Wednesday, December 16, 2009 1:00 PM by Alan Boyle

    David A. Aguilar / CfA
    An artist's conception shows the planet known as GJ 1214b passing across the disk
    of its parent star, a red dwarf just one-fifth as big as our sun.
    Astronomers say they have detected a planet just six and a half times as massive as Earth - at a distance so close its atmosphere could be studied, and with a density so low it's almost certain to have abundant water.
    The alien world known as GJ 1214b orbits a red dwarf star one-fifth the size of our own sun, 40 light-years away in the constellation Ophiuchus, the astronomers reported in Thursday's issue of the journal Nature.
    "Astronomically speaking, this is on our block," David Charbonneau of the Harvard-Smithsonian Center for Astrophysics, lead author of the study, told reporters this week. "This is a next-door neighbor. For perspective, our own TV signals have already passed beyond the distance of this star."
    He said the planet was detected using an array of eight off-the-shelf, 16-inch telescopes equipped with commercially available cameras.
    "Since we found the super-Earth using a small ground-based telescope, this means that anyone else with a similar telescope and a good CCD camera can detect it too," Charbonneau said in a news release. "Students around the world can now study this super-Earth."
    Super-Earths - planets that are roughly two to 10 times Earth's mass - represent the hottest frontier in the years-long search for worlds beyond our solar system. Planet-hunters reported finding their first transiting super-Earth in February, and earlier this week, other researchers added two more super-Earths to the list.
    Those planets orbit stars like our own sun, but the brightness of GJ 1214b's parent star is hundreds of times dimmer. The planet is also much closer to the star than any of our own solar system's planets, orbiting at a distance of only 1.3 million miles (2 million kilometers). That combination suggests that the planet's surface temperature would be about 400 degrees Fahrenheit (200 degrees Celsius), Charbonneau's research team reported.
    Charbonneau speculated that GJ 1214b was a little too hot for life as we know it, "but it didn't miss it by very much."
    The planet's discovery was hailed as a potential breakthrough by Geoffrey Marcy, an astronomer at the University of California at Berkeley who is a pioneer in the planet quest. In a commentary written for Nature, Marcy said Charbonneau and his colleagues "provide the most watertight evidence so far for a planet that is something like our own Earth, outside our solar system."
    How it was found
    GJ 1214b was detected thanks to an innovative telescope system, a cleverly focused observation campaign - and perhaps a little bit of luck. The eight-telescope array, dubbed the MEarth Project, was set up at the Whipple Observatory on Mount Hopkins in Arizona. The telescopes were programmed to gaze at 2,000 low-mass stars and check for slight, regular dips in light that could be caused by a dark planet's transit across the star's disk.
    Relatively dim, relatively close stars were favored because the planet's dimming effect would be more noticeable than it would be with brighter, bigger, farther-out stars.
    Just a few months after the MEarth Project began, graduate student Zachory Berta spotted the signature of GJ 1214b's 38-hour orbit. Based on the pattern of the dimming, the team figured out that the planet was 2.7 times as wide as Earth.
    The astronomers then turned to another instrument, the HARPS spectrometer on the European Southern Observatory's La Silla telescope in Chile, to figure out the planet's mass. Such mass calculations depend on another technique that checks for the slight wobble in a star's motion caused by a planet's gravitational pull. The HARPS observations indicated that the planet was 6.55 times as massive as Earth.
    Putting those measurements together, the team was able to model the planet's density and composition. The best fit for the data was a mixture consisting of about three-quarters water and other ices, one-quarter rock and a gaseous atmosphere.
    Implications of a water world
    Although the surface temperature on GJ 1214b would be well above water's boiling point on Earth's surface, Charbonneau said the planet could nonetheless possess an exotic form of liquid water due to extreme atmospheric pressure at the surface. In today's news release, Berta said the pressure may turn at least some of the water into a rare crystalline form known as ice-seven.
    "Despite its hot temperature, this appears to be a water world," Berta said.
    On Earth, organisms have been found living near deep-sea hydrothermal vents, where superheated water is held under high pressure. But Charbonneau said he wouldn't want to bet that life could endure under GJ 1214b's crushing conditions.
    In fact, it's too early to bet heavily on any detailed description of GJ 1214b. Fortunately, Charbonneau said, the star is close enough that the Hubble Space Telescope could someday analyze the composition of the planet's atmosphere. "That will make it the first super-Earth with a confirmed atmosphere - even though that atmosphere probably won't be hospitable to life as we know it," he said.
    Knowing what the atmosphere is made of, and how thick it is, could help astronomers determine whether their characterization of GJ 1214b as a water world is correct. "It's possible that what you have is a ball of rock with a much bigger envelope of light gas," Charbonneau said.
    The larger implication of the Nature study is that other super-Earths may be waiting out there with just the right conditions for life. "We found this planet in the first six months," Charbonneau noted. "We had only looked at a small fraction of the stars that we planned to look at through the entire project. That means that either we got really lucky - which is possible - or these planets are common."
    Two planet-hunting spacecraft, NASA's Kepler and the European Space Agency's COROT, are expected to find hundreds of super-Earths and Earth-sized planets in the years to come. The first scientific results from the Kepler mission are due to be reported next month in Washington at the winter meeting of the American Astronomical Society.
    More on the planet boom: