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    Major Discovery: New Planet Could Harbor Water and Life - Forum

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    Forum » Main » Science, Astronomy, Nature » Major Discovery: New Planet Could Harbor Water and Life
    Major Discovery: New Planet Could Harbor Water and Life
    ManuDate: Thursday, 20-May-2010, 8:27 PM | Message # 1
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    The star Gliese 581, located 20.5 light years away in the constellation Libra. Credit: Digital Sky Survey

    An Earth-like planet spotted outside our solar system is the first found that could support liquid water and harbor life, scientists announced today.

    Liquid water is a key ingredient for life as we know it. The newfound planet is located at the "Goldilocks" distance-not too close and not too far from its star to keep water on its surface from freezing or vaporizing away.

    And while astronomers are not yet able to look for signs of biology on the planet, the discovery is a milestone in planet detection and the search for extraterrestrial life, one with the potential to profoundly change our outlook on the universe.


    "The goal is to find life on a planet like the Earth around a star like the Sun. This is a step in that direction," said study leader Stephane Udry of the Geneva Observatory in Switzerland. "Each time you go one step forward you are very happy."

    The new planet is about 50 percent bigger than Earth and about five times more massive. The new "super-Earth" is called Gliese 581 C, after its star, Gliese 581, a diminutive red dwarf star located 20.5 light-years away that is about one-third as massive as the Sun.

    Smallest to date

    Gliese 581 C is the smallest extrasolar planet, or "exoplanet," discovered to date. It is located about 15 times closer to its star than Earth is to the Sun; one year on the planet is equal to 13 Earth days. Because red dwarfs, also known as M dwarfs, are about 50 times dimmer than the Sun and much cooler, their planets can orbit much closer to them while still remaining within their habitable zones, the spherical region around a star within which a planet's temperature can sustain liquid water on its surface.

    Because it lies within its star's habitable zone and is relatively close to Earth, Gliese 581 C could be a very important target for future space missions dedicated to the search for extraterrestrial life, said study team member Xavier Delfosse of Grenoble University in France.

    "On the treasure map of the universe, one would be tempted to mark this planet with an X," Delfosse said.

    Two other planets are known to inhabit the red dwarf system. One is a 15 Earth-mass "hot-Jupiter" gas planet discovered by the same team two years ago, which orbits even closer to its star than does Gliese 581 C. Another is an 8 Earth-mass planet discovered at the same time as Gliese 581 C, but which lies outside its star's habitable zone.

    Possible waterworld

    Computer models predict Gliese 581 C is either a rocky planet like Earth or a waterworld covered entirely by oceans.

    "We have estimated that the mean temperature of this super-Earth lies between 0 and 40 degrees Celsius [32 to 104 degrees Fahrenheit], and water would thus be liquid," Udry said.

    The scientists discovered the new world using the HARP instrument on the European Southern Observatory 3.6 meter telescope in La Sille, Chile. They employed the so-called radial velocity, or "wobble," technique, in which the size and mass of a planet are determined based on small perturbations it induces in its parent star's orbit via gravity.

    Udry said there was a fair amount of time between the calculation of Gliese 581 C's size and the realization it was within its star's habitable zone. "That came at the end," Udry said.

    When it did hit him, Udry knew he would be spending time fielding phone calls from the media. "You right away think about the journalists who will like it very much," he told SPACE.com.

    More to come

    David Charbonneau, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) who was not involved in the study, said the new finding is an "absolutely fantastic discovery."

    "It means there probably are many more such planets out there," Charbonneau said in a telephone interview. Whether Gliese 581 C harbors life is still unknown, but "it satisfies for the first time a key requirement."

    Charbonneau also praised the team's technical skills. "The wobble induced on the star by each of these planets is really tiny-it's just a few meters a second. That means their measurement precision is exquisite," he said.

    David Latham, another astronomer at Harvard-Smithsonian CfA, echoed other scientists' praise of the discovery but said the next step is to find a similar world where the orbit of the habitable planet carries it between Earth and its parent star. This will allow scientists to observe it using the transit technique, whereby the small dimming starlight caused by the planet's passage across the face of its sun can be used to calculate its size.

    Only then can scientists determine for certain whether the world is rocky or covered by water, Latham said.

    Alan Boss, a planetary theorist at the Carnegie Institution of Washington, said the new planet's potential for liquid water made it "fascinating." Gliese 581 C "is the closest planet to another Earth that has been found to date. I hope the SETI folks are listening," Boss said.

    Seth Shostak, a senior astronomer at the SETI institute, said the Gliese 581 system has in fact been looked at twice before for signs of intelligent life. The first time was in 1995 using the Parkes Radio Telescope in Australia; the second time occured in 1997 using the 140-foot telescope in Greenbank,West Virgina. Both times revealed nothing.

    "It has been looked at twice, but that doesn't mean we shouldn't look at it again," Shostak said. "And indeed we should because this is the best candidate the extrasolar planet guys have come up with yet."

    Shostak said he was "jazzed" by the discovery. "This is pointing to something that in the past has only been an assumption, namely that Earth-sized worlds are not rare," he said. "We know of only two [planets in the habitable zone]. We know this one and we know our own. But two is better than one."

    Shostak said the Gliese 581 system will likely be looked at again over much wider range of the radio spectrum when the new Allen Telescope Array begins operations this summer.

    "You could say it's going to the head of the class," he said.

    ---------------------------
    http://www.space.com/
    By Ker Than
    Staff Writer
    posted: 24 April 2007
    04:23 pm ET

     
    ManuDate: Thursday, 20-May-2010, 8:31 PM | Message # 2
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    Earth-Like Planet Spotted Outside Solar System Likely a Volcanic Wasteland

    ScienceDaily (Jan. 7, 2010) — When scientists confirmed in October that they had detected the first rocky planet outside our solar system, it advanced the longtime quest to find an Earth-like planet hospitable to life.


    How similar is exoplanet CoRoT-7b to Earth? The newly discovered extra-solar planet (depicted in the above artist's illustration) is the closest physical match yet, with a mass about five Earths and a radius of about 1.7 Earths. Also, the home star to CoRoT-7b, although 500 light years distant, is very similar to our Sun. Unfortunately, the similarities likely end there, as CoRoT-7b orbits its home star well inside the orbit of Mercury, making its year last only 20 hours, and making its peak temperature much hotter than humans might find comfortable. (Credit: ESO/L. Calcada)


    Rocky planets -- Earth, Mercury, Venus and Mars -- make up half the planets in our solar system. Rocky planets are considered better environments to support life than planets that are mainly gaseous, like the other half of the planets in our system: Jupiter, Saturn, Uranus and Neptune.

    The rocky planet CoRoT-7 b was discovered circling a star some 480 light years from Earth. It is, however, a forbidding place and unlikely to harbor life. That's because it is so close to its star that temperatures might be above 4,000 degrees F (2,200 C) on the surface lit by its star and as low as minus 350 F (minus 210 C) on its dark side.

    Now scientists led by a University of Washington astronomer say that if CoRoT-7 b's orbit is not almost perfectly circular, then the planet might also be undergoing fierce volcanic eruptions. It could be even more volcanically active than Jupiter's moon Io, which has more than 400 volcanoes and is the most geologically active object in our solar system.

    "If conditions are what we speculate, then CoRoT-7 b could have multiple volcanoes going off continuously and magma flowing all over the surface," says Rory Barnes, a UW postdoctoral researcher of astronomy and astrobiology. Any planet where the surface is being remade at such a rate is a place nearly impossible for life to get a foothold, he says.

    Calculations about CoRoT-7 b's orbit and probable volcanism were presented at the American Astronomical Society meeting in Washington, D.C., during a session Jan. 5 and as part of a press briefing Jan. 6. CoRoT-7 b was discovered by a French-led team using the CoRoT -- Convection, Rotation and Planetary Transits -- satellite.

    The next step to finding a planet that harbors life may have to wait until astronomers are better able to detect rocky planets that are farther from their stars, Barnes says. "Because it is easier to detect planets that orbit close to their host stars, a significant fraction of the first wave of rocky planets being found outside our solar system may be more Io-like than Earth-like."

    Barnes and his colleagues suspect CoRoT-7 b is subject to extreme volcanism partly because it is so close to its sun, the distance between the two being about 1.6 million miles (2.5 million kilometers). That's about 60 times closer than the Earth is to the sun.

    Volcanism is then triggered by even a tiny deviation from a circular orbit. How tiny of a deviation? About 155 miles (250 kilometers), according to calculations done by Barnes based on how bodies in our solar system influence each other's orbits. That's about the distance from Washington, D.C., to Philadelphia. That amount of deviation, or more, could be caused by the gravitational pull of the next planet out from CoRoT-7 b.

    Deviations in its orbit would set tidal forces in motion that flex and distort the whole shape of CoRoT-7 b. This is different from what happens on Earth, where oceans absorb the energy of tidal forces.

    "CoRoT-7 b most certainly has no oceans. A planet on a non-circular orbit experiences different amounts of gravitational force at different points along the orbit, feeling the strongest gravitational pull when it is closest to the star and the weakest when it is most distant. As the planet moves between these two points, it stretches and relaxes. This flexing produces friction that heats the interior of the planet resulting in volcanism on the surface," Barnes says.

    "This scenario is exactly what is occurring on Jupiter's moon Io. For planets like CoRoT-7 b, however, the heating may be much, much stronger than on Io."

    The work was funded by NASA's Virtual Planetary Laboratory. Co-presenters at the American Astronomical Society are Sean Raymond, University of Colorado, Boulder; Richard Greenberg, University of Arizona; Nathan Kaib, a NASA postdoctoral program fellow at the UW; and Brian Jackson, NASA's Goddard Space Flight Center, Greenbelt, Maryland.

     
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