New 'Super Earth 2' Discovered in Constellation Libra
It looks as though our search for extraterrestrial life and civilizations with advanced intelliegence will continue in the fast and furious race afoot among the world's nomally placid astronomy community to discover potential Earth-like planets.
In mid-April we posted about the Geneva-based European Space agency team's discovery of Gliese 581c, using the ESA's Southern European La Silla Paranal Observatory in Chile. Gliese 581c was described as a potential Super Earth, a possible twin of our planet (see the Video of the Discovery of Gliese 581c).
But glory, as the ancient Gods and history has taught us, is often fleeting.
The point of view of the Galaxy staff is that advanced extraterrestrial civilizations are most likely capable of fooling our telescopes, detectors and space probes, and will deliberately and wisely conceal themselves from discovery for security reasons, which also offers a plausible explanation for the Fermi Paradox.
Gliese 581c orbits at a distance of about 7 million miles, within the star's so-called habitable 'Goldilocks' zone where it is neither too hot nor too cold for water to exist on its surface, making it the most promising spot for life yet found outside the solar system.
"On the treasure map of the universe, one would be tempted to mark this planet with an X," said one member of the discovery team, Xavier Delfosse of Grenoble University in France.
Far from Chile's La Silla Observatory, where Gliese 581c was discovered and hailed as a Super Earth and Earth's Twin, Dr. Manfred Cuntz of The University of Texas at Arlington and fellow scientists at the Potsdam Institute for Climate Impact Research in Germany reported a surprise discovery during their search for a second Earth.
With the assistance of a model for the evolution of Earth-like planets along with a with a climate model, they were able to demonstrate habitable conditions on the planet Gliese 581d, while determining that its smaller more famous brother, Gliese 581c -both located in the constellation Libra 20 short light-years away- has to be classified as uninhabitable.
Both planets are classified as so-called Super-Earths; i.e. planets with a mass of up to 10 times higher than that of the Earth. In fact, Gliese 581d very likely has a mass of eight Earths, whereas Gliese 581c has a mass of five Earths.
A new analysis by German and Texas astronomers assuming Earthlike characteristics for its geology and atmosphere has concluded that planet 581c is probably a steaming greenhouse unsuitable for Life As We Know It.
In a strange twist, however, the astronomers said that 581d, heavier at eight times the mass of Earth and farther from its star, had emerged from the calculations as possibly a pleasant abode, the new Goldilocks candidate. Gliese 581d, orbits at a distance of 23 million miles, which would normally make it too cold for liquid water, but the same greenhouse effect that would torch the smaller, closer planet would warm the larger outer one and make it livable.
“Gliese 581c is just too hot for life to exist,” said Cuntz, who was part of a team of theorists led by Werner von Bloh of the Potsdam Institute for Climate Impact Research, in Germany, “owing to the fact that the planet is too close to its host star – just like Venus, is too close to the Sun.”
This contradicts the findings of another research team in April of this year that proclaimed Gl 581c the first habitable planet outside our solar system. The new investigations incorporate the thermal evolution of planets, i.e. the cooling of the planetary body from its formation and the connected geodynamic parameters. Because of their heavy masses, the Potsdam scientists consider it likely that both Gliese 581c and Gliese 581d have dense atmospheres. Previous calculations for Gliese 581c derived the habitability of this planet only from temperatures calculated for the radiation balance of the planetary surface without an atmosphere.
Gliese 581d orbits at a distance of 23 million miles, which would normally make it too cold for liquid water. However, the same greenhouse effect that torches Gliese 581c, the smaller and closer planet, would be able to warm the larger outer one and make it habitable, Cuntz said.
Dimitar D. Sasselov of the Harvard-Smithsonian Center for Astrophysics, who has also been studying the Gliese system, agreed that it was reasonable to expect that the greenhouse effect would warm the outer planet to comfortable temperatures. "I would trust that result because I am getting the same numbers."
Cuntz said the planetary system Gliese 581, with probably three planets orbiting a red dwarf star, contains the closest analogues to the Earth that have been found so far. The central star has about 100 times less luminosity than our Sun.
Another complication is that the planets are so close to their star that they are almost certainly tidally locked, with the same side always facing the star, leading to constant heating on one side and cooling on the other. The resulting extreme weather, Cuntz said, made it likely that only simple forms of life could exist on Gliese 581d, the outer planet.
So the search continues. Will we soon discover life? Yes, but we believe with Steven J. Dick, NASA's chief historian, that a biologically based (vs a machine based-intelligence) technological civilization is a brief phenomenon limited to a few thousand years, and "exists in the universe in the proportion of one thousand to one billion, so that only one in a million civilizations are biological."
Astronomers will learn more about these planets when upcoming space missions like NASA’s Terrestrial Planet Finder and the European Space Agency's Darwin, designed to study terrestrial planets in the realms beyond our solar system, are in operation.
Cuntz said, "We really have to do more work." The Gliese planets, he said, are still the closest analogues to the Earth that have been found. "This is really to the credit of the Swiss group," he said. "These two planets are really the best two cases we have."
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