Immense Cloud of Hydrogen Observed Bleeding From an Alien Planet

"This cloud is very spectacular, though the evaporation rate does not threaten the planet right now," explains David Ehrenreich of the Observatory of the University of Geneva in Switzerland. "But we know that in the past, the star, which is a faint red dwarf, was more active. This means that the planet evaporated faster during its first billion years of existence because of the strong radiation from the young star. Overall, we estimate that it may have lost up to 10 percent of its atmosphere over the past several billion years." Astronomers using NASA's Hubble Space Telescope have discovered an immense cloud of hydrogen dubbed "The Behemoth" bleeding from a planet orbiting a nearby star. The enormous, comet-like feature is about 50 times the size of the parent star. The hydrogen is evaporating from a warm, Neptune-sized planet, due to extreme radiation from the star. This phenomenon has never been seen around an exoplanet so small. It may offer clues to how other planets with hydrogen-enveloped atmospheres could have their outer layers evaporated by their parent star, leaving behind solid, rocky cores. Hot, rocky planets such as these that roughly the size of Earth are known as Hot-Super Earths. The planet, named GJ 436b, is considered to be a "Warm Neptune," because of its size and because it is much closer to its star than Neptune is to our sun. Although it is in no danger of having its atmosphere completely evaporated and stripped down to a rocky core, this planet could explain the existence of so-called Hot Super-Earths that are very close to their stars. These hot, rocky worlds were discovered by the Convection Rotation and Planetary Transits (CoRoT) and NASA's Kepler space telescope. Hot Super-Earths could be the remnants of more massive planets that completely lost their thick, gaseous atmospheres to the same type of evaporation. Because the Earth's atmosphere blocks most ultraviolet light, astronomers needed a space telescope with Hubble's ultraviolet capability and exquisite precision to find "The Behemoth." "You would have to have Hubble's eyes," says Ehrenreich. "You would not see it in visible wavelengths. But when you turn the ultraviolet eye of Hubble onto the system, it's really kind of a transformation, because the planet turns into a monstrous thing." Because the planet's orbit is tilted nearly edge-on to our view from Earth, the planet can be seen passing in front of its star. Astronomers also saw the star eclipsed by "The Behemoth" hydrogen cloud around the planet. Ehrenreich and his team think that such a huge cloud of gas can exist around this planet because the cloud is not rapidly heated and swept away by the radiation pressure from the relatively cool red dwarf star. This allows the cloud to stick around for a longer time. The team's findings will be published in the June 25 edition of the journal Nature. Evaporation such as this may have happened in the earlier stages of our own solar system, when the Earth had a hydrogen-rich atmosphere that dissipated over 100 to 500 million years. If so, the Earth may previously have sported a comet-like tail. GJ 436b resides very close to its star - less than 2 million miles -- and whips around it in just 2.6 Earth days. In comparison, the Earth is 93 million miles from our sun and orbits it every 365.24 days. This exoplanet is at least 6 billion years old, and may even be twice that age. It has a mass of around 23 Earths. At just 30 light-years from Earth, it's one of the closest known extrasolar planets. Finding "The Behemoth" could be a game-changer for characterizing atmospheres of the whole population of Neptune-sized planets and Super-Earths in ultraviolet observations. In the coming years, Ehrenreich expects that astronomers will find thousands of this kind of planet. The ultraviolet technique used in this study also may also spot the signature of oceans evaporating on smaller, more Earth-like planets. It will be extremely challenging for astronomers to directly see water vapor on those worlds, because it's too low in the atmosphere and shielded from telescopes. However, when water molecules are broken by the stellar radiation into hydrogen and oxygen, the relatively light hydrogen atoms can escape the planet. If scientists spot this hydrogen evaporating from a planet that is slightly more temperate and less massive than GJ 436b, it could be an indication of an ocean on the surface. The Daily Galaxy via NASA/Goddard Space Flight Center. 'Source: The Behemoth'

Read More........→June 27, 2015

Billions of habitable worlds lurking in Milky Way

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Hindustan Times: Our galaxy may be teeming with billions of habitable planets, which could have huge consequences on the search for extra-terrestrial life, according to a recent survey. Two Princeton researchers recently contemplated that we really might be alone in the universe, but the study of red dwarf stars in the Milky Way discovered nine super-Earths - and two in the ‘habitable zone’ where liquid water could exist.Red dwarf stars account for 80 per cent of the 200 to 400 billion stars in our galaxy and scientists now believe that 40 per cent of those might have a planet in the habitable zone, the Daily Mail reported. The news that the Milky Way may include billions of habitable planets has given California-based SETI institute - the Search for Extraterrestrial Intelligence scientists something to smile about “SETI is looking for Mr. Right or maybe Ms. Right, depending on your point of view. It helps to find 

Star V838 Monocerotis's (V838 Mon) light echo, which is about six light years in diameter, is seen from the Hubble space telescope in this in this February 2004 handout photo released by NASA. It became the brightest star in the Milky Way Galaxy in January 2002 when its outer surface greatly expanded suddenly. Reuters/File

out that there''s 10 times as many candidates as there were before,” SETI Senior Astronomer Seth Shostak said. However, Shostak has cautioned that because red dwarfs are comparatively dim, planets would need to orbit very close to them to get enough heat for life to grow, which would mean they’d receive potentially fatal doses of radiation. Protection may exist, though, in the form of a magnetic field around the planet – or large oceans, which would guard aquatic life. “We''re not sure intelligent life, if under water, will be building radio transmitters and we''re going to hear from them,’ Shostak said. “But it’s possible.” The revelation that the Milky Way may be packed with habitable planets came from an international team of star gazers led by Dr Xavier Bonfils, from Grenoble University in France. “Because red dwarfs are so common - there are about 160 billion of them in the Milky Way - this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone,” he said. The astronomers surveyed a cautiously chosen sample of 102 red dwarfs using the European Southern Observatory’s 3.6-metre telescope at La Silla, Chile. A total of nine super-Earths - planets with masses between one and 10 times that of Earth - were discovered. Two were situated within the habitable zones of the stars Gliese 581 and Gliese 667 C. These data were combined with other observations, including those of stars that did not have planets. The astronomers worked out that habitable zone super-Earths orbiting red dwarfs occurred with a frequency of nearly 41 per cent. On the other hand, massive planets, similar to Jupiter and Saturn, were rare around red dwarfs. Less than 12 per cent of the stars were expected to have such ‘gas giants’. As red dwarfs are common near the sun, many ‘super-Earths’ may not be far away in astronomical terms. The scientists have estimated that there could be about 100 habitable zone planets within 30 light years. The research has been published in the journal Astronomy ‘n’ Astrophysics. Source: Hindustan Times

Read More........→May 01, 2012