tagged w/ exoplanet
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IN DECEMBER, a pair calling themselves "The Benevolent Fisted Rulers" offered up 4-hectare plots of Gliese 581 g, the most habitable exoplanet yet discovered, for sale on eBay.
Setting aside the ethics of exoplanetary land grabs, the move seems a touch premature. The alien world is 20 light years away and its very existence is not confirmed. Still, if the planet does exist, it is possible that it has some good exo-real estate.
Raymond Pierrehumbert at the University of Chicago examined the range of climates that Gliese 581 g might have and found one that would have a pool of water on one side, making it look like an eyeball. Even if further observations disprove the existence of Gliese 581 g, the work could help determine the habitability of exo-Earths still to be discovered.
First spotted in September via wobbles in the light emitted by its host star, Gliese 581 g is likely to be rocky. That, combined with the fact that it orbits the star at just the right, "Goldilocks" distance to provide the warmth needed for liquid water, made it the first planet discovered outside our solar system with the potential to host life.
But Gliese 581 g also differs from Earth. For a start, it orbits its dim, red dwarf star so closely that its year lasts just 37 days. This boosts the chance that its star's gravitational tug has caused the planet to spin at the same rate that it moves around the star, so that one side of the planet always faces the star and the other is always dark. Pierrehumbert assumed that the planet is indeed locked in this configuration when he looked at the various climates it might support.
One option is that the planet has no atmosphere. Although all water on the surface would remain frozen, at least there would be no gas to transport heat away from the starlit side. This could keep temperatures there high enough to thin the ice, allowing light that could support life to reach liquid water beneath the surface.
The scenario most likely to support life, though, was one with an atmosphere containing carbon dioxide. A greenhouse effect would heat mainly the region directly facing the host star, producing an ice-covered planet with a large area of liquid water - the "eyeball Earth" (The Astrophysical Journal Letters, DOI: 10.1088/2041-8205/726/1/L8).
"The most habitable case is where you have enough CO2 to actually have this open water swimming pool," Pierrehumbert says. The pool's diameter would be about a quarter of the planet's circumference (see diagram). It would arise if the atmosphere contained about 20 per cent CO2 - much higher than Earth but within the limits imposed by the carbon available to form planets.
NASA's infrared James Webb Space Telescope, due to launch in 2014, should help resolve what Gliese 581 g actually looks like. That's assuming the exoplanet exists: it was spotted once, but a second set of planet hunters failed to find evidence of it in their data.
In any case, the new work could aid studies of the habitability of planets orbiting red dwarfs that are yet to be discovered, says Manoj Joshi of the University of Reading in the UK. "Hopefully we're getting to the point when we can shift from theorising what the climates might look like, to what we think they should look like".
http://www.newscientist.com/article/mg20927953.700-is-first-lifefriendly-exoplanet-an-eyeball.htmlIN DECEMBER, a pair calling themselves "The Benevolent Fisted Rulers"... more
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NASA spots smallest planet yet discovered outside sun's solar system
By the CNN Wire Staff
January 10, 2011 4:35 p.m. EST
An artist's depiction of Kepler-10b, which NASA says is too close to its star to maintain liquid water and potential life.
STORY HIGHLIGHTS
* The object is the first rocky planet discovered by NASA's Kepler spacecraft
* The discovery has scientists optimistic about what else could be found
* Kepler is capable of finding Earth-size planets in a habitable zone, NASA says
(CNN) -- A NASA spacecraft has detected a rocky planet that is the smallest ever discovered outside our sun's solar system, the agency announced Monday.
The exoplanet -- so named because it orbits a star other than the sun -- has been dubbed Kepler-10b. It measures 1.4 times the Earth's diameter and was confirmed after more than eight months of data collection, the agency said. It is the first rocky, or Earth-like, planet discovered by Kepler.
"All of Kepler's best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our sun," said Natalie Batalha, deputy science team leader for the NASA mission. "The Kepler team made a commitment in 2010 about finding the telltale signatures of small planets in the data, and it's beginning to pay off."
Kepler-10b's size and rocky composition would make it more likely than gaseous planets to contain liquid water, and perhaps life of some kind, if it were the right distance from its star, NASA said. However, it is much too close to the star -- 20 times closer than Mercury is to our sun.
Still, the discovery has scientists optimistic about what else Kepler might be able to reveal.
"Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come," Kepler program scientist Douglas Hudgins said.
The mission is the agency's first capable of finding Earth-size planets near the habitable zone, or the distance from a star where a planet can maintain liquid water and potential life.
The spacecraft measures size and other details by noting the tiny decrease in a star's brightness that occurs when a planet crosses in front of it.NASA spots smallest planet yet discovered outside sun's solar system
By the CNN... more
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A Qatar astronomer teamed with scientists at the Harvard-Smithsonian Center for Astrophysics (CfA) and other institutions to discover a new alien world. This "hot Jupiter," now named Qatar-1b, adds to the growing list of alien planets orbiting distant stars.
LINK : http://www.sciencedaily.com/releases/2010/12/101214085333.htmA Qatar astronomer teamed with scientists at the Harvard-Smithsonian Center for... more
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A team led by a former postdoctoral researcher in MIT's Department of Earth, Atmospheric and Planetary Sciences and the MIT Kavli Institute for Astrophysics, recently measured the first-ever planetary atmosphere that is substantially enriched in carbon. The researchers found that the carbon-to-oxygen ratio of WASP-12b, an exoplanet about 1.4 times the mass of Jupiter and located about 1,200 light years away, is greater than one. As they report in a paper to be published on Dec. 8 in Nature, this carbon-rich atmosphere supports the possibility that rocky exoplanets could be composed of pure carbon rocks like diamond or graphite rather than the silica-based rock found in Earth.
LINK : http://www.sciencedaily.com/releases/2010/12/101208132212.htmA team led by a former postdoctoral researcher in MIT's Department of Earth,... more
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A New Planet — from Beyond the Galaxy
Read more: http://www.time.com/time/health/article/0,8599,2032054,00.html#ixzz15hGdcBa9
By Michael D. Lemonick Thursday, Nov. 18, 2010
Picture: This artist's impression shows HIP 13044 b, an exoplanet orbiting a star that entered our galaxy, the Milky Way, from another galaxy.
AFP / Getty Images
Read more: http://www.time.com/time/health/article/0,8599,2032054,00.html#ixzz15hH2S4xq
Billions of years before the Sun was born, the Milky Way galaxy flicked out its gravitational tongue and slurped down a tiny neighboring galaxy that had ventured too close. The evidence for that ancient act of cosmic cannibalism is the still-digesting remains of the meal: a handful of relatively nearby stars known as the Helmi Stream, whose weird orbits — above and below the plain of the galaxy — are a tipoff to their weird origin.
Now one of those stars has a second claim to fame. HIP 13044, as it's unglamorously known, has a planet whirling around it — the first planet ever found from outside the Milky Way. Aside from its extra-galactic origin, the planet itself, found with a medium-size telescope at the European Southern Observatory in Chile, and described in a new paper in Science, isn't especially remarkable. It's a bit bigger than Jupiter and orbits its parent star in about 16 days — a "year" so short it would once have been considered impossible for so giant a planet, until multiple discoveries of many similar worlds proved such a revolution rate to be pretty common. (See pictures of the labor of space exploration.)
It's the star itself that makes the discovery of a planet surprising, for a couple of reasons. For one thing, its age — perhaps 7 or 8 billion years — means that while HIP 13044 was once much like the Sun, it's gone through a dramatic change of life. As it burned through its supply of hydrogen, the star would have swelled to become a so-called red giant, tens, or even hundreds of times its original size. When that happens to our Sun billions of years from now, Earth will probably be destroyed. Indeed, there's some circumstantial evidence that HIP 13044 may have gulped down a few planets itself, says the paper's lead author Johny Setiawan, of Germany's Max Planck Institute for Astronomy, in Heidelberg. "The star is a fast rotator," he says, "and theory predicts that if a star swallows a planet its rotation rate should increase."
But the new planet, called HIP 13044b, survived the cataclysm. That's probably because the Jupiter-size world originally occupied a Jupiter-like orbit, much farther from its star than Earth is from the Sun. It spiraled in to its present orbit only after HIP 13044 shrank back to a more dignified size — another common stage of life for stars, which return to their original dimensions when they start burning the helium in their core. A tiny handful of planets have been seen orbiting stars that are currently red giants, but this is the first to be found in the next chapter of a star's life. (See pictures of Russia's cosmonaut training center.)
The other thing that makes the star unusual is its composition. The Sun is mostly hydrogen and helium, but it also has significant traces of heavier elements like oxygen, carbon and iron, a quality astronomers call "metallicity" despite the non–metallic nature of some of those elements.
"In the Milky Way," says Setiawan, "the more metals a star has, the more likely it is to have planets." The reason for that is simple: both stars and planets coalesce out of the same vast pool of dust and gas. The higher the metallicity, the bigger the supply of building material and the likelier that some will be left over to form planets.
Dwarf galaxies like the one in which HIP 13044 was born, however — and like the two dozen or so that still orbit the Milky Way — have stars that are notably metal-poor. It was unclear until now whether that meant they'd also be planet-poor. The fact that Setiawan and his colleague Rainer Klement, also of the Max Planck Institute, found one so easily suggests this isn't the case. "Either they were incredibly lucky," says Eric Ford, a planet-searcher at the University of Florida, "or planets aren't uncommon around stars like these."
Whatever the answer, HIP 13044b is clearly a very different world from any we've seen before, one that — without the aid of celestial metals — formed in a very different way. And that in turn suggests that the field of planetary science, which seemed so tidy and settled as recently as the 1990s, is still full of surprises.A New Planet — from Beyond the Galaxy
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WASP-18b is highly unusual, as far as exoplanet discoveries go, because it's incredibly close to its host star — it takes less than one Earth day for the planet to make a complete orbit.WASP-18b is highly unusual, as far as exoplanet discoveries go, because it's... more
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