It’s the size of Jupiter, orbits at about the distance of Mercury, and isn’t too far from the temperature range of Earth. Meet Corot-9b, the newest find in the cavalcade of exoplanets and the one its discoverers say is most like the worlds of our own solar system.
“Like our own giant planets, Jupiter and Saturn, the planet is mostly made of hydrogen and helium,” said team member Tristan Guillot of the Côte d’Azure Observatory in Nice, France. “And it may contain up to 20 Earth masses of other elements, including water and rock at high temperatures and pressures” [Space.com]. The large group of astronomers reporting the find in Nature estimate the planet’s temperature at a range between just below zero and slightly above 300 degrees Fahrenheit. It completes an orbit in 95 days, though it’s about 1,500 light years away.
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As the count of known planets in distant star systems continues to grow (the number now exceeds 400), so too does the number of ways we have to learn about them. Reporting in Nature this week, a team of astronomers say they have measured the makeup of an exoplanet’s atmosphere using an Earth-based telescope for the first time.
Mark Swain’s team directed NASA’s Infrared Telescope Facility toward HD 189733 b, a planet 63 light years away, discovered back in 2005. HD 189733 b was already known from space-borne observations to harbor several specific molecules in its atmosphere: water, methane, carbon dioxide and carbon monoxide [Scientific American]. Swain’s analysis confirmed those previous findings using spectrography, in which the light from an object is broken down into its component wavelengths, allowing the identification of atoms or molecules by their unique emission or absorption properties [Scientific American]. Swain’s team also turned up something else—a spike in emissions at a very particular wavelength of light, 3.3 microns, that the earlier observations didn’t detect and that Swain’s team can’t explain–at least not yet.
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Once, most of exoplanets that astronomers spotted were giants, but now they’re seeing more and more new planets with masses not far off from the Earth’s. One of those newly found Earth-like exoplanets, however, may not have always been so similar to our own world: An astronomer made the case last week that the small, sweltering planet was once a mighty gas giant that shrank.
Astronomers discovered Corot-7b in September. Its diameter is roughly 1.7 times that of Earth. Based on its size and mass, its density is similar to Earth’s, indicating that it is a rocky Earth-like orb [ABC News]. But the comparisons end there. While it’s rocky like Earth, this fiery hellhole is no place for life. It orbits its star at a distance of only 1.6 million miles (we’re presently at a much more comfortable 93 million miles from our sun) and completes a revolution in only 20 hours’ time. And, NASA’s Brian Jackson argued at last week’s American Astronomical Society meeting, Corot-7b is probably just a shell of its former self, and once was a type of gas giant called a “hot Jupiter.”
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NASA’s new eye in the sky has spotted the first handful of what it hopes will be a flood of new exoplanets. The Kepler telescope, launched last year with the express purpose of planet-hunting, has found its first five new worlds, with the results forthcoming in the journal Science this week. Just don’t get any ideas about living on any of them.
“One of the planets is amazingly light – like Styrofoam,” said William J. Borucki, the astronomer from NASA’s Ames Research Center…. “And all five simply glow,” he said, “they’re like looking into a blast furnace – but that’s simply no place to look for life” [San Francisco Chronicle]. The scalding-hot planets measure in excess of 2,000 degrees Fahrenheit, hotter than molten lava. These planets all orbit their stars in a hurry, taking between three and five days to make a circuit. Ground measurements confirmed Kepler’s findings.
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And the exoplanet count marches on. A few days ago astronomers announced they had found a handful of new planets around sun-like stars, some only 29 light years away. Now, in a study published today in Nature, a team led by David Charbonneau unveils a new super-Earth that’s hot, watery, and only 2.68 times the size of our own world.
The planet currently bares the name GJ 1214b, and while Charbonneau says it’s probably not habitable (because of the 400-degree Fahrenheit surface temperature), it’s not too far off the mark. Geoffrey W. Marcy, a planet hunter from the University of California, Berkeley, wrote in an accompanying article in Nature that the new work provided “the most watertight evidence so far for a planet that is something like our own Earth, outside our solar system” [The New York Times].
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As the tally of known planets beyond our solar system continues to grow, so does the number of them that look familiar—planets close to Earth’s size around stars that resemble our sun. Today astronomers announced that they’ve found a new batch of planets that not only fit that description but also reside in our cosmic neighborhood.
Three planets with masses ranging from 5.3 to 24.9 Earth masses were found orbiting the star 61 Virginis, which is 28 light years from Earth in the constellation of Virgo [Herald Sun]. That star can be seen with the naked eye under dark skies, and team member Chris Tinney says the system is strikingly like our own, noting that Neptune is only 17 Earth masses. In addition, NASA’s Spitzer Space Telescope recently found a ring of dust around 61 Virginis that’s about twice the distance from that star as Pluto is from our sun. The region between the newly discovered planets and that disk remains unexplored, the astronomers say, and could be the home of even more planets.
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The quest to find a second Earth–a potentially habitable planet that’s about the size of our home, but that lies in a distant solar system–has hit a snag. The Kepler space telescope was expected to be well on its way to detecting Earth-sized exoplanets by now, but an electronic glitch is slowing it down. The delays are caused by noisy amplifiers in the telescope’s electronics. The team is racing to fix the issue by changing the way data from the telescope is processed, but the delay could mean that ground-based observers now have the upper hand in the race to be the first to spot an Earth twin [Nature News].
Kepler, which was launched in March, uses the transit method to detect exoplanets; it’s watching a patch of 100,000 stars in hopes of detecting the brief dimming of a star’s light, which indicates that a planet has passed in front of the star. Kepler focuses light onto 42 light-detecting chips, called CCDs, each of which monitors stars in a different part of the telescope’s field of view. Each CCD is split into two for the purposes of sending data back to Earth, for a total of 84 data channels. Three of these channels are plagued by electronic noise that makes stars in their field of view appear to flicker – “like it’s changing its brightness at a rapid rate”, says Kepler chief scientist William Borucki [New Scientist]. That’s awkward, since the artificial flickers could obscure the real dimming that occurs during a planet’s transit.
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Planets, planets, everywhere! Astronomers have announced the discovery of 32 new planets orbiting distant stars, bringing the list of known exoplanets up to more than 400. The batch of freshly discovered worlds include four that are only five or six times the mass of Earth, an encouraging sign in the quest for a truly Earth-like world that could support life. Researcher Stephane Udry says the discovery is exciting because it suggests that low-mass planets could be numerous in our galaxy. “From [our] results, we know now that at least 40% of solar-type stars have low-mass planets. This is really important because it means that low-mass planets are everywhere, basically” [BBC News].
The discovery was made with the HARPS telescope at the European Southern Observatory’s facility in Chile. HARPS uses the so-called wobble method to detect planets, in which researchers look for the slight quiver in a star’s regular movements that indicates the gravitational tug of an orbiting planet.
Planets were found around a surprising variety of star types. Gas giant planets were found orbiting “metal-poor” stars — those lacking in elements other than hydrogen and helium — which until now had been considered unlikely places for planets to form [Washington Post]. Researchers also located four exoplanets around relatively cool, small stars known as M-class red dwarfs, and will continue to examine such stars for signs of Earth-like planets. The team expects to keep spotting planets by the dozen, says Udry: “Nature doesn’t like a vacuum so if there is space to put a planet it will put a planet there” [Reuters].
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Image: European Southern Observatory. Artist’s impression of a newly discovered planet orbiting the star Gliese 667 C, which is part of a triple star system.
The exoplanet Corot-7b has earned a reputation as one of the most interesting planets yet spotted outside our solar system, mostly because of its similarities to Earth: Astronomers have determined that it’s rocky, like Earth, and it’s only about five times more massive than our home planet. But the dissimilarities are just as fascinating. In the latest twist, a new study has suggested that storm fronts on Corot-7b may bring a rain of pebbles.
The alien planet is extraordinarily close to its parent star, and researchers think that it’s tidally locked so that one hemisphere always faces the star’s blasting heat. On that side, temperatures are thought to reach about 4,220 degrees Fahrenheit—hot enough to vaporize rock. So unlike the much cooler Earth, COROT-7b has no volatile gases (carbon dioxide, water vapor, nitrogen) in its atmosphere. Instead it’s atmosphere consists of what might be called vaporized rock. “The only atmosphere this object has is produced from vapor arising from hot molten silicates in a lava lake or lava ocean” [SPACE.com], says study coauthor Bruce Fegley Jr.
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Astronomers have conclusive evidence that a planet spotted in a star system 500 light years away is rocky and solid, just like Earth. Scientists have long figured that if life begins on a planet, it needs a solid surface to rest on, so finding one elsewhere is a big deal. “We basically live on a rock ourselves,” said co-discoverer Artie Hartzes…. “It’s as close to something like the Earth that we’ve found so far. It’s just a little too close to its sun” [AP].
Yes, for while the exoplanet, Corot-7b, is rocky like Earth and is only about five times more massive than our home planet, it’s hardly our twin. Its close proximity to its star means that it completes an orbit (its “year”) in just 20 hours, and the climate extremes are punishing. Temperatures soar above 2,000 degrees on its day side and sink to minus 200 degrees on the night side. It means the surface could be covered with molten lava or boiling oceans and it certainly could not hold any form of life as we know it [Scientific American].
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In a star system 330 light years away from Earth, astronomers have spotted a giant planet that booms around its parent star in tight, fast circles, completing an orbit (the planet’s “year”) in less than one Earth day. The exoplanet, known as Wasp-18b, is so close to its star that researchers say it appears to be spiraling inwards to its fiery doom. But the odds of seeing a planet in its death throes are so low that researchers are searching for alternate explanations, and say the planet could force scientists to rethink established ideas about planetary forces known as tidal interactions [National Geographic News].
The planet is known as a “hot Jupiter,” meaning that it’s a massive gas giant like our own solar system’s Jupiter, but it orbits in close proximity to its star. Current theories say that such a massive planet so close to its star should be pulling on the host star, creating a tidal effect similar to the moon’s pull on Earth. At that range the planet’s pull would be so strong that it would drain energy from its orbit, causing the planet to rapidly fall into the star [National Geographic News]. But if that’s the case, the planet would meet its death in less than a million years. Since the star system is thought to be about 1 billion years old, the odds of catching the planet in its last stages are one in a thousand.
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Scientists have spied a new exoplanet–and not only is it the biggest one yet, but it’s also moving the wrong direction. Unlike other planets, which orbit the same way their stars rotate, WASP-17 moves the opposite way, according to a study published in Astrophysical Journal.
Planets are born from the same ball of rotating gas that creates their parent star, which is why they usually orbit — and spin — in the same direction as their star. While WASP-17 is the first planet known to orbit backwards, some planets in our own solar system, such as Venus, are spinning backwards [Wired]. WASP-17’s backwards motion is known by astronomers as a retrograde orbit.
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NASA’s Kepler spacecraft has only been in operation for 10 days, but it’s already spotted a planet, according to a report in Science. That leaves experts optimistic about the craft’s potential to find other Earth-like planets.
Scientists already knew that the planet Kepler found existed. It’s called HAT-P-7b, and it’s a planetary body that’s too heavy and too hot to support life. Still, Kepler gave scientists new details about the planet, including that the planet has a hazy, ozone-like atmosphere. The analysis proves that Kepler’s onboard telescope and light-detecting instruments are at least 100 times more precise than the ground-based detectors that originally found HAT-P-7b [L.A. Times], because Earth-based telescopes must wrestle with distortion from the atmosphere, while Kepler only looks through the clear near-vacuum of space.
Scientists say that Kepler’s capabilities should be sufficient to find Earth-like planets in the “habitable zone” of a star system–that is, the ring where temperatures climb high enough to allow liquid water to exist, but aren’t so scorching as to burn up the surface of the planet.
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Only 20 years ago, astronomers were arguing over whether a colleague had discovered the first exoplanet–a planet beyond our solar system that is in orbit around an alien sun. Fast forward to the present day, and researchers have now spotted more than 300 exoplanets in our Milky Way galaxy, and the new topic of discussion is whether a group of astronomers has detected the first extragalactic planet in the Andromeda galaxy.
A new study to be published in the Monthly Notices of the Royal Astronomical Society explains that it should be possible to identify extragalactic planets with the technique of gravitational microlensing, in which a distant source star is briefly magnified by the gravity of an object passing in front of it. This technique has already found several planets in our galaxy, out to distances of thousands of light years. Extending the method from thousands to millions of light years won’t be easy, says [study coauthor] Philippe Jetzer, … but it should be possible [New Scientist]. In fact, it may have already been accomplished.
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By pretending to observe the sunlight shining through the Earth’s atmosphere from the vantage point of the moon, astronomers have gained a clue that may help them in the search for Earth-like exoplanets that could be harboring life.
The astronomers made their observations on 16 August 2008 during a lunar eclipse — in which the Moon moves into Earth’s shadow. Even when the Moon is totally eclipsed by Earth, it is still bathed in a dim red light — from sunlight that has been bent as it passes through the edge of Earth’s atmosphere. Using Earth-based telescopes, the astronomers detected some of this light after it bounced back from the Moon [Nature News].
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