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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Planet-hunters have yet another tool to use in their quest to discover distant worlds that could harbor life. A group of astronomers has discovered a gas giant with six times the mass of Jupiter orbiting a small, weak red dwarf star by means of a method called astrometry. It’s the first time researchers have spotted an exoplanet with this technique, which they say could be useful for finding a different type of planet than those detected by tried and true methods.
Most of the 300-plus known extrasolar planets have been found by tracking changes in a star’s light output over time. The most prolific approach, the radial velocity method, looks for shifts in that light caused by the Doppler effect as the tug of an orbiting planet pulls the star nearer and more distant to us along our line of sight. The other approach, the transit method, tracks the periodic dimming of a star caused by a planet passing in front of it [Scientific American]. In contrast, astrometry doesn’t focus on a star’s light output, but rather on its precise location.
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Water is crucial to the only kinds of living things we’ve ever seen, so the presence of the wet stuff on another planet could be a sign of potential life. Unfortunately, scientists have been unsure how to detect water on distant planets. But the Deep Impact spacecraft has recently given researchers a glimpse of what a wet planet looks like from far away by turning its detectors onto the Earth itself.
Essentially, Deep Impact has turned Earth into a case study of a planet replete with water. The spacecraft, which is 30 million miles away, or halfway to Venus from Earth, has shown scientists how overlapping continents and bodies of water alter the way that light of seven different wavelengths reflects off of the planet’s surface. When scientists observed light from Earth twice over a 24-hour period, they found small deviations in colour caused when clouds or oceans rotated into view. The results mean they should now be able to recognise similar features on alien planets using giant telescopes in space [Scientific American].
The researchers were able to identify key features that could help identify a water-laden planet using telescopes, chemical-analyzing spectrographs and other instruments…. As Earth completed a 24-hour rotation, the change in brightness varied by about 30 percent up and down. The shift is caused by the planet’s reflectivity as the sun [alternately] shines on oceans and then continents [Discovery News]. The findings will be published in an upcoming issue of Astrophysical Journal.
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Four hundred years ago, Galileo observed the phases of Venus as the planet orbited our sun and caught its light in different ways, helping to disprove the idea that all celestial bodies twirled around the Earth. Now, the professional descendants of Galileo have observed the phases of an exoplanet for the first time, observing the distant planet in the act of orbiting a foreign star.
The planet, CoRoT-1b, is about 1,600 light years away from Earth, and was discovered about 2 years ago. It’s a “hot Jupiter,” a class of exoplanets that are the size of Jupiter but orbit very closely to their stars (CoRoT-1b orbits its star in just 36 hours). Hot Jupiters are expected to be tidally locked, with one side always facing their stars, the other permanently dark (our own moon is tidally locked with the Earth, only showing its “near side” to us) [SPACE.com].
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Astronomers still haven’t discovered Earth’s twin orbiting another star out in the cosmos, but they’re beginning to find worlds with a passing resemblance to our own. New studies of the red dwarf star Gliese 581 have revealed a small, rocky exoplanet with only twice the mass of Earth, and have also shed new light on a larger planet orbiting farther out, which researchers now say could have liquid water. Team member Stephane Udry believes that the larger planet could have a “large and deep” ocean. “It is the first serious ‘water-world’ candidate,” Udry said [AP].
Researchers had previously discovered three planets orbiting the star, including the potential water world, Gliese 581 d. Based on earlier observations, researchers thought that the planet took 83 days to orbit its star, which would indicate that the planet was too far from the red dwarf’s weak heat to have liquid water. But more extensive observations have shown that the planet actually has an orbital period of 66 days, putting the planet just inside the star’s “habitable zone.” Lead researcher Michel Mayor says the planet may be warm enough to bear oceans that are thousands of miles deep. “Maybe this is the first of a new class of ocean planets. That is my favourite interpretation,” says Mayor. “Whether there is life or not, I don’t know” [New Scientist]. However, not everyone is convinced that Gliese 581 d is wet and wild. Other experts say it’s more likely to be an ice giant, like Neptune and Uranus.
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The Kepler space telescope, which was launched in early March, has taken and sent home its first images of the region in the galaxy where it will spend the next three years searching for Earth-like planets.
The images sent to NASA show a “vast starry field” in the Cygnus-Lyra region of the Milky Way galaxy, according to NASA’s Jet Propulsion Laboratory. One image shows millions of stars in the craft’s full field of view, while two other images zoom in specific sections of that region [Computerworld]. Kepler’s primary mission is to survey stars for regular slight dips in their brightness, a sign that an orbiting planet is blocking the star’s light [Nature blog]. Eventually, the craft will measure the stars’ brightness every half hour.
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The first ever picture of an exoplanet was taken 11 years ago–but no one noticed. Now, in a new study, astronomers have subtracted the starlight from an image taken by the Hubble in 1998, and found the exoplanet by its dim infrared glow. While some exoplanets were detected before 1998, they were discovered indirectly by observing their influence on their parent stars; this was was seen directly.
The new technique has excited researchers wondering how many more new planets can be found in old, archived data. “They’ve dug up old Hubble images and found a planet! Crazy!” Geoff Marcy, an astronomer at the University of California, Berkeley, commented by email. “This will spawn a wild race by astronomers everywhere in the world to dig out their old Hubble images to hunt for planets lost in the rubble of the Hubble” [National Geographic News].
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