Spacecraft to blast off in search of 'Earths'
By A. Pawlowski | Source:
cnn.com
Calling it a mission that may fundamentally change humanity's view of itself, NASA on Friday prepared to launch a telescope that will search our corner of the Milky Way galaxy for Earth-like planets.
The Kepler spacecraft is scheduled to blast into space on top of a Delta II rocket from Cape Canaveral Air Force Station in Florida March 6, 2009. "This is a historical mission. It's not just a science mission," NASA Associate Administrator Ed Weiler said during a pre-launch news conference.
"It really attacks some very basic human questions that have been part of our genetic code since that first man or woman looked up in the sky and asked the question: Are we alone?"
Kepler contains a special telescope that will stare at 100,000 stars in the Cygnus-Lyra region of the Milky Way for more than three years as it trails Earth's orbit around the Sun.
The spacecraft will look for tiny dips in a star's brightness, which can mean an orbiting planet is passing in front of it -- an event called a transit. The instrument is so precise that it can register changes in brightness of 20 parts per million in stars that are thousands of light years away.
"Being able to make that kind of a sensitive measurement over a very large number of stars was extremely challenging," Kepler project manager James Fanson said. "So we're very proud of the vehicle we have built. This is a crowning achievement for NASA and a monumental step in our search for other worlds around other stars."
Are we alone?
The $600 million mission is named after Johannes Kepler, a 17th-century German astronomer who was the first to correctly explain planetary motion.
His discoveries combined with modern technology may soon help to answer whether we are alone in the universe or whether Earth-like worlds inhabited by some type of life are common.
"We won't find E.T., but we might find E.T.'s home," said William Borucki, science principal investigator for the Kepler mission. About 330 "exoplanets" -- those circling sun-like stars outside the solar system -- have been discovered since the first was confirmed in 1995.
Most are gas giants like Jupiter, but some have been classified as "super earths," or worlds several times the mass of our planet, said Alan Boss, an astronomer with the Carnegie Institution who serves on the Kepler Science Council.
They are too hot to support life, he added, calling them "steam worlds." Europe's COROT space telescope caused a stir last month when it spotted the smallest terrestrial exoplanet ever found.
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Nearest Star System Might
Harbor Earth Twin
By Andrea Thompson
Excerpt: space.com
March 2008 - Earth may have a twin orbiting one of our nearest stellar neighbors, a new study suggests.
University of California, Santa Cruz graduate student Javiera Guedes used computer simulations of planet formation to show that terrestrial planets are likely to have formed around one of the stars in the Alpha Centauri star system, our closest stellar neighbors.
Guedes' model showed planets forming around the star Alpha Centauri B (its sister star, Proxima Centauri, is actually our nearest neighbor) in what is called the "habitable zone," or the region around a star where liquid water can exist on a planet's surface.
The model also showed that if such planets do in fact exist, we should be able to see them with a dedicated telescope. "If they exist, we can observe them," Guedes said.
Astronomers have for some time pinned the Alpha Centauri system as one that was likely to form planets, said study co-author Gregory Laughlin, a UCSC professor.
Because the planet would form in a triple star system, the processes that form large Jupiter-mass gas giants, which account for most of the extrasolar planets found so far, would be suppressed. So it would be more likely for the system to produce terrestrial planets.
Laughlin also noted that a number of factors make Alpha Centauri B a good candidate for astronomers to actually detect an Earth-sized terrestrial planet.
Training telescopes
The Doppler detection method, which has revealed the majority of the 228 known extrasolar planets, measures shifts in the light from a star to detect the tiny wobble induced by the gravitational tug of an orbiting planet.
Because Alpha Centauri B is so bright and nearby, detecting a small terrestrial planet's miniscule wobble would be that much easier. Also, its position high in the sky of the Southern Hemisphere means it is observable for most of the year, just as the Big Dipper is observable for most of the year in the Northern Hemisphere.
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Excluding Alpha Centauri Planets
Excerpt: centauri-dreams.org
You would think Alpha Centauri would be a prime hunting ground for extrasolar planets simply because of its proximity. But the problem for direct imaging is the sheer brightness of Centauri A and B, creating a halo of diffuse light around the pair.
Getting through the glare isn’t easy, but a search based on twin techniques — adaptive optics and CCD imaging — covering a wide-field around the Centauri system has just been completed. Results on the CCD work, using European Southern Observatory equipment, have now been made available and they’ve come up short on planetary detections.
As reported by Pierre Kervella (Observatoire de Paris-Meudon) and Frederic Thévenin (Observatoire de la Côte d’Azur), the team found no co-moving companion objects between 100 and 300 AU. And that’s useful information, because it puts some constraints on possible planets around these stars. From the paper:
Within the explored area, this negative result sets an upper mass limit of 15-30 M J to the possible companions orbiting a Cen B or the pair, for separations of 50-300 AU. When combined with existing radial velocity searches…and our adaptive optics results…this mostly excludes the presence of a 20-30 M J companion within 300 AU.
First of all, note what this is not telling us. We can draw no conclusions about possible terrestrial-sized worlds orbiting within 3-4 AU of either Centauri A or B, for the equipment is not sensitive enough to detect planets that small. Thus the scenario that continues to fire the imagination of many of us — habitable planets around one or both Centauri stars — is still viable.
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Earth-like planets around Alpha Centauri?
Excerpt: astronomynow.com
Alpha Centauri, the closest star system to our Solar System, should harbour detectable Earth-like planets, according to a new study by astronomers at the University of Santa Cruz.
Computer simulations of planet formation were performed to show that terrestrial planets are likely to have formed around one of the three stars in the system, Alpha Centauri B. Moreover, the planets would have formed in the 'habitable zone", where liquid water can exist on the planet's surface.
Although many different simulations were performed, starting with a variety of different initial conditions, in every case a system of multiple planets evolved with at least one planet about the size of Earth.
The team are confident that a rocky, Earth-like planet could be detected around Alpha Centauri B using the existing Doppler detection method, which has already revealed the majority of the 228 known extrasolar planets.
"If they exist, we can observe them," said Guedes, who is the first author on the paper describing the new findings.
The Doppler method measures the shift in light from a star to detect the tiny wobble induced by the gravitational tug of an orbiting planet.
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Alien worlds suggest Earth-like planets
By Roger Highfield | Source: telegraph.co.uk
Britain's leading team of planet-hunters says it has found three new alien worlds that lie beyond our solar system, boosting confidence that Earth-like worlds are waiting to be discovered.
The discovery of the planets will be announced by the Wide Area Search for Planets (WASP) project this week at an international conference in Suzhou, China, and have been called WASP-3, WASP-4 and WASP-5.
The WASP project is the most ambitious in the world designed to discover large planets and relies on "super cameras" that monitor millions of stars in the sky.
Prof Andrew Cameron, of St Andrews University says the new finds add to two alien planets found by the team last year:
"All three planets are similar to Jupiter, but are orbiting their stars so closely that their 'year' lasts less than two days. These are among the shortest orbital periods yet discovered".
Being so close to their star, the surface of the newly-found planets will be more than 2000ºC, so it is unlikely that life as we know it could survive there.
"But the finding of Jupiter-mass planets around other stars supports the idea that there are also many Earth-sized planets waiting to be discovered as astronomers' technology improves," he says.
These new planets were detected as they pass in front of, or "transit," their host star. This blocks some starlight and causing a small dip in the brightness of the star. The WASP cameras monitor myriad stars, looking for these tell-tale dips.
Dr Coel Hellier, of Keele University, comments: "When we see a transit we can deduce the size and mass of the planet and also what it is made of, so we can use these planets to study how solar systems form."
Over 200 extra-solar planets (those that orbit other stars, rather than our Sun) are currently known to astronomers. WASP-4 and WASP-5 are the first planets discovered by the WASP project's cameras in South Africa, and were confirmed by Swiss and French astronomers. "These two are now the brightest transiting planets in the Southern hemisphere" said Dr Hellier.
WASP-3 is the third planet that the team has found in the North, using the SuperWASP camera sited in the Canary Islands.
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Galaxy may be full of 'Earths,' alien life
By A. Pawlowski | Source:
cnn.com
As NASA prepares to hunt for Earth-like planets in our corner of the Milky Way galaxy, there's new buzz that "Star Trek's" vision of a universe full of life may not be that far-fetched.
Pointy-eared aliens traveling at light speed are staying firmly in science fiction, but scientists are offering fresh insights into the possible existence of inhabited worlds and intelligent civilizations in space.
There may be 100 billion Earth-like planets in the Milky Way, or one for every sun-type star in the galaxy, said Alan Boss, an astronomer with the Carnegie Institution and author of the new book "The Crowded Universe: The Search for Living Planets."
He made the prediction based on the number of "super-Earths" -- planets several times the mass of the Earth, but smaller than gas giants like Jupiter -- discovered so far circling stars outside the solar system. Boss said that if any of the billions of Earth-like worlds he believes exist in the Milky Way have liquid water, they are likely to be home to some type of life. "Now that's not saying that they're all going to be crawling with intelligent human beings or even dinosaurs," he said.
"But I would suspect that the great majority of them at least will have some sort of primitive life, like bacteria or some of the multicellular creatures that populated our Earth for the first 3 billion years of its existence."
Putting a number on alien worlds
Other scientists are taking another approach: an analysis that suggests there could be hundreds, even thousands, of intelligent civilizations in the Milky Way. Researchers at the University of Edinburgh in Scotland constructed a computer model to create a synthetic galaxy with billions of stars and planets. They then studied how life evolved under various conditions in this virtual world, using a supercomputer to crunch the results.
In a paper published recently in the International Journal of Astrobiology, the researchers concluded that based on what they saw, at least 361 intelligent civilizations have emerged in the Milky Way since its creation, and as many as 38,000 may have formed. Duncan Forgan, a doctoral candidate at the university who led the study, said he was surprised by the hardiness of life on these other worlds. "The computer model takes into account what we refer to as resetting or extinction events.
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In search of Earth’s long-lost twin
MIT prof says technology is bringing us closer to an answer
By Daniel Ting | Excerpt: mcgilldaily.com
One of the defining moments of the scientific revolution occurred 400 years ago. In the spring of 1609, Johannes Kepler published Astronomia nova, which provided strong evidence for Copernicus’ heliocentric model of the universe.
In the fall of the same year, Galileo used a telescope to observe the night sky for the first time. In recognition of these seminal events, the United Nations declared 2009 the International Year of Astronomy, and McGill University’s Faculty of Science has organized a triumvirate of commemorative public lectures entitled “Black Holes, New Worlds, and the Universe.”
Sara Seager, a professor at the Massachusetts Institute of Technology (MIT), presented the first of these lectures, “Origins and Aliens: The Search for Other Earths,” on September 21 to a near-capacity crowd in Leacock 132. Seager’s research focuses on trying to find and analyze exoplanets – planets outside our solar system that orbit a star, and which are most likely to harbour alien life. Seager, an expert in analyzing the way that light diffracts in an alien atmosphere to reveal the gas composition, calls the resulting pattern formations the “fingerprints of a planet.”
These fingerprints are useful for detecting tell-tale signs of life like oxygen, carbon dioxide, and water vapour. “Oxygen is such a reactive gas, and if you find that an atmosphere has 20 per cent oxygen [as Earth’s does], you have to ask, ‘Why should it be there?’” Seager said. The main difficulty in searching for hospitable exoplanets, according to Seager, is that the glare from stars obscures planets with Earth-like orbits. To illustrate this problem, consider that Earth is 10 billion times fainter than the Sun, meaning that our current ability to resolve planets vanishes at about 20 times the Earth-Sun distance.
The ability to directly see an exoplanet with an Earth-like orbit would demand a massive, near-perfect space telescope, which would use non-circular mirrors to reduce the amount of glare observed. Alternatively, a screen could be set up to diffract sun rays to a smaller, non-perfect telescope. But this solution also has its shortcomings, as it would require extreme spatial coordination between the 15 metre-wide screen and the telescope, which would be tens of thousands of kilometres apart. Fortunately, there are other ways to find an Earth-like exoplanet.
The closest star to Earth is Alpha Centauri, approximately four light-years away, and though we might consider the claim that humans could travel at one-tenth the speed of light, such a journey would still take 80 years, round-trip. We can still learn a lot about planets by studying them from afar. Current research can identify planets’ densities, atmospheres, and the different phenomena that they experience – for example, how heat is transferred across tidally-locked objects like Earth’s moon.
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Alpha Centauri 3
Simulations of Multiple-planet systems
Excerpt: solstation.com
On February 25, 2008, a team of astronomers released a paper on simulation results which support the conclusions of previous studies that multiple-planet systems could have formed in close orbits around both heavy-element rich, Alpha Centauri A and B.
Focusing on Star B, the simulations frequently generated a Earth-like planet in or near Star B's habitable zone (where liquid water could exist on the planet's surface).
Star B, a orange-red dwarf with a relatively calm chromosphere and acoustic p-wave mode oscillations, is an easier target for detecting wobbles from terrestrial planets.
Sol's three closest stellar neighbors are located in the southeastern corner of Constellation Centaurus, the Centaur. Proxima Centauri (or Alpha Centauri C) is only 4.22 light-years (LY) away but is too dim to be seen with the naked eye. The two bright stars, Alpha Centauri A and B, are a little farther away at about 4.36 LY. They form a close binary that is separated "on average" by only about 24 times the Earth-Sun distance of an orbital semi-major axis -- which is only slightly greater than the distance between Uranus and the Sun ("Sol").
Alpha Centauri A
Since Alpha Centauri A is very similar to our own Sun, many speculate whether it might contain planets that harbor life. According to Weigert and Holman, the distance from the star where an Earth-type planet would be "comfortable" with liquid water, is centered about midway between the orbits of the Earth and Mars in the Solar System -- with an orbital period of 1.34 years using calculations based on Hart, but more recent calculations based on Kasting et al, allow for a wider "habitable zone."
As viewed from a hypothetical planet around Stars A and B, the brightness of the other increases as the two approach and decreases as they recede. However, the variation in brightness is considered to be insignificant for life on Earth-type planets around either star. At their closest approach, Stars A and B are almost farther apart than the average orbital distance of Saturn around the Sun, while their widest separation is farther than the average orbital distance of Neptune.
Alpha Centauri B
This much dimmer companion star is a main sequence, reddish-orange dwarf. It appears to have a little over 90% of Sol's mass, about 86.5% of its diameter, and 45 to 52% of its luminosity. Viewed from a planet at Earth's orbital distance around Alpha Centauri A, this companion B star would provide more light than the full Moon does on Earth as its brightest night sky object, but the additional light at a distance greater than Saturn's orbital distance in the Solar System would not be significant for the growth of Earth-type life.
According to Weigert and Holman, the distance from the star where an Earth-type planet would be comfortable with liquid water is centered somewhat beyond the orbital distance of Venus in the Solar System -- with an orbital period under an Earth year using calculations based on Hart, but more recent calculations based on Kasting et al, allow for a wider habitable zone.
Proxima Centauri
Proxima (Alpha Centauri C) is a very cool and very dim, main sequence red dwarf that appears to have only 0.107 ± 0.021 percent of Sol's mass and 14.5% of its diameter. The star is as much as 19,000 times fainter than the Sun, and so if it was placed at the location of our Sun from Earth, the disk of the star would barely be visible. The distance from Proxima where an Earth-type planet would be "comfortable" with liquid water is around 0.02 to 0.06 AU (Endl et al, 2003, in pdf) -- much closer than Mercury's orbital distance of about 0.4 AU from Sol -- with an orbital period of two to 16 days.
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Magnitude of an exoplanet orbiting within the habitable zone.
By Abdul Ahad | Excerpt:
astroscience.org
Extrasolar planets ("exoplanets") orbiting around their parent stars in the life-supporting habitable zones may some day be directly photographed by using a technique whereby an occulting disk placed inside the telescope would mask out the glare of the star itself, thus enabling the faint planetary body to be imaged.
This may prove especially feasible for nearby stars, where the angular separation between the planet and its parent star is greatest.
But at what visual magnitude would such an exoplanet ("New Earth") be expected to shine when it has been successfully isolated from its parent star in the manner described?
This paper sets out a numerical model for evaluating such possible magnitudes for New Earth, based on it having assumed Earth or Jupiter-like photometric properties, a range of potential sizes and % phase illuminations as the planet revolves about its parent star.
If the Earth were placed at a standard distance of 1 AU from the observer in its heliocentric orbit and it exhibited a phase of 100% (full disk), the planet would shine with an apparent visual magnitude of -3.86. This quantitity is denoted V(1,0) and is an IAU approved photometric parameter for each planet listed in NASA factsheets. Now, the Sun shines at a visual magnitude of -26.8 as viewed from a standard distance of 1 AU. Hence, by equation (1) above we note that the Earth is overpowered by the Sun by a total brightness factor of some 1,499,684,836 to 1.
Through a similar calculation, we find that Jupiter's brightness ratio to the Sun (if it were placed at a standard distance of 1 AU from both the observer AND the Sun and it exhibited a phase of 100%, V(1,0)=-9.40) would be about 9,120,108 to 1. In equation (2) above, let m1 be the visual magnitude of the brighter source (i.e the Sun or the parent star) and let m2 be the visual magnitude of the fainter source (i.e. the planet).
Imagine if the Sun were viewed from a remote location in space at the distance of nearby stars when it would be totally 'starlike' in appearance and shine at a magnitude of m1. Since we know the brightness ratios, equation (2) above can be used to accurately determine the expected visual magnitude, m2, of either an Earth-like planet or a Jupiter-like planet located in the habitable zone around our Sun, as seen from such a location.
Application of Model to Determine Exoplanet Magnitudes
If the Earth were hypothetically placed in the habitable zone around another star, then by the default definition of a "habitable zone", it would experience a total light flux exactly equivalent to that which it experiences in our own solar system. Hence, the brightness ratio between that star and the Earth will always be constant, irrespective of the candidate star's own intrinsic or apparent brightness. Likewise, for Jupiter, we would expect an identical brightness ratio to that experienced in our solar system.
Hence, this model can be used to predict the apparent visual magnitude of an exoplanet orbiting *any* star within its habitable zone as seen from Earth. Conversely, if the apparent magnitude of such a planet were to be estimated by direct observation, we can deduce an approximation for its size/mass based on the assumed Earth/Jupiter photometric comparisons.
A Tiny Ray of Hope in the Eternal Darkness
Successfully locating an Earth-like planet in the habitable zone around one of the two principal 'suns' of the Alpha Centauri system will surely rank as one of the greatest discoveries in the entire history of science. Such a discovery would indeed be a 'revelation' and far outweigh all the extrasolar planets logged in all the world's scientific journals to date put together!
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Hubble Telescope Snaps Alien Planet
The first planet to be directly seen outside of our own solar system has been revealed in a photograph by the Hubble Space Telescope.
By Richard Gray | Source:
telegraph.co.uk
November 14, 2008 - The alien planet pictured by Hubble appears as a tiny red dot in the midst of a giant red dust ring.
The planet, which has been named Fomalhaut b and is around the same size as our own solar system's largest planet Jupiter, appears as a tiny red dot in the midst of a giant red dust ring orbiting the star Fomalhaut, which is around 25 light years from Earth.
The picture reveals for the first time what an alien planet outside our own solar system looks like to the human eye.
Astronomers believe studying the planet and its star will provide a vital insight into how our own solar system will have looked a hundred million years ago. Normally the bright glare from stars makes it impossible to see planets any planets that might be orbiting them with visible light and astronomers have to look for planets indirectly by spotting tiny wobbles that their gravity can induce in a star. The unprecedented image of Fomalhaut b is the culmination of more than eight years of work to find a planet orbiting Fomalhaut after scientists first began to suspect the star may have planets surrounding it.
They now believe that the star, which is one of the 20 brightest stars visible from Earth, may also host other planets around it and could even be orbited by planets with liquid water on their surface, a vital component for life. "I nearly had a heart attack when I confirmed that Fomalhaut b orbits its parent star," said Paul Kalas, a professor of astronomy at the University of California, Berkeley. "It's a profound and overwhelming experience to lay eyes on a planet never before seen."
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Ed Weiler, associate administrator of NASA's science mission directorate in Washington, added: "In the 1990s just before we launched Hubble, no one had detected other planets around other stars. This is an 18 and a half year dream come true and we are showing you the first image using light that you can see with your own eye of a planet."
The Hubble Space Telescope is a space telescope that was carried into orbit by the Space Shuttle Discovery in April 1990. It is named for the American astronomer Edwin Hubble.
Although not the first space telescope, the Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. wikipedia.org
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Hunting for a Second Earth
Researchers are racing to find the first planet
that might support life as we know it.
by Robert Kunzig | Source:
discovermagazine.com
October 10, 2008 - Gliese 876 is a modest star, just one-third the mass of our sun and only 15 light-years away, but it has a history-making planetary system all its own.
In 1998 a team led by Geoff Marcy of the University of California at Berkeley detected the first sign of something interesting there: a giant planet, twice the mass of Jupiter, circling Gliese 876 once every two months, its gravity yanking the star back and forth at the speed of a jet plane.
Three years later the same group found a second planet, half the mass of Jupiter and closer in, pulling the star around at the speed of a race car.
Although the planets are too faint to be seen directly, their motions cause the star’s spectrum to wobble back and forth across the digital detector of an astronomical telescope. In the past decade, announcements of Jupiter-size planets have become commonplace; about 300 of them have been found so far. In 2005, however, with the help of improved detection software, Marcy’s team turned up something else orbiting Gliese 876—something truly new. This invisible object added one more regular component to the star’s motion, like the third note, faint and high, of a piano chord.
It has to happen from space. In space, above our atmosphere, stars do not twinkle; in space a telescope is also beyond day and night and can thus stare at the same star for weeks on end, gradually teasing from its light the barely perceptible but regular flickers caused by a small orbiting planet.
A French satellite called Corot, the first space telescope devoted primarily to looking for rocky planets, is in orbit now. An even more capable American mission, Kepler, will be launched in April. It is expected to find hundreds of Earths, including the first ones orbiting stars like the sun at distances like that of our own Earth.
Then, in 2013, NASA will launch a giant infrared telescope called the James Webb Space Telescope. An all-purpose observatory, the Webb was not designed to follow up on the discoveries of Corot and Kepler. But if pushed to the limit, it just might be able to provide the first indication of life—a telltale molecule, such as oxygen, in the planet’s atmosphere—on a super-Earth circling another star. By 2014 headlines could be announcing the first tentative evidence of life beyond our solar system.
Arriving late for her rendezvous at the café, wearing the dark pink coat she had said would make her recognizable, Baglin explained that her car had been towed—apparently the traffic wardens were not on strike. From the café Baglin would be proceeding to her dentist to have a tooth extracted. On the plus side, her spacecraft was performing beautifully.
As Baglin launched? into the story of the little spacecraft that could, in principle, find many rocky planets, her high, thin voice sometimes disappeared into the noise of the sirens outside.
She is a shortish woman of 70, with close-cropped gray hair and a warm, no-nonsense demeanor—her parents were both schoolteachers. A brief profile of her on the Paris Observatory Web site is titled “Annie Baglin—Never Say Die.” Getting Corot to the launchpad, she explained, was a long, hard slog, marked by bureaucratic near-death experiences.
She never intended to be a planet hunter. In the mid-1980s she and her colleagues proposed a space telescope to do stellar seismology—to study the inner workings of stars from vibrations on their surface, much as seismologists study Earth’s interior by analyzing earthquakes. The French and European space agencies were noncommittal about the idea. Then came 1995 and the announcement of the discovery of the first exoplanet, by Michel Mayor and his colleagues at the Geneva Observatory.
Launched in December 2006, Corot is thus a 1,300-pound spacecraft that does two very different things. No telescope yet exists that can take a picture of even a giant exoplanet; astronomers compare the task to taking a picture of a firefly next to a searchlight thousands of miles away. Mayor and his colleagues showed instead that it was possible, through a technique called astrometry, to detect the slight wobble in a star’s light caused by the gravitational pull of an orbiting planet.
Most of the 300-some exoplanets discovered since have been found that way. But Corot relies on a different technique that has lately come to the fore in ground-based searches as well. Called photometry, it detects the slight but regular dimming in a star’s light when a planet transits in front of it.
What the search for planetary transits has in common with the observation of starquakes is the need to stare at the same stars for a long time—long enough to detect very slow vibrations or to detect at least three transits of a planet. Otherwise, you can’t be sure it was really a starquake or a planet you saw, and not random fluctuations in the starlight. Corot stares at the same spot in the sky for 150 days before switching to another. “Corot is Zen,” Baglin says. “Once we’re set up, we don’t move. We don’t even breathe.”
The spacecraft’s 27-centimeter (10.6-inch) telescope monitors up to 12,000 sunlike stars at once. Getting a big sample is crucial because only one in a hundred of those stars that do have planets will be oriented so that the passage of the planet in front of the star is visible from Earth. The precision of the telescope’s measurements has exceeded its makers’ hopes. “If Corot were to observe the million lightbulbs that shine along the Champs-Elysées at Christmas,” said a press release from the Paris Observatory a few days before Christmas in 2007, “it would be able to detect whether a single bulb was flashing.”
Not long after the launch, the Corot science team, including Baglin, published a description of the mission. It concluded with this prediction: “The first confirmed terrestrial planets are expected in the spring of 2008.” By last spring, however, the Corot team had announced only two new “hot Jupiters” and one unconfirmed super-Earth, with 40 more candidates in the pipeline.
Seeing transits is not enough; periodic dips in a star’s light could be caused by a small companion star too dim to detect directly.
To confirm a planet, Corot’s candidates have to be observed from the ground using the wobble technique, which determines the mass of the transiting object; a planet will be much lighter than a companion star. But competition for telescope time on the ground is fierce, especially with so many planet hunters around. “It’s a real bottleneck,” Laughlin says.
Baglin has little patience for impatience or for the pressure on her to announce discoveries quickly. “Finding these things isn’t like finding the nose on your face!” she exclaimed, shortly before leaving the café last November to head for the dentist. The Swiss astronomer Mayor gathered data for 20 years, she pointed out, before announcing his first exoplanet. “So when people tell me, ‘You haven’t got any results,’ when we’ve only been in orbit for a year, I say, ‘Stop! Have mercy!’ In three years we’ll have results indicating how common small planets are.
Borucki and Koch first proposed their mission to NASA in 1994; they called it FRESIP, for “Frequency of Earth-Size Inner Planets.” They proposed it again in 1996, 1998, and 2000.
“Each time they came back with a list of reasons why we weren’t selected,” Koch says. “It won’t work because of this, it won’t work because of that, they said. And we went back and worked on it until we eliminated every reason they couldn’t select us.”
The researchers made sure, for instance, that the minute vibrations of the spinning gyroscopes that kept the telescope pointed at its target would not drown out the signal from a planet. The name of the spacecraft was an easier sell.
After the first proposal, Koch suggested naming it Kepler, after the discoverer of the laws of planetary motion. In 2001 NASA finally approved the mission. Over in Europe Corot was getting the go-ahead at around the same time, albeit at a much lower budget. Though the French won the race into orbit, Kepler will have a telescope measuring 95 centimeters (37.4 inches), 3.5 times the diameter of Corot’s, with a field of view more than 10 times as large. Above all, it will be in orbit around the sun, trailing behind Earth, whereas Corot is in low Earth orbit over the poles.
Even if a habitable Earth-like world is found first from the ground, it will most likely take a space observatory to search for the chemical signals that tell us what we really want to know: Is anything living out there? If the planet is one that can be observed transiting, it just might be possible to provide a hint of an answer in the next few years.
As a transiting planet passes in front of its star, some starlight passes through the planet’s atmosphere and continues on toward Earth—minus certain spectral frequencies that have been absorbed by molecules in the atmosphere.
In 2001, using Hubble, Charbonneau and his colleagues detected the first exoplanetary atmosphere that way; it belonged to a hot Jupiter called HD 209458 b, and it contained sodium, they said.
Three years later Charbonneau found himself locked in a race with Deming to be the first to detect the flip side of a planetary transit—the moment, called secondary eclipse, when a planet passes behind its star. This time it was Deming who was observing HD 209458 b, with the Spitzer Space Telescope, an orbiting infrared observatory. Charbonneau, he knew, had collected data on a different hot Jupiter a month earlier. “We didn’t want to be second,” Deming recalls. “I was analyzing data while I was eating Christmas dinner. I had to catch Dave.” In the end they published papers simultaneously and held a joint press conference.
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