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It’s a big universe, but it’s full of small planets.
Astronomers announced on Tuesday that they had found eight new planets orbiting their stars at distances compatible with liquid water, bringing the total number of potentially habitable planets in the just-right “Goldilocks” zone to a dozen or two, depending on how the habitable zone of a star is defined.
NASA’s Kepler spacecraft, now in its fifth year of seeking out the shadows of planets circling other stars, has spotted hundreds, and more and more of these other worlds look a lot like Earth — rocky balls only slightly larger than our own home, that with the right doses of starlight and water could turn out to be veritable gardens of microbial Eden.
As the ranks of these planets grow, astronomers are planning the next step in the quest to end cosmic loneliness: gauging which hold the greatest promise for life and what tools will be needed to learn about them.
The planets unveiled on Tuesday were detected by a group led by Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics.
On Monday, another group of astronomers said they had managed to weigh precisely a set of small planets and found that their densities and compositions almost exactly matched those of Earth.
Courtney Dressing, also of the Harvard-Smithsonian Center for Astrophysics, said at a news conference, “I’m going to give you the recipe for a rocky planet.”
She began, “Take one cup of magnesium ...”
Both groups announced their findings at a meeting of the American Astronomical Society in Seattle.
Reviewing the history of exoplanets, Debra Fischer, a Yale astronomer, recalled that the first discovery of a planet orbiting another normal star, a Jupiter-like giant, was 20 years ago. Before that, she said, astronomers worried that “maybe the ‘Star Trek’ picture of the universe was not right, and there is no life anywhere else.”
Dr. Fischer called the progress in the last two decades “incredibly moving.”
And yet we still do not have a clue that we are not alone.
Continue reading the main story
So far, Kepler has discovered 4,175 potential planets, and 1,004 of them have been confirmed as real, according to Michele Johnson, a spokeswoman for NASA’s Ames Research Center, which operates Kepler.
Most of them, however, including those announced Tuesday, are hundreds of light-years away, too far for detailed study. We will probably never know any more about these particular planets than we do now.
“We can count as many as we like,” said Sara Seager, a planet theorist at the Massachusetts Institute of Technology who was not involved in the new work, “but until we can observe the atmospheres and assess their greenhouse gas power, we don’t really know what the surface temperatures are like.”
Still, she added, “it’s heartening to have such a growing list.”
Finding Goldilocks planets closer to home will be the job of the Transiting Exoplanet Survey Satellite, to be launched in 2017. But if we want to know what the weather is like on these worlds, whether there is water or even life, more powerful instruments will be needed.
Dr. Seager is heading a NASA study investigating the concept of a starshade, which would float in front of a space telescope and block light from a star so that its much fainter planets would be visible.
Another group, led by Karl Stapelfeldt of NASA’s Goddard Space Flight Center, is studying a method known as a coronagraph, in which the occulting disk is inside the telescope.
Both studies are expected to be completed in the next few months, and could affect plans for a former spy telescope bequeathed to NASA three years ago. Astronomers hope to launch it in the early 2020s to study dark energy, and they plan to include a coronagraph to search for exoplanets, according to Paul Schechter of M.I.T., chairman of a design team. Depending on the probe’s orbit, Dr. Seager said, it could also be made “starshade ready.”
NASA’s James Webb Space Telescope, due for a 2018 launch, will have a coronagraph capable of seeing Jupiter-size planets, but it is too late to adapt it to a starshade.
Meanwhile, Dr. Seager and Julianne Dalcanton of the University of Washington are writing a separate report for a consortium of universities that runs observatories. The goal is to have a pool of dozens of “exo-Earths” to study in order to have any chance of seeing signs of life or understanding terrestrial planets, Dr. Seager said. Amassing them will require a space telescope 10 or 12 meters in diameter (the Webb will be 6.5 meters, and the largest currently on Earth is 10).
All of this will be grist for the mill at the end of the decade when a panel of the National Academy of Sciences produces its wish list for astronomy in the 2020s.
For all of Kepler’s bounty, a planet like Earth, of the same size orbiting the same type of star, has not yet been confirmed. The most terrestrial of the new worlds announced Tuesday are a pair known as Kepler 438b and Kepler 442b, both orbiting stars slightly smaller, cooler and redder than our sun. Kepler 438b is only 12 percent larger than Earth in diameter and has a 35-day year; Kepler 442 is a third larger than Earth and has a 112-day year.
“All these are small, all are potentially habitable,” said Doug Caldwell of the SETI Institute and NASA Ames at a news conference in Seattle.
In a news release, Dr. Torres said, “Most of these planets have a good chance of being rocky, like Earth.” That thought was reinforced by his colleagues, led by Ms. Dressing, a doctoral candidate at Harvard. Her group combined data from Kepler, which measures the sizes of planets, with spectrographic observations from an Italian telescope in the Canary Islands. That instrument measures planets’ masses to determine their densities, and by combining the information Ms. Dressing’s group was able to infer the densities and compositions of a set of small planets.
All five of the planets smaller than 1.6 times the size of Earth fell on a line consistent with Earth and Venus. Planets larger than that, Ms. Dressing and her colleagues found, were fluffier, perhaps because as planets get bigger their mass and gravity increase, and they are better able to hang on to gas and lighter components.
The work complements and tightens studies done last year by Geoffrey Marcy and his colleagues at the University of California, Berkeley; that group looks into the nature of so-called super Earths, planets bigger than ours and smaller than Neptune.
There are no planets in this range in our solar system, but according to Kepler they are common in the galaxy. Are they rocks like Earth or blobs like Neptune? The break point now seems to be 1.6 times the size of Earth, according to Ms. Dressing, and it is on those planets, perhaps, that we should concentrate our search for cosmic company.
As she said in her presentation, “Doubling the recipe doesn’t work.”
http://www.nytimes.com/2015/01/07/s...row-astronomers-consider-whats-next.html?_r=0
Astronomers announced on Tuesday that they had found eight new planets orbiting their stars at distances compatible with liquid water, bringing the total number of potentially habitable planets in the just-right “Goldilocks” zone to a dozen or two, depending on how the habitable zone of a star is defined.
NASA’s Kepler spacecraft, now in its fifth year of seeking out the shadows of planets circling other stars, has spotted hundreds, and more and more of these other worlds look a lot like Earth — rocky balls only slightly larger than our own home, that with the right doses of starlight and water could turn out to be veritable gardens of microbial Eden.
As the ranks of these planets grow, astronomers are planning the next step in the quest to end cosmic loneliness: gauging which hold the greatest promise for life and what tools will be needed to learn about them.
The planets unveiled on Tuesday were detected by a group led by Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics.
On Monday, another group of astronomers said they had managed to weigh precisely a set of small planets and found that their densities and compositions almost exactly matched those of Earth.
Courtney Dressing, also of the Harvard-Smithsonian Center for Astrophysics, said at a news conference, “I’m going to give you the recipe for a rocky planet.”
She began, “Take one cup of magnesium ...”
Both groups announced their findings at a meeting of the American Astronomical Society in Seattle.
Reviewing the history of exoplanets, Debra Fischer, a Yale astronomer, recalled that the first discovery of a planet orbiting another normal star, a Jupiter-like giant, was 20 years ago. Before that, she said, astronomers worried that “maybe the ‘Star Trek’ picture of the universe was not right, and there is no life anywhere else.”
Dr. Fischer called the progress in the last two decades “incredibly moving.”
And yet we still do not have a clue that we are not alone.
Continue reading the main story
So far, Kepler has discovered 4,175 potential planets, and 1,004 of them have been confirmed as real, according to Michele Johnson, a spokeswoman for NASA’s Ames Research Center, which operates Kepler.
Most of them, however, including those announced Tuesday, are hundreds of light-years away, too far for detailed study. We will probably never know any more about these particular planets than we do now.
“We can count as many as we like,” said Sara Seager, a planet theorist at the Massachusetts Institute of Technology who was not involved in the new work, “but until we can observe the atmospheres and assess their greenhouse gas power, we don’t really know what the surface temperatures are like.”
Still, she added, “it’s heartening to have such a growing list.”
Finding Goldilocks planets closer to home will be the job of the Transiting Exoplanet Survey Satellite, to be launched in 2017. But if we want to know what the weather is like on these worlds, whether there is water or even life, more powerful instruments will be needed.
Dr. Seager is heading a NASA study investigating the concept of a starshade, which would float in front of a space telescope and block light from a star so that its much fainter planets would be visible.
Another group, led by Karl Stapelfeldt of NASA’s Goddard Space Flight Center, is studying a method known as a coronagraph, in which the occulting disk is inside the telescope.
Both studies are expected to be completed in the next few months, and could affect plans for a former spy telescope bequeathed to NASA three years ago. Astronomers hope to launch it in the early 2020s to study dark energy, and they plan to include a coronagraph to search for exoplanets, according to Paul Schechter of M.I.T., chairman of a design team. Depending on the probe’s orbit, Dr. Seager said, it could also be made “starshade ready.”
NASA’s James Webb Space Telescope, due for a 2018 launch, will have a coronagraph capable of seeing Jupiter-size planets, but it is too late to adapt it to a starshade.
Meanwhile, Dr. Seager and Julianne Dalcanton of the University of Washington are writing a separate report for a consortium of universities that runs observatories. The goal is to have a pool of dozens of “exo-Earths” to study in order to have any chance of seeing signs of life or understanding terrestrial planets, Dr. Seager said. Amassing them will require a space telescope 10 or 12 meters in diameter (the Webb will be 6.5 meters, and the largest currently on Earth is 10).
All of this will be grist for the mill at the end of the decade when a panel of the National Academy of Sciences produces its wish list for astronomy in the 2020s.
For all of Kepler’s bounty, a planet like Earth, of the same size orbiting the same type of star, has not yet been confirmed. The most terrestrial of the new worlds announced Tuesday are a pair known as Kepler 438b and Kepler 442b, both orbiting stars slightly smaller, cooler and redder than our sun. Kepler 438b is only 12 percent larger than Earth in diameter and has a 35-day year; Kepler 442 is a third larger than Earth and has a 112-day year.
“All these are small, all are potentially habitable,” said Doug Caldwell of the SETI Institute and NASA Ames at a news conference in Seattle.
In a news release, Dr. Torres said, “Most of these planets have a good chance of being rocky, like Earth.” That thought was reinforced by his colleagues, led by Ms. Dressing, a doctoral candidate at Harvard. Her group combined data from Kepler, which measures the sizes of planets, with spectrographic observations from an Italian telescope in the Canary Islands. That instrument measures planets’ masses to determine their densities, and by combining the information Ms. Dressing’s group was able to infer the densities and compositions of a set of small planets.
All five of the planets smaller than 1.6 times the size of Earth fell on a line consistent with Earth and Venus. Planets larger than that, Ms. Dressing and her colleagues found, were fluffier, perhaps because as planets get bigger their mass and gravity increase, and they are better able to hang on to gas and lighter components.
The work complements and tightens studies done last year by Geoffrey Marcy and his colleagues at the University of California, Berkeley; that group looks into the nature of so-called super Earths, planets bigger than ours and smaller than Neptune.
There are no planets in this range in our solar system, but according to Kepler they are common in the galaxy. Are they rocks like Earth or blobs like Neptune? The break point now seems to be 1.6 times the size of Earth, according to Ms. Dressing, and it is on those planets, perhaps, that we should concentrate our search for cosmic company.
As she said in her presentation, “Doubling the recipe doesn’t work.”
http://www.nytimes.com/2015/01/07/s...row-astronomers-consider-whats-next.html?_r=0
