It’s a big universe, but it’s full of small planets. A group of astronomers led by Guillermo Torres of the Harvard-Smithsonian Center for Astrophysics announced Tuesday they had found eight new planets orbiting their stars at distances compatible with liquid water, bringing the total number of potentially habitable “Goldilocks planets” to a few dozen, depending on how the habitable zone 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 beginning to plan 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.
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. Both groups announced their findings at a meeting of the American stronomical Society in Seattle.
Alluding to the popularity of food shows and cooking apps, 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.”
Reviewing the history of exoplanets, Debra Fischer, a Yale astronomer, recalled that the first planet found orbiting another sun-like star, a Jupiter-like giant, was discovered 20 years ago. Before that, she recalled, astronomers worried that “maybe the Star Trek picture of the universe was not right, and there is no life anywhere else”.
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 at NASA’s Ames Research Center, which operates Kepler.
Most of them, however, 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, including whether anybody can or does live on them.
“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.”