One in five stars has an Earth-sized planet in the habitable zone, according to researchers with University of Hawaii and University of California, Berkeley.
“We answered a long-standing question,” UH astronomer Andrew Howard said. “Twenty-two percent of stars like the sun we think have an Earth-like planet in the habitable zone. Twenty-two percent is a pretty big number.”
Astronomers used NASA’s Kepler telescope, which has been sending data and observations to Earth for several years, and the W.M. Keck Observatory to reach the conclusion, Howard said. The finding, which took UC Berkeley graduate student Erik Petigura, who has been in residence at UH Manoa, about two years to study the data and reach the 22 percent figure, Howard said.
“It was a major computational and intellectual task,” Howard said, referring to the work Petigura completed, with the help of a super computer. “He performed this amazing technical feat to (reach) this measurement.”
But the finding helps Kepler achieve its ultimate goal, which was to determine how many of the approximately 100 billion stars in the galaxy may have habitable planets, he added.
Kepler was aimed at one patch of sky, observing about 150,000 stars. Scientists used the telescope to obtain a census of those stars, and a number of potentially Earth-sized planets have since been identified in that area of the galaxy.
The fifth-closest star to our sun is only 12 light-years away, Howard said. Likely one of those five closest stars could have an Earth-sized planet in the habitable zone, sometimes called the Goldilocks zone, because it’s not too hot and not too cold to support life. Thus far, Earth-sized planets have been found, and most recently, a rocky planet was found, although it was too close to its host star to support life.
Ultimately, the astronomers’ work is about the possibility of finding life elsewhere in the universe, Howard said.
“It means life is probably more common in the universe than we thought before,” he said. “That’s great.”
The conclusion of Kepler’s mission brings NASA a step closer to its next big goal, he added, taking a picture of an Earth-like planet orbiting a star. That’s an especially tricky proposal, Howard said, because stars are so bright it can be difficult to make out a planet near them.
Kepler took photos every 30 minutes for four years. NASA’s Kepler team reported seeing more than 3,000 planet candidates, many of which are larger than Earth, a press release about the discovery said. In addition to some being so close to the host star that no life would be possible, others have thick atmospheres and some are gas giants.
Howard said Keck’s telescopes were critical in studying the images.
