We still don’t know whether we’re alone in the universe, but there’s been some exciting progress in the search.
“We are now closer than we have ever been to finding a twin for the Earth around another star,” according to Fergal Mullally, SETI Institute Kepler scientist at NASA/Ames Research Center. Mullally spoke at a news conference about the latest discoveries regarding exoplanets, held in Seattle Jan. 6 at the 225th meeting of the American Astronomical Society.
The Kepler team announced a new bunch of exoplanet candidates and added three new confirmed exoplanets to the list of those that are about the size of Earth and in the habitable zone of their parent star. It’s still a short list.
“We have significantly increased the number of these verified, small, habitable-zone planets from Kepler,” said Doug Caldwell, another SETI Institute Kepler scientist at Ames. “They really make up a special population that is of interest for understanding the prevalence of life in the universe. Yesterday we had five Kepler exoplanets in this special hall of fame; today we have eight in this elite club.”
“These are the planets that Kepler was designed to find, and we’re delighted to be finally finding them,” Mullally added.
The Kepler crew also announced 554 new exoplanet candidates, bringing the total from the mission to 4,175. More than a thousand of those are now verified planets.
Of the elite eight, Caldwell said two are likely to be rocky, Kepler 438b and 442b, and three others are pegged as potentially rocky. There’s a lot of uncertainty about those numbers as the research continues.
While most exoplanets have been discovered by spotting their transits or measuring radial velocity, there may be nothing better than a visual look. So far, though, scientists have only been able to image a few planets around faraway stars, mostly huge planets far from their stars.
“It’s the tip of the iceberg, the easiest planets to see,” said Marshall Perrin of the Space Telescope Science Institute. “Easy is relative; these planets are about a million times fainter than their parent stars and are a small fraction of an arcsecond from them.”
Perrin, however, is heading up the Gemini Planet Imager (GPI), which saw first light about a year ago at the Gemini South Observatory in Chile and holds great promise to improve exoplanet imaging. While much of its first year was spent getting set up and working out the bugs, GPI also made some interesting and detailed observations of exoplanets.
GPI is about the size of an automobile.
“What’s inside the box is a lot of sophisticated technology,” Perrin said, including, “an adaptive optic system to correct for atmospheric jitter and deliver images with the same sharpness for the specific stars we’re looking at that the James Webb will see in space several years from now.”
The advantages of imaging are that you don’t have to wait for full orbits to confirm planets, and you can start taking spectra that can reveal a lot about the nature of the planets.
“In the long run we think that imaging offers perhaps the best path to characterizing rocky planets in Earth-like orbits,” Perrin said. He notes that GPI is gearing up for more science.
“We’re going to be opening up a lot of new discoveries, hopefully, over the next few years in terms of exoplanet imaging and, in the long run, taking these technologies and scaling them to future 30-meter telescopes, perhaps large telescopes in space.”
Marc Kuchner of NASA Goddard Space Flight Center is marshaling a huge cadre of volunteers working to identify disks of potentially planet-forming material around distant stars. NASA’s WISE mission found hundreds of thousands of possible sources. It’s the sort of data that takes a human eye to sort out, so NASA fired up DiskDetective.org, in connection with Zooniverse, to involve volunteers. More than 28,000 of them have made a million characterizations through the site in its first year.
“They found 478 objects of interest so far,” Kuchner noted. Once one of those is identified they get some telescope time for a closer look.
“We now have at least 37 solid new disk candidates, and we haven’t even looked at all the new telescope data yet,” Kuchner said. He invites more volunteers to visit the site and join in the effort to identify places where planets may form and we might spot other Earths.