"Long before it's in the papers"
December 05, 2011

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First Earth-like planet around Sun-like star reported

Dec. 5, 2011
Courtesy of the Carnegie Institution
and World Science staff

As­tro­no­mers have found a plan­et with balmy tem­per­a­tures and a sun-like star, mak­ing it per­haps the best can­di­date so far for a plan­et apart from ours that could host life, they say.

It’s the “first de­tec­tion of a pos­sibly hab­it­a­ble world in or­bit around a Sun-like star,” said a state­ment Mon­day the Car­ne­gie In­sti­tu­tion for Sci­ence in Wash­ing­ton, D.C., which par­ti­ci­pated in the re­search. But the plan­et could be five to 10 times heav­i­er than Earth, mean­ing the ef­fects of gra­vity for its in­hab­i­tants might be a bit nas­ti­er than they are for Earth’s.

Artist's con­cep­tion of the plan­et Kep­ler-22b. (Cour­tesy Car­ne­gie In­sti­tu­tion)
Re­search­ers with NASA’s Kep­ler mis­sion re­ported find­ing the large, probably rocky plan­et with a sur­face tem­per­a­ture of about 72 de­grees Fahr­en­heit, com­pa­ra­ble to a com­fort­a­ble spring day on Earth. The find­ing is to be pub­lished in The As­t­ro­phys­i­cal Jour­nal.

The re­search team, led by Wil­liam Borucki of the NASA Ames Re­search Cen­ter, used da­ta from the NASA Kep­ler space tel­e­scope, which mon­i­tors the bright­ness of 155,000 stars. Earth-size plan­ets whose or­bits hap­pen to take them be­tween us and their stars cre­ate ti­ny dim­mings of their host star’s light. Kep­ler can pick up those ef­fects, and they can help sci­en­tists draw a few con­clu­sions about those plan­ets.

The host star in this case lies about 600 light-years away from us to­ward the con­stella­t­ions of Ly­ra and Cyg­nus, re­search­ers said. The star is slightly smaller than our Sun and about one-fourth less lu­mi­nous, but com­pen­sat­ing for that, the plan­et is 15 per­cent clos­er to it than we are to the Sun. The plan­et or­bits the star once eve­ry 290 days, so that’s the length of its year.

The new plan­et, dubbed Kep­ler-22b, is an es­ti­mat­ed 2.4 times wid­er than Earth, put­ting it in­to a class of plan­ets that sci­en­tists call super-Earths.

Its weight is un­known, but it may be about five to 10 times heav­i­er than Earth, based on pre­vi­ous find­ings of com­pa­ra­ble plan­ets, the re­search­ers said. That by it­self would mean any ob­ject on Kep­ler-22b “feels” five to 10 times heav­i­er than it would on Earth. But in real­ity, Kep­ler-22b’s great­er size should mit­i­gate that ef­fect. That’s be­cause ob­jects on its sur­face would be far­ther from the cen­ter the plan­et—which is al­so the cen­ter of its gravita­t­ional field­—than we are from our own gravita­t­ional field cen­ter on Earth.

So in real­ity, if the above width and weight es­ti­mates for Kep­ler-22b turn out to be cor­rect, then any vis­i­tors to the new world from Earth would feel as though they weighed some­where be­tween a tou­ch more than they did on Earth, and twice as much.

“This dis­cov­ery sup­ports the grow­ing be­lief that we live in a uni­verse crowd­ed with life,” said Al­an Boss of the Car­ne­gie In­sti­tu­tion, one of the re­search­ers. “Kep­ler is on the verge of de­ter­min­ing the ac­tu­al abun­dance of hab­it­a­ble, Earth-like plan­ets in our ga­laxy.”

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Astronomers have found a planet with balmy temperatures and a sun-like star, making it perhaps the best candidate so far for a planet apart from ours that could host life, they say. It’s the “first detection of a possibly habitable world in orbit around a Sun-like star,” said a statement Monday the Carnegie Institution for Science in Washington, D.C., which participated in the research. But the planet could be five to 10 times heavier than Earth, meaning the effects of gravity for its inhabitants might be a bit nastier than they are for Earth’s. Researchers with NASA’s Kepler mission reported finding the large, probably rocky planet with a surface temperature of about 72 degrees Fahrenheit, comparable to a comfortable spring day on Earth. This finding is to be published in The Astrophysical Journal. The research team, led by William Borucki of the NASA Ames Research Center, used data from the NASA Kepler space telescope, which monitors the brightness of 155,000 stars. Earth-size planets whose orbits happen to take them between us and their stars create tiny dimmings of their host star’s light. Kepler can pick up those effects, and they can help scientists draw a few conclusions about those planets. The host star in this case lies about 600 light-years away from us toward the constellations of Lyra and Cygnus, researchers said. The star is slightly smaller than our Sun and about one-fourth less luminous, but compensating for that, the planet is 15 percent closer to it than we are to the Sun. The planet orbits the star once every 290 days, so that’s the length of its year. The new planet, dubbed Kepler-22b, is an estimated 2.4 times wider than Earth, putting it into a class of planets that scientists call super-Earths. Its weight is unknown, but it may be about five to 10 times heavier than Earth, based on previous findings of comparable planets, the researchers said. That by itself would mean any object on Kepler-22b “feels” five to 10 times heavier than it would on Earth. But in reality, Kepler-22b’s greater size should mitigate that effect. That’s because objects on its surface would be farther from the center the planet—which is also the center of the gravitational field—than we are from our own gravitational field center on Earth. So in reality, if the above width and weight estimates for Kepler-22b turn out to be correct, then any visitors to the new world from Earth would feel as though they weighed somewhere between a touch more than they did on Earth, and twice as much. “This discovery supports the growing belief that we live in a universe crowded with life,” said Alan Boss of the Carnegie Institution, one of the researchers. “Kepler is on the verge of determining the actual abundance of habitable, Earth-like planets in our galaxy.”