"Long before it's in the papers"
January 27, 2015


Possible Earth-sized, habitable planets found

Feb. 2, 2011
Courtesy of NASA
and World Science staff

NASA’s Kep­ler space tel­e­scope seems to have dis­cov­ered five plan­ets that are about the size of Earth and could sup­port liquid water, the space agen­cy has an­nounced.

Pre­vi­ously, as­tro­no­mers had re­ported only one or two plan­ets fit­ting si­m­i­lar de­scrip­tions, and these were es­ti­mat­ed to be some­what larg­er than Earth.

A di­a­gram show­ing the dis­tru­bi­tion of plan­e­tary can­di­dates found so far by the Kep­ler tel­e­scope, color-coded by size. (Im­age cred­it: NA­SA/Wendy Sten­zel )

Although further tests are needed to verify the finds, “in one genera­t­ion we have gone from ex­tra­ter­res­tri­al plan­ets be­ing a main­stay of sci­ence fic­tion, to the pre­s­ent, where Kep­ler has helped turn sci­ence fic­tion in­to to­day's real­ity,” NASA Ad­min­is­tra­tor Charles Bolden said this week. They are part of sev­er­al hun­dred new plan­et can­di­dates iden­ti­fied in new Kep­ler mis­sion da­ta.

A to­tal of 54 new plan­et can­di­dates found in hab­it­a­ble zones, areas in the or­bits around stars where tem­per­a­tures should al­low for liq­uid wa­ter, re­search­ers said. 

These bodies are estim­ated to range from about Earth-size in dia­me­ter to larg­er than Ju­pi­ter. The find­ings are based ob­serva­t­ions con­ducted May 12 to Sept. 17, 2009, of more than 156,000 stars in Kep­ler's field of view, which co­vers about one 400th of the sky and lies in the con­stel­la­tions Cyg­nus and Ly­ra.

“The fact that we've found so many plan­et can­di­dates in such a ti­ny frac­tion of the sky sug­gests there are count­less plan­ets or­biting Sun-like stars in our ga­laxy,” said Wil­liam Borucki of NASA's Ames Re­search Cen­ter in Mof­fett Field, Calif., the mis­sion's sci­ence prin­ci­pal in­ves­ti­ga­tor. “We went from ze­ro to 68 Earth-sized plan­et can­di­dates and ze­ro to 54 can­di­dates in the hab­it­a­ble zone, some of which could have moons with liq­uid wa­ter.” 

Among the stars with plan­etary can­di­dates, 170 show ev­i­dence of mul­ti­ple plan­etary can­di­dates, the sci­en­tists added. The star Kep­ler-11, lo­cat­ed about 2,000 light years from Earth, is de­cribed as the most tightly packed plan­etary sys­tem yet dis­cov­ered. The Kep­ler-11 find­ings are to ap­pear in the Feb. 3 is­sue of the jour­nal Na­ture.

The Kep­ler tel­e­scope looks for plan­ets by meas­ur­ing ti­ny de­creases in the bright­ness of stars caused by plan­ets cross­ing in front of them. The Kep­ler sci­ence team uses ground-based tel­e­scopes and the Spitzer Space Tel­e­scope to re­view ob­serva­t­ions on plan­etary can­di­dates and oth­er ob­jects of in­ter­est the space­craft finds.

* * *

Send us a comment on this story, or send it to a friend


Sign up for

On Home Page         


  • St­ar found to have lit­tle plan­ets over twice as old as our own

  • “Kind­ness curricu­lum” may bo­ost suc­cess in pre­schoolers


  • Smart­er mice with a “hum­anized” gene?

  • Was black­mail essen­tial for marr­iage to evolve?

  • Plu­to has even cold­er “twin” of sim­ilar size, studies find

  • Could simple an­ger have taught people to coop­erate?


  • F­rog said to de­scribe its home through song

  • Even r­ats will lend a help­ing paw: study

  • D­rug may undo aging-assoc­iated brain changes in ani­mals

NASA's Kepler space telescope has discovered five planets that seem to be about the size of Earth and located in a habitable zone, the agency has announced. Previously, astronomers had reported only one or at most two planets fitting similar descriptions, and these were estimated to be somewhat larger than Earth. A habitable zone is an area in the orbit of a star where temperatures should allow for liquid water. “In one generation we have gone from extraterrestrial planets being a mainstay of science fiction, to the present, where Kepler has helped turn science fiction into today's reality,“ said NASA Administrator Charles Bolden in announcing the findings. The discoveries are part of several hundred new planet candidates identified in new Kepler mission data. A total of 54 new planet candidates found in habitable zones, researchers said, ranging from about Earth-size to larger than Jupiter. The findings are based observations conducted May 12 to Sept. 17, 2009, of more than 156,000 stars in Kepler's field of view, which covers approximately one 400th of the sky. “The fact that we've found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting Sun-like stars in our galaxy,“ said William Borucki of NASA's Ames Research Center in Moffett Field, Calif., the mission's science principal investigator. “We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone, some of which could have moons with liquid water.“ Among the stars with planetary candidates, 170 show evidence of multiple planetary candidates, the scientists added. The star Kepler-11, located about 2,000 light years from Earth, is decribed as the most tightly packed planetary system yet discovered. The Kepler-11 findings are to appear in the Feb. 3 issue of the journal Nature. The Kepler telescope looks for planets by measuring tiny decreases in the brightness of stars caused by planets crossing in front of them. Since transits of planets in the habitable zone of Sun-like stars occur about once a year and require three transits for verification, it's expected to take three years to locate and verify Earth-size planets orbiting Sun-like stars. The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planetary candidates and other objects of interest the spacecraft finds.