Four More Po­ten­tially Hab­it­able Plan­ets Dis­cov­ered Nearby

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Only 12 light-years away from us, four Earth-size plan­ets have been dis­cov­ered that ap­pear to have all they might need to sup­port water – and maybe life.

The dis­cov­ery of the plan­ets, which was dis­closed in a pa­per soon to be pub­lished in The Astro­nom­i­cal Jour­nal, was made by ob­serv­ing wob­bles in the path of Tau Ceti, the sun­like star that is clos­est to Earth. The plan­ets are or­bit­ing the star, which is also vis­i­ble to the naked eye – un­like the four pos­si­ble Earths that or­bit around it.

To find the plan­ets, an in­ter­na­tional team of as­tronomers stud­ied the wob­bles in the move­ment of Tau Ceti. To do so re­quired tech­nol­ogy that could pick up vari­a­tions in the move­ment of the star that were as tiny as 30 cen­time­ters per sec­ond.

What they found was per­haps one of the most sig­nif­i­cant dis­cov­er­ies of Earth-like plan­ets. The plan­ets are of rel­a­tively low mass, only about 1.7 times the mass of our Earth, and among the small­est plan­ets ever de­tected near sun­like stars. Fur­ther anal­y­sis showed that two of the four plan­ets are what the study team called “su­per-earths” and just hap­pen to be in Tau Ceti’s “hab­it­able zone.” That means th­ese plan­ets might sup­port liq­uid sur­face water.

Find­ing the plan­ets was quite chal­leng­ing, re­quir­ing the devel­op­ment of spe­cial noise-re­duc­tion tech­niques to gather Tau Ceti’s wob­ble data with suf­fi­cient ac­cu­racy. The re­searchers also took care­ful time, mak­ing sure that what they had de­tected were the signs of, as they put it, “four rocky plan­ets or­bit­ing the star,” not just ghost signatures from the stel­lar outer sur­face.

Be­cause of their sim­i­lar­ity to our sun, the in­ves­ti­ga­tion of sun­like stars has long been con­sid­ered the best pos­si­ble way to find hab­it­able Earth-like plan­ets. Th­ese sun­like stars are also not so faint that any plan­ets or­bit­ing them would be what is known as “tidally locked,” which means the same side is also fac­ing the star. With tidally locked plan­ets, one side is con­tin­u­ally bom­barded with so­lar ra­di­a­tion while the other side is not, cre­at­ing a num­ber of eco­log­i­cal chal­lenges for them – chal­lenges that would tend to rule out the pres­ence of liq­uid water.

The in­ter­na­tional team who dis­cov­ered th­ese plan­ets in­cludes lead au­thor Fabo Feng of the Univer­sity of Hert­ford­shire, UK; Stephen Vogt, pro­fes­sor of as­tron­omy at the Univer­sity of Cal­i­for­nia, Santa Cruz; Mikko Tuomi of the Univer­sity of Hert­ford­shire; John Barnes of The Open Univer­sity, UK; Guillem Anglada-es­cude of Queen Mary Univer­sity of Lon­don; and Paul But­ler of the Carnegie In­sti­tu­tion for Sci­ence, Wash­ing­ton, DC.

The dis­cov­er­ies are out­lined in a pa­per soon to be pub­lished in The Astro­nom­i­cal Jour­nal. A copy is also avail­able on­line.

Photo by Alive Uni­verse Im­ages, CC

Photo by Алексей М, CC

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