Seven Earth-size plan­ets or­bit­ing nearby star

New worlds found less than 40 light-years away may sup­port life: NASA

The Hamilton Spectator - - FRONT PAGE - MAR­CIA DUNN

CAPE CANAVERAL, FLA. — For the first time, as­tronomers have dis­cov­ered seven Earth-size plan­ets or­bit­ing a sin­gle nearby star — and th­ese new worlds could hold life.

The clus­ter of plan­ets is less than 40 light-years away in the con­stel­la­tion Aquarius, ac­cord­ing to NASA and the Bel­gian-led re­search team who an­nounced the dis­cov­ery Wed­nes­day.

The plan­ets cir­cle tightly around a dim dwarf star called TRAPPIST-1, barely the size of Jupiter. Three are in the so-called hab­it­able zone, the area around a star where wa­ter and, pos­si­bly life, might ex­ist. The oth­ers are right on the doorstep.

Sci­en­tists said they need to study the

at­mos­pheres be­fore de­ter­min­ing whether th­ese rocky, ter­res­trial plan­ets could sup­port some sort of life. But it al­ready shows just how many Earth-size plan­ets could be out there — es­pe­cially in a star’s sweet spot, ripe for ex­trater­res­trial life. The more plan­ets like this, the greater the po­ten­tial of find­ing one that’s truly hab­it­able. Un­til now, only two or three Earth-size plan­ets had been spot­ted around a star.

“We’ve made a cru­cial step to­ward find­ing if there is life out there,” said the Univer­sity of Cam­bridge’s Amaury Tri­aud, one of the re­searchers.

The po­ten­tial for more Earth-size plan­ets in our Milky Way Galaxy is mind-bog­gling. The his­tory of planet-search­ing shows “when there’s one, there’s more,” said Mas­sachusetts In­sti­tute of Tech­nol­ogy astro­physi­cist Sara Sea­ger.

“With this amaz­ing sys­tem, we know that there must be many more po­ten­tially life-bear­ing worlds out there just wait­ing to be found,” said Sea­ger, who is a Toronto na­tive and Univer­sity of Toronto grad­u­ate.

NASA’s Thomas Zur­buchen, as­so­ciate ad­min­is­tra­tor for the sci­ence mis­sion, said the dis­cov­ery “gives us a hint that find­ing a sec­ond Earth is not just a mat­ter of if, but when,” and ad­dresses the age-old ques­tion of “Are we alone out there?”

“We’re mak­ing a step for­ward with this, a leap for­ward in fact, to­ward an­swer­ing that ques­tion,” Zur­buchen said at a news con­fer­ence.

Last spring, the Univer­sity of Liege’s Michael Gil­lon and his team re­ported find­ing three plan­ets around TRAPPIST-1. Now the count is up to seven, and Gil­lon said there could be more. Their lat­est find­ings ap­pear in the jour­nal Na­ture.

This crowded yet com­pact so­lar sys­tem — 235 tril­lion miles away — is rem­i­nis­cent of Jupiter and its Galilean moons, ac­cord­ing to the re­searchers.

Pic­ture this: if TRAPPIST-1 were our sun, all seven plan­ets would be in­side Mer­cury’s or­bit. Mer­cury is the in­ner­most planet of our own so­lar sys­tem.

The ul­tra­cool star at the heart of this sys­tem would shine 200 times dim­mer than our sun, a per­pet­ual twi­light as we know it. And the star would glow red — maybe salmon-coloured, the re­searchers spec­u­late.

“The spec­ta­cle would be beau­ti­ful be­cause ev­ery now and then, you would see an­other planet, maybe about as big as twice the moon in the sky, de­pend­ing on which planet you’re on and which planet you look at,” Tri­aud said Tues­day in a tele­con­fer­ence with re­porters.

Years are ex­ceed­ingly short in this star sys­tem — the plan­ets take just 1 ½ to 20 days to or­bit TRAPPIST-1.

The Lei­den Ob­ser­va­tory’s Ig­nas Snellen, who was not in­volved in the study, is ex­cited by the prospect of learn­ing more about what he calls “the seven sis­ters of planet Earth.” In a com­pan­ion ar­ti­cle in Na­ture, he said Gil­lon’s team could have been lucky in nab­bing so many ter­res­trial plan­ets in one stel­lar swoop.

“But find­ing seven tran­sit­ing Earth-sized plan­ets in such a small sam­ple sug­gests that the so­lar sys­tem with its four (sub-) Earth­sized plan­ets might be noth­ing out of the or­di­nary,” Snellen wrote.

Gil­lon and his team used both ground and space tele­scopes to iden­tify and track the plan­ets, which they la­bel sim­ply by lower case let­ters, “b” through “h.” As is typ­i­cal in th­ese cases, the let­ter “A” — in up­per case — is re­served for the star.

Plan­ets cast shad­ows on their star as they pass in front of it; that’s how the sci­en­tists spot­ted them.

The TRAPPIST-1 star, an ul­tra­cool dwarf, is or­bited by seven Earth-size plan­ets.

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