Is there life out there?

For first time, as­tronomers have found seven Earth-size plan­ets or­bit­ing a sin­gle star and these new worlds could hold life.


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

This 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, where liq­uid 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 take­away from all this is, “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.

“There are 200 bil­lion stars in our gal­axy,” said co-au­thor Em­manuel Je­hin of the Univer­sity of Liege. So do an ac­count. You mul­ti­ply this by 10, and you have the num­ber of Earth-size plan­ets in the gal­axy — which is a lot.”

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 com­pact so­lar sys­tem 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-col­ored, 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. 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-) Earth-sized plan­ets might be noth­ing out of the ordinary,” Snellen wrote.

While faint, the Trap­pist-1 star is close by cos­mic stan­dards, al­low­ing as­tronomers to study the at­mos­pheres of its seven tem­per­ate plan­ets. All seven look to be solid like Earth — mostly rocky and pos­si­bly icy, too.

They all ap­pear to be tidally locked, which means the same side con­tin­u­ally faces the star, just like the same side of our moon al­ways faces us. Life could still ex­ist at these places, the re­searchers ex­plained.

“Here, if life man­aged to thrive and re­leases gases sim­i­lar to that that we have on Earth, then we will know,” Tri­aud said.

Chem­i­cal analy­ses should in­di­cate life with per­haps 99 per cent con­fi­dence, Gil­lon noted. But he added: “We will never be com­pletely sure” with­out go­ing there.


This im­age pro­vided by NASA/JPL-Cal­tech shows an artist’s con­cep­tion of what the sur­face of the ex­o­planet TRAP­PIST-1f may look like, based on avail­able data about its di­am­e­ter, mass and dis­tances from the host star.

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