Nasa dis­cov­ers new so­lar sys­tem TRAP­PIST-1where life may have evolved on three plan­ets

The Star (St. Lucia) - - IN­TER­NA­TIONAL - - tele­

Life may have evolved on at least three plan­ets within a newly dis­cov­ered so­lar sys­tem that is 39 light years from Earth. Astronomers at the Na­tional Aero­nau­tics and Space Ad­min­is­tra­tion (Nasa) have de­tected no less than seven roughly Earth-sized worlds or­bit­ing a dwarf star in the sys­tem.

Sci­en­tists had pre­vi­ously only iden­ti­fied a tiny num­ber of so-called “ex­o­plan­ets”, which are be­lieved to have the qual­i­ties needed to sup­port life. How­ever, the new sys­tem con­tains an un­prece­dented num­ber of Earth-sized, prob­a­bly rocky plan­ets, and is be­ing hailed as an “ac­cel­er­ated leap for­ward” in the search for ex­trater­res­trial life.

Three of the new plan­ets are said to be par­tic­u­larly promis­ing be­cause they could sus­tain oceans. Thomas Zur­buchen, as­so­ciate ad­min­is­tra­tor of Nasa’s Science Mis­sion Direc­torate, told a press con­fer­ence in Wash­ing­ton: “This gives us a hint that find­ing a sec­ond Earth is not a mat­ter of ‘if’, but ‘when’.”

The plan­ets were de­tected us­ing Nasa’s Spitzer Space Te­le­scope and sev­eral ground­based ob­ser­va­to­ries. Lead re­searcher Michaël Gil­lon, of the Univer­sity of Liège, said: “The plan­ets are all close to each other and very close to the star, which is very rem­i­nis­cent of the moons around Jupiter. Still, the star is so small and cold that the seven plan­ets are tem­per­ate, which means that they could have some liq­uid wa­ter – and maybe life, by ex­ten­sion – on the sur­face.”

The team de­ter­mined that all the plan­ets in the sys­tem are sim­i­lar in size to Earth and Venus, or slightly smaller. And den­sity mea­sure­ments sug­gest that at least the in­ner­most six plan­ets are rocky. Be­cause the star is so dim, the plan­ets are warmed gen­tly de­spite hav­ing or­bits much smaller than that of Mer­cury, the planet clos­est to our Sun.

Key ob­ser­va­tions were made by the Trap­pist ro­botic te­le­scope at La Silla, Chile which gives the sys­tem its name. Three plan­ets – clas­si­fied as TRAP­PIST-1e, f and g – or­bit in the “hab­it­able” or so-called “Goldilocks” zone where tem­per­a­tures are suited to sur­face oceans of liq­uid wa­ter.

The star at the cen­tre of the so­lar sys­tem has a tem­per­a­ture of 2550K and is at least 500 mil­lion years old. In com­par­i­son, the Sun is about 4.6 bil­lion years old and has a tem­per­a­ture of 5778K. The six in­ner plan­ets lie in a tem­per­ate zone where sur­face tem­per­a­tures range from zero to 100C.

Nasa’s Hub­ble Space Te­le­scope is al­ready be­ing used to search for at­mos­pheres around the plan­ets. Fu­ture tele­scopes, in­clud­ing the pro­posed Eu­ro­pean Ex­tremely Large Te­le­scope and the James Webb Space Te­le­scope, may be pow­er­ful enough to de­tect mark­ers of life, such as oxy­gen, in the at­mos­pheres of ex­o­plan­ets.

Prof Sara Sea­ger, an ex­pert in plan­e­tary science and physics at the Mas­sachusetts In­sti­tute of Tech­nol­ogy, said: “In this plan­e­tary sys­tem, Goldilocks has many sis­ters. We have made a gi­ant ac­cel­er­ated leap for­ward in the search for hab­it­able worlds and life in other worlds.”

The Spitzer te­le­scope, which uses in­frared tech­nol­ogy, was able to track how fast each of the plan­ets crossed TRAP­PIST-1 and com­pleted an or­bit.

From this the re­search team cal­cu­lated how far the plan­ets were from their star, and there­fore how likely they are to be hab­it­able. They were as­sisted by astronomers from Liver­pool John Moores Univer­sity, op­er­at­ing a ground­based te­le­scope in the Ca­nary Is­lands.

The Liver­pool te­le­scope helped de­tect the plan­ets as they passed in front of their star. The plan­ets were found us­ing the “tran­sit” method that looks for tiny amounts of dim­ming caused by a world block­ing light from its star.

Bri­tish as­tronomer Dr Chris Cop­per­wheat, from Liver­pool John Moores Univer­sity, who co-led the in­ter­na­tional team said: “As a ro­botic te­le­scope and the largest in the world, the Liver­pool te­le­scope is very sen­si­tive to the small, less than 1 per cent, dips in bright­ness through which the plan­ets are dis­cov­ered.”

The new plan­ets are very close to each other and Dr Gil­lon said a per­son stand­ing on the sur­face of one would have a view of its neigh­bours, sim­i­lar to see­ing the Moon from Earth.

The first ex­o­planet was con­firmed to have been dis­cov­ered in 1992, since when a to­tal of 3,577 have been found. Of th­ese, less than a dozen are thought to be well suited to sup­port­ing life, and Nasa said only three pre­vi­ously known ex­o­plan­ets were as ideal as those in the new so­lar sys­tem.

Around a fifth of Sun-like stars are thought to have an Earth-sized planet in their hab­it­able zones. Astronomers es­ti­mate there could be as many as 40 bil­lion po­ten­tially hab­it­able worlds in our gal­axy, the Milky Way. Prof Zur­buchen said that now was a “gold-rush phase” in the search for th­ese ex­o­plan­ets.

As­tronomer Royal Sir Martin Rees thinks the dis­cov­ery of th­ese new worlds is just the start. “There are many more life-sup­port­ing plan­ets out there wait­ing to be dis­cov­ered,” he says.

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