As­tronomers dis­cover rocky Earth-like planet in hab­it­able zone.

Scientists to look for signs of life

The Washington Times Daily - - FRONT PAGE - BY SETH BOREN­STEIN

As­tronomers have found yet an­other planet that seems to have just the right Goldilocks com­bi­na­tion for life: Not so hot and not so cold. It’s not so far away, ei­ther.

This big, dense planet is rocky, like Earth, and has the right tem­per­a­tures for wa­ter, putting it in the hab­it­able zone for life, ac­cord­ing to a study pub­lished Wed­nes­day in the jour­nal Na­ture.

It’s the fifth such life-pos­si­ble planet out­side our so­lar sys­tem re­vealed in less than a year, but still rel­a­tively nearby Earth. Rocky plan­ets within that hab­it­able zone of a star are con­sid­ered the best place to find ev­i­dence of some form of life.

“It is as­ton­ish­ing to live in a time when dis­cov­ery of po­ten­tially hab­it­able worlds is not only com­mon­place but pro­lif­er­at­ing,” said Sara Sea­ger, an as­tronomer at the Mas­sachusetts In­sti­tute of Tech­nol­ogy who wasn’t part of the study.

The first dis­cov­ery of a planet out­side our so­lar sys­tem was in 1995, but thanks to new tech­niques and es­pe­cially NASA’s planet-hunt­ing Ke­pler tele­scope, the num­ber of dis­cov­er­ies has ex­ploded in re­cent years. As­tronomers have now iden­ti­fied 52 po­ten­tially hab­it­able plan­ets and more than 3,600 plan­ets out­side our so­lar sys­tem.

The lat­est dis­cov­ery, called LHS 1140b, reg­u­larly passes in front of its star, al­low­ing as­tronomers to mea­sure its size and mass. That makes as­tronomers more con­fi­dent that this one is rocky, com­pared to other re­cent dis­cov­er­ies.

In the next sev­eral years, more ad­vanced tele­scopes should be able to use the planet’s path to spy its at­mos­phere in what could be the best-aimed search for signs of life, said Har­vard as­tronomer David Char­bon­neau, a co-au­thor of the study. If scientists see both oxy­gen and some car­bon in an at­mos­phere, that is a promis­ing sign that some­thing could be liv­ing.

Out­side as­tronomers have put the most re­cent planet near the top of their must-see lists for ground and space­based tele­scopes.

“This is the first one where we ac­tu­ally know it’s rocky,” Mr. Char­bon­neau said. “We found a planet that we can ac­tu­ally study that might be ac­tu­ally Earth-like.”

Make that su­per­sized, be­cause it be­longs to a class of plan­ets called su­perEarths that are more mas­sive than Earth but not quite the size of gi­ants Nep­tune or Jupiter.

Com­pared with Earth, the newly dis­cov­ered planet pushes near the size limit for rocky plan­ets. It’s 40 per­cent wider than Earth, but it has 6.6 times Earth’s mass, giv­ing it a grav­i­ta­tional pull three times stronger, Mr. Char­bon­neau said. A per­son weigh­ing 167 pounds would feel like 500 pounds on this planet.

While many su­per-Earths are too big to have the right en­vi­ron­ment for life, 1140b is just small enough to make it a good can­di­date. Thirty-two of the po­ten­tially hab­it­able plan­ets found so far are con­sid­ered su­per-Earth sized.

The planet was found us­ing eight small tele­scopes in Chile and help from an am­a­teur planet hunter, Mr. Char­bon­neau said.

In the con­stel­la­tion Ce­tus, it is 39 light years or 230 tril­lion miles away. So are a group of seven mostly Earth-sized plan­ets in or near the hab­it­able zone found cir­cling a star called Trappist-1 ear­lier this year, but it in a dif­fer­ent di­rec­tion.

In Au­gust, as­tronomers found that the near­est planet to Earth out­side our so­lar sys­tem, only 25 tril­lion miles away, also could have the right tem­per­a­ture for life, but as­tronomers can’t get a peek at its at­mos­phere.

“If you pic­ture the Milky Way as the size of the United States, then these sys­tems are all within the size of Cen­tral Park,” Mr. Char­bon­neau said. “These are your neigh­bors.”

The lat­est dis­cov­er­ies have their founders at odds over which of the plan­ets are the most promis­ing. Mr. Char­bon­neau said stud­ies show that the Trappist plan­ets may not be rocky like Earth, while Trappist dis­cov­erer Michael Gil­lon said the new­est planet has such in­tense grav­ity that its at­mos­phere may be smooshed down so tele­scopes can’t get a good look at it.

Seven out­side as­tronomers said the Milky Way is big enough for all the dis­cov­er­ies to be ex­cit­ing, re­quir­ing more ex­plor­ing.


An artist’s ren­der­ing de­picts the newly dis­cov­ered ex­o­planet LHS 1140b, in the liq­uid wa­ter hab­it­able zone sur­round­ing its host star 39 light years away.

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