"Long before it's in the papers"
June 01, 2013

RETURN TO THE WORLD SCIENCE HOME PAGE


“Boom times” in star birth gone, never to return, study suggests

Nov. 8, 2012
Courtesy of the Royal Astronomical Society
and World Science staff

While parts of the world suffer eco­nom­ic hard­ship, as­tro­no­mers have found an even big­ger slump un­der way on a cos­mic scale: forma­t­ion of new stars has crashed, per­haps per­ma­nent­ly.

“You might say that the uni­verse has been suf­fer­ing from a long, se­ri­ous ‘cri­sis:’ cos­mic GDP out­put is now only 3 per­cent of what it used to be at the peak in star pro­duc­tion!” said Da­vid So­bral of the Uni­vers­ity of Lei­den in the Neth­er­lands.

This di­a­gram in­di­cates the chang­ing ‘GDP’ of the Uni­verse over time. The new re­sults in­di­cate that, meas­ured by mass, the pro­duc­tion rate of stars has dropped by 97 per­cent since its peak 11 bil­lion years ago. (Cred­it: D. So­bral)


“If the meas­ured de­cline con­tin­ues, then no more than 5 per­cent more stars will form over the re­main­ing his­to­ry of the cos­mos, even if we wait for­ev­er. The re­search sug­gests that we live in a uni­verse dom­i­nat­ed by old stars.”

In the larg­est ev­er study of its kind, the in­terna­t­ional team of as­tro­no­mers has con­clud­ed that the rate of forma­t­ion of new stars in the Uni­verse is now only 1/30th of its peak. The group, led by So­bral, is re­port­ing its re­sults in the jour­nal Monthly No­tices of the Roy­al As­tro­nom­i­cal So­ci­e­ty.

The most ac­cept­ed mod­el for the ev­o­lu­tion of the Uni­verse pre­dicts that stars be­gan to form about 13.4 bil­lion years ago, or around 300 mil­lion years af­ter the its birth. Many of these first stars are thought to have been mon­sters by to­day’s stan­dards, and were probably hun­dreds of times more mas­sive than our Sun. Such beasts would have aged very quick­ly, ex­hausted their fu­el, and ex­plod­ed with­in a mil­lion years or so. Light­er stars in con­trast live much long­er, for bil­lions of years.

Much of the dust and gas from stel­lar ex­plo­sions was (and is still) re­cy­cled to form newer genera­t­ions of stars, as­tro­no­mers say. Our Sun, for ex­am­ple, is thought to be a third genera­t­ion star, and has a typ­i­cal mass, or weight, by to­day’s stan­dards. But re­gard­less of their prop­er­ties, stars are key in­gre­di­ents of ga­lax­ies like our own Milky Way. Sci­en­tists say un­veil­ing the his­to­ry of star forma­t­ion is fun­da­men­tal to un­der­stand­ing how ga­lax­ies form and evolve.

In the stu­dy, as­tro­no­mers used the U.K. In­fra­red Tel­e­scope, the Very Large Tel­e­scope and the Sub­aru tel­e­scope to car­ry out what they called the most com­plete sur­vey ev­er made of star-form­ing ga­lax­ies at dif­fer­ent dis­tances, with around ten times the da­ta of any pre­vi­ous ef­fort. With the range of dis­tances, the time tak­en for the light to reach us means that we see iden­tic­ally se­lected ga­lax­ies at dif­fer­ent pe­ri­ods in the his­to­ry of the uni­verse, they said, so we can really un­der­stand how con­di­tions change over time.

By look­ing at the light from clouds of gas and dust in these ga­lax­ies where stars are form­ing, the team es­ti­mat­ed the rate at which stars are be­ing born. They found that the pro­duc­tion of stars has been con­tin­u­ously de­clin­ing over the last 11 bil­lion years, be­ing 30 times low­er to­day than at its likely peak, 11 bil­lion years ago.

“Half of these were born in the ‘boom’ that took place be­tween 11 and 9 bil­lion years ago and it took more than five times as long to pro­duce the rest,” So­bral said. “The fu­ture may seem rath­er dark, but we’re ac­tu­ally quite lucky to be liv­ing in a healthy, star-form­ing gal­axy which is go­ing to be a strong con­trib­u­tor to the new stars that will form.

“Moreo­ver, while these mea­sure­ments pro­vide a sharp pic­ture of the de­cline of star-forma­t­ion in the Uni­verse, they al­so pro­vide ide­al sam­ples to un­veil an even more fun­da­men­tal mys­tery which is yet to be solved: why?”


* * *

Send us a comment on this story, or send it to a friend









 

Sign up for
e-newsletter
   
 
subscribe
 
cancel

On Home Page         

LATEST

  • Pov­erty re­duction, environ­mental safe­guards go hand in hand: UN re­port

  • Astro­nomers hope to find al­ien civiliza­tions through heat

EXCLUSIVES

  • Was black­mail essen­tial for marr­iage to evolve?

  • Plu­to has even cold­er “twin” of sim­ilar size, studies find

  • Could simple an­ger have taught people to coop­erate?

  • Diff­erent cul­tures’ mu­sic matches their spe­ech styles, study finds

MORE NEWS

  • F­rog said to de­scribe its home through song

  • Even r­ats will lend a help­ing paw: study

  • D­rug may undo aging-assoc­iated brain changes in ani­mals

While parts of the world undergo economic hardship, astronomers have found an even bigger slump happening on a cosmic scale: formation of new stars has crashed, perhaps permanently. “You might say that the universe has been suffering from a long, serious ‘crisis:’ cosmic GDP output is now only 3% of what it used to be at the peak in star production!” said David Sobral of the University of Leiden in the Netherlands. “If the measured decline continues, then no more than 5% more stars will form over the remaining history of the cosmos, even if we wait forever. The research suggests that we live in a universe dominated by old stars.” In the largest ever study of its kind, the international team of astronomers has concluded that the rate of formation of new stars in the Universe is now only 1/30th of its peak. The group, led by Sobral, is reporting its results in the journal Monthly Notices of the Royal Astronomical Society. The most accepted model for the evolution of the Universe predicts that stars began to form about 13.4 billion years ago, or around three hundred million years after the Big Bang. Many of these first stars are thought to have been monsters by today’s standards, and were probably hundreds of times more massive than our Sun. Such beasts would have aged very quickly, exhausted their fuel, and exploded within a million years or so. Lighter stars in contrast live much longer, for billions of years. Much of the dust and gas from stellar explosions was (and is still) recycled to form newer and newer generations of stars, astronomers say. Our Sun, for example, is thought to be a third generation star, and has a typical mass, or weight, by today’s standards. But regardless of their properties, stars are key ingredients of galaxies like our own Milky Way. Scientists say unveiling the history of star formation is fundamental to understanding how galaxies form and evolve. In the study, astronomers used the U.K. Infrared Telescope, the Very Large Telescope and the Subaru telescope to carry out what they called the most complete survey ever made of star-forming galaxies at different distances, with around ten times the data of any previous effort. With the range of distances, the time taken for the light to reach us means that we see identically selected galaxies at different periods in the history of the universe, they said, so we can really understand how conditions change over time. By looking at the light from clouds of gas and dust in these galaxies where stars are forming, the team estimated the rate at which stars are being born. They found that the production of stars in the universe as a whole has been continuously declining over the last 11 billion years, being 30 times lower today than at its likely peak, 11 billion years ago. “Half of these were born in the ‘boom’ that took place between 11 and 9 billion years ago and it took more than five times as long to produce the rest,” Sobral said. “The future may seem rather dark, but we’re actually quite lucky to be living in a healthy, star-forming galaxy which is going to be a strong contributor to the new stars that will form. ‘Moreover, while these measurements provide a sharp picture of the decline of star-formation in the Universe, they also provide ideal samples to unveil an even more fundamental mystery which is yet to be solved: why?”