"Long before it's in the papers"
January 27, 2015

RETURN TO THE WORLD SCIENCE HOME PAGE


Blast lights up invisible galaxy from “dark ages”

Aug. 6, 2013
Courtesy of the Har­vard-Smith­son­ian 
Cen­ter for As­t­ro­phys­ics
and World Science staff

More than 12 bil­lion years ago a star ex­plod­ed, rip­ping it­self apart and blast­ing its re­mains out­ward in twin jets at nearly the speed of light. At its death it glowed so brightly that it out­shone its en­tire gal­axy by a mil­lion times. This bril­liant flash trav­eled across space for 12.7 bil­lion years to a plan­et that had­n’t even ex­isted at the time of the ex­plo­sion—our Earth. 

By an­a­lyz­ing this light, as­tro­no­mers learn­ed about a gal­axy that was oth­er­wise too small, faint and far away for even the Hub­ble Space Tel­e­scope to see.

This artist's il­lus­tra­tion de­picts a gamma-ray burst il­lu­mi­nati clouds of in­ter­stel­lar gas in its host gal­axy. By an­a­lyz­ing a re­cent gamma-ray burst, as­tro­no­mers were able to learn about the chem­is­try of a gal­axy 12.7 bil­lion light-years from Earth. They found it con­tains on­ly one-tenth of the heavy el­e­ments (met­als) found in our so­lar sys­tem. (Cred­it: Gem­i­ni Ob­ser­va­to­ry, art­work by Lyn­ette Cook )


“This star lived at a very in­ter­est­ing time, the so-called dark ages just a bil­lion years af­ter the Big Bang,” said Ryan Chornock of the Har­vard-Smith­son­ian Cen­ter for As­t­ro­phys­ics in Cam­bridge, Mass., lead au­thor of a re­port on the find­ings. The Big Bang is an ex­plos­ive event be­lieved to have created the uni­verse itself.

“In a sense, we’re fo­ren­sic sci­en­tists in­ves­ti­gat­ing the death of a star and the life of a gal­axy in the ear­li­est phases of cos­mic time,” he added.

The star an­nounced its death with a flash of gam­ma rays, an event known as a gam­ma-ray burst. This one was clas­si­fied as a “long” burst since lasted for more than four min­utes. NASA’s Swift space­craft de­tected it on June 6. Chornock and his team quickly or­gan­ized fol­low-up ob­serva­t­ions by the MMT Tel­e­scope in Ar­i­zo­na and the Gem­i­ni North tel­e­scope in Ha­waii.

“We were able to get right on tar­get in a mat­ter of hours,” Chornock said. “That speed was cru­cial in de­tect­ing and stu­dy­ing the af­terglow.”

A gam­ma-ray burst af­terglow oc­curs when jets from the burst slam in­to sur­round­ing gas, sweep­ing that ma­te­ri­al up like a snow­plow, heat­ing it, and caus­ing it to glow, as­tro­no­mers say. As the af­terglow’s light trav­els through the dead star’s host gal­axy, it passes through clouds of gas. Chem­i­cal el­e­ments with­in those clouds ab­sorb light at cer­tain wave­lengths, or col­ors, leav­ing “fin­ger­prints.” By split­ting the light in­to a rain­bow spec­trum, as­tro­no­mers can study those fin­ger­prints and learn what gas­es the dis­tant gal­axy con­tained.

All chem­i­cal el­e­ments heav­i­er than hy­dro­gen, he­li­um, and lith­i­um are cre­at­ed by stars, ac­cord­ing to as­tro­no­mers. As a re­sult those heavy el­e­ments, which as­tro­no­mers col­lec­tively call “met­als,” took time to ac­cu­mu­late. Life could not have ex­isted in the early uni­verse be­cause the el­e­ments of life, in­clud­ing car­bon and ox­y­gen, did not ex­ist.

Chornock and his col­leagues found that their gal­axy con­tained only about one-tenth of the “met­als” in our so­lar sys­tem. The­o­ry sug­gests that al­though rocky plan­ets might have been able to form, life probably could not thrive yet. “The uni­verse was still get­ting ready for life. It did­n’t have life yet, but was build­ing the re­quired el­e­ments,” said Chornock.

At a dis­tance of 12.7 bil­lion light-years, the burst, dubbed GRB 130606A, is one of the most dis­tant gam­ma-ray bursts ev­er found. A light-year is the dis­tance light trav­els in a year. “In the fu­ture we will be able to find and ex­ploit even more dis­tant [gam­ma-ray bursts] with the planned Gi­ant Ma­gel­lan Tel­e­scope,” said Edo Berger of the cen­ter, a co-au­thor on the pub­lica­t­ion.

The team’s re­sults are to be pub­lished in the Sept. 1 is­sue of The As­t­ro­phys­i­cal Jour­nal and are availa­ble on­line.


* * *

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

Sign up for
e-newsletter
   
 
subscribe
 
cancel

On Home Page         

LATEST

  • St­ar found to have lit­tle plan­ets over twice as old as our own

  • “Kind­ness curricu­lum” may bo­ost suc­cess in pre­schoolers

EXCLUSIVES

  • Smart­er mice with a “hum­anized” gene?

  • 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?

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

More than 12 billion years ago a star exploded, ripping itself apart and blasting its remains outward in twin jets at nearly the speed of light. At its death it glowed so brightly that it outshone its entire galaxy by a million times. This brilliant flash traveled across space for 12.7 billion years to a planet that hadn’t even existed at the time of the explosion—our Earth. By analyzing this light, astronomers learned about a galaxy that was otherwise too small, faint and far away for even the Hubble Space Telescope to see. “This star lived at a very interesting time, the so-called dark ages just a billion years after the Big Bang,” said lead author Ryan Chornock of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “In a sense, we’re forensic scientists investigating the death of a star and the life of a galaxy in the earliest phases of cosmic time,” he added. The star announced its death with a flash of gamma rays, an event known as a gamma-ray burst. GRB 130606A was classified as a “long” burst since lasted for more than four minutes. NASA’s Swift spacecraft detected it on June 6. Chornock and his team quickly organized follow-up observations by the MMT Telescope in Arizona and the Gemini North telescope in Hawaii. “We were able to get right on target in a matter of hours,” Chornock said. “That speed was crucial in detecting and studying the afterglow.” A gamma-ray burst afterglow occurs when jets from the burst slam into surrounding gas, sweeping that material up like a snowplow, heating it, and causing it to glow, astronomers say. As the afterglow’s light travels through the dead star’s host galaxy, it passes through clouds of gas. Chemical elements within those clouds absorb light at certain wavelengths, or colors, leaving “fingerprints.” By splitting the light into a rainbow spectrum, astronomers can study those fingerprints and learn what gases the distant galaxy contained. All chemical elements heavier than hydrogen, helium, and lithium are created by stars, according to astronomers. As a result those heavy elements, which astronomers collectively call “metals,” took time to accumulate. Life could not have existed in the early universe because the elements of life, including carbon and oxygen, did not exist. Chornock and his colleagues found that their galaxy contained only about one-tenth of the metals in our solar system. Theory suggests that although rocky planets might have been able to form, life probably could not thrive yet. “At the time this star died, the universe was still getting ready for life. It didn’t have life yet, but was building the required elements,” said Chornock. At a distance of 12.7 billion light-years, GRB 130606A is one of the most distant gamma-ray bursts ever found. A light-year is the distance light travels in a year. “In the future we will be able to find and exploit even more distant [gamma-ray bursts] with the planned Giant Magellan Telescope,” said Edo Berger of the center, a co-author on the publication. The team’s results are to be published in the Sept. 1 issue of The Astrophysical Journal and are available online.