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Newfound star shouldn’t be, physicists say

Aug. 31, 2011
Courtesy of ESO
and World Science staff

As­tro­no­mers have found a star in our gal­axy that many thought could not ex­ist, as it’s made of el­e­ments too light to have come to­geth­er through gra­vity to form a star.

Anal­y­sis of the light rays ar­riv­ing from the star in­di­cate it con­sists al­most wholly of the two light­est el­e­ments, hy­dro­gen and he­li­um. The pro­por­tion of heav­i­er el­e­ments is es­ti­mat­ed as more than 20,000 times smaller than that of the Sun.

At the cen­ter of this pic­ture is an un­re­mark­a­be look­ing faint star, too faint to be seen through all but the larg­est am­a­teur tele­scopes. This star, in the con­stel­la­tion of Le­o (The Li­on), is called SDSS J102915+172927 and has been found to have the low­est amount of el­e­ments heav­i­er than he­li­um of all stars yet stud­ied. (Cred­it: ES­O/Dig­i­tized Sky Sur­vey 2)


The find­ings, made us­ing the Eu­ro­pe­an South­ern Ob­ser­va­to­ry’s Very Large Tel­e­scope in Chil­e, to are to ap­pear in the Sept. 1 is­sue of the jour­nal Na­ture. The star, dubbed SDSS J102915+172927, is de­scribed as faint, smaller than the Sun, very old and and found in the di­rec­tion of the con­stella­t­ion of Le­o or The Li­on. 

“We may have to re­vis­it some of the star forma­t­ion mod­els” ac­cept­ed by as­tro­no­mers, said Elis­a­betta Caf­fau of the the Uni­vers­ity of Hei­del­berg in Germany and the Par­is Ob­serv­a­to­ry, lead au­thor of the report.

Cos­mol­o­gists be­lieve hy­dro­gen and he­li­um formed shortly af­ter the Big Bang, an explosion-like event that cre­at­ed our uni­verse. Most oth­er el­e­ments were formed lat­er in stars. Dy­ing stars then spread that ma­te­ri­al around when they ex­plod­ed. New stars form from this en­riched ma­te­ri­al, so the pro­por­tion of these heav­i­er el­e­ments in a star tells us how old it is.

This log­ic in­di­cates that the new­found star “is very prim­i­tive. It could be one of the old­est stars ev­er found,” said Lo­ren­zo Mon­a­co of the Eu­ro­pe­an South­ern Ob­serv­a­to­ry in Chil­e, who was al­so in­volved in the stu­dy. But the re­search­ers say the star is probably not alone in its freak­ish­ness. “We have iden­ti­fied sev­eral more can­di­date stars” with si­m­i­lar com­po­si­tions, said Caf­fau, adding that fur­ther ob­serva­t­ions are planned.


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Astronomers have tracked down a star in our galaxy that many thought could not exist, as it’s made of elements too light to have come together through gravity to form a star. Analysis of the light rays arriving from the star indicate it consists almost wholly of the two lightest elements, hydrogen and helium. The proportion of heavier elements is is estimated as more than 20,000 times smaller than that of the Sun. The findings, made using the European Southern Observatory’s Very Large Telescope in Chile, to are to appear in the Sept. 1 issue of the journal Nature. The star, dubbed SDSS J102915+172927, is described as faint, smaller than the Sun, very old and and found in the direction of the constellation of Leo or The Lion. “We may have to revisit some of the star formation models” accepted by astronomers, said Elisabetta Caffau of the the University of Heidelberg in Germany and the Paris Observatory, lead author of the paper. Cosmologists believe hydrogen and helium formed shortly after the Big Bang, an explosion-like event that created our universe. Most other elements were formed later in stars. Dying stars then spread that material around when they exploded. New stars form from this enriched material, so the proportion of these heavier elements in a star tells us how old it is. This logic indicates that the newfound star “is very primitive. It could be one of the oldest stars ever found,” said Lorenzo Monaco of the European Southern Observatory in Chile, who was also involved in the study. But the researchers say the star is probably not alone in its freakishness. “We have identified several more candidate stars” with similar compositions, said Caffau, adding that further observations are planned.