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Thank Your Dusty Stars For Our Existence

We owe ourexistence to a star that exploded long, long ago.

That's theconclusion of a study that aimed to solve the mystery of why oursolar system is enriched in a rare form of oxygen.

The study suggeststhat the sun and the material for what became the eight major planets formed inthe vicinity of one or more supernovasand were enriched in the matter that stellar explosions left behind, includingthat strange type of oxygen.

Astronomerscan probe the galaxy for signatures of different elements and their isotopes(atoms that have the same number of protons, but a different number ofneutrons) to see how they vary from region to region. They have long known thatthe solar system has a peculiarly high ratio of the two rarest forms of oxygen,but haven't known exactly why.

"Thishas been a problem for a long time," said study author Edward Young ofUCLA, who announced the finding Thursday at the 215th meeting of the AmericanAstronomical Society in Washington, D.C.

Someresearchers initially thought the discrepancy between the ratio of those oxygenisotopes seen in the solar system and those elsewhere in the galaxy was amatter of measurement error. Another possibility was that while values for thesolar system came from the observations of one star - the sun - those for otherparts of the galaxy came from stars across large swaths of theMilky Way.

Nowscientists have been able to determine the oxygen isotope ratios for individualstar systems elsewhere in the galaxy, and the new measurements matched up withprevious ones.

"Theyconfirm that the solar system is indeed unusual," Young said. It"sticks out like a sore thumb above the rest."

Sosomething must have enriched the neighborhood where the solar system formedwith these rare types of oxygen.

"Andin this case I think it's supernovae that are the culprit," Young said.

To get thevalues of oxygen isotopes that exist in the solar system, you would have to mixthe material from the small supernova of an early star with the normal galacticbackground material, Young said.

Knowingwhat kind of environment our solarsystem formed in tells us more about how our solar system compares to otherplanetary systems in the galaxy.

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