Old Star Sheds Light on Early Universe

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Old star sheds light on early universe

Lowest-metal star is a cosmic relic near our galaxy’s center

By Rick Callahan

ASSOCIATED PRESS

Oct. 30 — Astronomers have discovered an ancient star near the center of our galaxy that may shed light on the universe’s composition shortly after it was blasted into existence by the Big Bang.

THIS COSMIC RELIC is thought to be more than 12 billion years old — meaning it came into being about a billion years after the Big Bang. The star has an extremely low metal content, some 1/200,000th of that found in our sun. That is 20 times less metal than the previous lowest-metal star, found in 1977.

The star’s age and composition place it among the second wave of stars that formed after the universe’s violent creation, its discoverers said. Researchers had predicted this type of ultra-low metal star 25 years ago, but an example eluded them until now.

Michael S. Bessell, an astronomers at Australia’s Mount Stromlo Observatory, said the newly discovered star arose from the debris of a first-generation star, so it contains only a very small amount of heavy elements.

“This really traces things back to the very early stages of the universe because stars are records of that time. This is an indicator of those times,†said Bessell, the star’s co-discoverer.

MILKY WAY’S CENTER

The star is described in Thursday’s issue of the journal Nature.

Dubbed HE0107-5240, it is located 36,000 light-years from Earth, near the center of the Milky Way, and is about four-fifths the size of our sun. It is located in the constellation Pisces but is too dim to be seen with the naked eye.

Scientists believe that after the Big Bang, the universe was composed only of hydrogen, helium and a trace of lithium — the lightest elements — and that the other naturally occurring elements were forged inside stars, which are essentially gigantic nuclear furnaces.

The first generation of stars that formed from the gas and dust cast outward by the explosion were massive, fast-burning and short-lived. When they exploded as supernovae they began tainting the universe with the first doses of heavier elements, which astronomers call metals. This debris formed stars like HE0107-5240, scientists said.

DECADES-LONG QUEST

The star’s discovery is exciting for astronomers, who had grown frustrated after decades of searching, said Volker Bromm of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Bromm, who was not involved in the research, said this star and others that may yet be found could yield clues to the evolution of star formation.

“It’s clear that these very first stars were very different from present-day stars. The question is, when and how did the transition in the way of forming stars take place between these first stars that predominantly formed and massive stars to the more normal mode ... in our Milky Way?†he said.

George W. Preston, an astronomer and retired director of the Carnegie Observatories in Pasadena, Calif., said the next step will be finding more members of what he jokingly called “The Class of 13 Billion B.C.â€

“Finding this star confirms in a general way one of the expectations of the Big Bang theory, but finding one is hardly useful for making far-reaching conclusions,†he said.

Bessell said the nine-member team that took part in the research found it after reviewing some of 8,000 stars they had culled from hundreds of thousands of candidates. So far, they are only a quarter of the way through that list.