First generation of stars was massive and fast-spinning, scientists say | Science| In-depth reporting on science and technology | DW | 28.04.2011
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First generation of stars was massive and fast-spinning, scientists say

In a new paper, an international team showed that the first generation of stars in our universe consisted of substantial, rapidly-rotating stars. The scientists showed these stars' traces can still be found today.

Simulation of how the first stars with rotation emerged

Massive "spinstars" were able to create new chemicals

The first stars in our universe were massive and fast-spinning, according to results from an international team of astronomers led by Cristina Chiappini, at the Leibniz Institute for Astrophysics in Potsdam. The team's findings were published in the science journal Nature on Thursday.

The scientists found heavy elements in one of the oldest star clusters in the universe. This suggests that the first stars created after the Big Bang were fast-spinning ones - the so-called "spinstars".

"Fast-rotating massive stars can enrich the early universe with chemicals that were thought to be produced by low-mass stars only," Chiappini said, in an interview with Deutsche Welle.

"But the very old, low-mass stars we observed could not have been enriched by low mass-stars in the early universe because it takes to long for them to die. Low-mass stars can live for a very long time, most still live today."

Star cluster with some 4,000 billion stars

The universe was enriched with additional chemical elements over time

The scientists used data from the Very Large Telescope (VLT) in Chile and re-analyzed spectra of a group of very old stars in the Galactic Bulge, one of the oldest sections of the Milky Way galaxy.

These stars are so old that only very massive, short-living stars with masses larger than ten times the mass of the sun could have had the time to die and distribute the gas.

A look into the stars' past

"Since I can't observe the massive stars in the past - as they are dead, I have to observe the imprints left by them in the oldest stars still alive today," the astronomer said. "It's the only way to know about the nature of the first stellar generations in our universe."

The chemical composition of the stars showed typical elements of enrichment by massive stars, but also other elements such as strontium and yttrium that usually were thought to be generated by low-mass stars only.

"The massive fast rotating, first-generation stars could die fast, and produce strontium and yttrium," she added. "If a star spins fast, this can create a mixture between inner and outer nuclear-burning gas layers and can then create new chemical elements."

The gravitational force and pressure created in the spinning of a massive star makes it possible to create a new element.

Chiappini added that the fast rotating stars could also have led to an increase in gamma-ray explosions in the early universe. Fast rotation also affects a star's color, its lifetime and its luminosity. Therefore, the spinning stars probably influenced the appearance of the first galaxy.

Very Large Telescope in Chile

The team has requested more time on the Very Large Telescope in Chile

More data is needed

While the paper has sent ripples throughout the astronomy community, many are awaiting further data.

"It's an additional, interesting piece of the mosaic, but I wouldn't consider it a breakthrough," said Matthias Bartelmann, an astronomy professor at the University of Heidelberg.

"They looked at eight stars in one cluster only. You have to wait and see to what extent this has been an anomaly of the cluster."

Cristina Chiappini has already requested more time at the Very Large Telescope to examine additional stars to further bolster the group's findings.

Author: Sarah Steffen
Editor: Cyrus Farivar

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