Supersurvey of Milky Way's Stars Exposes Galaxy's Turbulent Past

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Observations from more than 1,000 starry nights are helping scientists to better understand the galaxy we inhabit. A team of European astronomers has analyzed 15 years' worth of Milky Way data in a report published today in the Astronomy and Astrophysics Journal. The findings, which catalogue the movements of more than 14,000 sunlike stars, indicate that our galaxy has a more chaotic past than was previously believed.

Scientists led by Birgitta Nordstr¿m of the Niels Bohr Institute in Copenhagen compiled a three-dimensional animated map of our solar neighborhood from data collected by telescopes in Chile, France and the U.S. "For the first time we have a complete set of observed stars that is a fair representation of the stellar population in the Milky Way disk in general," Nordstr¿m explains. "It is large enough for a proper statistical analysis and also has complete velocity and binary star information." The new census is based on 63,000 precise observations of thousands of so-called F and G dwarf stars and includes their locations, ages, chemical constitutions, velocities and orbits.

With the velocity information in hand, astronomers can now compute how the stars may have moved in the galaxy in the past and where they might travel in the future. The team determined that older stars tend to have the highest speeds in our solar neighborhood and that many of the stars closest to us are actually just passing through from places much farther afield. "Galaxy models have long assumed that the Milky Way disk near the sun evolved quietly and essentially in isolation," Nordstr¿m says, "but now we see that its entire life has been rather turbulent. Our new results will lead to much more realistic models of how our home galaxy formed and evolved."

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