Washington, Dec 22 (ANI): Some nearby stars are not so young as previously thought and may be more than twice as old, a new study has revealed.
New research by astrophysicists from the University of Rochester focused on stars in the north part of the constellation, known as Upper Scorpius, which is a part of the Scorpius-Centaurus OB association, one of the best studied groups of young stars and a benchmark sample for investigating the early lives of stars and the evolution of their planet-spawning disks.
The Upper Scorpius stellar group lies roughly 470 light years from Earth.
While those stars have been thought to be just five million years old, the team concludes that those stars are actually more than twice as old, at 11 million years of age.
The findings by graduate student Mark Pecaut and Assistant Professor Eric Mamajek of Rochester, and Assistant Professor Eric Bubar of Marymount University are surprising given Upper Scorpius's status as one of the best-studied samples of young stars in the sky.
The scientists came to their conclusions after analyzing hundreds of optical spectra measured with the SMARTS 1.5-meter telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile, as well as reanalyzing previously published data on the stars.
"We combined our new estimates for the temperatures of the stars based on our spectra, with data on the brightnesses and distances to estimate accurate luminosities," said Pecaut.
"Then we used state-of-the-art stellar evolution models to determine the ages."
While similar methods were used in the past to calculate ages for some of the Upper Scorpius stars, Pecaut said that no previous study has determined independent age estimates for members of the group over such a wide range of stellar masses.
The new analysis shows that stars over a wide range of masses in Upper Scorpius - from slightly more massive than our Sun, up to the mass of the bright star Antares (17 times the mass of our Sun) are giving ages consistent with a mean age of 11 million years.
"For one thing, the distances to the stars are now much more accurately known," said Pecaut.
"Also, the newer computer models take into account the rotation of the stars and its effect on the mixing on the star's hydrogen - its nuclear fuel source."
Pecaut said that with more accurate estimates of the ages of stars, scientists could better understand how long it takes planets to form. For example, if 11-million-year-old stars do not have gas accreting around them, it means that gas-rich planets like Jupiter and Saturn would have to form in less than 11 million years.
"If a stellar group as well-studied as Upper Scorpius can be twice as old as previously believed, then all bets are off on the accuracy of the previously published ages for other similar groups of young stars," said Mamajek.
The study has been published in the Astrophysical Journal. (ANI)
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