Space

A better model for star aging

A better model for star aging
With current methods, it's much easier to determine the ages of stars in clusters, such as NGC 1783, as pictured here by the Hubble Space Telescope
With current methods, it's much easier to determine the ages of stars in clusters, such as NGC 1783, as pictured here by the Hubble Space Telescope
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With current methods, it's much easier to determine the ages of stars in clusters, such as NGC 1783, as pictured here by the Hubble Space Telescope
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With current methods, it's much easier to determine the ages of stars in clusters, such as NGC 1783, as pictured here by the Hubble Space Telescope

Working out the age of any given star in the night sky can be a very difficulttask, and estimates are easier to make based on readings fromgroups rather than individual objects. A new model mightsignificantly improve the situation, providing a conceptual frameworkto explain the rotation of stars, the intensity of their stellarwinds and their X-ray emissions, arriving at a much more accurateestimate of age.

With current models, determiningstellar age can be difficult. Astronomers have an easier time workingout the age of stars residing within clusters, using mutualproperties to obtain enough data to make an estimate, but thosefigures can be rather inaccurate, with a margin of error up to 25percent – often equal to billions of years.

Working out the age of a star that'snot in a cluster is even more difficult. There's less data to go on,so astronomers calculate the age based on known factors, such as thefact that older stars spin more slowly, or have lower X-rayluminosities. A team from the University of Rochester believed that it could improve the situation, creating a much moreadvanced system that brings together observable data and astrophysicstheory.

The new model is designed to bring datatogether, working out how rotation, magnetic fields, X-ray activityand loss of mass are linked and affect one another. Most previousapproaches have only looked at these factors individually or inpairs, but by looking at the complete problem, the new model can, theresearchers believe, much more accurately determine stellar age.

Specifically, the model is designed toanalyze stars with a similar mass and radius to our own Sun, whichwas used as a calibration point during development. The model isstill a work in progress, but it's already revealing importantinformation about Sun-like stars.

"Our model shows that stars youngerthan our Sun can vary quite significantly in the intensity of theirX-ray emission and mass loss," said lead author Eric Blackman. "Butthere is a convergence in the activity of the stars after a certainage, so you could say that our Sun is very typical for stars of itsmass, radius, and its age. They get more predictable as they age."

The findings of the work are publishedonline in the Monthly Notices of the Royal Astronomical Society.

Source: University of Rochester

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