Stars may not be as old as thought



    It was believed that the oldest stars in the galaxy were 18 billion years old, but recent studies by a BYU professor show the oldest stars may be a lot younger.

    “They are more youthful, if you can call 13 billion years youthful,” said D.H. McNamara, professor of physics and astronomy.

    McNamara said he was interested in stars and decided to conduct the study. “I’ve been working on these stars for a long time,” he said.

    He produced his findings using his own data and the data generated from the Hipparcos satellite.

    Globular clusters are groups of approximately 100,000 stars and contain the oldest stars. The clusters also containRR Lyrae stars, which are a group of stars that vary in light.

    “We are using RR Lyrae stars to estimate their ages,” McNamara said.

    The luminosity of the RR Lyrae stars was determined through two techniques. The first technique was to improve the star’s temperature. These findings showed the stars to be 250 degrees hotter, which makes them a little brighter, McNamara said.

    The second technique was the study of another group of stars found in globular clusters, which are less bright. The intrinsic brightness of these stars has been determined by new satellite data, which helped to determine the absolute brightness of the RR Lyrae stars.

    The two methods are in agreement, which indicates that the stars are more luminous, McNamara said. Increased luminosity means the point at which the stars have exhausted their hydrogen supply, or the turn off point, is higher and therefore brighter than previously believed.

    “The stars burn their hydrogen supply faster than before thought and that makes them younger,” he said. Because they are younger, these stars are also a little bit brighter.

    The main goal of the study was to find a relationship between a star’s brightness and its heavy elements, McNamara said. The studies show the stars that are most deficient in heavy elements are intrinsically brighter.

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