Identifying the Age of a Star

On a clear night, a star gazer can see thousands of stars with the naked eye. These stars range in level of brightness, size and distance away from Earth. These differences are all characteristics that can be measured and recorded, when studying different stars; there is one characteristic for stars that is not as simple to decipher though. A star’s age is very difficult to determine and has been a source of frustration for astronomers. For years, the only way that scientists could determine a star’s age was if the star was part of a cluster. All of the stars in a cluster are formed at the same time and by investigating brightness and color, scientists can determine the age of all the stars in that cluster. While this process is simple once a cluster is identified, the process of eliminating stars that are not actually a part of a particular cluster becomes quite time consuming. The worst part still is the fact that this method is completely useless when trying to identify the age of an individual star. Fortunately, a recent discovery by astronomer Soren Meibom may have helped to solve the seemingly impossible problem of determining a star’s age.

According to Meibom, a star’s age can be measured by the speed of its rotation. Just like the secret to telling a tree’s age is its rings, stars also have tell-tale signs of age and he argues that, “a star’s rotation slows down steadily with time, like a top spinning on a table, and can be used as a clock to determine its age.” The new technology of the Kepler space telescope has allowed for this discovery. The technique was first used by Meibom on a previously discovered cluster, NGC 6811. With the use of predetermined cluster ages, astronomers can then use rotation to discover a more accurate prediction of a star’s age. By using dark spots or the equivalent of sunspots, on the surface of stars as indicators, scientists can then monitor the time it takes for a star to complete a rotation. In this sense, the younger the star, the less time it will take to complete a rotation. It is the hope of astronomers that with enough research, a clear relationship between stellar rotation and age can be officially established which would allow for the official practice of deriving a star’s age from its rotation; a process that would be known as gyrochronology.

Finding the age of stars is very relevant to astronomers trying to find planets with similar, life-sustaining qualities as Earth. While astronomers have been working tirelessly to discover stars with orbiting planets, knowing the age of these stars would greatly help their efforts. It is understood by scientist that the older a star is, the longer the star and planet have had to develop. More developed planets are much more likely to have achieved life-sustaining properties than planets in infancy. By applying a more accurate understanding of a star’s ages, the workings and evolution of the new planetary system discovered by the Kepler telescope can be more easily understood. For this reason alone, the ability to determine a star’s age is an invaluable discovery.

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