Researchers Recalibrate Decade-old Method to Measure the Age of Stars


A team of researchers spotted a major flaw in gyrochronology, a method to measure stellar age by looking at the star’s spin rate.

A group of scientists at the Carnegie Mellon University in Pittsburgh, PA, found that there was an error in how scientists calculated the age of stars that are older than our star. After they recalibrated the theory they found that the Sun’s magnetic field may see some critical changes sooner than expected.

A recently developed technique to tell how old a star really is is by looking at its spin rate. The slower a star revolves around its own axis the older that star is, scientists believe.

Scientists explained that as a star grows older its magnetic field acts as a brake because it attracts more gas from the star’s outer layers, ejects it, and influences the stellar angular momentum.

Over the last decade, based on data on a star’s mass and spin rate, scientists have calculated the age of thousands of stars. The relatively freshly-developed method was dubbed gyrochronology.

But the Carnegie team believes that the theory may be outdated since stars do not slow down as previously calculated as they age. If the theory is flawed, the age of many older stars may be miscalculated.

Before gyrochronology was developed, astronomers estimated stellar age based on their surface temperature and brightness. But because changes in brightness and temperatures are very subtle and need a lot of time to occur, the method was prone to erroneous results.

Others methods look at the sound waves within a star’s interior to estimate its age. But the techniques require very bright stars and expensive technology, so they have some limitations.

As a result,  since looking at the spin rate was a more convenient method, it has been widely used in recent years. Scientists now plan to recalibrate the theory and turn it into a fail-proof method to measure the ages of many aging stars.

Carnegie scientists found that the influence of the magnetic field on the star’s rotation rate is weaker than previously estimated. If the new theory is correct, our star could be on the verge to see its magnetic field’s breaking power lose strength. Scientists do not know yet how long it would take, but they are currently working on it.

Nevertheless, they noted that gyrochronology is more accurate for young stars and it should not be anymore applied to objects that are more than halfway through their life span.
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