Changes

Knowing the age of the host star of a [[planetary system]] helps astronomers understand how planetary systems change over time.  

Knowing the age of the host star of a [[planetary system]] helps astronomers understand how planetary systems change over time.  

The research shows that the rotation period of a star changes steadily and predictably in line with its age and color. Thus, by measuring two of these attributes you can determine the third. The star’s color is a visible sign of its [[mass]] or surface temperature. The age of the [[Sun]] is known (4.6 billion years) and can be used to calibrate the gyrochronology of most other stars.

The research shows that the rotation period of a star changes steadily and predictably in line with its age and color. Thus, by measuring two of these attributes you can determine the third. The star’s color is a visible sign of its [[mass]] or surface temperature. The age of the [[Sun]] is known (4.6 billion years<ref>http://cosmos.phy.tufts.edu/~zirbel/ast21/handouts/Energy-of-Sun-better.PDF</ref>) and can be used to calibrate the gyrochronology of most other stars.

There are other methods of working out a star’s age, but they have much larger uncertainties than gyrochronology. Unlike some other methods, gyrochronology also works well for stars not found in star clusters (‘field’ stars). It is used to calculate the age of stars that burn their hydrogen fuel at a predictable and steady rate; it does not work so well for younger stars, although the researchers hope to do future work to extend the method to these.

There are other methods of working out a star’s age, but they have much larger uncertainties than gyrochronology. Unlike some other methods, gyrochronology also works well for stars not found in star clusters (‘field’ stars). It is used to calculate the age of stars that burn their hydrogen fuel at a predictable and steady rate; it does not work so well for younger stars, although the researchers hope to do future work to extend the method to these.