Astronomers routinely provide the ages of the stars they study. But the methods of measuring ages aren’t 100% accurate. Measuring the ages of distant stars is a difficult task.
The Nancy Grace Roman Space Telescope should make some progress.
Stars like our Sun settle into their main sequence lives of fusion and change very little for billions of years. It’s like watching middle-aged adults go about their business during their working lives. They get up, drive to work, sit at a desk, then drive home.
But what can change over time is their rotation rate. The Sun now rotates about once a month. When it was first formed, it rotated more rapidly.
But over time, the Sun’s rotation rate, and the rotation rate of stars the same mass or lower than the Sun’s, will slow down. The slowdown is caused by interactions between the star’s magnetic fields and the stellar wind, the stream of high-energy protons and electrons emitted by stars. Over time, these interactions reduce a star’s angular momentum, and its rotation slows. The phenomenon is called “magnetic braking,” and it depends on the strength of a star’s magnetic fields.
