Stellar mid-life crisis

Stellar mid-life crisis

Subject: Science and Technology

Context: IISER scientist’s study peeks into Sun’s ‘stellar midlife crisis’ The Sun and other stars constantly spew electrically-charged particles also called the stellar wind. This steady drain causes stars to slow down their rotation over billions of years.

• Calcutta scientists have proposed an explanation for a mysterious phenomenon called the stellar midlife crisis under which the Sun and many other stars display abrupt, dramatic declines in their output of high energy particles and radiation.
• At about 4.6 billion years of age, the sun is middle aged, that is, it will continue to live for roughly the same period. There are accurate methods for estimating the age of the Sun, such as by using radioactive dating of very old meteorites that have fallen on the Earth.
• However, for more distant stars which are similar in mass and age to the Sun, such methods are not possible. One of the methods used is called ‘stellar gyrochronology’. There is a relationship between rotation rate and age, that is the rotation rate of a star slows down with age.
• Recent observations, however, indicate that this intimate relationship breaks down around middle age because after midlife, a star’s rate of spin does not slow down with age as fast as it was slowing down earlier.
• This allows stars to exist in two distinct activity states – low activity mode and active mode. A middle-aged star like the sun can often switch to low activity mode resulting in drastically reduced angular momentum losses by magnetised stellar winds.