Stellar Mid-Life Crisis

Context

• A team of astronomers from India and Nepal have detected that stars also go through a midlife crisis.
• During this time they experience dramatic breaks in their activity, rotational rates, transitioning into an inactive phase.
• The study provides a new technique to measure the age of stars past their middle age.

What happens when stars reach midlife?

• Spread over billions of years, the development leads to a decline in the numbers of sunspots, flares, outbursts, and similar phenomena in the atmospheres of stars.
• These developments are directly linked to the strength of their magnetic fields.
• Researchers using the dynamo models of magnetic field generation in stars found that at about the age of the Sun the magnetic field generation mechanism of stars suddenly becomes sub-critical or less efficient.
• The falling field generations lead to two activity states a low activity mode and an active mode.
• A middle-aged star like the Sun can often switch to the low activity mode resulting in drastically reduced angular momentum losses by magnetized stellar winds.

Significance of the study

• This hypothesis of sub-critical magnetic dynamos of solar-like stars provides a self-consistent, unifying physical basis for a diversity of solar-stellar phenomena, such as why stars beyond their midlife do not spin down as fast as in their youth, the breakdown of stellar gyrochronology relations et.
• The recent findings suggesting that the Sun maybe transitioning to a magnetically inactive future.
• It will also shed light on recent observations indicating that the Sun is comparatively inactive.

Do you know?

• The Sun is currently a main sequence star and will remain so for another 4-5 billion years.
• It will then expand and cool to become a red giant, after which it will shrink and heat up again to become a white dwarf.
• The white dwarf star will run out of nuclear fuel and slowly cool down over many billions of years.