New Delhi: Stars, in their childhoods flare up frequently, and shine in intense, energetic light, that have implications for any planets that they host. New research indicates that young Sun-like stars calm their intense X-ray output more rapidly than previously thought. This improves the prospects for life on any orbiting exoplanets. The research is based on observations by NASA’s Chandra X-ray observatory. Astronomers observed eight star clusters aged between 45 million and 750 million years. Stars with masses similar to the Sun in these clusters emitted only a quarter to a third of the expected X-ray emissions.
Stars about three million years old, containing about as much mass as the Sun produce about 1,000 times more X-rays than the present-day Sun, while 100 million year old equivalents are about 40 times brighter. The new data indicates that stars in similar mass to the Sun quieten after a few hundred million years, whereas lower-mass stars, that are far more common, maintain high X-ray levels for far longer. The rapid decline occurs because the magnetic field generation of the stars become less efficient as they age, causing X-ray activity to drop about 15 times faster than models had predicted. This natural dimming benefits the potential for life.
Influence on Planetary Habitability
Intense X-rays can strip away the atmospheres of planets and hinder the formation of organic molecules, that include carbon, oxygen and hydrogen. The reduced output, combined with lower X-ray energies and the disappearance of energetic particles streaming out of the newborn star allows for the development of more robust atmospheres. The Sun would have followed a similar evolutionary path in its infancy, about 4.6 billion years ago. The research fills a gap in the conventional understanding of the evolution, or stellar life cycles of solar mass stars. A paper describing the research has been published in The Astrophysical Journal.