- Young Sun-like stars dim in X-rays faster than previously thought, study finds
- Stars emit 25-33% of expected X-rays after a few hundred million years
- Decline in X-rays may help preserve planetary atmospheres and support life
A new study has revealed an important change in how young stars behave, offering fresh clues about the chances of life beyond Earth. Scientists have found that stars similar to our Sun become quieter and dim faster in X-rays than earlier believed. The findings come from observations made using NASA's Chandra X-ray Observatory, with the research published in The Astrophysical Journal on Monday, reported NASA.
According to NASA, unlike the scenario shown in the film Project Hail Mary, where stellar dimming is linked to a threat, scientists say this natural quieting of young stars could actually support the development of life on nearby planets.
Astronomers have sought to understand how intense radiation, especially the dangerous X-rays emitted by young stars, affects planets around them. Until now, it was unclear how long these high-energy rays persist. The new study analysed eight stellar clusters, ranging from 45 million to 750 million years old, and revealed that Sun-like stars are emitting only a quarter to a third of the expected X-rays.
Konstantin Getman of Penn State University said that while science fiction often portrays alien life as dimming a star's energy, observations suggest that young Sun-like stars are themselves dimming in X-rays. He explained that this is not due to any external factor, but rather because the process of generating magnetic fields within them is becoming less effective.
According to scientists, this slowing down could be beneficial for planets orbiting such stars. Strong X-rays can destroy planetary atmospheres and hinder the formation of molecules essential for life. Young stars, especially those about 3 million years old, emit about a thousand times more X-rays than the Sun today, while even stars as young as 100 million years old are about 40 times more luminous in X-rays.
Vladimir Airapetian of NASA's Goddard Space Flight Center said that the existence of human life may be linked to the fact that the Sun underwent a similar gradual cooling process billions of years ago. He said that this actual change may seem speculative, but it is even more interesting because it provides a glimpse into our Sun's true history.
The study also revealed that stars with a mass comparable to the Sun cool down rapidly within a few hundred million years, while stars with lower masses remain active for longer. As X-ray energy decreases and energetic particles decrease, Sun-like stars may become more favorable for planets with stable atmospheres and potentially life.
The research team used additional data from the European Space Agency's Gaia satellite and ROSAT mission to identify stars in stellar clusters and measure their X-ray emissions. The new observations were combined with older data to study clusters of different ages.
Previously, scientists had limited information about stars in this age group and relied on models that estimated X-ray emissions based on age and rotation. However, the team found that X-ray emissions during this stage decline about 15 times faster than previously estimated.
Eric Feigelson of Penn State University said that scientists can only observe the Sun in the present, so studying similar stars of different ages helps understand its past.
Researchers believe this rapid decline may be linked to the diminishing efficiency of the process of magnetic field formation in stars, although further research is ongoing. The Chandra program is operated by NASA's Marshall Space Flight Center, while its scientific work is handled by the Smithsonian Astrophysical Observatory.
