Frequent Stellar Eruptions Could Lessen the Oxygen of Planets in Red Dwarf's Habitable Zone
A new study from NASA revealed that planets orbiting in the habitable zone of young red dwarfs might not actually support life due to the negative impact of high stellar activity to the their atmospheric oxygen.
The study, published in the Astrophysical Journal Letters, showed that the frequent stellar eruptions from a young red dwarf have the ability to lessen the oxygen in an exoplanet's atmosphere.
"When we look at young red dwarfs in our galaxy, we see they're much less luminous than our sun today," said Vladimir Airapetian, a solar scientist at NASA's Goddard Space Flight Center and lead author of the study, in a press release.
Airapetian explained tha the red dwarf's habitable zone is normally 10 to 20 times closer than Earth's distance from the Sun. Considering the close proximity, the ultraviolet and X-ray emission as well as the frequent solar flares from red dwarfs, the planet within the habitable zone could have less oxygen.
Despite being the coolest and smallest star in the universe, red dwarfs are prone to more frequent and powerful stellar eruptions compared to our sun. During stellar eruptions, a star chokes out a huge amount of stellar material and radiation.
Eventhough our sun also emits X-ray and has stellar eruptions, its capacity for ion escape is more minimal than in red dwarfs. Ion escape is a process where extreme ultraviolet and X-ray emissions ionize atmospheric gases and break down molecules into atoms. During this process, electrons -- which are not influenced by gravity because of its lightness -- are then released into space, where they attract positively charged ions.
The researchers noted that stellar activity in red dwarfs is much stronger and more frequent than our sun. They believe that violent storms produced by red dwarfs could generate enough high-energy radiation to facilitate the escape of oxygen and nitrogen.
As more electrons are produced by more powerful X-ray and ultraviolet energy, the effects of ion escape becomes stronger and more apparent. Taking into consideration the oxygen escape produced by the high stellar activity of the red dwarf, the researchers estimate that a close-in exoplanet could become uninhabitable within a few tens to a hundred million of years.
This means that the loss of atmospheric oxygen and hydrogen could eliminate the planet's water supply before life would have a chance to develop.