Obervations made by Kepler suggested that Earth-like planets are abundant in the universe, which raises questions about the possibility that they might harbor extraterrestrial life.
However, a new study found that young stars can destroy the atmosphere of habitable exoplanets, creating another obstacle for life to form outside of the solar system.
An Active Young Star Can Destroy Earth-Like Atmosphere
Researchers from the University of Vienna and the Space Research Institute at the Austrian Academy of Sciences investigated for the first time how rapidly an atmosphere of an Earth-like exoplanet will disappear from the activities of a very young star it orbits. They found that it will only take less than a million years for extreme hydrodynamic losses of the atmosphere to take place.
Their findings are scheduled to appear in the journal Astronomy & Astrophysics Letters.
Potential For Extraterrestrial Life
The researchers explained that the discovery would have serious implications to an exoplanet's potential to harbor extraterrestrial life of any form, especially if the exoplanet is orbiting M-dwarf stars.
Recent efforts focused on exoplanets in orbit around M-dwarf stars, which are a lot smaller and dimmer than the sun. M-dwarfs, known as red dwarfs, are also the most common type of stars, comprising of up to 70 percent of stars in the galaxy. M-dwarfs are also very active.
A star's activity is the primary driver of a planet's atmospheric loss. A young star exhibits high levels of activities, emitting extreme amounts of X-ray and ultraviolet radiations that interact with a planet's atmosphere and cause gas to flow out.
When stars grow older, their activities rapidly mellow down. In Earth's case, the planet did not lose its atmosphere because, in its earlier years, it was dominated by carbon dioxide. The composition of the early atmosphere cooled its upper region, protecting itself from heating due to the high levels of the sun's activities.
"The Earth's atmosphere could not have become Nitrogen dominated, as it is today, until after several hundred million years when the Sun's activity decrease to much lower levels," a press release by the University of Vienna reads.
Meanwhile, M-dwarfs maintain high levels of activities for billions of years. Exoplanets orbiting M-dwarfs can only form Earth-like atmospheres and surfaces after the levels of activity of the star decreased.