Sad news for fans of Proxima B: a new NASA study suggests exoplanets in what were considered red dwarf habitable zones may not be able to support life after all.
Discovered in 2016, exoplanet Proxima B had been touted as the "Earth Next Door" as it is located more than 4 light years away from our home planet.
And because Proxima B lies within the habitable zone of its own star system, many scientists wondered whether crucial, life-sustaining liquid water could exist in it.
Unfortunately, all hope for existence of life on the exoplanet may be lost. In the new study, NASA researchers suggest that frequent stellar eruptions from red dwarf stars may threaten the atmosphere of an exoplanet.
These stellar eruptions release huge amounts of radiation and material out into space, potentially causing loss of oxygen in the exoplanet's atmosphere, scientists said.
Determining A Planet's Habitability
In the past, scientists typically considered the conditions of parent stars in a star system to determine whether a planet was livable.
For instance, they often attempt to measure how much light and heat the star produces. Stars that are larger than our sun emit more light and heat, so its habitable zone must be located farther out. Smaller and cooler stars have nearby habitable zones.
Along with light and heat, however, stars also emit ultraviolet and X-ray radiation, as well as stellar eruptions such as coronal mass ejections and flares.
NASA researchers took into account all these space weather, investigating the impact of stellar eruptions on exoplanets and effectively producing a new model for habitable zones.
"We're coming closer to understanding what kind of parent stars we need," said solar scientist and study lead author Vladimir Airapetian.
Atmospheric Erosions
The hunt for habitable planets often end up in red dwarf stars systems, because red dwarfs are cooler, smaller, and among the most numerous stars in the universe.
Using their new model, Airapetian and his colleagues postulate that one possible effect of the stellar radiation is a phenomenon called atmospheric erosion.
Atmospheric erosions involve high-energy particles that drag molecules of liquid water -- oxygen and hydrogen -- out into space.
Although red dwarf systems are more amenable to detections of small planets, the downside is that they are also prone to powerful and frequent stellar eruptions, researchers said.
Furthermore, the age of the star may also be an important factor in habitability. Matured stars such as the sun produce superflares that are observed every 100 years, while young stars release at powerful eruptions 10 times more powerful.
So when researchers accounted for X-ray superflares, they found that violent storms of young red dwarfs produce enough high-energy radiation to allow the escape of oxygen and nitrogen in the atmosphere.
Astrophysicist Alex Glocer, co-author of the paper, said with more extreme ultraviolet and X-ray energy there is, more electrons are produced.
"The stronger the ion escape effect becomes," he added.
Proxima B May Be Unable To Support Life
In the study, Airapetian and his colleagues considered the age of Proxima B's host star and the exoplanet's proximity to it. After performing calculations, they expect that the exoplanet is often subjected to extreme ultraviolet radiation and superflares that occur every two hours.
What's more, intense bouts of stellar wind and magnetic activity worsen harsh space conditions on the exoplanet. NASA researchers conclude that it is unlikely exoplanet Proxima B is habitable and that oxygen would escape its atmosphere in 10 million years.
Details of the study are published in The Astrophysical Journal Letters. Watch the video below.
