Stellar Flares Affect the Habitability of Exoplanets

The evolution of planetary atmospheres is influenced by space weather which generally comprises of events on the Sun and near-Earth space. In a recent study, researchers analyze the relationship between stars and planets outside the Solar System called exoplanets. Researchers from New York University Abu Dhabi (NYUAD) published their findings in the journal Monthly Notices of the Royal Astronomical Society.

Since the confirmation of the first exoplanet in the early 1990s, scientists have searched for signs of life in these planets, such as traces of liquid water. Today, several studies have confirmed the existence of thousands of exoplanets with some categorized as habitable.

In the study, the team discusses how stellar flares affect the atmosphere of exoplanets, affecting their habitability. A great example of this is how solar flares affect the Earth's atmosphere.

Space Weather

Solar flares are sudden bursts of energy on the giant star due to magnetic fields near sunspots. Occasionally, the explosions are accompanied by a coronal mass ejection or plasma expulsions.

When the plasma is released by the solar wind, they make their way into space, affecting the weather and could cause a geomagnetic storm on Earth or a disturbance on the planet's magnetic fields. The solar wind could cause damage to satellites and potentially expose astronauts to dangerous levels of radiation.

NASA and other scientists have also recently announced the new solar cycle this year, or when the Sun's magnetic poles switch over. The cycle affects solar activity which then has an impact on space weather and the Earth's upper atmosphere.

Stellar Flares Affecting Atmospheres

In the study, the researchers noted that "Space weather-induced effects include planetary atmospheric losses," like the relationship between exoplanets and surrounding stars. One other factor of stars is the emissions of extreme ultraviolet (EUV) radiation.

Stellar EUV "heats up a planetary atmosphere and can lead to hydrodynamic escape," wrote the authors. Hydrodynamic escape is when hydrogen gags escape a planet's atmosphere even if it has a strong gravity field.

The team identified specific stars that may host habitable exoplanets according to how their atmospheres have eroded over time. They also discovered that frequent, low energy flares impacted planetary atmospheres more than high energy flares that were less frequent.

The results gave new insights on factors that affect the habitability of planets beyond the Solar System and how the Sun provides a good example of stellar flares affecting planetary atmospheres. Also, the scientists noted the need for better models of atmospheric escape which leads to atmospheric erosion and makes exoplanets less habitable or inhabitable.

"Given the close proximity of exoplanets to host stars, it is vital to understand how space weather events tied to those stars can affect the habitability of the exoplanet," said Dimitra Atri. "The next research step would be to expand our data set to analyze stellar flares from a larger variety of stars to see the long-term effects of stellar activity, and to identify more potentially habitable exoplanets."

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