“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”
– Dimitra Atri, NYU Abu Dhabi
Habitability of a planet is essentially the measurement of potential of a planet to maintain environments to sustain life. It is one of the most important concepts in exoplanet studies. Life may be generated naturally on a planet as in case of earth or may have to be transferred from another body through the hypothetical concept of Panspermia that is life exists throughout the universe distributed by asteroids, planetoids, space dust etc. Since earth is the only planet known to mankind that sustains life, planetary habitability on other planets or satellites is predominantly an extrapolation of conditions on Earth and the attributes of the Sun and Solar System of the Milky way which appear favorable for life to thrive. The analysis of environments which are likely to support life, a comparison is usually made between simple, unicellular organisms such as bacteria and large multicellular organisms such animals.
Since unicellular life undoubtedly precedes multicellular life in any hypothetical tree of life, so we comprehend that if single-celled organisms do emerge there is no assurance that greater complexity will eventually develop.Factors such as Mass,Radius,Orbit and rotation, Geochemistry, Microenvironments and extremophiles and Ecological Factors are considered crucial for live to thrive. The ability to sustain an atmosphere that supports life is the most important requirement for making an exoplanet habitable. But, these exoplanets are subjected to space weather in the form of stellar flares, emissions of radiation from stars. Stellar flares that are fundamentally very similar to solar flares have been found to reduce the chances of sustainable habitat on exoplanets. The radiation from stellar flares are influenced by continuum emission and almost equal amounts of energy has been recorded by the optical, UV, and X-ray regions of the spectrum. In solar flares strong emission is rarely recorded and a large collection of bright emission lines takes prominence. Small flares occur more frequently than large ones and the large flares have longer time-scales.
In a recent study at NYU Abu Dhabi , stars that were most likely to host habitable exoplanets based on the calculated erosion rates of the planetary atmospheres have been identified.The study led by Research Scientist Dimitra Atri of the Center for Space Science has used data from NASA’s Transiting Exoplanet Survey Satellite (TESS) observatory to present the process of analysing flare emissions. Erosion rates of planetary atmospheres were calculated for the research that led to the results that more frequent, low energy flares have a greater impact on an exoplanet’s atmosphere than less frequent, high energy flares. Also, different types of stars extreme ultraviolet radiation (XUV) through stellar flares, from different types of stars affect nearby space-bodies too. This research has provided novel understanding of the habitability of exoplanets. This study also explains the need for better numerical modeling of atmospheric escape about how planets release atmospheric gasses into space, as the released gases can lead to the abrasion of surface atmosphere and the decline of the planet’s habitability. According to the statement of scientists involved , the research would further continue to expand data sets used to analyse stellar flares from a congregation of other stars to see the long-term effects of stellar activity, and to identify exoplanets that have more potentially habitable conditions.