Scientists have now looked at the presence of the ozone layer on exoplanets to look for signs of life on Earth.
The ultimate objective of space exploration remains the discovery of life beyond Earth or even signs that life once existed in these far-out worlds. Astronomers have so far discovered over 5000 planets in our Milky Way galaxy, but most of them seem to be devoid of any life so far.
As more and more worlds begin to appear with advancements in exoplanet hunt, scientists have worked on a way to narrow down the worlds which could have potential life. The team has now focused on studying the ozone layer of the planets. As ozone layer protects the terrestrial biosphere against harmful ultraviolet (UV) radiation from the star.
The team showed how the metallicity of a star is connected to the ability of its planets to surround themselves with a protective ozone layer.
The study published in the journal Nature Communication states that during the evolution of the universe, newly formed stars progressively become more metal-rich, exposing organisms to increasingly intense ultraviolet radiation. “Our findings imply that planets hosted by stars with low metallicity are the best targets to search for complex life on land,” the paper read.
It is worth mentioning that most of the stars found with planets around them are in temperatures ranging from about 5,000 to about 6,000 degrees Celsius. The Sun also falls in the same group.
“In the Earth’s atmospheric chemistry, ultraviolet radiation from the Sun plays a dual role. It was, therefore, reasonable to assume that ultraviolet light may have a similarly complex influence on exoplanet atmospheres as well,” Dr. Anna Shapiro, whose past research interest focused on the influence of solar radiation on Earth’s atmosphere, said in a statement.
Researchers calculated exactly which wavelengths make up the ultraviolet light emitted by the stars and for the first time considered the influence of metallicity. They then investigated how the calculated UV radiation would affect the atmospheres of planets orbiting at a life-friendly distance around these stars.
“It is feasible that the history of the Earth and its atmosphere holds clues about the evolution of life that may also apply to exoplanets,” says Jos Lelieveld, who was part of the story. The team found that stars with high metal content allow a dense ozone layer to form, giving more chances for life to emerge.
“Each newly forming star, therefore, has more metal-rich building material available than its predecessors. Stars in the universe are becoming more metal-rich with each generation,” says Dr. Anna Shapiro.