Under which Sun life develops?

A group of researchers at Cornell University recently conducted an analysis on the effect of ultraviolet radiation emitted by parent stars received by the planets that revolve around them. Under certain conditions it may lead to the development of life making these planets similar to our Earth.
In order to simplify the understanding of the complex biological processes that govern a hypothetical system of planets like Earth, a team of astronomers has developed digital models to analyze the effect of ultraviolet radiation that radiates the same exoplanets as they rotate around their own. Its scientific article was recently published in the Astrophysical Journal.


Credit: David A. Aguilar (CfA)

“Depending on the intensity, the ultraviolet radiation may be beneficial or detrimental to the development of life,” says Lisa Kaltenegger of Cornell University. “We are trying to ascertain the value of the ultraviolet radiation that invests other planets similar to the young Earth, and whether it can be compatible with life.”
“We will observe the planets in all their stages of development, comparing them with four times champion of Earth’s history,” said Sarah Rugheimer, also of Cornell University. “In the next generation of missions we expect to find a wide variety of extrasolar planets.”
Delving into the history of the Earth, Rugheimer and co-authors of the study, they have shaped the first time, a pre-biotic world with an atmosphere consisting mostly of carbon dioxide, similar to Earth’s 3.9 billion of years ago. The second era, which dates back to about 2 billion years ago, would have created the first small amount of oxygen, since there was a biosphere active and the ability to complete the process of biosynthesis. The percentage of oxygen would then be grown by the first cyanobacteria until reaching a concentration equal to 1% of the current one.
“Both the intensity and the type of ultraviolet radiation cause specific biological consequences,” said Rugheimer. “In addition to calculating the total value of the radiation, we take care to assess which wavelengths are the most damaging to DNA and other biomolecules.”
Multicellular life began about 800 million years ago, a period over which the group has modeled a third time, in which oxygen reaches 10% of the current concentration. The fourth period corresponds to the modern Earth, with current levels of oxygen in the atmosphere and a percentage of carbon dioxide equal to about 355 parts per million.
The researchers observed that in all periods subsequent to the appearance of oxygen, is the hottest stars that cooler stars are radiation biologically less effective. In the case of the hot stars, this is due to the concentration of ozone that protects the environment from excessive ultraviolet activities; in the case of cool stars, it is due to a lack of flow UV absolute.
Rugheimer explained that astrobiology fascinates researchers from many disciplines, emphasizing that this work “provides a link between the astrophysical conditions that we expect to find on other planets and the origin of life experiments conducted here on Earth.”

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