In the quest for life beyond Earth, a planet with oxygen in its atmosphere is considered the Holy Grail. But appearances can be deceiving.
So says a team of scientists studying a particular type of star known as an M dwarf, or red dwarf. These long-lived stars, which are smaller than the sun, account for about 75 percent of the stars in our galaxy.
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Astronomers found that M dwarf stars have relatively high levels of far-ultraviolet radiation -- 1,000 times more than the sun. These emissions could trigger chemical reactions in an orbiting planet's atmosphere that create oxygen and ozone.
"This could be taken as a false positive (for life)," said astronomer Feng Tian, with the Center for Earth System Science at Tsinghua University in Beijing, China.
"If you observe these planets' atmospheres, you'll see oxygen and you may think ‘Oh the oxygen could come from life, like plants on our own planet,' but actually that is not the case," Tian told reporters during a webcast press conference at the American Astronomical Society meeting in Denver this week.