The universe is 13.8 billion years old, and our planet was formed only 4.5 billion years ago. Some scientists believe that such a gap in time means that life on other planets may be billions of years older than ours. Nonetheless, new theoretical work suggests that modern life may in fact be cosmic premature.
“When asked when life is most likely to arise, many people naively say now,” says lead author Avi Loeb of the Harvard-Smithsonian Astrophysical Center. "But we have found that the chances of life emerging in the future are much higher."
Life as we know it became possible about 30 million years after the Big Bang, when the first stars seeded space with essential elements like carbon and oxygen. It will disappear in 10 trillion years, when the last stars go out and disappear. Loeb and colleagues examined the relative likelihood of life emerging between these two limits.
The dominant factor was the lifetime of the stars. The higher the mass of a star, the shorter its life span. Stars with a mass three times the mass of the Sun will disappear before life has a chance to develop.
Conversely, the smallest stars with a mass less than 10% of the Sun will shine for 10 trillion years, giving life enough time to develop. As a result, the likelihood of life emerging increases over time. In fact, the chances of life emerging in the future are 1,000 times higher than now.
“And here you can rightly say that we do not live next to a low-mass star,” says Loeb. “We may have appeared prematurely. Another option: the environment of a low-mass star is life-threatening."
Although low-mass red dwarf stars live for long periods of time, they also pose unique threats. When young, they emit strong flares and ultraviolet radiation that can disrupt the atmosphere of any solid world in a potentially habitable zone.
To determine which possibility is closer to the truth - our premature appearance or the danger of low-mass stars - Loeb recommends studying the nearest red dwarf stars and their planets for potential habitability. Future space missions like TESS and the James Webb Space Telescope should help us answer these questions.
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ILYA KHEL