Ultraviolet light key to life search, too?Too little UV light, and life might not ever start. Too much, in the form dramatic UV flares from stars, and the atmospheres of orbiting planets might undergo damage. Our sun emits its own unique balance of “light,” a combination of different forms of radiation across most of the electromagnetic spectrum. It emits visible light, of course, and our eyes are most sensitive to that form of the sun’s radiation. And it also emits in the ultraviolet, which is the form of radiation we’re trying to block when we apply sunscreen. But some stars emit light primarily in the ultraviolet, or UV, part of the spectrum. Recent research from Harvard astronomers suggests that UV light might have played a critical role in the emergence of life on Earth. These astronomers believe it could be a key for where to look for life elsewhere in the universe, too. Their study was published this summer in the peer-reviewed Astrophysical Journal and is available online. Sukrit Ranjan of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts led the new study. It suggests that red dwarf stars – by far the most common sort of stars, and thought by some to be the best star systems in which to search for life – might not emit enough UV light to kick-start the biological processes most familiar to our planet. The statement from the Harvard astronomers pointed out:
Ranjan further explained:
Red dwarf stars are smaller and less massive than our sun. Recently discovered planetary systems with potential habitable zones – zones at distances from their stars where liquid water can exist – include red dwarfs such as Proxima Centauri, TRAPPIST-1, and LHS 1140. These scientists used computer models and the known properties of red dwarfs to estimate that the surface of rocky planets in the potentially habitable zones around red dwarfs would experience 100 to 1,000 times less of the ultraviolet light that may be important to the emergence of life than the young Earth would have. They said that chemistry that depends on UV light might shut down at such low levels, and even if it does proceed, it could operate at a much slower rate than on the young Earth, possibly delaying the advent of life. And there’s another wrinkle in the question of life on exoplanets, related to UV radiation. Previous studies have shown that the red dwarf stars in systems such as TRAPPIST-1 might erupt with dramatic flares in UV. If the flares deliver too much energy, they might severely damage surrounding planets’ atmosphere, inhibiting life. Ironically, these UV flares might also provide enough energy to compensate for the lower levels of UV light steadily produced by the star. Co-author Robin Wordsworth of the Harvard School of Engineering and Applied Science said:
Another co-author, Dimitar Sasselov, also of the CfA said:
Read more about this new study from CfA Bottom line: Scientists at Harvard studied the role of ultraviolet, or UV, radiation in the possibility of life on other planets.
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. |