Life in the Red

Life on Earth is sustained by photosynthesis. Plants and some bacteria combine water, carbon dioxide, and sunlight to make sugars and oxygen, which they release into the air and water. Without that process, modern life wouldn’t exist.

Scientists have been wondering whether the most common stars in the galaxy might sustain photosynthesis on their planets.

M dwarfs are the smallest and coolest of all stars. But they probably account for more than half the stars in the galaxy, which makes them of special interest in the search for life. In addition, M dwarfs live a long time, so there’s plenty of time for life to develop. And because the stars are small and cool, any possible life-bearing planets would be close in, making them easier to find.

The light produced by M dwarfs is different from sunlight. It’s much redder, and there’s a lot more infra-red. Scientists have considered whether those wavelengths could support photosynthesis.

One study said that M dwarfs don’t produce enough ultraviolet light. But another said the spectrum of an M dwarf should be just fine for life. And yet another one, released last year, agreed. That study subjected bacteria that live by photosynthesis to lighting conditions like those around M dwarfs. And the organisms did well.

The issue is complicated by the fact that most M dwarfs produce big outbursts of X-rays. But it seems at least possible that microscopic life could get by on these little but common stars.
 

Script by Damond Benningfield