Some corals on Earth glow an ethereal green
Paulo Oliveira / Alamy
Planets that glow could be a telltale sign they are home to life.
Most of the nearest potentially habitable planets we have found are orbiting a type of star called a red dwarf. When these stars are young, they tend to blast out ultraviolet (UV) light that can be deadly to life as we know it. That has made some astronomers question whether life can survive near these stars.
If it can, Lisa Kaltenegger and Jack O’Malley-James at Cornell University in New York have an idea about what it might look like.
They realised that there are some species of coral that have adapted to deal with UV light. These coral get their energy from algae, and to protect the algae from UV damage, the coral absorbs the light and re-emits it at a lower, safer wavelength. This gives the coral an ethereal glow.
On a planet subjected to far more UV radiation, this sort of adaptation might be more common, says Kaltenegger. The glow would be tied to the star’s activity, making it easier to disentangle from other factors that might make a planet appear brighter than expected but wouldn’t indicate life (Monthly Notices of the Royal Astronomical Society, doi.org/c9mp). Depending on factors like whether the planet has clouds, the glowing could make the planet more than 100 times brighter, says Kaltenegger.
“If you and I would have evolved on such a world, we would probably glow too, as that would have had advantages in survival,” she says.
That means that planets around red dwarfs are more likely to glow, and we might see it someday. “This counterintuitively makes highly active flaring stars good places to look [for life],” says Kaltenegger.
Journal reference: Monthly Notices of the Royal Astronomical Society, DOI: 10.1093/mnras/stz1842