Photosynthetic organisms leave a cosmic signature on their planet: a change in atmospheric composition and a distinctive surface color. This autograph can be seen through telescopes like JWST, which split the light of distant exoplanets into a spectrum. Thus, the method of spectroscopy allows us to search for biosignatures — traces of life.

A striking feature of this signature is the "red edge": a sharp jump in reflectance at the boundary between visible and infrared light. Chlorophyll stops absorbing, and the cells scatter the rays, making vegetation bright in the infrared range. That's why forests appear crimson in satellite images.

But on planets around red dwarfs, whose light is dimmer than the Sun's, life might use other pigments. As Cecilia Payne-Gaposchkin discovered, different types of stars have different compositions, meaning potential biosignatures also vary. Earthly bacteria already demonstrate this: some can capture infrared light up to 1020 nanometers — far beyond the visible limit. Meanwhile, the oxygen signature isn't always obvious: photosynthesis emerged on Earth hundreds of millions of years before the accumulation of oxygen in the atmosphere, so a seemingly lifeless world might hide oceans of life.