Why Cold Stars Lead Scientists Astray ✎ express
Astronomers listen to starlight using spectroscopy: they spread it into a rainbow and read the dark 'voices' of chemical elements. But the very cool star TRAPPIST-1 didn't sound as the models predicted: water and iron were barely audible, though there should be plenty.
The error lay in the 'volume' of the environment. In hot stars like the Sun, molecules constantly jostle each other, and their voices blend into a cacophony — we only hear noise. In TRAPPIST-1's cold, thin atmosphere, collisions are rare, and each voice rings out clearly. Yet the models applied the rules of a noisy street to a quiet library. After correction, everything matched up. Most stars in the galaxy are such 'quiet ones', and we're just now learning to listen to them. Now we can more accurately search for water and signs of life on exoplanets.
TRAPPIST-1 is so cool that its temperature is only about 2500°C — half as hot as the Sun. If it were in the Sun's place, Earth would receive less light than Pluto does now.