A Breakthrough Way to See Distant Planets
theatlantic.com
theatlantic.com
https://arxiv.org/pdf/1610.01610.pdf
The element they used is sodium:
"During primary transits, the spectral signatures of exoplanet atmospheres can be measured using transmission spectroscopy. We can obtain information on the upper atmosphere of these planets by investigating the exoplanets’ excess sodium absorption in the optical region."
How prevalent is that condition?
The article goes into some detail about the significance of this planet having water and carbon monoxide, but not methane or ammonia.