Researchers at the University College London (UCL) used a supercomputer to compute 10-billion “transition lines” of the spectral signature of methane, 200 times more comprehensive than previous best efforts. As methane is a biosignature, the development is an advancement toward the detection of life in planets outside our solar system.
Every molecule absorbs and emits light in a characteristic pattern called the absorption and emission spectrum. In order to determine the atmospheric composition of the exoplanets, astronomers break down the full atmospheric spectrum into known patterns to identify the component molecules.
Detecting methane in the study of astrobiology is important because it is an unstable molecule in the atmosphere that only lasts 300-600 years as it is broken down by solar ultraviolet radiation. Since it is unstable, one explanation for its presence on an exoplanet’s surface is continual production by a carbon-based life. The caveat is that geological processes also replenish methane so detection is suggestive of but does not guarantee life.
The previous methane spectra are incomplete in that they contain far fewer transition lines than the new effort so do not properly reflect methane in high temperature atmospheres (i.e. hotter than Earth). At high temperatures there are more transitions because the methane molecule is excited to higher energy states. As a result the methane levels of hot exoplanets and cool stars are detected only partially or incorrectly.