This is a transmission spectrum of an Earth-like exoplanet. The graph, based on a simulation, shows what starlight looks like as it passes through the atmosphere of an Earth-like exoplanet. As the exoplanet moves in front of the star, some of the starlight is absorbed by the gas in that exoplanet’s atmosphere and some is transmitted through it. Each element or molecule in the atmosphere’s gas absorbs light at a very specific pattern of wavelengths. This creates a spectrum with dips that show where the wavelengths of light are absorbed, as seen in the graph. Each dip is like a “signature” of that element or molecule.
If you recognize the signature of that element or molecule, you know it exists in the exoplanet atmosphere’s gas and can tell what the atmosphere is made of. This transmission spectrum of an Earth-like planet’s atmosphere shows wavelengths of starlight that molecules like the oxygen that we breathe, ozone, water, carbon dioxide, and methane absorb.
NASA’s James Webb Space Telescope will be able to detect some of the most prominent absorption features of certain gas molecules. Even these features will be extremely faint. The more light Webb gathers while looking at the passing planet’s atmosphere, the more confidently scientists can identify these features.
Credits
Image
NASA, ESA, CSA, STScI, Joseph Olmsted (STScI)
