Exploring Spectroscopy
Combining the spectra of individual atoms to represent compounds detected in the atmospheres of distant exoplanets.
As part of the research for my Invisible Planets series I’ve been studying spectroscopy. This is the process that allows astronomers to analyse the chemical composition of stars and distant planets. When light is focused in a particular way then any chemicals it passes through will produce lines in the more familiar rainbow spectrum, creating a unique signature for each element. This allows us to examine the composition of atmospheres of exoplanets hundreds of light years away from Earth. Astronomers also look for biosignatures – signs that life may be present on the planet.
These images are compiled from the spectra of individual elements, combined to represent the number of these elements present in molecules and compounds that have been identified on distant planets, with the heights of the spectra adjusted to reflect the atomic numbers of the elements represented.
From top left: H20 (two hydrogen atoms combined with one oxygen atom) is the chemical formula for water. Water is one of the most abundant molecules in the universe and so important for life on Earth that astronomers search for evidence of it within the atmospheres of exoplanets and also on the moons and planets within our own solar system in the hope that it will lead us to other forms of life.
CH4 (four hydrogen atoms and one carbon atom), HCN (one hydrogen, one carbon and one nitrogen atom) and C2H2 (two carbon and two hydrogen atoms) are the chemical formulas for methane, hydrogen cyanide and acetylene. These are all compounds that have been detected on the exoplanet HD209458b, also known informally as ‘Osiris’. This planet is a gas giant orbiting a solar analogue star in the constellation of Pegasus, 159 light years from Earth.
CH3Cl (three hydrogen, one carbon and one chlorine atom) and (CH3)2S (two sets of three hydrogen and one carbon atoms combined with one sulphur atom) are the chemical formulas for methyl chloride (also known as chloromethane) and dimethyl sulphide. These two molecular signatures are biomarkers – less abundant on Earth but promising indicators of life on planets with hydrogen rich atmospheres where oxygen or ozone are not as abundant.