The dispersed light is known as a spectrum. The resolving power of a spectrograph is a measure of how fine the wavelengths of light, or colors, can be separated. The wavelength range observable by FUSE is extremely rich in these fingerprints. One can make a direct analogy to looking at a set of overlapping fingerprints - it is difficult to resolve the whorls and lines of the individual prints unless a magnifying glass is used. FUSE is a high-resolution spectrograph with a resolving power of 30,000, meaning that the divisions of light observable with FUSE are 30,000 times smaller than the wavelengths of the light itself.
Astronomers can learn a lot from a spectrum.
The patterns of spectral features tell them what elements are present in the gas how many atoms of each element are present. Shifts in the patterns tell them how fast the atoms are moving and whether they are approaching us or moving away. Spectral analysis of light provides a powerful tool for understanding the properties of astronomical objects in ways simple pictures cannot. Return to the FUSE education page, or you can Return to the FUSE home page.