Final answer:
Astronomers use red and blue shifts in spectral lines, caused by the Doppler effect, to determine the radial velocities of celestial objects and identify the elements within them. The comparison between observed wavelengths and known rest wavelengths of elements allows for the precise identification of atoms responsible for specific spectral lines.
Step-by-step explanation:
Astronomers observing red shifts or blue shifts in spectral line wavelengths can determine various characteristics of celestial objects. In particular, these shifts, which are caused by the Doppler effect, reveal the radial velocities of stars or galaxies moving towards or away from us. By comparing shifted wavelengths to known rest wavelengths of specific elements, astronomers can identify which type of atom is responsible for each absorption or emission line, thus determining the chemical composition of the object. Furthermore, line broadening caused by the Doppler effect provides a measure of an object's rotational velocity.
Identification of Atoms in Spectral Lines
The specific patterns of absorption and emission lines in the spectrum of an object correspond to the unique electronic transitions of atoms and molecules within the object. Each element has a characteristic set of spectral lines at known wavelengths (rest wavelengths). When we observe a shifted spectral line, we can compare it to these known rest wavelengths to identify the element that caused the line. The amount of shift, either red or blue, informs us of the object's movement relative to us, and using sophisticated equipment, even small Doppler shifts can indicate the presence of orbiting planets or measure the star's rotation.