This causes most of the atoms to lose some of their electrons. Atoms which have had one or more of their electrons removed are called ions . The higher the temperature, the more electrons which are missing from the ions. If an ion moves to a cooler place, nearby electrons will be captured again. This means that each different kind of ion can survive only in places where the temperature is just right.
Astronomers reply upon atomic physics in order to dig information out of solar and stellar spectra.
Atomic physics is the branch of science that deals with atoms, ions, and the light that comes from atoms and ions. Each different type of atom and each different type of ion emits light waves at a combination of wavelengths which is special to that particular type of atom or ion. In other words, the wavelengths of the light waves that are sent out by one kind of atom or ion are different from the wavelengths of light waves that are sent out by another kind of atom or ion . These light waves have become known as emission lines because light at these particular wavelengths looked like many straight lines in a spectrum when astronomers first obtained them. Each different type of atom and each different type of ion emits its own special, unique set of emission lines.