Stars and Nebulae...


The Elements
Electron Energy Levels
Light Photons
Atomic Absorption Spectra
Atomic Emission Spectra
Stellar Spectra

These pages explain how astronomers find out what stars and interstellar dust clouds are made of.

Michael Gallagher
Eaglehawk Secondary College
September 2002, August 2003


An atom has a central nucleus surrounded by a cloud of orbiting electrons. The nucleus contains positive protons and uncharged neutrons. Electrons are negatively charged. Atoms usually have no charge because each positive proton is balanced by a negative electron. The type or name of an atom is determined by its number of protons: hydrogen has one proton. Oxygen has 8 and Uranium has 92. Every type of atom has a unique number of protons.