Most people know them as shooting stars. These streaks are actually meteoric dust particles shooting through the upper atmosphere and glowing with the heat created by this rapid passage. Most of these meteors are no brighter than a dim star. Slightly larger fist-size pieces of material cause a much brighter and spectacular shooting star. These are known as fireballs and can be startling, not only because of their brilliance but also because of their vivid colour.
Fireballs can be green, yellow, orange, blue, red, as well as brilliant white.
The light of a fireball comes from the glowing gas surrounding the solid meteoroid, rather than from the meteoroid itself. Each element glows with its characteristic set of colours. The eerie green light so common in many fireballs comes from atmospheric oxygen. Nitrogen from our atmosphere contributes blue, and sodium from the meteoroid can add yellow to the light. Magnesium, iron, calcium, and dozens of other elements add their own colours.