We live in exciting times for a sky gazer. This month is the month of Meteor showers. The most prominent of them being the Perseids shower that celebrates it's annual return by rewarding sky gazers with streaks of light dancing across the Skys in mid August. Usually best show is on a clear night around the 12th to the 15th in a place well removed from artificial lighting.
WHY ARE SO MANY METEORS GREEN? The Moon is not made of green cheese. Neither are meteors. But if that's true, why are so many meteors green? During the recent Perseid meteor shower, sky watchers witnessed hundreds of green meteors. Take a look at this fireball. And this one. And this one. And, last but not least, this one:
"This green Perseid cut right through the Double Cluster (h Persei and χ Persei) in Perseus," says photographer David Blanchard of Flagstaff, Arizona, who caught the verdant streak during a 30 second exposure with his Nikon digital camera.
The source of the green is not cheese, it's air. Green is caused by oxygen in Earth's atmosphere. When a meteoroid rips through the atmosphere, air in its path becomes so hot that oxygen molecules briefly lose one of their electrons. They recombine (e- + O2+) very rapidly, emitting green photons as a side-effect. A similar process is responsible for the green colors of many auroras.
Blanchard's meteor has a fringe of yellow alongside the green. Yellow, it turns out, is due to the meteor. When a sodium-rich meteoroid cuts through the atmosphere, hot sodium vapors glow yellow like a sodium discharge lamp.
