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.