Astronomy Picture of the day!

Edgar

Aurora Over White Dome Geyser

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Description

Colorful aurorae erupted unexpectedly a few years ago, with green glow appearing near the horizon and brilliant bands of red glow blooming high overhead. A bright Moon lit the foreground of this picturesque scene, Familiar stars could be seen far in the distance. The white dome geyser also happened to blast steam. Robert Howell, the man who took the picture actually got quite lucky.

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The picture was taken back in 2012. camera is unknown. Location is Yellowstone national park, in western USA.

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What are these auroras ?

"The aurora is caused by the interaction of high-energy particles (usually electrons) with neutral atoms in earth’s upper atmosphere. This process is similar to the discharge in a neon lamp, or the fluorescence of a television screen. The strongest auroras are quite bright, comparable to moonlight. The aurora occurs only above altitudes of 80 km, and infrequently above 500 km. The average altitude for a normal intensity aurora is between 110 and 200 km."


What gives the color?

"The color of the aurora depends on the wavelength of the light emitted. This is determined by the specific atmospheric gas and its electrical state, and the energy of the particle that hits the atmospheric gas. The atmosphere consists mainly of nitrogen and oxygen, which emit the characteristic colors of their respective line spectra. Atomic oxygen is responsible for the two main colors of green (wavelength of 557.7 nm) and red (630.0 nm). Nitrogen causes blue and deep red hues."

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sources

-Robert. "Astronomy Pic of the Day." NASA. NASA, 2 Oct. 2016. Web. 05 Oct. 2016.


-"The Cause | Causes of Color." The Cause | Causes of Color. N.p., n.d. Web. 05 Oct. 2016.