July 25, 2012
Another birthday means another year in which the universe got to experience itself through your particular combination of wonder and will.
Pink Aurora Over Crater Lake
Birthday · July 25, 2012
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APOD published July 25, 2012. Credit: Brad Goldpaint (Goldpaint Photography). A publication-date match, not a photo taken on your date. Independent of NASA.
Why is this aurora strikingly pink? When photographing picturesque Crater Lake in Oregon, USA last month, the background sky lit up with auroras of unusual colors. Although much is known about the physical mechanisms that create auroras, accurately predicting the occurrence and colors of auroras remains a topic of investigation. Typically, it is known, the lowest auroras appear green. These occur at about 100 kilometers high and involve atmospheric oxygen atoms excited by fast moving plasma from space. The next highest auroras -- at about 200 kilometers up -- appear red, and are also emitted by resettling atmospheric oxygen. Some of the highest auroras visible -- as high as 500 kilometers up -- appear blue, and are caused by sunlight-scattering nitrogen ions. When looking from the ground through different layers of distant auroras, their colors can combine to produce unique and spectacular hues, in this case rare pink hues seen above. As Solar Maximum nears over the next two years, particle explosions from the Sun are sure to continue and likely to create even more memorable nighttime displays. Students: Browse a free online astronomy course.
Image credit: Brad Goldpaint (Goldpaint Photography)