The aurora borealis, or northern lights, which is featured in The 2014 Old Farmer’s Almanac, is one of the more magical celestial illuminations.
Ancient civilizations saw the northern lights but lacked the cosmic perspective and technology to grasp what was playing out in the skies—so they invented stories. Eskimos believed the light to be playful spirits of the departed. The Norse said that it was the glint off the armor of Valkyrie warriors. The Chinese imagined its twisting, snakelike forms as celestial serpents.
Today, we know that the source of auroras is the Sun—specifically, the bursts of electrically charged particles that it emits during coronal mass ejections (CMEs). Some of the particles are captured in Earth’s protective magnetosphere, causing a geomagnetic storm over the north and south magnetic poles. In our planet’s rarefied upper atmosphere, the particles slam into atoms and molecules of oxygen and nitrogen, causing them to glow in colors ranging from green—the most common—to red, blue, pink, and purple. Invisible and unknown to many observers is the amount of energy produced by even the most modest display: more than 100 million kilowatts, equivalent to the capacity of all of the world’s power plants combined.
Mysteries and Misconceptions
Many mysteries about auroras elude scientists: Why do the lights form patterns and movements? Do the lights make sound, as many observers have reported? How can we predict more accurately when auroras will appear and how they will look? (You can find aurora predictions at SpaceWeatherLive.com.)
To photograph the lights, you need a camera that can be set and focused manually and a solid tripod. If you’re in a dark, rural area, start with settings such as 15 seconds at f/2.8 and ISO 800. Focus on infinity (∞) and remove all filters from your lens. Review your photos on the camera’s LCD screen and change the settings to get the best possible image. Experiment to ensure that you get a good shot.