An aurora's colors depend on which types of atoms cause the splash of light. In most cases, auroral lights appear when charged particles from the solar wind collide with oxygen atoms in Earth's atmosphere, according to a NASA statement.
"This produces a green photon, so most auroras appear green. However, lower-energy oxygen collisions—as well as collisions with nitrogen atoms—can produce red photons, so sometimes auroras also show a red band, as seen here."
Such auroral displays are triggered when clouds of charged particles from the sun—known as coronal mass ejections (CMEs)—slam into Earth's magnetic field.
A "severe" CME hit September 26, sparking auroras at both Poles and inducing light shows visible in five U.S. states, including Michigan, New York, South Dakota, Maine, and Minnesota, according to NASA.
As solar particles get funneled along Earth's field lines toward the Poles, they collide with molecules in the atmosphere, infusing them with extra energy. The molecules in turn release the energy as light.
Capturing the above aurora required "a long night of waiting-but the activity picked up," photographer Jonathan Tucker wrote on SpaceWeather.com.
Photographer Fabiano Belisário Diniz caught the monster sunspot in a picture he took of the sun setting over Curitiba, Brazil, on September 26.
"It was overcast and cold all day long, but at the end of the day a break in the clouds revealed the sun and AR1302," Diniz told SpaceWeather.com. "What a great sight!"
For more on solar flares, sunspots, and solar wind, read "The Sun-Living With a Stormy Star," in National Geographic magazine
The finding is based on new high-resolution pictures of Enceladus from NASA's Cassini orbiter, as well as global maps of color patterns that help reveal the ages of surface features. Above, an artist's rendering shows an active tiger stripe, including bluish regions that indicate freshly exposed water ice.
—Richard A. Lovett