Northern lights dazzle sky watchers

Nighttime sky watchers got an unanticipated treat this week.

The northern lights appeared Thursday in a brilliant display, said local astronomers, and they are expecting them to reappear intermittently through this weekend.

A newly formed sun spot the size of the planet Jupiter could eject enough solar wind to fire up the aurora borealis again tonight and over the next few days, scientists said.

“People should be aware it’s going on, and go out and look for it,” said Zeke Zechmeir, president of the Spokane Astronomical Society.

“The aurora last night was quite beautiful,” Zechmeir said of the Thursday night display.

The Web site SpaceWeather.com predicted today that there is a 30 percent chance of solar activity sufficient to spark an aurora over the Inland Northwest tonight. Solar energy could continue to sweep across the Earth’s magnetic field while the sun spot remains active, causing periodic displays of the northern lights.

Satellite readings showed potential aurora activity across the northern half of the United States today. Maps showing the satellite imagery can be found on the Web at http://sec.noaa.gov/pmap/.

Zechmeir said he was waiting for skies to darken under a favorable crescent moon when a dispersed glow appeared near the Big Dipper at dusk Thursday. He was at a locally favored star viewing spot near Fishtrap Lake southwest of Spokane. As the sky darkened, he said, the aurora transformed into sheets of light. The display intensified for periods of 20 minutes or so and then subsided, only to strengthen later.

He advised sky watchers to keep checking the northern sky throughout the evening since solar energy, which causes the northern lights, often streams through the Earth’s magnetic field in periodic pulses or waves. A new moon will allow for darker skies and help in viewing any northern lights that might appear.

Zechmeir said that locations on the north sides of Spokane, Spokane Valley, Post Falls and Coeur d’Alene will provide better viewing since city lights won’t be casting as much of a glare into the night sky. For example, spots to the north of Wandermere on the north side of Spokane provide dark enough conditions for good viewing of the northern lights, he said.

Here is how Zechmeir described Thursday’s aurora in an e-mail to astronomical society members: “There was a glow all across the northern horizon and as I came home at about 12:45 (a.m.), the aurora was bright enough to be seen as I came down Sunset Hill (on Interstate 90).”

Auroras appear as bands of bright light in blue, green or red, and may take on the more classic curtain-like appearance familiar in photographs if solar activity is sufficiently strong. The lights are caused by an interaction between electrically charged solar particles and the Earth’s magnetic field.

Normally, the aurora band hovers above the Earth at latitude 67 degrees north, but an increase in solar wind from a coronal mass ejection (sun spot activity) can cause the northern lights to extend into middle latitudes, including the Spokane region at about 47 degrees north.

Sky and Telescope magazine this week reported that the sun had been free of spots until recent days when a large region the size of the planet Jupiter erupted near the center of the sun. The active region has been visible without magnification when seen through proper filters to protect the eyes.