Heads up! Aurora alert for Friday night, April 16

The aurora simmers near the bottom of the northern sky around 12:45 a.m. Friday morning, April 16. The green patches were dim but apparent, while the occasional rays were very faint. To see them I had to avert my vision. Details: 35mm lens at f/2.8, ISO 2500, 25 seconds exposure. Bob King

The northern lights put in a delicate appearance early Friday morning, April 16 from my moveable, open-air, frog-chorus observatory in Duluth, Minn. While not the kind of display you'd croak about unless you were a frog, it felt good to see them return. I watched from 12:30 - 1 a.m. as the lights sloshed around the bottom of the northern sky. Occasional patches and rays pulsed in and out of view so sluggishly it seemed they simply didn't have the energy.

A meteor flashed during this time exposure of the northern lights early Friday morning. At center left you can see the W-shape of Cassiopeia, while the two fuzzy dots to its left are two side-by-side star clusters called the Double Cluster. Bob King

That was last night when the numbers didn't look good for an aurora-sighting at all. Things may be different tonight. The forecast calls for a minor G1 geomagnetic storm from about 7 p.m. until midnight-ish Central Time. G1 storms typically produce brighter, more active displays with obvious green arcs and low, short-lived rays. The northern states and Canada are favored.

As always, you'll need a spot with an unobstructed view of the northern sky. Be sure to allow your eyes at least 5-10 minutes to adapt to the darkness. Although the moon will shine tonight, it's still a crescent and won't affect the aurora's visibility. Watch for it near Mars tonight (see below).

While you're waiting for the aurora, look westward, where the crescent moon sits about 5° below Mars in Taurus. Stellarium

The sun remains near the bottom or minimum of its 11-year activity cycle when solar flares are infrequent. Tonight's display, should it happen, will be brought to you by a gusty wind of particles streaming from a hole in the sun's outer atmosphere called a coronal hole. Since these holes often linger for months, this one is probably related to the one that showered us with multiple displays of northern lights in mid-March.

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