Mercury Joins Forces With The Aurora

Flames of aurora flickered not far above the northern horizon at the start of dawn this morning Sept. 28 as seen from Duluth, Minn. At right, the Big Dipper stands on its handle. Credit: Bob King
Flames of aurora flickered not far above the northern horizon at the start of dawn this morning (Sept. 28) as seen from Duluth, Minn. At center right, the Big Dipper stands on its handle. Credit: Bob King

Late last night I could see the start of our three-day affair with the aurora as a glow behind a low bank of clouds. Early this morning, soft flames of the stuff flickered in the belly of the northern sky as dawn swelled in the east. Yesterday’s cheery forecast for G2 geomagnetic storms still holds for both tonight and tomorrow night, pretty much all night long.

What a way to wake up! The crescent moon is filled out by earthshine, while Mercury clears the treetops at lower left. Credit: Bob King
What a way to wake up! The crescent moon is filled out by earthshine, while Mercury clears the treetops at lower left. The planet will remain in view low in the eastern sky at dawn for the next week and a half. Credit: Bob King

While it’s often easiest to view the aurora in the evening hours, a display will evolve overnight. In my experience, instead of arcs or rays, morning auroras are often of the flicker-pulse variety with rapidly moving waves shimmying up the northern sky. This type aurora is difficult to take a photo of because it’s melty-looking and moving fast, resembling flames licking sticks in a campfire.

Thursday morning Sept. 29, the wiry moon will be in conjunction with Mercury at dawn. Stellarium
Thursday morning Sept. 29, the wiry moon will be in conjunction with Mercury at dawn. Stellarium

For whatever reason, if you find yourself awake around 5-6 a.m. the next few mornings, cast a glance to the north to see how the aurora’s doing. If you’re feeling a bit more adventurous, find a place with an open view of the eastern horizon, and you’ll get an extra jolt of celestial pleasure in seeing the planet Mercury. It’s a solitary spark of light low in the east in the blue light of dawn. Very easy to see! I saw it this morning an hour and 15 minutes before sunrise around 5:45 a.m. It was joined by a beautiful crescent moon fully rounded out by light reflected from the Earth called earthlight.

The Kp index, a measure of magnetic activity in the upper atmosphere, has been on the high side most of the past two days. A red bar topping out at Kp 6 indicates a moderate geomagnetic storm and good chance for mid-northern latitude skywatchers to see an aurora. Credit: NOAA
The Kp index, a measure of magnetic activity in the upper atmosphere, has been on the high side most of the past two days. A red bar topping out at Kp 6 indicates a moderate geomagnetic storm and a good chance for mid-northern latitude skywatchers to see an aurora. Credit: NOAA

Tomorrow morning, Sept. 29, watch as Mercury and an even thinner crescent will be in conjunction just 1.5° apart in morning twilight. This will be something both to relish with the naked eye as well as take a photo of for your Facebook page. Place your camera on a tripod and try exposures of 1-3 seconds at ISO 400.

Happy skywatching!