Update 9 a.m. Jan. 10: The blast of particles from the solar flare in big sunspot group 1944 was much weaker than expected. Some of it slid by Earth yesterday afternoon but only fired up auroras in Arctic latitudes that were in darkness at the time. There’s still one more chance for auroras tonight as the remainder of blast passes by.
– 12:05 a.m. Jan. 10: Still nothing visible from Duluth though there’s been a generally upward trend in activity over the past few hours. You can check the extent of the auroral oval HERE. The red line indicates the southern limit of aurora visibility. Though more technical, a good indicator of an impending aurora is the real-time Bz graph from the ACE spacecraft. If the red squiggly line dips sharply southward – toward the bottom of the chart (lower than -10) – be alert for potential northern lights.
While you’re out facing north hoping the aurora paints your sky tonight take a look around your backside to the south. Starting around 8-8:30 p.m. local time the complete Winter Hexagon – a beautiful hexagonal array of the brightest stars of the winter – tilts upward in the southeastern sky.
Each star or stars, as in the case of Castor and Pollux, which both belong to Gemini the Twins, heads up a particular constellation:
* Capella in Auriga the Charioteer
* Aldeabaran / Taurus the Bull
* Rigel / Orion
* Sirius / Canis Major the Great Dog
* Procyon / Canis Minor the Little Dog
What about the “+2″. These odd stars out – Betelgeuse and the planet Jupiter – aren’t part of the Hexagon but just happen to be fenced in by it. Count them all up and you’ve got nine shimmering sky objects, eight of which are first magnitude or brighter (Castor is magnitude 1.9) and located in the same tract of sky. What an attention grabber.
You might be surprised to know that winter skies are often more light polluted than those of other seasons. Streetlights and other forms of lighting reflect off the snow cover and bounce straight up into the sky. The difference is striking from where I live – the wash of light from the city reaches half again as high in the southern sky as during the fall.
The Hexagon’s concentrated radiance plus additional bright stars in the region leave the impression that winter is the clearest, darkest time of year when it may very well not be.
Parts of the world that don’t receive snow in the winter are better off, and if your haze and humidity levels are lower than as well, the winter stars may indeed sparkle that much brightly.
So enjoy the Hexagon tonight, and may a fine display of northern lights make you turn around the other way.