Observing The Aurora Borealis

With our “Daytime Star” now revving up for another sunspot maximum in 2013, displays of  the beautiful Aurora Borealis are becoming increasingly numerous. They are considered nature’s grandest light show and if you’ve never witnessed one, be prepared to be “wowed”!  And the best part is that no equipment is needed-just your eyes (with their amazing “all-sky” viewing capability) and a clear night. 

The Aurora Borealis (better-known as the “Northern Lights” when seen from the Northern Hemisphere) and the Aurora Australis (or “Southern Lights” seen from the Southern Hemisphere) are wonderful atmospheric displays directly tied into sunspot activity. Charged particles from the Sun excite gases like neon and oxygen in our upper atmosphere causing them to glow. And here we’re talking about an amazing light show quite unlike any earthly counterpart-multicolored undulating curtains, shimmering arcs, and pulsating rays so bright in some cases that they cast shadows on the ground! While relatively infrequent around sunspot minimum, displays often occur several times a week centered on maximum activity. Whenever a big naked-eye sunspot appears near the center of the Sun’s disk during the day, you can be fairly sure of an auroral display that night or the one following. (See the May Sky Talk for information on safely viewing the Sun with the unaided eye.) If a large sunspot or sunspot group is seen, news flashes are often posted on www.astronomy.com and www.skyandtelescope.com among other Internet sites alerting readers to an impending display, should you prefer to learn about it that way instead of actually looking at the Sun itself.

The higher your latitude (or closer to the poles) the more likely that an aurora will be seen. A total eclipse of the Sun is without question nature’s grandest spectacle. But an intense auroral display is unquestionably its greatest light show! Many (including myself) witnessing one experience a heady exhilaration. As we approach sunspot maximum, make it a practice to always check the northern sky on clear nights for a possible display. That is, except when the Moon is full and “washes out” their visibility. (There actually have been auroras bright enough to be seen even then, but they are relatively rare.)

Since this is November, we can’t close without alerting readers to the Leonid Meteor Shower, which peaks on the night of the 16th-17th. Normally, a modest 15 to 20 meteors an hour will be seen under good conditions. But occasionally-and almost always unpredictably-the sky is literally filled with “shooting stars” radiating from the constellation of Leo. On a November morning just before dawn in 1966, most of the worldwide astronomical community wherever it was still dark (both amateur and professional) was totally blown away when the Leonids unexpectedly reached a rate of 40 meteors per second (that’s 144,000 per hour) and looked like snowflakes coming at you in a driving snowstorm! There have been other Leonid outbursts since, but none to date that have matched that amazing display. (Ones similar to that in 1996 had also been seen in 1799, 1833 and 1866.) So, as with auroras themselves, it’s best to check the sky just in case the meteor shower turns out to be a meteor storm!

- James Mullaney
Former assistant editor at Sky & Telescope magazine & author of eight books on stargazing.