With the moon nearing first quarter or 'half-a-pie' phase, the sky is still dark enough to go out and look for constellations. Some observers even prefer a little moonlight because it snuffs out the fainter stars that might otherwise add confusion. This week we'll make one final swim with the sky's dolphin, a slippery fellow near the Summer Triangle called Delphinus , and learn an old secret.
I say a final because although the dolphin's been up since late spring, it's now in the western sky and sinking closer to the western horizon each night. Soon it will be lost in the treetops and then transition to the morning sky. If you're not familiar with Delphinus, let's get oriented.
The best viewing time is the same as that for the International Space Station that we talked about last week — around 6-6:30 p.m. local time. Since space station passes always begin somewhere in the western sky, you might know the direction by heart, but if you don't, you can find west approximately by facing toward the sunset. Better, activate the compass on your iPhone (Settings - Privacy - Location Services - Compass) then locate the compass icon on your screen and click. For Android, you may have to install a compass app .
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Once you're facing west, look about halfway from the horizon to the zenith or overhead point for a brilliant bluish-white star. That's Vega, the brightest star in the big pattern or asterism called the Summer Triangle. I know it's December, but summer has a way of taking slow leave of the night sky.
Now reach your fist to the sky and measure off about 2 ½ fists above and left of Vega to land on Deneb, the brightest star in Cygnus the Swan, better known as the Northern Cross. OK, so that's two corners of the triangle. Now measure four fists below and a little left of Deneb to arrive at Altair. Connect all three bright stars for one mighty big triad!
To find Delphinus, look a little more than a fist above and left of Altair for the small group of five fainter stars that with a little imagination looks like a dolphin standing on its tail. Give yourself a pat on the back if it jumps into view.
Delphinus is ancient constellation as familiar to the ancient Greeks as it still is to us today. My favorite Delphinus story concerns the names of its two brightest stars, Sualocin and Rotanev. They certainly look and sound like other star names we might encounter, but no, these two are the result of a practical joke by one Niccolo Cacciatore .
Cacciatore worked at the Palermo Observatory in Italy in the early 1800s helping Giuseppe Piazzi, the discover of the first asteroid, Ceres, compile a new edition of the Palermo (Star) Catalog. When the work was eventually published in 1814, the British astronomer Reverend Thomas Webb noticed that two unremarkable stars in Delphinus were labeled with unfamiliar names: Sualocin and Rotanev. After some thought, he hit upon the explanation. Cacciatore's name translated into English is 'Nicholas Hunter', which when Latinized becomes 'Nicolaus Venator.' If you spell the name backwards, guess what you get?
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So old Niccolo Cacciatore has been pulling out collective leg for more than two centuries with his stellar joke. And it gets better. Late last month, the International Astronomical Union formally cataloged the names of 227 stars including — drum roll please — Sualocin and Rotanev!
