Like the raspberries in the woods, summer is ripening. Stars that were once prominent in June are on their way westward. And if you’re out at dawn, be prepared for a shock – the early winter constellations of Taurus and Auriga have returned. Last night I noticed that the Big Dipper has dropped considerably in the northwestern sky. It’s tipped at the same angle I tipped the little rubbed-coated spoon we used to feed our daughters when they were babies.
Once the Dipper is in your sights, it’s simple to “Arc to Arcturus” and bop into Bootes. Don’t forget to make a stop at the small, two-star constellation of Canes Venatici (KAY-nees ven-AT-iss-see). I know it’s a meager group, but if you own a small telescope, the brighter of the two stars, called Cor Caroli, is one of the prettiest double stars in the sky.
While you’re out, you may notice more meteors than usual this time of year. We’re now in a multi- meteor shower season with contributions from several different minor showers. Meteor showers occur when Earth’s orbit intersects a debris trail left by a comet (or rarely, an asteroid). Meteors or ‘shooting stars’ are the glowing trails left by bits of comet dust when they strike our atmosphere at speeds of many thousands of miles per hour and vaporize in a flash. Each meteor shower has its own ‘parent’ comet. The familiar Perseid shower of mid-August originates from dust left by Comet Swift-Tuttle.
* Alpha Capricornids: this shower appears to radiate from near the star Alpha in Capricornus about three outstretched fists to the lower left of the Summer Triangle. It’s active from mid-July to mid-September and peaks around August 1. With only about a half dozen meteors per hour, it’s definitely in the ‘minor’ category, but it has a saving grace – the shower’s known for its slow, bright meteors. Best viewing time is from 11:30 p.m. until the start of dawn. The 169P/NEAT.
* Southern Delta Aquarids (SDA): Active from mid-July to mid-August. This shower is the best of the bunch with a peak on the night of July 29-30 (Friday night-Saturday morning). From a dark sky site, especially from the southern U.S. where the radiant is higher up, an observer would expect to see 15-20 meteors per hour. Face south or southeast for the best view.
Because the radiant lies in Aquarius, the best time for viewing the shower is from about midnight until dawn, when the constellation is high enough in the south for meteors to clear the horizon. The parent comet is one of the ‘sungrazers’ that closely approach the sun, often breaking up or partially vaporizing under the influence of its gravity and heat. The SDA produces medium-speed meteors that speed into our atmosphere at 26 miles per second or over 93,000 mph!
* Northern Delta Aquarids: This weaker shower radiates from northern Aquarius and is active from mid-July into September with a maximum of 10 meteors per hour in mid-August.
You can tell which is which by following a meteor’s path backward in the sky. If it points to below the Summer Triangle, it’s probably an Alpha Capricornid. If you can trace it back to a spot in the sky above the bright star Fomalhaut, it’s a southern Delta Aquarid.
Granted, with all these meteoric dribs and drabs, it might be hard to know exactly which meteor belongs to which shower, but it’s still fun watching them. Sharpening your meteor-watching skills will prepare you for the bigger Perseid shower due to peak in a little more than two weeks. Hey, you might even see a few early Perseids later this week. If so, they’ll originate from Perseus in the northeastern sky.