The Big Dipper pops out into your northwestern sky on August evenings. Tonight, we star-hop from the Big Dipper to two bright summer stars: Arcturus and Spica. The Big Dipper, Arcturus and Spica are so bright that you can often see them on a moonlit night or even from cities mildly beset by light pollution. In 2013, these stars can also lead you to the planet Saturn.
As shown on the above sky chart, we extend the Big Dipper handle “to arc to Arcturus and to drive a spike to Spica.” Arcturus is the brightest star in your western sky, so you can’t miss this yellow-orange beacon. Blue-white Spica, the brightest star in the constellation Virgo, is nowhere as bright as Arcturus but it’s still a first-magnitude star. This blue-white gem appears to the southwest (lower left) of Arcturus. In the year 2013, the golden light above Spica is the ringed planet Saturn.
Spica, Arcturus and Saturn descend westward throughout the evening hours. Spica sets beneath the west-southwest horizon by mid to late evening. Saturn sets after Spica. Then Arcturus sets beneath the west-northwest horizon at or around midnight. These stars will appear in almost the same place in the sky at the same time tomorrow – but not quite!
Spica and Arcturus set 4 minutes earlier with each passing day. Spica will disappear from the evening sky by late September, and Arcturus will disappear from the evening stage in November. As these stars sink westward day by day, it’s a sure sign of cooler weather to come!