Tonight, the just past-full waning gibbous moon beams near two bright and beautiful stars, Arcturus and Spica. Sparkling above the eastern horizon at early evening, these stars travel westward (along with the moon) throughout the night. They shine high in the southern sky in the wee hours after midnight, and as dawn starts to color the sky, these gems light up the western sky.
Although yellow-orange Arcturus appears much brighter than blue-white Spica to our eye, that’s only because Spica is so much farther away from us. Arcturus resides about 37 light-years away, whereas Spica lies some 7 times farther off than that, at 260 light-years distant. If Arcturus stood at the sun’s distance from us, it’d shine over 100 times more brightly than the sun. But Spica at the sun’s distance away would shine with the firepower of over 2,000 suns!
Unlike the fickle moon, the Big Dipper guides you to these springtime stars, Arcturus and Spica, with the utmost faithfulness, day after day. At nightfall, the Big Dipper stands on its handle in your northeast sky, looking like a kite flying in the March wind.
Bottom line: Use the moon to find Arcturus and Spica tonight, and then use the Big Dipper to locate these colorful stars for months to come!