Most of the stars that twinkle across the night sky aren’t alone — they consist of two stars or more. They’re so far away, though, that their light blurs together to form a single pinpoint. A couple of prominent examples in this evening’s sky include brilliant yellow-orange Capella, which is high in the east-northeast at nightfall; and directly below it, Castor, one of the twins of Gemini, which consists of six stars or more. The multiple nature of thousands of stars was discovered by an astronomer who was born 150 years ago today in California. Robert Grant AitkenRobert Grant Aitken’s mother wanted him to become a minister, but he was drawn to science instead. He studied astronomy, and joined the faculty of the University of the Pacific, which had a small observatory. In 1895, Aitken moved to the new Lick Observatory outside San Jose. He stayed there for 40 years, eventually serving as director. At the time Aitken began his career, most astronomers thought they’d found just about all
