Observing in Ursa Major
When we look up at Ursa Major, the Great Bear, we’re seeing a constellation that barely rises above the horizon from much of the southern hemisphere. In cities like Sydney, Cape Town, or Buenos Aires, it’s a challenge to spot even a portion of it. But from mid-northern latitudes, Ursa Major is a year-round presence—one of the most easily recognized constellations in the sky, thanks to the prominent asterism known as the Big Dipper. That familiar pattern of seven stars—Alkaid, Mizar, Alioth, Megrez, Phecda, Merak, and Dubhe—has featured in stories and sky lore for thousands of years. But the constellation holds more than myth: many of its stars are physically related, part of the Ursa Major Moving Cluster—a collection of stars that formed together and still travel through space in the same general direction.* I was reminded of all this while during an observing session one moonlit night. The sky wasn’t ideal—washed out by city lights and a nearly full gibbous moon—but I set up my 203mm ...