AstroBob: It's September, time for my Orion fix
Each summer, I look forward to seeing Orion return to the morning sky. Hidden by daylight from May through early August, we share nights instead with the Summer Triangle crew and favorite sky animals Draco the dragon and Delphinus the dolphin. But Earth keeps a movin' around the sun, displacing one set of constellations for another, and sure enough, Orion's back in view.
I got my dose early Sept. 3 while checking in on a couple of comets and a recent supernova. Quietly opening the front door just after 3:30 a.m., I stepped out as Orion stepped up. Betelgeuse, Rigel, Saiph and Bellatrix made their usual big box around the three-stars-in-a-row as the constellation cleared the treetops in the southeastern sky. What a refreshing sight after a summer of heat and humidity. Orion's wintertime associations give it that "cooling effect" we're all looking for by the opening of September. And it's just wonderful to look at.
This month and next are also the best times to explore the constellation's many double stars and nebulae without getting frozen fingers. Temperature that morning: 53 degrees, perfect for a light jacket. The Orion Nebula, located a short distance below the three-star belt, got my attention. I swung the scope in its direction and happily lapped up the view. Seeing it again was like seeing the first bloodroots bloom in April. So nice to have you back again.
The nebula and many of Orion's stars are located in the Orion Arm (sometimes, called the Orion Spur), a minor spiral arm of the Milky Way. The arm is about 3,500 light-years across and 10,000 light-years long. Guess who else lives there? You do!
The solar system lies within the arm as do many of the bright stars that dot the night sky. Betelgeuse may be 642 light-years away and the Orion Nebula 1,344 but viewed on a galactic scale, we're just across the street from each other.