“The Sky This Week” appears every Tuesday. It is written by Ian Clarke, Director of the Hatter Planetarium at Gettysburg College. The planetarium offers regular educational presentations about the stars and the skies; there’s something for early elementary through adults. Field trip requests are welcome. NOTE: field trip request form for 2022-23 is now live. Shows have concluded for Fall 2022, but we will post the schedule for the next semester around the new year. Images created with Stellarium.
The Sky this Week, December 20-26
We’ve been looking at notable features of the winter skies, and this week I’d like to stick with the constellation Orion. Go outside on a dark night and let your eyes adapt. Then look at the middle star in the sword that hangs from Orion’s belt. You may notice that it’s kind of fuzzy. A decent pair of binoculars will confirm this view, showing you a hazy patch surrounding some stars. That’s not a smudge on your lenses; it’s a cloud of gas (mostly hydrogen) about 12 light-years across and 1,300 light-years away from earth called the Orion Nebula. (“Nebula” is Latin for “cloud” or “fog.”) The colors you see in photographs won’t be visible in binoculars or a small telescope; instead, it will look monochrome or slightly greenish. The Orion Nebula is a stellar nursery where hundreds of pockets of slightly denser gas are coalescing into new stars even now.
Finally, this week brings us the Winter Solstice on Wednesday at 4:48 p.m. EST. That’s the moment the sun reaches its southernmost position in our sky, and for that reason, it’s the shortest day of the year and the day the sun’s elevation at noon is lowest. But good news: for us the earliest sunset occurs about two weeks before the solstice, so the sun is already setting slightly later each night.
Ian Clarke is the director of the Hatter Planetarium at Gettysburg College. In addition he has taught introductory astronomy labs and first-year writing there for over 30 years (not necessarily all at the same time). He was educated at Biglerville High School, the University of Virginia, and the University of Iowa. He lives in Gettysburg.