Don’t Overlook Our Southern Skies
– Eric Saltmarsh
One of the aspects of our local skies that I love is our view to the south. There are numerous locations that offer unrestricted access to the southern sky, right down to the horizon.
Objects near the southern horizon don’t receive much attention because they’re low in the sky to most northern hemisphere observers and because only 10% of the world’s population lives south of the equator, where the southern sky is best seen.
Since we live at 35 degrees north latitude (about the same as San Luis Obispo, California and Raleigh, North Carolina) and have dark skies that allow us to view stars right down to our low southern horizon, we can see 55 degrees of sky below the celestial equator (the celestial equator is an imaginary line in the sky, directly above the Earth’s equator). We can’t see the entire southern sky, but we can see more than half of it.
If you go outside after dark this week, there are a number of interesting objects you can find low in the south. One is Canopus, the second brightest star in the night sky, which currently rises in the SSE, about 7pm MST. Canopus is a white star of magnitude -0.74, situated in the constellation Carina. It’s only outshone by Sirius.
While Canopus truly is the second brightest star, its brilliance lacks luster because it never appears more than three degrees above the horizon, as seen from Santa Fe. Canopus’ proximity to the horizon causes us to view it through more atmosphere than a star overhead, significantly dimming it.
Three open star clusters (i.e., NGC 2451, NGC 2477, and NGC 2546) sit close together within the winter Milky Way, in the constellation Puppis. NGC (New General Catalogue) 2451 and NGC 2546 appear as neighboring broad clusters of stars, visible to the unaided eye and easily viewed in binoculars. The third cluster, NGC 2477, is a compact group of 300 stars that requires a small telescope to resolve.
A favorite object of mine is Omega Centauri, a large globular cluster located in the constellation Centaurus. Globular clusters are tight balls of myriad stars, held close to one another by gravity. They’re old objects that form halos around a galaxy’s core. Comprised of 10 million stars, omega Centauri is the largest globular cluster in our galaxy.
Omega Centauri is visible to the unaided eye from the 285 Corridor, but – owing to our latitude – it never rises more than 8 degrees above the southern horizon. For centuries prior to the invention of the telescope, this ‘fuzzy star’ was an object of speculation to ancient astronomers.
There are many other objects worthy of our attention that never climb far above our southern horizon. Fortunately, our southern horizon is fairly flat and relatively free of light pollution, so we can view stars and deep sky objects in the southern sky – at least for the time being.