South of the Equator, You Need to Relearn the Stars

A couple of weeks ago, the staff at New York's Hayden Planetarium, of which I'm a proud member, discussed possible subjects for 2019 lectures in their domed space theater. I suggested we use our state-of-the-art Zeiss planetarium projector to show what the night sky looks like from below the equator. 

I have already touched upon this subject in a Space.com column I penned a couple of years ago. In it, I described a tour I led to Easter Island and the Chilean Andes in the spring of 1986 to see Halley's Comet. 

That comet was predicted to be at its very best when moving through the far-southern sky. Unfortunately for most viewers at north-temperate latitudes, this placed the comet very low near the southern horizon. Places farther south had a bit of an advantage, as the comet appeared somewhat higher up in the sky. But for the very best views, many skywatchers headed south of the equator. The tour I was to lead would take me all the way down to latitude 30-degrees south. [Wow! Surprise Storm Gets Skywatcher 's First Southern Lights Shot]

But I had a bit of a problem.

I had never been that far south before, and the night sky would appear considerably different compared to what I was accustomed to seeing back in New York. 

Getting acclimated

That's when I wrote a letter to the then-chairman of the Hayden Planetarium, Bill Gutsch, with a request. I asked if I could come to the planetarium some afternoon and, in between shows, have him set the Zeiss projector to simulate what the sky looked like from far-southerly latitudes. Gutsch quickly responded positively to my request, and a few days later, he was taking me on a trip south to lands where unfamiliar stars and constellations such as the Southern Cross shine high in the sky. 

As I watched these new stars appear over the southern horizon of the Hayden sky, I felt the adrenalin course through my body, knowing that I would soon see these actual stars in the real night sky.

And what a sky it was! At that (and this) time of the year, spanning the horizon from east to west and arching high in the south is a celestial necklace of brilliant jewels: a string of primarily blue giant stars that follow along the southern Milky Way. Why are these luminous beacons strung out along the spine of our galaxy? Such stars are the brightest members of the spiral galaxy's arms. Although they comprise well under 1 percent of the total stellar population in the Milky Way, their brilliance still dominates the scene. 

The "Four Stars" 

The centerpiece of this belt of bright stars is the Southern Cross, known as Crux. The celebrated Italian navigator Amerigo Vespucci was the first European to see the Cross, in 1501, and he referred to its constituents as simply "the Four Stars." Vespucci also sighted two bright nearby stars, which we know today as Alpha and Beta Centauri, the former being the closest known naked-eye star to our own sun.

I got my first in-person look at Crux through the window of a commercial airliner flying from New York to Santiago, Chile, in the early hours of April 1, 1986. I will always remember that moment, and I was absolutely thrilled to finally see these stars. But my ultimate view of the southern stars came from a specially selected and very dark observing site near the town of La Serena, Chile. I guided my group around that unfamiliar, star-saturated sky using a five-cell flashlight as a pointer (today, I would use a laser pointer). 

Fortunately, my many weeks of scrutinizing southern star atlases, plus the advance look at these stars I got under the planetarium sky, paid off. I was able to locate constellations that I had never seen in person before. Still, under such a star-spangled sky, I had to pause every so often to make sure I had them right. 

The "Pit"

The south pole of the sky, always out of sight to us in the United States, was elevated one-third of the way above the southern horizon of La Serena. Indeed, one really noteworthy aspect of the far-southern sky is the increasing emptiness encountered as you look nearer to the south-celestial pole, in contrast to the celestial riches along the southern Milky Way. Of course, we have a prominent North Star — Polaris, located at the end of the handle of the Little Dipper and three-quarters of one degree from the north celestial pole. But there is no bright "South Star" near the South Pole. 

Is it any wonder, then, that long ago this area received the nickname of the "South Polar Pit?" 

To find the general area of the south celestial pole, we can use the Southern Cross, whose longer bar points almost directly toward the pole. 

A world turned upside down

Another aspect of the southern sky is that many of the familiar northern constellations appear inverted. As H.A. Rey pointed out in his classic star guide, "The Stars: A New Way to See Them" (Houghton-Mifflin Co.), those who live between roughly 10 and 30 degrees south latitude are "out of luck in one respect: For them, the constellation figures stand on their heads more often than in the Northern Hemisphere, because they were originally conceived by northern observers who could not know that, one day, there might be stargazers down under." [Constellations of the Night Sky: Famous Star Patterns Explained (Images)]

Even the familiar countenance of the "man in the moon" is strangely altered; his face is scarcely recognizable when turned upside down. And while all the constellations still appear to rise in the east and set in the west, their first appearance as they come above the horizon is different. Orion, for example, seems to rise in an awkward, legs-up manner. Cygnus the Swan rises neck up, while back home, its neck is parallel to the horizon. 

The star seasons are reversed, as well. Orion, a star pattern associated up here with frosty winter nights, is at its best during the Southern Hemisphere winter. Scorpius the Scorpion climbs almost directly overhead during South America and Australia's winter season of July and August. During the sultry summer of those same months in the United States, Canada and Europe, by contrast, Scorpius skims above the southern horizon.

Stargazing can be so fascinating and enjoyable from Down Under. And it can be a real challenge for northerners because of the drastically different orientations, paths across the sky and locations of even familiar star groups, not to mention the novelty of locating unfamiliar ones. Good luck!  

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications, and he is also an on-camera meteorologist for Fios1 News in Rye Brook, N.Y. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.