The southern Milky Way holds such contrasting gems as the Eta Carinae Nebula (left center) and the Coal Sack (center). Photo by Luke Dodd
When Bart Bok left Harvard to direct Mount Stromlo Observatory in Australia he said, "All of the good stuff is in the Southern Hemisphere." For someone who lives in the Northern Hemisphere, the first observing session from the Southern Hemisphere is an epiphany. My defining moment came when I had the opportunity the first time since I was eight years old to learn 20 or 30 new constellations at once.
The fun begins during the daytime. From the Southern Hemisphere, the sun still rises in the East and sets in the West, but it moves from right to left across the northern sky. So does the moon, whose features are rotated 180°. When we first arrived in Chile, a friend remarked that the moon was upside down. I said, "No, you're upside down." The planets also move across the northern sky, and the equatorial constellations are upside down. I could still recognize some of the constellations easily, such as Orion, Delphinus, and Capricornus. Others, such as Ophiuchus or Cetus, I didn't recognize at all, until I worked them out with a star map.
To Southern Hemisphere observers, the mighty hunter, Orion, appears to stand on his head. Bill and Sally Fletcher
A good time of year for your Southern Hemisphere observing adventure is between May and July, during the southern (or austral) midwinter. Constellations such as Sagittarius the Archer and Scorpius the Scorpion pass dramatically overhead. So does the Milky Way. This edge-on, barred spiral galaxy's galactic bulge is plainly visible on clear, dark nights.
In May, one can see the lower third of the southern Milky Way (from Scorpius to Orion) in its entirety. This is the section we never see from the Northern Hemisphere. Following the Milky Way south from its center in Sagittarius, south and east through Scorpius, leads you to the large, bright constellation Centaurus the Centaur. Centaurus is too far south to be seen by most northern observers. This is unfortunate, because Centaurus is one of the grandest constellations in the sky, ranking right up with Orion. The mythological Centaur is depicted as spearing Lupus the Wolf, another large, bright constellation that extends into the Milky Way.
The two brightest stars in Centaurus are 1st-magnitude Alpha and Beta Centauri. Alpha is an easy visual double star through small telescopes, and its brighter, yellow component is much like the sun. Following Alpha and Beta Centauri westward along the Milky Way leads to the Southern Cross. To remember this path, just remember your ABCs, "Alpha, Beta, and the Cross." Northward from Alpha and Beta Centauri is Omega (w) Centauri, by far the largest, brightest, and grandest globular cluster in the sky. M13, the famous northern globular in Hercules, falls a paltry third behind Omega Centauri and 47 Tucanae, which is also in the south.
At 4th magnitude, Omega Centauri is an easy naked-eye object. Through binoculars, one can resolve stars right through to the center, and it gets even better. The stars in Omega Centauri are bright enough that a view through a 16-inch telescope provides enough light to activate color vision. The stars reveal their topaz, orange, and red glory. Seeing Omega Centauri in black-and-white is similar to looking at a picture of the Grand Canyon. The real thing is far more spectacular.
The Southern Cross, or Crux, lies in a dense region of the Milky Way. I once read the remark: "What's so special about the Southern Cross? It's the smallest constellation, and it consists of only five or so stars.'' Whoever wrote these lines couldn't possibly have seen the constellation. Crux is striking, a real jewel box. Three of the stars shine at 1st magnitude, the others at 3rd magnitude. The Southern Cross is distinctive, in a league with Orion's belt and little else. It's also adjacent to the remarkably dark Coalsack, an apparent hole in the Milky Way about 5° across. The Coalsack is actually an interstellar dust cloud that blocks the light from stars behind it. Because it's surrounded by a host of stars in the Milky Way, the black patch appears darker. The Coalsack is unlike any other dark region in the sky.
South (up) of the stars Alpha and Beta Muscae is a "globular filament" type of dark nebula nicknamed the Dark Doodad. Luke Dodd
Just north of the Coalsack is Beta Crucis, the 1st-magnitude star on the eastern end of the cross's crossbar. Between Beta Crucis and the Coalsack is the Jewel Box, or Kappa Crucis. An open cluster of more than 100 stars, the Jewel Box is more colorful than any similar object in the Northern Hemisphere.
Farther west along the southern Milky Way is the antiquated constellation Argo Navis the Ship. In the mid-18th century, the Great Ship was broken into four separate constellations: Carina the Keel, Vela the Sail, Pyxis the Compass, and Puppis the Stern (also known as the poop deck). I can never find Pyxis, it has only two or three faint stars, but Carina, Vela, and Puppis are bright, easy to spot, and extend far from the galactic plane.
If you follow the line from Alpha and Beta Centauri to the Southern Cross and then continue along the galactic plane about the same distance, you'll come to 5th-magnitude Eta Carinae. In 1843, Eta Carinae had an outburst that made it the second-brightest star in the night sky. The eruption threw off most of a large nebula surrounding the star. This star is brightening again (see "Scoping Out the Monster Star," February 2000). The chance to witness an outburst makes any time you invest in monitoring the star worthwhile. The nebula around Eta Carinae is roughly 2° across (about four times the apparent diameter of the moon) and an easy naked-eye object that doesn't require skies as dark as those needed to see the North America Nebula in Cygnus the Swan. Like the North America Nebula, the Eta Carinae Nebula looks like it does in wide-field photos. The only difference is that the eye sees a ghostly white and not the garish red that film brings out.
Continuing west along the Milky Way, from Alpha and Beta Centauri to Crux past Eta Carinae, we come to an area between Vela and Carina. Here lies an asterism called the False Cross. It's about the same size and shape as Crux, but not as bright, having "only" three 2nd-magnitude stars (Delta Velorum and Epsilon and Iota Carinae), and one 3rd-magnitude star (Kappa Velorum).
Canopus, the second brightest star in the sky, is at the end of the handle of Carina the Keel. Sirius, the brightest star, is farther west and north along the Milky Way in Canis Major. Here too is familiar Orion. His upside-down figure appears awkward with Lepus the Hare resting above his feet. South of Lepus rests Columba (not Columbia) the Dove.
Looking away from the southern Milky Way, we find two of the largest constellations in the sky: Eridanus the River and Hydra the mythical Water Snake. Both are long, thin, and wind their way around the sky similar to the north-circumpolar constellation Draco the Dragon.
Eridanus is distinctive where it begins near Orion's feet. After that, the constellation's meanderings are hard to follow. The River winds its way southward past the claws of Cetus the Whale and around Fornax the Furnace toward an unmistakable end at the 1st-magnitude star, Achernar.
Hydra also holds mainly faint stars, but it is worthwhile to spend the time puzzling out it's path with a star chart. The constellation begins in a small quadrilateral south of Leo and Cancer. From there it winds its way southward past Sextans the Sextant, Crater the Cup, and Corvus the Crow to its end near Centaurus. As the largest of 88 constellations, Hydra spans more than 100° of sky.
The Teapot asterism in Sagittarius is hard to spot when the view is south up. One consolation: the Milky Way splendors in Sagittarius pass high above the horizon when on the meridian. Luke Dodd
Many southern constellations were named during the 17th through 19th centuries. These recent additions reflect the scientific interests of that period. Constellations such as Horologium the Clock, Microscopium the Microscope, and Telescopium the Telescope are all faint and hard to find. Another, Octans the Octant, depicts an obsolete navigational instrument. Nearby, Mensa forms another grouping of faint stars. This constellation is named for Table Mountain near Cape Town, South Africa, where the southern sky was first surveyed in the 1820s. Mensa is the only constellation named for a geologic feature.
Small but distinctive Antlia the Air Pump takes us back toward the Milky Way. Air pumps were scientifically a big deal in the 1600s, since they contradicted Aristotle's dictum that nature abhorred a vacuum. The constellation is small and not unlike Delphinus the Dolphin in the northern Milky Way.
Though the list of constellations to be learned is impressive, deep-sky wonders also abound. The objects you've struggled to see in Sagittarius and Scorpius are high overhead in vivid splendor. The Trifid Nebula (M20) really does have those dust lanes that cut it into three parts. The Lagoon Nebula (M8) is spectacular to the naked eye. The view of M8 from southern latitudes rivals that of the Orion Nebula (M42). NGC 5128, an elliptical galaxy that is the optical counterpart to the radio galaxy Centaurus A, has a broad dust lane across its round face. Through the eyepiece of a 6-inch or larger telescope, the galaxy looks like the long exposure images taken with large telescopes. The Sombrero Galaxy (M104) in Virgo has a thinner dust lane. Through the eyepiece its large hat-like shape becomes apparent. It too looks like the pictures you've seen.
Viewing Scorpius and its deep-sky objects high above the murky horizon is a real treat for Northern Hemisphere observers. Luke Dodd
Two of the greatest marvels are the Large and Small Magellanic Clouds, both near declination 70° are south-circumpolar and only visible from the Southern Hemisphere. The Large Cloud is near Dorado the Swordfish; the Small Cloud is near Tucana the Toucan. Between these satellite galaxies of the Milky Way is the small, faint constellation Hydrus the Little Water Snake. Larger Hydra, its mate, is nowhere nearby. "Cloud Season" is October through December, or austral spring to early summer. During this time period, the Magellanic Clouds are impossible to miss. Even if you're unfamiliar with the southern constellations, you'll be able to pick out the Magellanic Clouds. Both are fairly large, bright areas separated a fair distance from the Milky Way.
The Large Cloud is about 5° across, roughly half the width of your fist at arm's length. The Small Cloud is about 2° across. Each is filled with wonderful binocular sights. Unequaled among more than 50 star clusters in the Large Cloud is the Tarantula Nebula (30 Doradus). This dense, star-forming region is brighter and larger than the Orion Nebula. The Tarantula Nebula gets its name from long, thin tendrils sticking out, not unlike those seen in deep images of M42.
If these sky views sound enticing, it's time to pack your binoculars and head south for the summer. You might want to plan your trip around one of the upcoming solar eclipses. On June 21, 2001, the eclipsed sun passes through Angola, Zambia, Zimbabwe, Mozambique, and Madagascar. On December 4, 2002, the sun's shadow falls on nearly the same region of Africa and also cuts across South Australia.
Whatever your itinerary, observing from the Southern Hemisphere will revive that initial exhilaration you felt when you first looked up.
Fred Ringwald is a faculty member at Florida Tech University.
This article originally appeared in the June 2000 issue of Astronomy.
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