How and when to see Alpha Centauri, southern star patterns such as the Southern Cross, and many other celestial sights on a trip south of the equator.
If you regularly spend time with the night sky in the Northern Hemisphere but you've never travelled south of the equator, you only know half the story.
Visiting the Southern Hemisphere just to go stargazing isn’t something most of us have the resources to do very often. Yet the southern sky is disorientating, surprising, and utterly transfixing — well worth the trip if you can make it. You’ll see arguably some of the greatest celestial sights: the nearest stars to our solar system, two close dwarf galaxies, and some drop-dead gorgeous clusters.
Here are a few reasons why you should visit southerly latitudes at least once in your life.
The first thing you'll notice after dusk south of the equator is that the northern constellations appear upside down. The North Star, Polaris, isn’t visible and the circumpolar northern constellations, such as the Big Dipper, Cassiopeia, Draco, and Cepheus become seasonal.
Finding the constellations and asterisms you thought you knew so well can be difficult: The Summer Triangle becomes the Winter Triangle down south, with Altair on top, and Deneb and Vega sinking as the night wears on. Low on the northern horizon in the southern hemisphere summer, Orion's sword points up toward Rigel, while brilliant Sirius is overhead at zenith. Around 35° from Sirius is the second brightest star, Canopus, the Great Star of the South. To southerners, it's a near-constant companion of Sirius, seen from October through May.
Here's a helpful tip: Take Sky & Telescope's 30°S planisphere with you in your travels to help you identify constellations.
The Nearest Star System
One reason to visit the Southern Hemisphere is to see the star system closest to us. The third brightest star in the night sky, Alpha Centauri is just 4.37 light-years away. It's more than one star — Alpha Centauri A, a Sun-like star, and its companion, the slightly less massive Alpha Centauri B, actually form a triple with Proxima Centauri (technically the nearest at just 4.22 light-years). All three stars appear as a single point to the naked eye, but a 3-inch telescope with 100× magnification can split Alpha Centauri A and B.
Alpha Centauri is circumpolar, so it’s visible year-round south of the equator, but it’s at its highest from March to September. You might also see it north of the equator: If you're at latitude 29°N at most (think Texas or northern Florida), Alpha Centauri can sometimes be visible a few degrees above the southern horizon in May.
Finding the Southern Cross
Once you've found Alpha Centauri, the next challenge is the Southern Cross, an asterism in the constellation Crux. This circumpolar constellation is easiest to find using a tried-and-tested star-hop because there’s also a False Cross nearby. Alpha Centauri and the dimmer blue-white Beta Centauri act as the Pointers: Hop from Alpha Centauri to Beta Centauri then continue three times the distance between them, and you'll arrive at Gacrux at the tip of the Southern Cross. The constellation is easiest to see between March and June (upside down in the spring, rightside up in the fall).
Its small size may initially disappoint, but that impression will dissipate once you realize what's in its vicinity. The jaw-dropping Jewel Box cluster (NGC 4755) is best seen through a small telescope, which can reveal more than a hundred sparkling blue jewels around a single red star. Nearby is the Coalsack, a dark nebula best viewed with the naked eye or binoculars.
A Naked-eye Globular Cluster
If you never tire of glimpsing the Andromeda Galaxy with the naked eye under dark country skies from the Northern Hemisphere, you'll love seeing a 13 billion-year old globular cluster with zero equipment. Most easily seen from April through September, Omega Centauri (NGC 5139) contains 10 million stars and possibly even a black hole at its center. It’s the most massive and most luminous globular cluster visible from anywhere on the planet. Because of its distinct properties, astronomers think it might be the nucleus of a dwarf galaxy that long ago collided with the Milky Way. Found deep in the constellation of Centaurus, Omega Centauri looks like a blob almost as large as the full Moon in dark skies, and appears as a speckled glow in amateur telescopes.
Now that you've seen the brightest globular cluster in the Milky Way, find the second brightest — 47 Tucanae (NGC 104) — which is highest in the sky from October through February.
Milky Way’s Largest Satellites
If you make it to clear, dark skies and let your eyes adjust, the sight of two unexpected clouds might surprise you. Many astronomers travel specifically to see the Small and Large Magellanic Clouds (SMC and LMC), the largest dwarf galaxies in the Milky Way’s retinue.
These two galaxies offer up dense star fields ideal for sweeping binoculars. Named after Portuguese explorer Ferdinand Magellan, who spotted them in 1519 while circumnavigating the globe for the first time, the LMC contains the Tarantula Nebula, also called 30 Doradus. It’s a massive star nursery, much like the Orion Nebula (M42), but on an entirely different scale. About 100 times the size of Orion Nebula, 30 Doradus is the largest star-forming region in the Local Group of galaxies, and so luminous that if it were as close to us as the Orion Nebula is (about 1,300 light-years), it would cast shadows.
Galactic & Planetary Sights
These are just a few of the arresting sights in the Southern Hemisphere sky, but there are many more. Galactic delights include Centaurus A (NGC 5128), the fifth-brightest galaxy crossed by a distinctive dust lane, and the Great Rift in the Milky Way, a dark lane that divides the Milky Way’s bright band lengthwise. In addition, the Southern Hemisphere offers the planet's best view of galactic center and all its glories — it's at its best between July and September.
Even Saturn looks better from the south. The ringed planet is moving through Scorpius, Ophiuchus, Sagittarius, and Capricorn until the mid 2020s, all of which are much higher in the sky in the Southern Hemisphere.
Need a reason to venture south? A total solar eclipse will roll through Chile and Argentina on July 2, 2019, centered on the Elqui Valley, home to professional telescopes and dozens of boutique observatories. It’ll be the perfect excuse to visit the Southern Hemisphere for its unique view of the universe.