As travelers descend on Rio, Brazil, to revel in the 2016 Summer Olympics, some visitors may be surprised to find a spectacle of the celestial kind in the skies above.
The Southern Hemisphere has been known for centuries as a stargazer’s paradise, as the night sky south of the Equator is endowed with more than its fair share of brilliant stars and deep-sky treasures. For northern skywatchers, that means the real stars of the Rio games may be the oodles of stunning celestial objects and constellations that normally lie hidden below their local horizons.
Light pollution will limit what can be seen from the city, but traveling for the games offers an opportunity to venture into darker locations that will present deeper views of the cosmos. No matter your location, quick viewing tips include turning off surrounding light sources so no direct lights are hitting your eyes, and allowing your eyes at least 15 to 20 minutes to adapt to the darkness before beginning skywatching in earnest.
Here is a sampling of some of the most famous stargazing sights Olympics spectators can check out after dark in the Brazilian skies.
Southern Cross. Arguably one of most famous of all southern constellations, the Southern Cross, known more formally as Crux, is a bright but very compact grouping of four stars. It can be easily viewed with nothing more than the naked eyes, and it features on many national flags in the south, including those for Australia, New Zealand, and Brazil.
Part of its claim to fame is that the Southern Cross points to the South Pole in the sky. However—unlike Polaris, the North Star—there is no conveniently bright star that marks the spot above Earth’s southern axis.
The Southern Cross is one of the tiniest stellar patterns in the entire sky: From top to bottom, the whole cross appears to be only six degrees long, just a bit more than the span of your three middle fingers held at arm’s length. For those that know northern skies better, the cross would almost fit inside the Big Dipper’s bowl.
During the Olympic games, the Southern Cross can be found almost halfway up the southwest sky soon after darkness falls.
Alpha Centauri. While Crux may be the most iconic pattern in the southern sky, Centaurus is one of the easiest and brightest southern constellations to spot. The mythical centaur is the ninth largest constellation in the entire sky and contains two of the top 10 most brilliant stars, making it a real jewel of the southern heavens.
Probably its most famous resident is Alpha Centauri, the closest star system to our own. An iconic object in science fiction, this triple star system is the brightest member of the constellation, mostly because of its proximity: The system lies just 4.3 light-years from our sun.
Nearby from our perspective sits Beta Centauri, known as Hadar, which is actually much farther away from Earth at 300 light-years distant. It competes in brightness with Alpha Centauri because it's a supergiant star that intrinsically shines brighter. Together, both stars are known as pointer stars that guide skywatchers to the Southern Cross, which is tucked away underneath the centaur’s hind quarters.
Alpha and Beta Centauri will be easy to spot this month since they are the brightest stars in this part of the early evening sky.
Brazilian Flag Stars. The Brazilian flag depicts 27 stars on a globe, one for every state or district. The five-pointed shapes depict nine real stars and constellations: Procyon, Canis Major, Canopus, Spica, Hydra, Crux Australis, Sigma Octantis, Triangulum Australe, and Scorpius. On the flag, the stars are placed as they were seen above Rio on November 15, 1889, when the nation was declared a republic.
These stellar groups are more easily seen from the Southern Hemisphere, and some will be on brilliant display during the 2016 Olympics. Scorpius, for instance, tends to only skim the southern skies across most of Europe, the United States, and southern Canada. But during the Rio games, it will appear nearly overhead at night above Brazil.
Magellanic Clouds. For those that get a chance to head to darker locations away from Rio’s lights, stranger sights abound. Perhaps the most famous southern objects are two dwarf galaxies that orbit our home galaxy, both of which can be spotted with the naked eye near the Milky Way’s stream of stars.
The Large Magellanic Cloud is the brighter of the two and looks like a fainter piece of the Milky Way that has broken off its arc. The cloud spans about 11-by-9 degrees, roughly equal to the width of your clenched fist held at arm’s length. But this seemingly small galactic island is really about 30,000 light-years across and contains a few billion stars. It only appears diminutive because it sits 160,000 light-years from Earth.
Its sibling, the Small Magellanic Cloud, is five degrees across and is distinctly fainter. It is estimated to be home to a few million stars and is even farther away from us, at 210,000 light-years. Both the Large and Small Magellanic Clouds are best seen during the time of the Olympics in pre-dawn hours, about a third of the way up the western sky.
Planet Lineup. Unlike the fixed positions of the stars, the planets seem to wander across the skies for both hemispheres, and so visitors from the north will be able to find some familiar celestial friends.
Jupiter, Mercury, and Venus will appear as bright star-like objects lined up in a nearly vertical row very low in the western sky. Meanwhile, ruddy Mars and yellowish Saturn will also be side by side but will sit significantly higher in the Southern Hemisphere sky than they will be in the north.