There are several constellations in our northern sky that have similar counterparts in the southern sky.
In our present evening sky, for example, there is the zodiac constellation Pisces, which consists of two fish tied together in a string or ribbon with their tails. One fish is made up of a faint circle of stars commonly known as the Diadem. “Pisces” is a Latin word meaning “fishes”; the singular form is “piscis”, and there is indeed a constellation of the Southern Pisces known as Piscis Austrinus. Using the Great Square of Pegasus, if you imagine a line drawn through the two stars on the right side of the Square (Markab and Sheat, also called Alpha Pegasus and Beta Pegasus) and go straight south, you will reach Fomalhaut, the brightest star in Austrian fishes and 18- I am the brightest star in the sky.
Another pair of analogues is the Northern Crown (Corona Borealis) and the Southern Crown (Corona Australis). Both are roughly circular in shape, and both are ancient star patterns dating back to the time of the 2nd century astronomer Claudius Ptolemy, or even earlier, perhaps Hipparchus almost three centuries before. These crown constellations were also called wreaths, indicating a very ancient type of characteristic head ornament made from beech, willow or laurel leaves, and in later times copied from them in precious metal into what we now know as a crown.
Related: Growing up watching the night sky in the Northern and Southern Hemispheres.
Northern Crown
The Corona Borealis is said to represent a crown given to Ariadne, daughter of Minos, king of Crete, by Dionysus, the ancient Greek god of wine and a very bucolic character who would consider a beautifully intertwined wreath of vines a sufficient tribute. However, Ariadne was reluctant to accept a marriage proposal from Dionysus (who was in mortal form) as she did not want to marry a mortal after being abandoned by Theseus, the mythical king and founding hero of Athens.
To prove that he was a god, Dionysus (or Bacchus as the Romans called him) took off his crown and threw it into heaven as a tribute to Ariadne. Satisfied, she married him and in the process became immortal herself.
southern crown
Unlike the bejeweled Corona Borealis, the Corona Australis is said to be a crown or wreath of laurel or olive leaves. According to one story from Greek mythology, the crown belongs to Chiron, the wisest of all centaurs.
Another story related to the Southern Crown comes from the Metamorphoses by the Roman poet Ovid. Juno, the Roman queen of the gods, discovered that her husband Jupiter was the lover of Semele, who was a mortal mother. Posing as Semele’s maid, Juno invites Semele to ask Jupiter to appear before her in all his glory. Jupiter was approached with such a request, but he did not refuse it. When she looked at Jupiter in all its glory, Semele burned in the fire. Somehow her unborn son was saved; he eventually became Bacchus, who in turn honored his mother posthumously by placing the Southern Crown in the sky.
So we can thank Bacchus (as well as the ancient Greeks and Romans) for making both crowns constellations.
On the subject: What lies behind the stars?
Constellation corona australis, or southern crown (Image credit: Astrocat Bali/Getty images) (will open in a new tab)
“Second Scoop”
On September evenings, the Northern Corona is midway in the western sky, while the Southern Corona lies close to the southern horizon, below the Sagittarius Teapot. Both crowns attract attention almost immediately as soon as the eye sweeps over them. Seven stars, one half magnitude (Gemma, crown jewel), form an incomplete circle of the Northern Crown; it actually looks more like a tiara than a crown.
However, when I gave celestial shows at New York’s Hayden Planetarium, the Northern Corona was something completely different: it was directly adjacent to the tip of the constellation Bootes, resembling an elongated kite. But for my audience, I suggested that Boötes would be much better represented as an ice cream cone with two scoops. “Unfortunately, the second spoon seems to have completely slipped off the top!” I would say. And then I would point to Corona Borealis.
“slice of lemon”
Despite the much fainter stars that suffer from low altitude for mid-north observers, the Southern Corona is quite attractive because there are many more stars (11) and the ring is almost complete. The late George Lovie (1939-1993), who lectured at the Hayden Planetarium in the 1980s and early 90s, found another use for this star pattern. First, he would point to the asterism of the Kettle of Sagittarius; he then asked his audience if they would like a lemon with their tea. Then he pointed to a slice of lemon: Corona Australis.
“I heard that some of you prefer milk with tea?” he would say. “The Milky Way is flowing right by!”
Two strange stars
One of the most remarkable stars in the sky is R Coronae Borealis, popularly known as R Cor Bor. Simply put, it’s a nova in reverse. Usually shining at magnitude 5.9 at quite irregular intervals, this star will suddenly dim, sometimes by as much as eight magnitudes (almost 1,600 times), when dark clouds of carbon material, or “soot clouds,” erupt in the star’s atmosphere. It then slowly regains its brightness as the material scatters. The fall occurs rather quickly, and the return to normal is much slower, with rare relapses. The fading of the bright red star Betelgeuse in the constellation Orion in 2019 was likely caused by a similar cloud of obscuring matter.
And then there’s T Coronae Borealis, also known as Blaze Star, which currently shines at magnitude 10.2, making it 30 times dimmer than the faintest star on the threshold of naked eye visibility. (A smaller magnitude indicates a higher brightness, and vice versa.) But over 150 years ago, on May 12, 1866, this star suddenly brightened up to magnitude 2, almost as bright as the Pole Star (Polar Star). Known as a recurring nova, T Coronae Borealis made a surprise repeat performance on the night of February 11th. September 9, 1946, and sometime in the future, perhaps it will happen again.
In fact, given that the 1866 and 1946 outbreaks were almost exactly 80 years apart, it’s possible that another outbreak could be around the corner.
the one that got away
In his autobiography Starry Nights (Harper and Row, 1965), Leslie S. Peltier (sometimes called “the world’s greatest amateur astronomer”) wrote that at every opportunity since 1920 – more than 25 years – he carefully watched T Crown. But on the one and only night in 1946, when the star suddenly flared up, Peltier was asleep!
On that cold February morning, the alarm clock rang at 2:30 am, but when he woke up, Peltier sneezed a couple of times and thought that maybe he had a cold, or maybe something worse. “Self-pity comes easily at 2:30 on a cold February morning,” he later wrote, “so I went back to my warm bed.”
Of course, after Peltier found out that he had missed the unexpected starburst he had been watching for over a quarter of a century, he was not a happy camper.
“I still have the feeling that T. [Coronae Borealis] could have paid more attention to me,” he wrote. We have been friends for many years; a thousand nights I watched him while he slept, and then he rose in my hour of weakness when I nodded to my post. I still watch it, but with apprehension. There is no more warmth between us.”
Joe Rao is an instructor and guest lecturer at the Hayden Planetarium in New York. (will open in a new tab). He writes about astronomy for Natural History magazine. (will open in a new tab)Farmer’s Almanac (will open in a new tab) and other publications. Follow us on Twitter @Spacedotcom (will open in a new tab) and on facebook (will open in a new tab).