The Watery Part of the Sky

SKY MAP: The Celestial Sea constellations as of 10 p.m. local time, as seen from mid-northern latitudes this time of year. Eridanus is mostly below the horizon. The constellations move up in the sky during the night, so most of Eridanus becomes visible low on the horizon by midnight. CREDIT:

We're now two weeks into the new autumn season and for those of us who live in the Northern Hemisphere, the days keep getting shorter and cooler, as the winter approaches.  During the mid-to-late evening hours, aside from the pumpkin-colored Mars blazing in the east, there are very few bright stars in the region that is spread across the southern skies. 

Little can be seen here when the sky is hazy or flooded with moonlight.  But on clear moonless evenings you will find some interesting constellations in this part of the sky, though their figures are all rather dim. 

This whole area can be called the "Watery" part of the sky.  It isn't really watery, of course.  It is watery in the sense that it is vague and dim, like a dark pool.  These watery constellations -- Capricornus, the Sea-Goat; Aquarius, the Water Bearer; Pisces, the Fishes; Piscis Austrinus, the Southern Fish; Cetus, the Whale; and finally Eridanus, the River -- may have commemorated a great flood of long ago.

Indeed, the first three constellations belong in the zodiac, and all members of this group have been associated with the rainy season of ancient Mideast lands.  There is also a mythological connection between these star pictures and an ancient great flood in the Tigris-Euphrates basin, which has sometimes been linked to the Deluge in Genesis. It's difficult to say for sure, because the original significance of many starry figures was lost when the Greeks recast the display with characters of their own legends.    

In Latin, Capricornus literally means, "horned goat."  You might have heard of the famous little island of Capri in Italy: its name means that it is the island of goats.  But in the old star atlases Capricornus is depicted by the figure of a Sea-Goat, combining the forequarters and head of a goat and the tail of a fish.  Indeed, it appears that in creating Capricornus, the imaginations of the ancient stargazers were working on overtime. This kind of weird creature might seem totally unintelligible to us today if we did not know the ancient myth that attempts to explain its origin.

The folklore behind Capricornus is rather amusing. Supposedly, there were some sea nymphs and goddesses having a wild picnic-party in a field one day when the mischievous god, Pan, saw them and joined in the fun. About this same time, however, a huge, ferocious monster called Typhon suddenly appeared.  To escape him, each god changed himself into an animal and fled.  However, in Pan's alarm (hence the word "panic") he jumped into a nearby river before completing his transformation into a goat. As a result, his lower extremities assumed the form of a fish!  Zeus, who just happened to be passing by, saw Pan's feat and was so amused that he decreed the perpetuation of this grotesque figure in our night sky.

It should also be emphasized to newcomers of astronomy that the currently accepted name of this constellation is Capricornus, and not Capricorn.  Principally astrologers (and some older astronomy books) use the latter for labeling the zodiacal sign of that name. But quite frankly, Capricornus is such a faint constellation, if it were not a zodiacal sign most people would not even know its name.

The fourth magnitude star, Algiedi is really a pair of stars (called Alpha 1 and Alpha 2) so widely separated that they can be easily distinguished without any optical aid.  Astronomers have discovered that each star has a small companion of its own, so when you look at Algedi you're actually seeing the combined light of four stars.  Interestingly, the two bright stars are not physically connected.  Alpha 2 is about 100 light years away, while Alpha 1 is about five times more distant.  Below Algiedi is the third-magnitude star Dabih, also a pair, though binoculars are needed to see the seventh-magnitude companion of the brighter star.  Below Dabih is a charming little trio of tiny stars: Rho, Pi and Omicron, which make for a pretty sight in binoculars. 

H.A. Rey (1898-1977) managed to turn the dim stars of Capricornus into a fairly convincing looking goat.  Although mythology tells us that Capricornus is a Sea-Goat, to most people it looks more like a roughly triangular figure, which may suggest an inverted cocked hat, or maybe a bird flying toward you.  

Or, perhaps keeping in the spirit of the watery nature of this part of the sky, some might even try to envision the south end of bikini!

Basic Sky Guides

• Full Moon Fever
• Astrophotography 101
• Sky Calendar & Moon Phases
• 10 Steps to Rewarding Stargazing
• Understanding the Ecliptic and the Zodiac
• False Dawn: All about the Zodiacal Light
• Reading Weather in the Sun, Moon and Stars
• How and Why the Night Sky Changes with the Seasons
• Night Sky Main Page: More Skywatching News & Features

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.