Sea of Constellations Visible For Northern Hemisphere Skywatchers

The traditional constellations of autumn in the Northern Hemisphere have returned to the evening sky and bring with them a rich body of lore and mythology ? though their stars are rather faint.

Several of these constellations are dwelling in the celestial "sea" ?  that is, they are of a watery nature. 

These constellations include Capricornus, the sea goat; Aquarius, the water carrier; Pisces, the fishes; Piscis Austrinus, the southern fish; Cetus, the sea monster; and Eridanus, the river. They are appearing this week in the southern part of the evening sky at around 8 p.m. local time in northern latitudes.

This sky map shows the constellations of the southern sky in the Northern Hemisphere this week.

The first three constellations mentioned here form part of the zodiac;w 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. Here's a tour of these water-themed constellations in the night sky:

Grotesque sea goat

Probably because the ancients knew very little about marine life, it is not surprising that they populated the deep with every manner of monster, including what we now call mermaids.  Capricornus, the sea goat, now leaning down in the southwest sky, is one of those odd land-sea animal hybrids the ancients were wont to create. 

It traces back to the Mesopotamian period. According to folklore, there were some sea nymphs and goddesses playing in a field one day when the mischievous god, Pan, saw them and joined in the fun.  In order to amuse them, he transformed himself into a goat and leaped into the river.  Instantly, the part of his body that was submerged in the water was turned into a fish while the part out of the water remained a goat. 

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. Although Capricornus is a goat, in the sky it looks more like a roughly triangular figure which may suggest an inverted cocked hat, perhaps a bird flying toward you, or even a boat. 

Once, I pointed it out to a friend of mine who remarked that (in keeping with the watery aspect) it looked "like the south end of a bikini."

Watery tale

The rich mythology of Aquarius, the water carrier, which hovers above and to the left of Capricornus, is very ancient, tracing back to the earliest civilizations in the Tigris and Euphrates valleys. 

In fact, on some of their cylinder seals they pictured these rivers as pouring out from Aquarius? water jar. The ancient Egyptians had an equally picturesque image of this constellation that they associated with the Nile?s annual flooding, which, far from being disastrous, added a new layer each year to the valley?s fertile soil. 

The Egyptians believed the flooding was caused by Aquarius dipping his water jar into the river to refill it. Quite a number of Aquarius' stars have proper names. The names Sadalmelik, Sadalsuud[s1] , Sadachbia, and Albali all indicate in Arabic that these are "lucky" stars astrologically. "Skat" means the lower foot in Arabic, while "ancha" comes from Medieval Latin and refers to the upper thigh or hip.

One fish, two fish

Were it not one of the 12 zodiacal signs, Pisces the fishes would not be deemed important at all.   

Astronomers measure star brightness in terms of magnitude ? the smaller the number (close to or less than one), the brighter the object. None of the stars in Pisces shine brighter than fourth magnitude ? though brilliant Jupiter currently resides here ? but the constellation does display a striking, though not bright, pattern now high in the southern sky.

It also has some historical affinities, including one related to Christmas. 

To the early Israelites, Pisces was a sacred part of the sky. Planetary gatherings or other occurrences of astrological significance were regarded as harbingers of important events if they happened there. 

For example, a favorite explanation of the Star of Bethlehem is a planetary grouping involving Mars, Jupiter and Saturn that took place in Pisces in 6 B.C.

The main legend to account for the Fishes is that Cupid and Venus ? the god and goddess of love ? escape the monster Typhon by jumping into a river and assuming a piscine form.

Long-necked bird and a southern fish

In addition to the six groupings I mentioned earlier, we might also include the constellation of Grus, the Crane, among the watery constellations, for this wading bird often inhabits swampy and marshy terrain.

It currently lies low near the southwest horizon. With its two second-magnitude stars marking the bottom of a distinctive inverted Y-shaped pattern, and with third-magnitude Gamma at the top, Grus is actually a prominent fall constellation for viewers in the tropics and the Southern Hemisphere. 

Directly above Grus is Piscis Austrinus, the southern fish, which has the only first- magnitude star ? Fomalhaut ? in this whole collection of watery constellations.

Aside from Jupiter ? which this year happens to be glowing brilliantly nearby in Pisces ? Fomalhaut usually appears as a solitary star in a very dull and unexciting region of the sky. 

Indeed, Fomalhaut is the only "true" first magnitude star of autumn. It's a white star, only about twice as large as the sun and about 14 times as bright. It appears prominent to us because it is only 25 light-years away.

Godzilla-fish?

East of Aquarius and south of Pisces is Cetus, a sea monster who in mythology was sent by the god Neptune to devour the princess Andromeda. 

This constellation is often called the Whale, but in the allegorical pictures found in many of the old star atlases it usually appears very un-whale-like (almost like Godzilla with a fish tail!). 

However, today we identify the scientific name for the whale order is Cetacea, and the study of whales is known as Cetacean Zoology; hence the name Cetus identifies this constellation as a whale.

Lazy celestial river

Lastly, now coming into view low in the southeast is a large, albeit faint and shapeless constellation known as the Celestial River, Eridanus.

It starts near the brilliant bluish-white star Rigel in Orion then flows southwestward just like a river would: a winding stream of dim stars whose meanderings wind all the way down to below the southern horizon. Unfortunately, stargazers in much of the United States never get to see the very end of the river, for it ends in a blaze of splendor. 

The bluish star Achernar glows at the end of the river, ninth-brightest star in the sky, yet so far south that only those who live near and along the Gulf Coast (Florida, New Orleans, south Texas), get a glimpse of it, poking a short distance above the horizon.

 Also in Eridanus is Epsilon Eridani, the third-nearest star visible to the unaided eye.

Located at a distance of just 10.8 light years from Earth, Epsilon has about one-third of the luminosity of our sun and is about 90 percent as large. Thus, here is a star that is reasonably comparable to our own sun.

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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.