Astronomers have been using the same constellation groupings for so long that most people have come to believe that the constellation names were lowered down from heaven on a string or invented by Og and Grog, the first stargazers.

In fact, the 88 constellations we use these days are simply subdivisions of the sky established by the first General Assembly of the International Astronomical Union in 1922.

During the preceding millennia, things were a bit more confused. The ancients concerned themselves with only the brighter stars in the heavens, and whole patches of sky were left unnamed.

After the telescope came along, astronomers began to invent constellations that covered undesignated sections of the sky. If they found a new object in the sky, they just wanted to say where it was. Thus, the constellations slowly transformed from the stick figures of ancient heroes to the patches of celestial real estate we see today.

The patch of faint stars to the left of much brighter Orion is a good example. In 1613, very soon after Galileo’s first use of the astronomical telescope, Dutch cartographer Petrus Plancius produced a map of the sky that filled in the undesignated space near Orion with Monoceros, the Unicorn.

Plancius was better known as a theologian than as an astronomer. He knew that the unicorn is mentioned several times in the Old Testament. He figured it was about time that somebody named a constellation after it.

Even so, it might be very old. Plancius may have borrowed the Unicorn from an ancient Persian constellation of a horse. RH Allen suggests that ancient Chinese stargazers placed an equine constellation somewhere in the area. Add a horn, and you have Monoceros.

Pity then the poor Unicorn. The gentle creature outshone by bright and famous constellations like Gemini to the north, Orion to the west, and Canis Major with its bright star Sirius to its south.

The whole constellation is barely visible to the naked eye, and most urbanites and even suburbanites have never seen it. Western astronomers didn’t even give this dim slice of sky a name until Plancius came along.

The oddest case of modern star naming is the sad tale of Puppis, the Poop, which doesn’t mean what you think. According to my online dictionary, the Poop is “some part of a ship. We’re not sure what part. Go ask a sailor.” So much for online dictionaries.

Seriously, the Poop is one of the decks at the stern of a sailing vessel. The stern is, naturally, the back end of the vessel. (I am beginning to wish I had stuck with the Unicorn.)

To the ancient Greeks, Argo represented the 50-oared galley that Jason and his Argonauts used to chase after the Golden Fleece. Unfortunately, the old constellation is enormous and much too unwieldy to be used to map the sky for scientific purposes. Thus, in 1752 French astronomer Louis de Lacaille dismembered the mighty Argo into three parts: Vela (The Sails), Carina (the Keel) and, of course, Puppis.

Those of you with a keen nautical sense will note a problem with the ship’s construction. Only the stern and sails are represented. What happened to the front half?

The whole story of the Argo’s adventure is too complex to be told here. Suffice it to say that Jason was ordered by the goddess Athena to steal the Golden Fleece from King Aeetes, the many-voweled monarch of the island of Colchis. Jason needed a ship, and Athena asked Argus, the greatest shipbuilder of the age, to construct one.

Argus created the greatest galley ever. It seated 50 oarsmen, and even had in its prow an oak plank that warned Jason in fluent Greek of any dangers that lay ahead. Yes, that’s right. The Argus had a talking board on board.

Jason and his hardy band of pillagers managed to procure the fleece and had many adventures along the way. For one thing, they learned to pronounce King Aeetes’ name. For another, they managed to navigate the fabled Clashing Rocks, which protected the entrance to the Black Sea like a set of out-of-control elevator doors.

When they returned home, Jason honored his vessel by beaching it at Corinth, dedicating it to Poseidon, the god of the sea, and leaving it to rot.

In his dotage, Jason returned to the deteriorating hulk to ruminate upon past glories and reflect on what a mess he had made of his life after the Argo’s momentous voyage. As he sat in deep contemplation, the decaying prow of the ship (that’s the front end, landlubbers) fell off and crushed him to death. Apparently, the gods had expected him to take better care of the mighty Argo.

Poseidon then placed its remains among the stars, which is why we see only its stern to this very day.

Only the Puppis portion of Argo’s stern is visible from our northern climes. Right now, you will find it underneath Canis Major, very low in the southeastern sky just after dark. You’d better go and take a look. One can never tell what the gods might do.

Both sections of sky are of some interest to modern astronomers, amateur and professional. Next week, I’ll write about a few of the objects in Monoceros.

Tom Burns


Tom Burns is director of the Perkins Observatory in Delaware.