Spring Sky Watching: Seafaring On The Milky Way

March is bringing big news for night-time sky watchers. Constellations slip into and out of the night sky over the course of the year, and this month will usher in the yearly arrival of the constellation, Argo Navis. It can be spotted early in the night, ten or eleven o’clock, and will be located in the in the southern horizon.

Yet strictly speaking, Argo Navis is not a single constellation but a collection of smaller ones. It was split up in the first half of the 20th century by the International Astronomical Union, which deemed that the whole of Argo was to a bit too hefty for a single constellation. It was subdivided into three major sections: Carina, the keel; Vela, the sails; and Puppis, the stern.

Had Argo not been split up it would be 1,888 square degrees, appreciably larger than the current largest constellation, the water serpent Hydra. In addition to the three larger sub-units, Argo was further broken down into a number of even smaller constellations.

What’s in the name Argo? The name is based in the Greek mythological story of Jason and his Argonauts who sailed about the Mediterranean and Black Sea in search of the fabled Golden Fleece. And you guessed it – their ship was named the Argo.

Knowledge of Argo Navis is nearly as old as the story of Jason. It was known in antiquity and was listed in the second century A.D. by the famed astronomer Ptolemy. For the Greeks, the ship would sail across their Mediterranean sky and remind them of Jason’s voyage.

Interestingly, the constellation is not so prominent for Greeks of today – or anyone in the Northern Hemisphere for that matter. Due to a process called precession, or the slow wobble of the Earth upon its axis over the course of many years, the constellation has moved to a more southerly view. The best place these days to get a view of ship is from the southern hemisphere.

However, all is not lost if you are located in the United States. The ex-constellation can still be viewed profitably with a keen eye and a patient watch. Grab yourself a good star atlas and hit the skies!

Gum 15 in the constellation of Vela