The constellation Puppis rows low across the south on early spring evenings. It represents the stern of the Argo, the boat that carried Jason and the Argonauts through many adventures.

Most of the stars of Puppis are faint. In fact, its leading light barely ranks among the 70 brightest stars of the night sky.

In most constellations — especially those from the ancient world — the brightest star has a name beginning with “alpha,” the first letter of the Greek alphabet. So in this case, the star would be known as Alpha Puppis. Instead, though, the star is called Zeta Puppis, using the sixth letter of the alphabet.

That naming system was devised by Johann Bayer more than four centuries ago. He generally gave the “alpha” designation to a constellation’s brightest star. The rest of the stars were labeled based on their brightness or their position in the sky.

At the time Bayer came up with his system, though, Puppis didn’t exist. Instead, it was part of a much larger constellation — Argo Navis — the ship Argo.

Well after Bayer’s time, another astronomer, Nicolas de Lacaille, split Argo Navis into three constellations. Puppis represents the ship’s stern, Carina is its keel, and Vela is its sail. But Lacaille kept the Greek letter designations from Argo Navis. So Carina has the first three letters, Vela has the next two, and Puppis starts with number six — Zeta.

We’ll have more about Zeta Puppis tomorrow.

Script by Damond Benningfield