Who invented the southern constellations?

Ian Ridpath uncovers how it took 150 years of exploration to fill the skies of the Southern Hemisphere with 26 new constellations.

- Ian Ridpath

On seeing a chart of the Southern Hemisphere constellations, the Lick Observatory astronomer Heber Doust Curtis is reputed to have declared: "It looks like somebody's attic!".

While it's true that the southern constellations include such technological relics as an air pump, a chemical furnace and a pendulum clock, there are also exotic animals such as a peacock, a bird of paradise and a dorado chasing a flying fish- not to mention the oak tree that was planted by Edmond Halley to commemorate King Charles II, only to be later felled by a Frenchman.

Before the first European seafarers ventured around the tip of Africa to open trade route's to India and the Far East, the sky around the south celestial pole was a blank slate for Western astronomers.

The 48 Greek constellations in Ptolemy's book the Almagest of 150 AD' went only as far south as Centaurus and Argo Navis. Beyond that lay the.. celestial equivalent of terra incognita, beneath the horizon for European observers.  

Exploring the southern sky

One man was determined to fill in this blank area of sky: the Dutch cartographer and theologian Petrus Plancius (1552-1622). When the first Dutch trading expedition to the East Indies, the Eerste Schipvaart, set sail in April 1595, Plancius instructed several members of the ships' crews to make positional observations of the southern stars. Foremost among these trusted observers was Pieter Dirkszoon Keyser (c1540-96), chief navigator on the Hollandia, joint largest of the four ships in the fleet.

The Dutch fleet arrived at Madagascar, latitude 23° south, in September 1595 where they remained for several months to resupply and recover from scurvy and malnutrition. It was during this stopover that Keyser made most of his observations, measuring star positions from the crow's nest of his ship, probably using an astrolabe given to him by Plancius.