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A small southern constellation invented by the Frenchman Nicolas Louis de Lacaille during his survey of the southern skies in 1751–52. Pyxis represents a magnetic compass as used by seamen. It is located near the stern of the ship Argo in the same area as the ship’s mast. For Lacaille’s original depiction of it, published in 1756 under the French name la Boussole, see here. Lacaille Latinized it to Pixis Nautica on the second edition of his chart in 1763, a name that was subsequently shortened, with amended spelling, to just Pyxis. The brightest stars in Pyxis are of only fourth magnitude and there are no legends associated with it – indeed, the magnetic compass was completely unknown to the ancient Greeks.

It is sometimes asserted that Pyxis is one of the parts into which Lacaille divided the former Argo Navis, but that is not the case. Lacaille split Argo into three – Carina (Corps), Puppis (Pouppe) and Vela (Voilure). Pyxis is an additional constellation invented by Lacaille, and he showed it separately from Argo on his map and in his catalogue. The four stars that Lacaille labelled Alpha to Delta Pyxidis had actually been catalogued by Ptolemy as lying in or around the mast of Argo. Johann Bayer did not assign Greek letters to them in his Uranometria atlas and catalogue of 1603 so Lacaille evidently felt free to appropriate them for his new constellation.

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Pyxis hovers over the mast of Argo in the Uranographia of Johann Bode (1801). Curling around it is a Bode invention, the now-obsolete Lochium Funis, the log and line.


In 1844 the English astronomer John Herschel proposed returning the stars of Pyxis to Argo by replacing it with a fourth subdivision of the ship which he called Malus, the mast, in deference to Ptolemy’s original description (see Point 5 on this page). His countryman Francis Baily (of Baily’s beads fame) included Malus in his British Association Catalogue of 1845, but otherwise Malus was not widely adopted.

In this same area of sky the German astronomer Johann Bode introduced another constellation, Lochium Funis, the Log and Line, now obsolete but shown coiling around Pyxis on Bode’s atlas, above.
Chinese associations
Tianmiao, ‘celestial temple’, was a Chinese constellation consisting of 14 stars describing an arch shape. Most of these were in present-day Pyxis, including the line Beta–Alpha–Gamma, with five in neighbouring Antlia. Tianmiao represented a temple dedicated to the Emperor’s ancestors.



© Ian Ridpath. All rights reserved


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