Genitive: Tucanae

Abbreviation: Tuc

Size ranking: 48th

Origin: The 12 southern constellations of Keyser and de Houtman

One of the 12 southern constellations devised by the Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman at the end of the 16th century. It represents the South American bird with a huge bill.

The Dutchman Petrus Plancius named it Toucan when he first depicted it on a globe in 1598, and Johann Bayer followed suit on his atlas of 1603. But de Houtman, in his catalogue of 1603, called it Den Indiaenschen Exster, op Indies Lang ghenaemt (‘the Indian magpie, named Lang in the Indies’, the word ‘lang’ referring to the bird’s long beak). De Houtman was apparently describing not a toucan but the hornbill, a similarly endowed bird that is native to the East Indies and Malaysia. This suggests that the original inventor of Tucana was in fact Keyser, who had visited South America before his voyage to the East Indies and could have seen the bird there. In some depictions which used de Houtman’s catalogue as a source, such as Willem Janszoon Blaeu’s globe of 1603, the bird was shown as a hornbill rather than a toucan, complete with casque above its bill, but the original identification by Plancius and Bayer as a toucan won out.

Globular cluster 47 Tucanae

Tucana’s brightest star, Alpha Tucanae, marking the tip of the bird’s beak, is of only third magnitude, but the constellation is distinguished by two features of particular interest: firstly, the globular star cluster 47 Tucanae, rated the second-best such object in the entire sky, so bright that it was given a catalogue number in the same way as a star; and the Small Magellanic Cloud, the smaller and fainter of the two companion galaxies of our Milky Way, termed Nubecula Minor on many old charts. These features were originally part of Hydrus but were transferred to Tucana when the French astronomer Nicolas Louis de Lacaille reorganized this part of the southern heavens in the 1750s on his planisphere and star catalogues.

Incidentally, 47 Tucanae is not a Flamsteed number; it comes from its listing in Johann Bode’s catalogue called Allgemeine Beschreibung und Nachweisung der Gestirne, published in 1801 to accompany his Uranographia star atlas. It was first recorded as a star by Keyser and de Houtman. Bayer showed it on his southern star chart of 1603 within one of the coils of Hydrus, beneath the claw of the toucan, but its nebulous nature was first noted by Lacaille a century and a half later. Lacaille gave it no identifying number, though, simply labelling it as ‘neb’.

None of the stars of Tucana is named, and there are no legends associated with it.

© Ian Ridpath. All rights reserved

Tucana, holding in its beak a branch with a berry, as seen on Chart XX of the Uranographia star atlas of Johann Bode (1801). Behind its tail lies Nubecula Minor, the Small Magellanic Cloud (just visible at the lower right edge of the image), which is within the constellation’s modern borders.

Tucana on Chart XX of the Uranographia star atlas of Johann Bode