Genitive: Normae
Abbreviation: Nor
Size ranking: 74th
Norma is one of the constellations introduced by the French astronomer Nicolas
Louis de Lacaille following his mapping of the southern skies in 1751–52. It consists of faint stars between Ara and Lupus that were not catalogued by
Ptolemy. On his 1756 planisphere Lacaille called it l’Equerre et la Regle, the Square and Rule, depicting it as a draughtsman’s set-square and ruler, although in the accompanying star catalogue the name was
given simply as l'Équerre.
Lacaille placed it next to another of his inventions, the compasses (le Compas, now known as Circinus), and the southern triangle (Triangulum Australe); this
latter figure was an earlier invention of the Dutch navigators Keyser and de
Houtman which Lacaille visualized as a builder’s level, thereby creating a trio of surveying and building instruments. On the 1763 edition of the planisphere Lacaille Latinized and shortened the name of the constellation to Norma; others,
though, preferred the fuller name Norma et Regula, as did Johann Bode on his
atlas of 1801 (see illustration below). The brightest stars of Norma are of
only fourth magnitude and none have names.
In his widely quoted book Star Names, Their Lore and Meaning, the historian R. H. Allen called this constellation ‘the Level and Square’. Allen said that the French edition of Flamsteed’s star atlas (i.e. the Atlas Céleste of Jean Fortin) showed it as Niveau, the level, but a glance at that atlas shows he is wrong. The alternative name ‘level’ was actually applied to the southern triangle, Triangulum Australe. Allen
seemingly misread the French map and transferred the name to the wrong
constellation, in a reprise of the way in which star names were misapplied
through misreadings of maps down the ages. Allen’s error has caused confusion ever since.
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Norma, shown under the name Norma et Regula on Chart XV of the Uranographia of Johann Bode (1801). ‘Rule and Square’ is a traditional English pub name.
Because of changes in the constellation’s boundaries since Lacaille’s time, Norma no longer has stars labelled Alpha or Beta. The stars that
Lacaille designated Alpha and Beta Normae are now part of Scorpius, where they
are known as N and H Scorpii respectively. For a modern chart of this region,
click here. Incidentally, Norma shares this distinction with Puppis and Vela, both of
which lack stars labelled Alpha and Beta because they were once part of a much
larger constellation, in their case Argo Navis; when Argo was split into three
by Lacaille, the stars Alpha and Beta ended up in the third subdivision,
Carina.
Chinese associations
Although Norma is a modern constellation, its stars are at similar declination
to those of its neighbours Ara and Lupus so they would have been visible to the
ancient Chinese, as they were to the Greeks. The Greeks did not incorporate any
of its stars into their constellations, but the Chinese did. Up to four stars
in northern Norma were part of Jizu, a battalion of soldiers, the bulk of which was in Scorpius. Sun and Kistemaker
identify the four stars as Delta, Epsilon, Mu, and Lambda Normae. Other
sources, while agreeing that stars in Norma were involved in Jizu, differ in their identity and number.
© Ian Ridpath. All rights reserved
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