Norma is a small, faint southern sky constellation that was one of 14 introduced by French astronomer Nicolas Louis de Lacaille following his expedition to South Africa from 1751-53. It represents a draughtsman’s level or set square, with the brightest star in the constellation, Gamma-2 Normae, a yellow giant found 127 light years from Earth with an apparent visual magnitude of +4.02.
Norma is the 74th largest constellation, taking up an area of 165 square degrees of the southern celestial sphere. It can be seen by observers located between +30° and -90° of latitude from April to June, but is difficult to view with its three main connected stars forming a rather dim “L” shape. Norma’s neighbors include Ara to its east, Circinus to its west, Scorpius to its north, Lupus to its northwest, and Triangulum Australe to its south.
Lacaille Constellation Family
Norma is a member of the Lacaille family of constellations, together with Antlia, Caelum, Circinus, Fornax, Horologium, Mensa, Microscopium, Octans, Pictor, Reticulum, Sculptor, and Telescopium.
Following his expedition to study the stars of the southern hemisphere from 1751-3, Nicolas Louis de Lacaille devised 14 new constellations, including one he called ‘l’Equerre et la Regle’, referring to the set-square and rule used by draughtsmen. Lacaille subsequently Latinized its name to ‘Norma et Regula’, and in 1763 shortened its name to just Norma.
The Gamma Normids is a weak meteor shower that occurs between March 7th and 23rd, with a peak on the 15th when 4 meteors per hour can be seen. Its radiant point is near Gamma Normae, the constellation’s brightest star, with the shower’s swift members often yellow in color.
– Gamma-2 Normae, the constellation’s brightest star, is a yellow giant (G8III) situated 127 light years from our solar system that shines with a visual magnitude of just 4.02. It is about 10 times bigger than the Sun, with 2.5 times its mass, and 45 times its luminosity. Gamma-2 Normae also has an optical double in the guise of Gamma-1 Normae, a yellow-white supergiant (F9Ia) of magnitude 4.98 that at 1500 light-years distant from Earth is not physically connected with Gamma-2 Normae.
– Epsilon Normae, the second brightest star in Norma, is a binary system found 400 light years away that shines with a visual magnitude of 4.53. It consists of two blue-white dwarf stars (B3V) of roughly equal mass that orbit each other once every 3.26 days. A third 7.5 magnitude blue star (B9V) is associated with the dimmer of the binary pair, and is found 550 light-years from Earth.
– Iota-1 Normae, the third brightest star in Norma, is a multiple system located 140 light years from the Sun of magnitude 4.63. It consists of a white subgiant (A7IV) of magnitude 5.2 that orbits its 5.76 magnitude companion every 26.9 years, with both stars around 2.7 times as massive as our Sun. Further away is a yellow main sequence (G8V) third component with a visual magnitude of 8.02 that is situated just 55 light years from Earth.
Other stars of interest in Norma includes the blue-white supergiant Mu Normae; the white dwarf Delta Normae; the yellow giants Eta Normae and Kappa Normae; the yellow dwarf stars HD 142415, HD 148156, HD 143361, and HD 330075; the red giant R Normae; and the Cepheid variable S Normae.
Notable Deep-Sky Objects
While there are no Messier objects in Norma, its location along the Milky Way means it does contain a number of noteworthy deep-sky objects.
– Ant Nebula (Menzel 3), a bipolar planetary nebula found 8,000 light years away of magnitude 13.8, is 1.6 light-year across and was given its intriguing name because of its strong resemblance to a garden-variety ant. Its distinctive shape is the result of two bipolar lobes emanating from its bright core, which is believed to be caused either by the star at its centre having a close companion, or by the dying, spinning star twisting its outflowing gas into intricate patterns.
– Norma Cluster (Abell 3627, ACO 3627) is a rich cluster of galaxies that at 220 million light years distant is the nearest massive galaxy cluster to our own Milky Way. The mass created by such a concentration has earned the region its Great Attractor title, as the influence it exerts extends over hundreds of millions of light-years as it pulls surrounding galaxies, including the Milky way, towards it, and on a collision course with each other, at a rate of more than 600 kms/sec.
– Fine-Ring Nebula (Shapley 1) is an unusual torus-shaped planetary nebula located 4,900 light years distant with a visual magnitude of 12.6. It is about 8700 years old, and at its center is a white dwarf star one-third of a light year across.
Other notable objects in Norma includes the open star clusters NGC 6067, NGC 6087, NGC 6021, NGC 6167, and NGC 6152. Other notable objects in Norma include the following: