Norm (constellation)

Norma or the Square is a small constellation in the southern celestial hemisphere between the constellations of Scorpio and Centaurus, one of the twelve collected in the 18th century by the French astronomer Nicolas-Louis de Lacaille and representing a scientific instrument. The Latin name is also sometimes translated as the ruler, the carpenter's square, or the level. It is one of the eighty-eight modern constellations. It so happens that this constellation lacks alpha and beta stars.

Four stars in this constellation, Gamma2, Delta, Epsilon, and Eta Normae, form a square in a field of faint stars. Gamma² Normae is in fact the brightest star with an apparent magnitude of 4, while Mu Normae is one of the most luminous stars known, with an average luminosity a million times that of the Sun. Others four stars have planetary systems. The Milky Way crosses Norma where up to eight open clusters visible with binoculars can be seen. Abell 3627, also known as the Norma Cluster, is one of the largest known galaxy groupings.

History

Norma was introduced in 1751-2 by Lacaille under the French name of L'Equerre et la Regle (The Square and the Rule)  after having observed and cataloged 10,000 stars of the southern hemisphere during the two years he stayed at the Cape of Good Hope. Altogether, he devised fourteen new constellations for the unexplored regions of the southern celestial hemisphere that are not visible from Europe. All but one represent scientific instruments symbolizing the Enlightenment. Lacaille depicts the constellations of Norma, Circinus, and Triangulum Australe as a square and ruler, a compass, and a surveying level respectively in a set of draftsman's instruments on celestial charts. which he drew up in 1756. The level hung from the vertex of a triangle, leading some astronomers to conclude that he was going to rename L'Equerre et la Regle to Le Niveau (the Level). In any case, the name of the constellation was Latinized and shortened by Lacaille himself in 1763.

Description

The Squad is surrounded to the north by the Scorpion, to the northwest by the Wolf, to the west by the Compass, to the south by the Southern Triangle and to the east by the Altar. It ranks 74th in size, covering 165.3 square degrees of the night sky, or 0.401%. The three-letter abbreviation adopted by the International Astronomical Union (IAU) in 1922 is "Nor". The official boundaries, as established by Eugène Delporte in 1930, they determine a ten-sided polygon. In the celestial coordinate system, the right ascensions that delimit these borders are between 15 h 12 m 13.6119 s and 16 h 36 m 08.3235 s, while the limit declinations are −42.27° and −60.44°. The entire constellation is visible to observers south of latitude 29° N, though parts of the constellation may become visible as far as 44° N.

Stars

Main Stars

• γ1 Normae, yellow supergiant of magnitude 4,97.
• γ2 Normae, a yellow giant of magnitude 4,01; it is the brightest star of constellation.
• ε Normae, triple system of magnitude 4,52.
• ι1 Normae, multiple star of magnitude 4,63, the third most brilliant constellation.
• ι2 Normae, white star of magnitude 5.57.

Other stars with Bayer names

• δ Nor 4.73; γ Nor 5.78; θ Nor 4.65; θ Nor 5.13; κ Nor 4.95; λ Nor 5.44; μ Nor 4.86

Other stars

• 39 Normae, a red giant of magnitude 6.03.
• S Normae, a strain whose brightness varies between magnitude 6,12 and 6.70 in a cycle of 9,754 days. It is the brightest star of the NGC 6087 cluster.
• QU Normae (HD 148379), blue supergiant of magnitude 5.36.
• V360 Normae, variable blue giant of magnitude 5.77.
• HD 142415, yellow dwarf orbited by a planet.
• HD 143361, star similar to the previous one also with a planet.
• HD 148937, blue supergiant of magnitude 6.77.
• HD 330036, one of the few known symbiotic stars; these are binary stars whose components, a red giant and a small and hot star, are surrounded by a nebulae.
• HD 330075, subgigante orange where an extrasolar planet has been discovered.
• Gliese 615, distant orange dwarf 45 light years.

Deep Sky Objects

• NGC 6087, the brightest of clusters opened in constellation, located between α Centauri and γ Arae.
• Nebula of the Hormiga (Mz 3), a very complex planetary nebula of magnitude 13,8, whose shape recalls the body of this insect. It is one of the most surprising bipolar nebulae, being formed by a brilliant core and at least four different material flows.
• Resto de supernova RCW 103; hosts inside 1E 161348-5055, the slowest rotation neutron star known.
• SNR G327.1-01.1, Kesteven 25, Kesteven 32 and SNR G330.2+01.0, supernova remains. The first two have a brilliant prayer in their center.