|Symbolism||the carpenter's square|
|Right ascension||16.05 h|
|Area||165 sq. deg. (74th)|
|Stars with planets||4|
|Stars brighter than 3.00m||0|
|Stars within 10.00 pc (32.62 ly)||0|
|Brightest star||γ2 Nor (4.01m)|
|Nearest star||HD 145417
(44.83 ly, 13.75 pc)
|Meteor showers||Gamma Normids|
|Visible at latitudes between +30° and −90°.
Best visible at 21:00 (9 p.m.) during the month of July.
Norma is a small and inconspicuous constellation in the southern hemisphere between Scorpius and Centaurus. Its name is Latin for normal, referring to a right angle, and is variously considered to represent a rule, a carpenter's square, a set square or a level.
Norma, originally named l’Equerre et la Regle in French, was one of the constellations invented by Abbé de Lacaille in the middle of the 1750s, when he was measuring about 10,000 stars at the Cape of Good Hope. Norma represents a carpenter's square, used in the Age of Exploration by carpenters on exploratory vessels.
The Milky Way passes through Norma.
Norma has no α or β star. These are now officially part of Scorpius - N Sco and H Sco respectively. Norma's brightest star, γ2 Normae, is only of magnitude 4.0. Among the constellation's principal stars are the following:
- γ1 Nor and γ2 Nor comprise an easy optical double. γ2 Nor is itself a close optical double (HJ 4841).
- ε Nor: a relatively fixed binary star (HJ 4853). The two components are of magnitude 4.54 and 6.68; the separation is 22" in PA 335°. The fainter component is itself a spectroscopic binary (mag 6.68 and 7.12).
- ι1 Nor: a multiple star. The AB (mag 5.6 and 5.8) pair comprise a rapid binary with a period of 26.9 years; in 2000 the separation was 0.5" in PA 285°. Component C, of magnitude 8.75, is 11" away in PA 242°; it is not a physical member of the system, being only 55 light-years away, while the AB pair lie at a distance of more than 140 ly.
- μ Nor is suspected of being an Alpha Cygni variable, with a range of 4.87–4.98. It is of spectral type O9.7 Iab.
- R Normae is a Mira variable. Its visual range is 6.5–13.9 and its average period is 507.5 days.
- S Normae is a well-known Cepheid variable with a range of 6.12–6.77 and a period of 9.75411 days. It is located at the centre of the open cluster NGC 6087.
Due to its location on the Milky Way, this constellation contains many deep-sky objects, the most notable of which is NGC 6087.
- NGC 6067 is an open cluster, which lies less than 1° north of Kappa Normae. It contains about 100 stars of the tenth magnitude and has an integrated magnitude of 5.6m.
- NGC 6087 is the brightest of the open clusters in Norma; it lies in the southeastern corner of the constellation between α Centauri and ζ Arae. It is about 3500 light-years away and contains about 40 stars of the seventh to the eleventh magnitude. Its brightest member is the Cepheid variable S Normae. It is of magnitude +5.4.
- Sp 1 (or PK 329+02.1) is a planetary nebula better known as the Fine-Ring Nebula. It lies about five degrees west-northwest of γ1 Nor, though its actual distance has been variously estimated at 1000–4700 ly. Its integrated magnitude is 13.6 and its mean surface brightness is 13.9. The central star is a white dwarf of mag 14.03.
- Abell 3627, also called the Norma Cluster, is a galaxy cluster located at a distance of approximately 200 million light-years from Earth with a redshift of 0.016. It is one of the most massive galaxy clusters known to exist, at ten times the average cluster mass, and is thus theorized to be the Great Attractor, a massive object that is pulling the Local Group, the Virgo Supercluster, and the Hydra-Centaurus Supercluster towards its location at 600-1000 kilometers per second.
- Burnham, Robert Jr. (1978), Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System (2nd ed.), General Publishing Company, Ltd., ISBN 0-486-23568-8
- Ridpath, Ian; Tirion, Wil (2007), Stars and Planets Guide, Princeton University Press, ISBN 978-0-691-13556-4
- Staal, Julius D.W. (1988), The New Patterns in the Sky: Myths and Legends of the Stars, The McDonald and Woodward Publishing Company, ISBN 0-939923-04-1
- Wilkins, Jamie; Dunn, Robert (2006), 300 Astronomical Objects: A Visual Reference to the Universe, Firefly Books, ISBN 978-1-55407-175-3
|Wikimedia Commons has media related to:|
- Norma on Robin Gatter's site
- Star Tales – Norma
- Norma on Richard Dibon-Smith's site
- Peoria Astronomical Society: Norma
- The Deep Photographic Guide to the Constellations: Norma
- Norma Constellation at Constellation Guide