Norma

Norma

Constellation
List of stars in Norma
Abbreviation	Nor
Genitive	Normae
Pronunciation	/ˈnɔrmə/, genitive /ˈnɔrmiː/
Symbolism	the Normal
Right ascension	16.05
Declination	−52.01
Area	165 sq. deg. (74th)
Main stars	2
Bayer/Flamsteed stars	13
Stars with known planets	4
Bright stars	0
Nearby stars	0
Brightest star	γ2 Nor (4.0m)
Nearest star	HD 139211 (101 ly)
Messier objects	0
Meteor showers	Gamma Normids
Bordering constellations	Scorpius Lupus Circinus Triangulum Australe Ara
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.

History

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 1750:ies, when he was measuring about 10,000 stars at the Cape of Good Hope.^[1]

Notable features

Stars

The Milky Way passes through Norma.

Norma has no α or β star; its 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.

Deep-sky objects

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.

References

• Burnham, Robert Jr. (1966, 1978). Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, v.2. General Publishing Company, Ltd., Toronto. ISBN 0-486-23568-8. 
• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.

External links

Wikimedia Commons has media related to: Norma

• Yale Bright Star Catalog
• 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

Coordinates: 16^h 03^m 00^s, −52° 00′ 36″