Norma (constellation)
Encyclopedia
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
.
.
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:
Scorpius
Scorpius, sometimes known as Scorpio, is one of the constellations of the zodiac. Its name is Latin for scorpion, and its symbol is . It lies between Libra to the west and Sagittarius to the east...
and Centaurus
Centaurus
Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.-Stars:...
. Its name is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for normal
T-square
A T-square is a technical drawing instrument used by draftsmen primarily as a guide for drawing horizontal lines on a drafting table. It may also guide a triangle to draw vertical or diagonal lines. Its name comes from the general shape of the instrument where the horizontal member of the T slides...
, referring to a right angle
Surface normal
A surface normal, or simply normal, to a flat surface is a vector that is perpendicular to that surface. A normal to a non-flat surface at a point P on the surface is a vector perpendicular to the tangent plane to that surface at P. The word "normal" is also used as an adjective: a line normal to a...
, and is variously considered to represent a rule
Ruler
A ruler, sometimes called a rule or line gauge, is an instrument used in geometry, technical drawing, printing and engineering/building to measure distances and/or to rule straight lines...
, a carpenter's square, a set square
Set square
A set square or triangle is an object used in engineering and technical drawing, with the aim of providing a straightedge at a right angle or other particular planar angle to a baseline....
or a level
Spirit level
A spirit level or bubble level is an instrument designed to indicate whether a surface ishorizontal or vertical . Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades workers, surveyors, millwrights and other metalworkers, and in some...
.
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 1750s, when he was measuring about 10,000 stars at the Cape of Good HopeCape of Good Hope
The Cape of Good Hope is a rocky headland on the Atlantic coast of the Cape Peninsula, South Africa.There is a misconception that the Cape of Good Hope is the southern tip of Africa, because it was once believed to be the dividing point between the Atlantic and Indian Oceans. In fact, the...
.
Stars
The Milky WayMilky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
passes through Norma.
Norma has no α or β star; its brightest star, γ2 Normae, is only of magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
4.0. Among the constellation's principal stars are the following:
- γ1 Nor and γ2 Nor comprise an easy optical doubleDouble starIn observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...
. γ2 Nor is itself a close optical double (HJ 4841).
- ε Nor: a relatively fixed binary starBinary starA binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star, comes, or secondary...
(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 NorMu NormaeMu Normae is a blue supergiant star in the constellation Norma. Though it has an apparent magnitude of only 4.914, its absolute visual magnitude -5.86 and a bolometric luminosity of 210,000 times that of the Sun...
is suspected of being an Alpha Cygni variableAlpha Cygni variableAlpha Cygni variables are variable stars which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time others parts expand. They are supergiant stars of spectral types B or A...
, with a range of 4.87–4.98. It is of spectral type O9.7 Iab.
- R NormaeR NormaeR Nor is a Mira variable star.-References:*...
is a Mira variableMira variableMira variables , named after the star Mira, are a class of pulsating variable stars characterized by very red colors, pulsation periods longer than 100 days, and light amplitudes greater than one magnitude in infrared and 2.5 magnitude in visual...
. Its visual range is 6.5–13.9 and its average period is 507.5 days.
- S NormaeS NormaeS Normae is a variable star in the constellation Norma. It is the brightest member of the open cluster NGC 6087.-References:*...
is a well-known Cepheid variableCepheid variableA Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation period, secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.Cepheid...
with a range of 6.12–6.77 and a period of 9.75411 days. It is located at the centre of the open clusterOpen clusterAn open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...
NGCNew General CatalogueThe New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...
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 6067NGC 6067NGC 6067 is an open cluster of stars in the constellation Norma. It is located to the north of Kappa Normae, with an angular diameter of 12′. The cluster can be observed with binoculars or a small telescope, while a 12-inch aperture telescope will reveal about 250 stars....
is an open clusterOpen clusterAn open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...
, 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 6087NGC 6087NGC 6087 is one of the brightest open clusters in the constellation Norma with a magnitude of 5.4. It is approximately 3500 light-years away and contains about 40 stars of the seventh to the eleventh magnitude, the brightest being 6.5 magnitude S Normae....
is the brightest of the open clusterOpen clusterAn open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...
s in Norma; it lies in the southeastern corner of the constellation between α CentauriAlpha CentauriAlpha Centauri is the brightest star in the southern constellation of Centaurus...
and ζ AraeZeta AraeZeta Arae is a star in the constellation Ara. It is an orange K-type giant with an apparent magnitude of +3.12. It is approximately 574 light years from Earth....
. 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 variableCepheid variableA Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable's luminosity and pulsation period, secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.Cepheid...
S NormaeS NormaeS Normae is a variable star in the constellation Norma. It is the brightest member of the open cluster NGC 6087.-References:*...
. It is of magnitude +5.4.
- Sp 1Shapley 1Shapley 1 is an annular planetary nebula in the constellation of Norma with a magnitude of +12.6. As viewed from Earth, it is peculiar in that it seems to be a non-bipolar, torus-shaped planetary nebula....
(or PK 329+02.1) is a planetary nebulaPlanetary nebulaA planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life...
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 brightnessSurface brightnessThe overall brightness of an extended astronomical object such as a galaxy, star cluster, or nebula, can be measured by its total magnitude, integrated magnitude or integrated visual magnitude; a related concept is surface brightness, which specifies the brightness of a standard-sized piece of an...
is 13.9. The central star is a white dwarfWhite dwarfA white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
of mag 14.03.