Norma is a small constellation in the Southern Celestial Hemisphere between Scorpius and Centaurus, one of twelve drawn up in the 18th century by French astronomer Nicolas Louis de Lacaille and one of several depicting scientific instruments. 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. It remains one of the 88 modern constellations
Norma is bordered by Scorpius to the north, Lupus to the northwest, Circinus to the west, Triangulum Australe to the south and Ara to the east. Covering 165.3 square degrees and 0.401% of the night sky, it ranks 74th of the 88 constellations in size. In the equatorial coordinate system, the right ascension coordinates of the constellation lie between 15h 12m 13.6119s and 16h 36m 08.3235s, while the declination coordinates are between −42.27° and −60.44°. The whole constellation is visible to observers south of latitude 29°N.
Norma, shown under the name Norma et Regula in the Uranographia of Johann Bode (1801)
[http://www.ianridpath.com/startales/norma.htm]
Norma was introduced in 1751–52 by Nicolas Louis de Lacaille with the French name ‘l’Equerre et la Regle,’ ‘the Square and Rule,’ after he had observed and catalogued 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised 14 new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honored instruments that symbolised the Age of Enlightenment. Lacaille portrayed the constellations of Norma, Circinus and Triangulum Australe, respectively, as a set square and ruler, a compass, and a surveyor’s level in a set of draughtsman instruments, in his 1756 map of the southern stars. The level was dangling from the apex of a triangle, leading some astronomers to conclude he was renaming l’Equerre et la Regle to ‘le Niveau,’ ‘the level.’ In any case, the constellation’s name had been shortened and Latinized by Lacaille to Norma by 1763.
Constellations of Centaurus, Lupus and Norma
[http://www.davidmalin.com/fujii/source/Cen.html]
[http://astropixels.com/constellations/charts/Nor.html]
Four of Norma’s brighter stars-Gamma, Delta, Epsilon and Eta- make up a square in the field of faint stars.
Gamma Normae is an optical double star composed of Gamma-1 Normae and Gamma-2 Normae, two line-of-sight companions.
Gamma-2 Normae, itself a close optical binary, is the brightest star in the constellation. It has the stellar classification of G8III, matching the spectrum of a yellow giant star. It has an apparent visual magnitude of 4.02 and is approximately 127 light years distant from Earth.
Gamma-1 Normae is a yellow-white supergiant belonging to the stellar class F9Ia. It has an apparent magnitude of 5.09 and an absolute magnitude of -3.25. The star is 1,436 light years distant from the solar system.
Epsilon Normae is a binary star with the stellar classification of B4V, matching the spectrum of a blue-white main sequence dwarf. It has a visual magnitude of 4.53 and is approximately 400 light years distant from the Sun. The dimmer star in the system is itself a spectroscopic binary.
Iota-1 Normae is a white subgiant star with the stellar classification of A7IV. It has an apparent visual magnitude of 4.63 and is about 140 light years distant from Earth. It is a really a multiple star. It consists of a rapid binary star with an orbital period of 26.9 years and a third component that lies in the same line of sight but is only 55 light years distant from Earth. Components A and B have apparent magnitudes of 5.6 and 5.8, and component C, 8.75.
Eta Normae is a yellow giant star belonging to the stellar class G8III. It has a visual magnitude of 4.65 and is about 218 light years distant from the Sun.
Delta Normae is a white, A-class star about 123 light years from Earth. It has an apparent visual magnitude of 4.73.
[http://www.constellation-guide.com/constellation-list/norma-constellation/]
Mu Normae is a blue supergiant star of spectral type O9.7 Iab in the constellation Norma. It is 339,000 times the luminosity of the sun and 40 times its mass. It varies in visual magnitude between 4.87 and 4.98, and is suspected of being an Alpha Cygni variable, which are named after the similar star Deneb.
It is in the same direction and at the same distance as the faint open cluster NGC 6169, although it is brighter than the combined magnitude of all the other stars in the cluster. It was considered the prototype of the μ Normae class of open clusters by Collinder.
[https://en.wikipedia.org/wiki/Mu_Normae]
R Normae is a Mira variable star located near Eta Normae in the constellation of Norma. This is an intermediate-mass red giant star that is generating part of its energy through hydrogen fusion. Because this fusion is thought to be occurring under conditions of convection, it is generating an excess of lithium. The star ranges from magnitude 6.5 to 12.8 and has a relatively long period of 496 days. Located around 2,900 light-years distant, it shines with a luminosity 7764 times that of the Sun and has a surface temperature of 3161 K.
[https://en.wikipedia.org/wiki/R_Normae]
RCW103 is a supernova remnant in the constellation Norma. It is approximately 2000 years old, 10,000 light years away, and contains x-ray source 1E 161348-5055 at its heart:
[https://en.wikipedia.org/wiki/RCW103]
[https://en.wikipedia.org/wiki/RCW103]
RCW 103: Young magnetar likely the slowest pulsar ever detected
The slowest spinning neutron star may have been detected using Chandra and other X-ray telescopes. The object is found in the middle of the RCW 103 supernova remnant, which is about 10,700 light years from Earth. While other neutron stars spin multiple times a minute, this object only rotates once about every 6.5 hours. Chandra data showed this object displays properties of a magnetar, a type of neutron star with extremely powerful magnetic fields.
Using NASA’s Chandra X-ray Observatory and other X-ray observatories, astronomers have found evidence for what is likely one of the most extreme pulsars, or rotating neutron stars, ever detected. The source exhibits properties of a highly magnetized neutron star, or magnetar, yet its deduced spin period is thousands of times longer than any pulsar ever observed.
For decades, astronomers have known there is a dense, compact source at the center of RCW 103, the remains of a supernova explosion located about 9,000 light years from Earth. This composite image shows RCW 103 and its central source, known officially as 1E 161348-5055 (1E 1613, for short), in three bands of X-ray light detected by Chandra. In this image, the lowest energy X-rays from Chandra are red, the medium band is green, and the highest energy X-rays are blue. The bright blue X-ray source in the middle of RCW 103 is 1E 1613. The X-ray data have been combined with an optical image from the Digitized Sky Survey.
Observers had previously agreed that 1E 1613 is a neutron star, an extremely dense star created by the supernova that produced RCW 103. However, the regular variation in the X-ray brightness of the source, with a period of about six and a half hours, presented a puzzle. All proposed models had problems explaining this slow periodicity, but the main ideas were of either a spinning neutron star that is rotating extremely slowly because of an unexplained slow-down mechanism, or a faster-spinning neutron star that is in orbit with a normal star in a binary system.
On June 22, 2016, an instrument aboard NASA’s Swift telescope captured the release of a short burst of X-rays from 1E 1613. The Swift detection caught astronomers’ attention because the source exhibited intense, extremely rapid fluctuations on a time scale of milliseconds, similar to other known magnetars. These exotic objects possess the most powerful magnetic fields in the Universe- trillions of times that observed on the Sun- and can erupt with enormous amounts of energy.
Seeking to investigate further, a team of astronomers led by Nanda Rea of the University of Amsterdam quickly asked two other orbiting telescopes- NASA’s Chandra X-ray Observatory and Nuclear Spectroscopic Telescope Array, or NuSTAR- to follow up with observations.
New data from this trio of high-energy telescopes, and archival data from Chandra, Swift and ESA’s XMM-Newton confirmed that 1E 1613 has the properties of a magnetar, making it only the 30th known. These properties include the relative amounts of X-rays produced at different energies and the way the neutron star cooled after the 2016 burst and another burst seen in 1999. The binary explanation is considered unlikely because the new data show that the strength of the periodic variation in X-rays changes dramatically both with the energy of the X-rays and with time. However, this behavior is typical for magnetars.
But the mystery of the slow spin remained. The source is rotating once every 24,000 seconds (6.67 hours), much slower than the slowest magnetars known until now, which spin around once every 10 seconds. This would make it the slowest spinning neutron star ever detected.
Astronomers expect that a single neutron star will be spinning quickly after its birth in the supernova explosion and will then slow down over time as it loses energy. However, the researchers estimate that the magnetar within RCW 103 is about 2,000 years old, which is not enough time for the pulsar to slow down to a period of 24,000 seconds by conventional means.
While it is still unclear why 1E 1613 is spinning so slowly, scientists do have some ideas. One leading scenario is that debris from the exploded star has fallen back onto magnetic field lines around the spinning neutron star, causing it to spin more slowly with time. Searches are currently being made for other very slowly spinning magnetars to study this idea in more detail.
[http://chandra.harvard.edu/photo/2016/rcw103/]
Four star systems are known to harbor planets. HD 330075 is a sunlike star around 164 light-years distant that is orbited by a hot Jupiter every 3.4 days. Announced in 2004, it was the first planet discovered by the HARPS spectrograph. HD 148156 is a star about 170 light-years distant. Slightly larger and hotter than the Sun, it was found to have a roughly Jupiter-size planet with an orbital period of 2.8 years. HD 143361 is a binary star system composed of a sunlike star and a faint red dwarf separated by 30.9 AU. A planet roughly triple the mass of Jupiter orbits the brighter star about every 1000 days. HD 142415 is approximately 113 light-years distant and has a Jupiter-sized planet with an orbital period of around 386 days.
Due to its location on the Milky Way, Norma contains many deep-sky objects such as star clusters, including eight open clusters visible through binoculars.
NGC 6087
NGC 6087 is an open cluster of 40 or more stars centered on the Cepheid variable S Normae in the constellation Norma. At a distance of about 3500 ly and covering a field of almost one quarter of a degree, the stars range from seventh- to eleventh-magnitude, the brightest being 6.5 magnitude S Normae. The aggregate visual magnitude of the cluster is about 5.4.
[https://en.wikipedia.org/wiki/NGC_6087]
NGC 6067
NGC 6067 is another open cluster in the constellation Norma. It is located to the north of Kappa Normae, with an angular diameter of 12′. Visible to the naked eye in dark skies, it is best observed with binoculars or a small telescope, and a 12-inch aperture telescope will reveal about 250 stars. Its brightest stars have an apparent magnitude of around 8. There are 84 member stars with an apparent magnitude brighter than 12.
This cluster is located in the Norma Star Cloud in the Norma Arm of the Milky Way, and is 15 to 20 times as rich as the Pleiades and about the same age. It is thought to be around 102 million years old, and contain 893 solar masses. Two Cepheid variables, QZ Normae and V340 Normae, have been identified as members of the cluster, while a third nearby Cepheid- GU Normae- is considerably closer. Its period is only 3.5 days compared with the longer period of V340 Normae, indicating it is intrinsically less luminous (and hence closer), and its age has been estimated at 134 million years and hence too old to belong to the cluster. V340 Normae is a yellow supergiant of spectral type G0Ib that varies between magnitudes 8.26 and 8.60 over 11.28 days, while the fainter QZ Normae varies between magnitudes 8.71 and 9.03 over 3.79 days.
[https://en.wikipedia.org/wiki/NGC_6067]
Shapley 1 (Fine Ring Nebula) 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. However, it is thought that this is due to the viewpoint of looking directly down on a binary system whose orbit is perpendicular to Earth. Discovered in 1936 by Harlow Shapley, it is approximately 4900 light years from Earth, and is around 8700 years old. At the center of the nebula is a magnitude 14 white dwarf star. It has an angular diameter of 1.1 arc minutes, which makes it about one-third (.32) of a light year across.
[https://en.wikipedia.org/wiki/Shapley_1]
The Ant Nebula, or Menzel 3, is a bipolar planetary nebula in Norma. It has an apparent magnitude of 13.8 an is approximately 8,000 light years distant from the solar system. It got the nickname the Ant Nebula because its shape resembles the head and thorax of an ant. The nebula has a bright core and is believed to have a symbiotic binary star at its center. It was discovered by the American astronomer and astrophysicist Donald Howard Menzel in 1922:
[http://www.constellation-guide.com/constellation-list/norma-constellation/]
Planetary Nebula Mz3: The Ant Nebula
Why isn’t this ant a big sphere? Planetary nebula Mz3 is being cast off by a star similar to our Sun that is, surely, round. Why then would the gas that is streaming away create an ant-shaped nebula that is distinctly not round? Clues might include the high 1000-kilometer per second speed of the expelled gas, the light-year long length of the structure, and the magnetism of the star visible above at the nebula’s center. One possible answer is that Mz3 is hiding a second, dimmer star that orbits close in to the bright star. A competing hypothesis holds that the central star’s own spin and magnetic field are channeling the gas. Since the central star appears to be so similar to our own Sun, astronomers hope that increased understanding of the history of this giant space ant can provide useful insight into the likely future of our own Sun and Earth.
[http://apod.nasa.gov/apod/ap150426.html]
Approximately 200 million light-years from Earth with a redshift of 0.016 is Abell 3627; also called the Norma Cluster, it is one of the most massive galaxy clusters known to exist, at ten times the average cluster mass. Abell 3627 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:
Hubble Focuses on ‘the Great Attractor’
A busy patch of space has been captured in this image from the NASA/ESA Hubble Space Telescope. Scattered with many nearby stars, the field also has numerous galaxies in the background.
Located on the border of Triangulum Australe (The Southern Triangle) and Norma (The Carpenter’s Square), this field covers part of the Norma Cluster (Abell 3627) as well as a dense area of our own galaxy, the Milky Way.
The Norma Cluster is the closest massive galaxy cluster to the Milky Way, and lies about 220 million light-years away. The enormous mass concentrated here, and the consequent gravitational attraction, mean that this region of space is known to astronomers as the Great Attractor, and it dominates our region of the Universe.
The largest galaxy visible in this image is ESO 137-002, a spiral galaxy seen edge on. In this image from Hubble, we see large regions of dust across the galaxy’s bulge. What we do not see here is the tail of glowing X-rays that has been observed extending out of the galaxy- but which is invisible to an optical telescope like Hubble.
Observing the Great Attractor is difficult at optical wavelengths. The plane of the Milky Way- responsible for the numerous bright stars in this image- both outshines (with stars) and obscures (with dust) many of the objects behind it. There are some tricks for seeing through this- infrared or radio observations, for instance- but the region behind the center of the Milky Way, where the dust is thickest, remains an almost complete mystery to astronomers.
This image consists of exposures in blue and infrared light taken by Hubble’s Advanced Camera for Surveys.
[http://www.nasa.gov/mission_pages/hubble/science/great-attractor.html]
[https://en.wikipedia.org/wiki/Norma_%28constellation%29]
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