Norma (constellation)

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Norma
Constellation
Norma
Abbreviation Nor
Genitive Normae
Pronunciation /ˈnɔrmə/,
genitive /ˈnɔrm/
Symbolism the carpenter's square
Right ascension 16.05
Declination −52.01
Family La Caille
Quadrant SQ3
Area 165 sq. deg. (74th)
Main stars 4
Bayer/Flamsteed
stars
13
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)
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[edit]

Norma was introduced in 1751–52 by Nicolas Louis de Lacaille with the French name l’Equerre et la Regle,[1][2] 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.[3] 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.[4] Its name had been Latinised by Lacaille to Microscopium by 1763.[1]

Characteristics[edit]

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.[5] The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Nor'.[6] The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of ten segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 15h 12m 13.6119s and 16h 36m 08.3235s, while the declination coordinates are between −42.27° and −60.44°.[7] The whole constellation is visible to observers south of latitude 29°N.[a]

Notable features[edit]

The constellation Norma as it can be seen by the naked eye.

Stars[edit]

Lacaille charted and designated ten stars with the Bayer designations Alpha through to Mu in 1756, however his Alpha Normae was transferred into Scorpius and left unnamed by Francis Baily, before being named N Scorpii by Benjamin Apthorp Gould, who felt its brightness warranted recognition. Beta Normae was left out of Lacaille's 1763 catalogue, was likewise transferred to Scorpio by Baily and named by H Scorpii Gould.[8] Norma's brightest star, γ2 Normae, is only of magnitude 4.0. Overall, there are 44 stars within the constellation's borders brighter than or equal to apparent magnitude 6.5.[b][5]

The Milky Way passes through Norma.

The four main stars—Gamma, Delta, Epsilon and Eta—make up a square in this region of faint stars.[10] Gamma1 and Gamma2 Normae comprise an easy optical double and unrelated in reality.

Located 129 ± 1 light-years away from Earth,[11] Gamma2 Normae is a yellow giant of spectral type G8III around 2 to 2.5 times as massive as the Sun that has swollen to a diameter 10 times that of the Sun and shines with 45 times its luminosity. It is itself a close optical double, with a magnitude 10 companion star related by line of sight only.[12] Gamma1 Normae is a yellow-white supergiant, located much further away at around 1500 light-years from Earth.[11]

Epsilon Normae is 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).

Located between 219 ± 4 light-years distant from Earth,[11] Eta Normae is a yellow giant of spectral type G8III with an apparent magnitude of 4.65..[13] It shines with a luminosity approximately 66 times that of the Sun.[14]

Iota1 Normae is 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 light-years.

Mu Normae is suspected of being an Alpha Cygni variable, with a range of 4.87–4.98. It is a distant luminous supergiant of spectral type O9.7 Iab.[15] Lying near Eta Normae is R Normae,[16] a Mira variable. Its visual range is 6.5–13.9 and its average period is 507.5 days. Located halfway between Eta Normae and Gamma Circini is T Normae, another Mira variable.[16] It ranges from magnitude 6.2 to 13.6 and a period of 244 days.[17] S Normae is a well-known Cepheid variable with a range of 6.12–6.77 and a period of 9.75411 days.[18] It is located at the centre of the open cluster NGC 6087. It is a yellow-white supergiant that is 6.3 times as massive as the Sun of spectral type F8-G0Ib. A binary, it has a 2.4 solar mass (M) companion that is a blue-white main sequence star of spectral type B9.5V.[19]

Four star systems are known to harbour 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. [20] HD 148156 is a star slightly larger and hotter than the Sun 168 ± 7 light-years distant that was found to have a roughly Jupiter-size planet with an orbital period of 2.8 years.[21] HD 143361 is a binary star system composed of a sunlike star and a red dwarf separated by 30.9 AU. A planet roughly triple the mass of Jupiter orbits the brighter star every 1057± 20 days.[22] HD 142415 is approximately 113 light-years distant and has a Jupiter-sized planet with an orbital period of around 386 days.[23]

Deep-sky objects[edit]

Due to its location on the Milky Way, this constellation contains many deep-sky objects such as star clusters,[16] the most notable of which is NGC 6087.

  • 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.

Notes[edit]

  1. ^ While parts of the constellation technically rise above the horizon to observers between 29°N and 48°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.[5]
  2. ^ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[9]

References[edit]

Citations
  1. ^ a b Ridpath, Ian. "Lacaille’s Southern Planisphere of 1756". Star Tales. self-published. Retrieved 19 March 2015. 
  2. ^ Lacaille, Nicolas Louis (1756). "Relation abrégée du Voyage fait par ordre du Roi au cap de Bonne-espérance". Mémoires de l'Académie Royale des Sciences (in French): 519- [589]. 
  3. ^ Wagman 2003, pp. 6-7.
  4. ^ Ridpath, Ian. "Lacaille's grouping of Norma, Circinus, and Triangulum Australe". Star Tales. Retrieved 27 June 2012. 
  5. ^ a b c Ian Ridpath. "Constellations: Lacerta–Vulpecula". Star Tales. self-published. Retrieved 21 March 2015. 
  6. ^ Russell, Henry Norris (1922). "The New International Symbols for the Constellations". Popular Astronomy 30: 469. Bibcode:1922PA.....30..469R. 
  7. ^ "Norma, Constellation Boundary". The Constellations (International Astronomical Union). Retrieved 21 March 2015. 
  8. ^ Wagman 2003, pp. 215-16.
  9. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 29 November 2014. 
  10. ^ Streicher, Magda (2005). "Deepsky Delights: Sparkling clusters in Norma". Monthly Notes of the Astronomical Society of Southern Africa 64 (5-6): 107–09. Bibcode:2005MNSSA..64..107S. 
  11. ^ a b c van Leeuwen, F. (2007). "Validation of the New Hipparcos Reduction". Astronomy and Astrophysics 474 (2): 653–64. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  12. ^ Kaler, James B. "Gamma-2 Normae". Stars. University of Illinois. Retrieved 23 March 2015. 
  13. ^ "Eta Normae". SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved 24 March 2015. 
  14. ^ McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental Parameters and Infrared Excesses of Hipparcos Stars". Monthly Notices of the Royal Astronomical Society 427 (1): 343–57. Bibcode:2012MNRAS.427..343M. 
  15. ^ Sota, A.; Maíz Apellániz, J.; Morrell, N.I.; Barbá, R.H.; Walborn, N.R.; Gamen, R.C.; Arias, J.I.; Alfaro, E.J. (2014). "The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars". The Astrophysical Journal Supplement 211 (1): 84. Bibcode:2014ApJS..211...10S. doi:10.1088/0067-0049/211/1/10. 10. 
  16. ^ a b c Arnold, H.J.P; Doherty, Paul; Moore, Patrick (1999). The Photographic Atlas of the Stars. Boca Raton, Florida: CRC Press. p. 176. ISBN 9780750306546. 
  17. ^ Otero, Sebastian Alberto (19 March 2011). "T Normae". AAVSO Website. American Association of Variable Star Observers. Retrieved 21 March 2015. 
  18. ^ Watson, Christopher (4 January 2010). "S Normae". AAVSO Website. American Association of Variable Star Observers. Retrieved 12 March 2014. 
  19. ^ Evans, Nancy Remage; Bond, Howard E.; Schaefer, Gail H.; Mason, Brian D.; Karovska, Margarita; Tingle, Evan (2013). "Binary Cepheids: Separations and Mass Ratios in 5M ⊙ Binaries". Astronomical Journal 146 (4): 93, 10 pp. arXiv:1307.7123v1. doi:10.1088/0004-6256/146/4/93. 
  20. ^ Pepe, F.; Mayor, M.; Queloz, D.; Benz, W.; Bonfils, X.; Bouchy, F.; Lo Curto, G.; Lovis, C.; M�gevand, D. (2004). "The HARPS search for southern extra-solar planets I. HD 330075 b: A new "hot Jupiter"". Astronomy and Astrophysics 423 (1): 385–89. arXiv:astro-ph/0405252. Bibcode:2004A&A...423..385P. doi:10.1051/0004-6361:20040389. 
  21. ^ Naef, D.; Mayor, M.; Curto, G. Lo; Bouchy, F.; Lovis, C.; Moutou, C.; Benz, W.; Pepe, F.; Queloz, D. (2010). "The HARPS search for southern extrasolar planets XXIII. 8 planetary companions to low-activity solar-type stars". Astronomy and Astrophysics 523. A15. arXiv:1008.4600. Bibcode:2010A&A...523A..15N. doi:10.1051/0004-6361/200913616. 
  22. ^ Minniti, Dante; Butler, R. Paul; López-Morales, Mercedes; Shectman, Stephen A.; Adams, Fred C.; Arriagada, Pamela; Boss, Alan P.; Chambers, John E. (2009). "Low-Mass Companions for Five Solar-Type Stars From the Magellan Planet Search Program". The Astrophysical Journal 693 (2): 1424–30. arXiv:0810.5348. Bibcode:2009ApJ...693.1424M. doi:10.1088/0004-637X/693/2/1424. 
  23. ^ Mayor, M.; Udry, S.; Naef, D.; Pepe, F.; Queloz, D.; Santos, N. C.; Burnet, M. (2004). "The CORALIE survey for southern extra-solar planets XII. Orbital solutions for 16 extra-solar planets discovered with CORALIE". Astronomy and Astrophysics 415 (1): 391–402. arXiv:astro-ph/0310316. Bibcode:2004A&A...415..391M. doi:10.1051/0004-6361:20034250. 
  24. ^ Wilkins & Dunn 2006.
References
  • Wilkins, Jamie; Dunn, Robert (2006), 300 Astronomical Objects: A Visual Reference to the Universe, Firefly Books, ISBN 978-1-55407-175-3 
  • Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, Virginia: The McDonald & Woodward Publishing Company. ISBN 978-0-939923-78-6. 

External links[edit]

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