Visible at latitudes between +90° and −1°. Best visible at 21:00 (9 p.m.) during the month of November.
Cepheus is aconstellation in the deep northern sky, named afterCepheus, a king ofAethiopia inGreek mythology. It is one of the 48 constellations listed by the second century astronomerPtolemy, and it remains one of the 88 constellations in the modern times.
Cepheus was theKing ofAethiopia. He was married toCassiopeia and was the father ofAndromeda, both of whom are immortalized as modern day constellations along with Cepheus.[5]
The constellation Cepheus as it may be seen by the naked eye. The 5 brightest stars make a asterism that is described as a child's drawing of a house[6]
Alderamin, also known as Alpha Cephei, is the brightest star in the constellation, with anapparent magnitude of 2.51.[7]Gamma Cephei, also known as Errai, is the second-brightest star in the constellation, with an apparent magnitude of 3.21.[8] It is abinary star, made up by anorange giant orsubgiant[9] and ared dwarf.[10] The primary component hosts one exoplanet,Gamma Cephei Ab (Tadmor).[11]Delta Cephei is a yellow-hued supergiant star 980 light-years from Earth and the prototype of the class of theCepheid variables. It was discovered to bevariable byJohn Goodricke in 1784. It varies between 3.5m and 4.4m over a period of 5 days and 9 hours. The Cepheids are a class ofpulsating variable stars; Delta Cephei has a minimum size of 40solar diameters and a maximum size of 46 solar diameters. It is also adouble star; the primary star also has a wide-set blue-hued companion of magnitude 6.3.[12]
There are fourred supergiants in the constellation that are visible to the naked eye.Mu Cephei is also known as the Garnet Star due to its deep red colour. It is asemiregular variable star with a minimum magnitude of 5.1 and a maximum magnitude of 3.4. Its period is approximately 2 years.[13] The star's radius has been estimated to be from 972solar radii (4.52 AU)[14] to 1,420 solar radii (6.6 AU).[15] If it were placed at the center of theSolar System, it would likely extend past the orbit ofJupiter. The second,VV Cephei A, is a semiregular variable star, located approximately 5,000 light-years from Earth. It has a minimum magnitude of 5.4 and a maximum magnitude of 4.8,[16] and is paired with a blue main sequence star called VV Cephei B. The red supergiant primary is around 1,050 times larger than the Sun.[17] VV Cephei is also an unusually long-periodeclipsing binary, but the eclipses, which occur every 20.3 years, are too faint to be observed with the unaided eye. The third,Zeta Cephei, is not as large as Mu Cephei and VV Cephei A with a diameter less than 200 times that of the Sun;[18] however, its surface would lie between the orbits ofVenus andEarth if placed at the center of the Solar System. Zeta Cephei has an apparent magnitude of 3.35,[15] being the fourth-brightest star in the constellation. The last and faintest isV381 Cephei Aa with a maximum magnitude of 5.5.[16] It is part of a triple star system similar to VV Cephei,[19][20] and has a diameter 980 times that of the Sun.[21] All four stars have initial masses more than eight times that of the Sun and are accepted core-collapsesupernova candidates.[22][23]
Nu Cephei is ablue supergiant similar to Deneb with an initial mass of over 20 solar masses. It belongs to the Cepheus OB2stellar association along with Mu Cephei and VV Cephei, which have similar initial masses.[24]
There are several prominentdouble stars andbinary stars in Cepheus.Omicron Cephei is a binary star with a period of 800 years. The system, 211 light-years from Earth, consists of an orange-hued giant primary of magnitude 4.9 and a secondary of magnitude 7.1.Xi Cephei is another binary star, 102 light-years from Earth, with a period of 4,000 years. It has a blue-white primary of magnitude 4.4 and a yellow secondary of magnitude 6.5.[13]
Krüger 60 is an 11th-magnitude binary star consisting of two red dwarfs. The star system is one of the nearest, being only 13 light-years away from Earth. It was once proposed as a possible home system for2I/Borisov, the first acceptedinterstellar comet, but this was later rejected.[25]
Emission nebula in Cepheus seen by the Northern Sky Narrowband Survey.
NGC 7354 is a planetary nebula located in the constellation Cepheus[26]
The constellation Cepheus is rich in star-forming regions and emission nebulae of various kinds. Most of the structures visible in the wide-field view on the right (the image height is 22°) lie in theOrion Arm of the Milky Way, roughly 2,800 to 3,600 light-years away. The following is an overview of some prominent deep-sky objects:
NGC 188 is anopen cluster that has the distinction of being the closest open cluster to the north celestial pole, as well as one of the oldest-known open clusters.
NGC 7023 is a reflection nebula with an associated star cluster (Collinder 429); it has an overall magnitude of 7.7 and is 1,400 light-years from Earth. The nebula and cluster are located nearBeta Cephei andT Cephei.[30]
Sh 2-155, also known as the Cave Nebula,[31] is a dim and very diffuse bright nebula within a larger nebula complex containing emission, reflection, and dark nebulosity.
Sh 2-131 is ionized by the stars of the clusterIC 1396[33](the two are often treated as essentially the same object). Embedded within it is a dark nebula known as theElephant’s Trunk.
NGC 7822 (also known as Sh 2-171) is anH II region with an apparent diameter of about 3°
Cepheus as depicted inUrania's Mirror, a set of constellation cards published in London,c. 1825
Cepheus is most commonly depicted as holding his arms aloft, praying for the deities to spare the life of Andromeda. He also is depicted as a more regal monarch sitting on his throne.[5]
^Neuhaeuser, Ralph; Mugrauer, Markus; Fukagawa, Misato; Torres, Guillermo; Schmidt, Tobias (February 2007). "Direct detection of exoplanet host star companion gamma Cep B and revised masses for both stars and the sub-stellar object".Astronomy & Astrophysics.462 (2):777–780.arXiv:astro-ph/0611427.Bibcode:2007A&A...462..777N.doi:10.1051/0004-6361:20066581.ISSN0004-6361.
^abLevesque, Emily M.; Massey, Philip; Olsen, K. A. G.; Plez, Bertrand; Josselin, Eric; Maeder, Andre; Meynet, Georges (August 2005). "The Effective Temperature Scale of Galactic Red Supergiants: Cool, But Not As Cool As We Thought".The Astrophysical Journal.628 (2):973–985.arXiv:astro-ph/0504337.Bibcode:2005ApJ...628..973L.doi:10.1086/430901.ISSN0004-637X.
^abSamus, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2009-01-01). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+, 2007-2017)".VizieR Online Data Catalog.1: B/gcvs.Bibcode:2009yCat....102025S.
^Dybczyński, Piotr A.; Królikowska, Małgorzata; Wysoczańska, Rita (2019-11-26). "Kruger 60 as a home system for 2I/Borisov -- a case study".arXiv:1909.10952 [astro-ph.EP].
^"Smoky Shells".ESA/Hubble Picture of the Week. Retrieved13 December 2012.
Staal, Julius D.W. (1988),The New Patterns in the Sky: Myths and Legends of the Stars (2nd ed.), The McDonald and Woodward Publishing Company,ISBN0-939923-04-1
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