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Perseus (constellation)
Encyclopedia
Perseus is a constellation
in the northern sky, named after the Greek
hero Perseus
. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy
, and remains one of the 88 modern constellations defined by the International Astronomical Union
. It contains the famous variable star
Algol (β Per), and is also the location of the radiant
of the annual Perseids
meteor shower
.
, an astronomical compilation dating to around 1000BCE.
H.A. Rey has suggested an alternative way to connect the stars into the shape of a man. Perseus' body is formed by the stars β Per, κ Per
, ι Per
, α Per
, σ Per, ν Per
, and ε Per
. α Per and β Per are of the second magnitude. The star ε Per is of the third magnitude. The stars α Per, γ Per
, τ Per, and ι Per form Perseus' head: gamma Persei is of the third magnitude. Stars γ Per, η Per
, and τ Per form Perseus' cap. The stars α Per, ψ Per
, δ Per
, 48 Per, μ Per, and λ Per form Perseus' left arm and hand: δ Per being of the third magnitude. The stars ι Per, θ Per
, and φ Per
form the right arm and hand. Perseus' right hand, φ Per, is yanking at one of Andromeda
's feet (51 Andromedae
), intent on liberating her. Stars ε Per, ξ Per
, ζ Per
, and ο Per
form Perseus' left leg and foot: ζ Per being of the third magnitude. Finally, stars β Per, ρ Per
, 16 Per (with π Per
) form Perseus' right leg and foot.
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
in the northern sky, named after the Greek
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
hero Perseus
Perseus
Perseus ,Perseos and Perseas are not used in English. the legendary founder of Mycenae and of the Perseid dynasty of Danaans there, was the first of the mythic heroes of Greek mythology whose exploits in defeating various archaic monsters provided the founding myths of the Twelve Olympians...
. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
, and remains one of the 88 modern constellations defined by the International Astronomical Union
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
. It contains the famous variable star
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
Algol (β Per), and is also the location of the radiant
Radiant (meteor shower)
The radiant or apparent radiant of a meteor shower is the point in the sky, from which meteors appear to originate. The Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus....
of the annual Perseids
Perseids
The Perseids are a prolific meteor shower associated with the comet Swift-Tuttle. The Perseids are so-called because the point from which they appear to come, called the radiant, lies in the constellation Perseus. The name derives in part from the word Perseides , a term found in Greek mythology...
meteor shower
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller...
.
Notable features
- α PerAlpha PerseiAlpha Persei is the brightest star in the constellation of Perseus, just outshining the constellation's best known star Algol. It also bears the traditional names Mirfak and Algenib...
(Mirfak): The brightest starStarA star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
of this constellation is also called Algenib (a name which is used for other stars as well, e. g. γ PegGamma PegasiGamma Pegasi is a star in the constellation of Pegasus. It also has the traditional name Algenib; confusingly however, this name is also used for Alpha Persei....
). Mirfak (Arabic for elbow) is a supergiant of spectral type F5 Ib with an apparent brightnessApparent magnitudeThe 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...
of 1.79m lying at a distance of ca. 590 light-yearLight-yearA light-year, also light year or lightyear is a unit of length, equal to just under 10 trillion kilometres...
s. Its luminosityLuminosityLuminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
is 5,000 times and its diameter is 42 times that of our sun. - Algol (β Per): This may not be the brightest star of this constellation, but it definitely is its most famous star. Algol (from Arabic al-Ghul, which means The Ghoul or The Demon Star) represents the eye of the gorgonGorgonIn Greek mythology, the Gorgon was a terrifying female creature. The name derives from the Greek word gorgós, which means "dreadful." While descriptions of Gorgons vary across Greek literature, the term commonly refers to any of three sisters who had hair of living, venomous snakes, and a...
Medusa. This star is the prototype of a whole group of eclipsing variable stars. Its apparent brightness ranges between 2.12m and 3.39m with a period of merely 2.867 days. It is a triple star with the brightest component having a spectral type B8 V. The Algol system lies at a distance of only 93 ly. - Nova Persei 1901GK PerseiGK Persei was a bright nova occurring in 1901. It reached a maximum magnitude of 0.2, the brightest nova of modern times until Nova Aquilae 1918...
(GK Per), a bright novaNovaA nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
discovered on February 21, 1901.
Deep sky objects
- h + χ Per: These two 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 (NGC 869NGC 869NGC 869 is an open cluster located 7600 light years away in the constellation of Perseus. The cluster is most likely around 13 million years old. It is the westernmost of the Double Cluster with NGC 884. Located in the Perseus OB1 association both clusters are located physically close to one...
and NGC 884NGC 884NGC 884 is an open cluster located 7600 light years away in the constellation of Perseus. The cluster is most likely around 12.5 million years old. It is the easternmost of the Double Cluster with NGC 869. Located in the Perseus OB1 association both clusters are located physically close to one...
respectively) belong to two objects of the night sky for binocularBinocularBinocular may refer to:* Binocular vision, seeing with two eyes* Binoculars, a telescopic tool* Binocular, a thoroughbred race horse* Binocular , Kevin Rudolf's band that released a self-titled album in 2001....
s and small telescopes. They are sometimes called the Double ClusterDouble ClusterThe Double Cluster is the common name for the naked-eye open clusters NGC 884 and NGC 869 , which are close together in the constellation Perseus. NGC 884 and NGC 869 are at distances of 7600 and 6800 light-years away, respectively, so they are also close to one another in space...
. Both lie at distances of more than 7,000 ly and are separated by several hundred light-years. - M34: This open cluster with an apparent brightness of 5.5m lies at a distance of approximately 1,400 ly and consists of about 100 stars that are scattered over an area larger than that of the full moonFull moonFull moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...
. Its true diameterDiameterIn geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
is about 14 ly. M 34 can be resolved even with good binoculars but is best viewed using a telescope at low magnifications. - M76Little Dumbbell NebulaThe Little Dumbbell Nebula, also known as Messier 76, NGC 650/651, the Barbell Nebula, or the Cork Nebula, is a planetary nebula in the constellation Perseus. It was discovered by Pierre Méchain in 1780 and included in Charles Messier's catalog of comet-like objects as number 76. It was first...
: This 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...
is also called Little Dumbbell Nebula. It measures about 65 arc seconds and has an apparent brightness of 10.1m. - NGC 1499California NebulaThe California Nebula is an emission nebula located in the constellation Perseus. It is so named because it appears to resemble the outline of the US State of California on long exposure photographs. It is almost 2.5° long on the sky and, because of its very low surface brightness, it is extremely...
: Also called California Nebula this emission nebulaEmission nebulaAn emission nebula is a cloud of ionized gas emitting light of various colors. The most common source of ionization is high-energy photons emitted from a nearby hot star...
, discovered in 1884-85 by the American astronomer Edward E. Barnard, is a great target for astrophotographers. Due to its low 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...
it's a very difficult object when observed visually. - NGC 1333NGC 1333NGC 1333 is a reflection nebula located in the constellation Perseus. It belongs to the Perseus molecular cloud.In 2011 researchers reported finding 30 to 40 brown dwarf objects in the cloud and in the Rho Ophiuchi cloud complex.-External links:* * *...
is a reflection nebula and the location of star formation. - NGC 1260NGC 1260NGC 1260 is a spiral galaxy in the constellation Perseus. In 2006, it was home to the second brightest object in the observable universe, supernova SN 2006gy.-External links:*...
contains the second brightest known object in the universe, SN 2006gySN 2006gySN 2006gy was an extremely energetic supernova, sometimes referred to as a hypernova or quark-nova, that was discovered on September 18, 2006. It was first observed by Robert Quimby and P. Mondol, and then studied by several teams of astronomers using facilities that included the Chandra, Lick, and...
. - Alpha Persei ClusterAlpha Persei ClusterThe Alpha Persei Cluster, also known as Melotte 20 or Collinder 39, is an open cluster in the constellation of Perseus. To the naked eye, the cluster consists of several blue spectral type B type stars. The most luminous member is the ~2nd magnitude white-yellow supergiant Mirfak, also known as...
(also known as Melotte 20 and Collinder 39) is an open cluster containing Alpha Persei. - Perseus also contains a giant molecular cloud, named Perseus molecular cloudPerseus molecular cloudThe Perseus molecular cloud is a nearby Giant Molecular Cloud in the constellation of Perseus and contains over 10,000 solar masses of gas and dust covering an area of 6 by 2 degrees. Unlike the Orion molecular cloud it is almost invisible apart from two clusters, IC 348 and NGC 1333, where...
; it belongs to the Orion Spur and is well-known for its low-star formation.
History
The Greek constellation may be an adaptation of the Babylonian constellation known as the Old Man (MUL.SHU.GI) which is associated with East (as a cardinal direction) in the MUL.APINMUL.APIN
MUL.APIN is the conventional title given to a Babylonian compendium that deals with many diverse aspects of Babylonian astronomy and astrology....
, an astronomical compilation dating to around 1000BCE.
Visualizations
Traditionally, the stars of Perseus are visualized as forming a 'Y' shape.Kappa Persei
Kappa Persei is a star in the constellation Perseus. It has the traditional name Misam.Misam belongs to the spectral class K0 and has apparent magnitude +3.8. It is 112 light years from Earth. Kappa Persei is a triple star system consisting of a spectroscopic double star with a wider companion....
, ι Per
Iota Persei
Iota Persei is a main sequence dwarf star in the constellation Perseus. It is somewhat larger and greater in mass than the Sun, and is located about 34 light years distant. Iota Persei has a relatively high proper motion across the sky, and moves at a net velocity of 92 km/s, relative to the...
, α Per
Alpha Persei
Alpha Persei is the brightest star in the constellation of Perseus, just outshining the constellation's best known star Algol. It also bears the traditional names Mirfak and Algenib...
, σ Per, ν Per
Nu Persei
Nu Persei is a Class F5, fourth-magnitude star in the constellation Perseus. Nu Persei is a highly luminous yellow-white giant located about 555 light-years from Earth.-External links:*...
, and ε Per
Epsilon Persei
Epsilon Persei is a Class B1V, third-magnitude star in the constellation Perseus. Epsilon Persei is actually a multiple star system consisting of two main components: a blue main-sequence star of class B0.5V and a magnitude of 2.90, and a lesser white companion of class A2V and a magnitude of 3.92...
. α Per and β Per are of the second magnitude. The star ε Per is of the third magnitude. The stars α Per, γ Per
Gamma Persei
Gamma Persei is a Class G8III, third-magnitude star in the constellation Perseus. Gamma Persei is actually a multiple star system consisting of two main components: a yellow giant star of class G8 and a magnitude of 2.91, and a lesser white companion of class A2V and a magnitude of 3.00...
, τ Per, and ι Per form Perseus' head: gamma Persei is of the third magnitude. Stars γ Per, η Per
Eta Persei
Eta Persei is a star in the constellation Perseus. It also has the traditional Arabic name Miram. Miram belongs to spectral class K3 and has an apparent magnitude of +3.76. It is approximately 1331 light years away from Earth....
, and τ Per form Perseus' cap. The stars α Per, ψ Per
Psi Persei
Psi Persei is a Be star in the constellation Perseus. This is a shell star that has a circumstellar disc of gas surrounding the equator. As a result of this disc, the spectrum of this star shows emission lines and the magnitude varies over a period of about a day...
, δ Per
Delta Persei
Delta Persei is a Class B5III, third-magnitude star in the constellation Perseus. Delta Persei is actually a blue giant star that is the second brightest star of the open star cluster known as the Alpha Persei, second only to Mirfak. The Delta Persei stellar system is located about 530 light-years...
, 48 Per, μ Per, and λ Per form Perseus' left arm and hand: δ Per being of the third magnitude. The stars ι Per, θ Per
Theta Persei
Theta Persei is a star system 37 light years away from Earth, in the constellation Perseus. The primary star is a yellowish dwarf star of spectral type F7V, which is somewhat larger and brighter than our sun, but still within the range considered to have the potential for Earth-like planets...
, and φ Per
Phi Persei
Phi Persei is a Class B2Vpe, fourth-magnitude star in the constellation Perseus. Due to its isolation and distance from Cassiopeia, Andromeda and the rest of Perseus, John Flamsteed never took thought to assign a number and constellation to Phi Persei.Phi Persei is binary consisting of a blue main...
form the right arm and hand. Perseus' right hand, φ Per, is yanking at one of Andromeda
Andromeda (constellation)
Andromeda is a constellation in the northern sky. It is named after Andromeda, the princess in the Greek legend of Perseus who was chained to a rock to be eaten by the sea monster Cetus...
's feet (51 Andromedae
51 Andromedae
51 Andromedae is a 4th magnitude star, the 5th brighest in the constellation Andromeda. It does not have a Bayer designation. It is occasionally called by the proper name Nembus in Bayer's Uranometria and Bode's star atlas Uranographia .Ptolemy included this star in Andromeda in the Almagest, but...
), intent on liberating her. Stars ε Per, ξ Per
Xi Persei
Xi Persei is a star in the constellation Perseus. It has the traditional name Menkib . Menkib has an apparent magnitude of +4.042 and is classified as a blue giant . It is approximately 1800 light years from Earth.Its apparent luminosity is 13,500 times that of the Sun...
, ζ Per
Zeta Persei
Zeta Persei is a star in the constellation Perseus.ζ Persei is of spectral class B1 and has an Apparent magnitude of +2.85. It is a supergiant star with a radius of 21 times that of the Sun with a luminosity of 105,000 times solar...
, and ο Per
Omicron Persei
Omicron Persei is a star in the constellation Perseus. It has the traditional name Atik ....
form Perseus' left leg and foot: ζ Per being of the third magnitude. Finally, stars β Per, ρ Per
Rho Persei
Rho Persei is a star in the constellation Perseus. It has the traditional name Gorgonea Tertia.Rho Persei is a semiregular variable star of the μ Cephei type, whose apparent magnitude varies between 3.3 and 4.0 with periods of 50 days and 1100 days. It is of spectral class M4 and is approximately...
, 16 Per (with π Per
Pi Persei
Pi Persei is a star in the constellation Perseus. It also has the traditional name Gorgonea Secunda.Pi Persei has an apparent magnitude of +4.7 and spectral class A2V...
) form Perseus' right leg and foot.