Delta Cygni
Encyclopedia
Delta Cygni is the third-magnitude star
in the constellation
Cygnus
. It has the traditional name Rukh. It will be the "North Star" for at least four centuries around 11,250.
This star belonged to the arabic asterism al-Fawāris , meaning "the Riders" in indigenous Arabic
., together with ζ
, ε
, and γ Cyg
, the transverse of the Northern Cross
.
In Chinese
, , meaning Celestial Ford
, refers to an asterism consisting of δ Cygni, γ Cygni
, 30 Cygni, α Cygni
, ν Cygni, τ Cygni
, υ Cygni, ζ Cygni
and ε Cygni
. Consequently, δ Cygni itself is known as
The bright naked-eye star is a blue-white subgiant of spectral class B9.5, with a temperature of 9,800 kelvin
s. It is nearing the end of its main-sequence life stage with a luminosity
180 times that of the Sun
, a radius
of 4.7 solar radii, and a mass
approximately 3.15 solar mass
es. Like many hot stars, it spins rapidly, at least 135 kilometers per second at the equator, about 60 times that of the Sun. Its close companion is a yellow-white class F of the sixth magnitude (6.33) with a luminosity about 6 times that of the sun, and a mass about 1.5 times that of the sun. The much more distant third companion is an orange (class K) twelfth magnitude star, being only 38% as luminous as the sun, and only 70% as massive as the sun. As seen from Earth
, the entire triple star system of Delta Cygni shines at a combined apparent magnitude
of 2.86.
that lay claim to the position of "North Star" over the course of Earth's 26,000-year precession
cycle.
The other seven stars are
Star
A 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...
in the constellation
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....
Cygnus
Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...
. It has the traditional name Rukh. It will be the "North Star" for at least four centuries around 11,250.
This star belonged to the arabic asterism al-Fawāris , meaning "the Riders" in indigenous Arabic
Arabic language
Arabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
., together with ζ
Zeta Cygni
Zeta Cygni and CCDM J21129+3014B form a binary star system in the constellation Cygnus, approximately 151 light-years away from Earth....
, ε
Epsilon Cygni
Epsilon Cygni is a star in the constellation Cygnus . It is also called Gienah, a traditional name it shares with Gamma Corvi...
, and γ Cyg
Gamma Cygni
Gamma Cygni is a star in the constellation Cygnus. It has the traditional name Sadr ....
, the transverse of the Northern Cross
Cygnus (constellation)
Cygnus is a northern constellation lying on the plane of the Milky Way. Its name is the Latinized Hellenic word for swan. One of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross...
.
In Chinese
Chinese language
The Chinese language is a language or language family consisting of varieties which are mutually intelligible to varying degrees. Originally the indigenous languages spoken by the Han Chinese in China, it forms one of the branches of Sino-Tibetan family of languages...
, , meaning Celestial Ford
Girl (Chinese constellation)
The Girl mansion is one of the Twenty-eight mansions of the Chinese constellations. It is one of the northern mansions of the Black Tortoise.- Asterisms :...
, refers to an asterism consisting of δ Cygni, γ Cygni
Gamma Cygni
Gamma Cygni is a star in the constellation Cygnus. It has the traditional name Sadr ....
, 30 Cygni, α Cygni
Deneb
Deneb is the brightest star in the constellation Cygnus and one of the vertices of the Summer Triangle. It is the 19th brightest star in the night sky, with an apparent magnitude of 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars...
, ν Cygni, τ Cygni
Tau Cygni
Tau Cygni is a binary star system in the constellation Cygnus, approximately 69 light years away from Earth. The main star, 4th magnitude GJ 822.1 A, is a yellowish white subgiant star of the spectral type F2IV. It therefore has a surface temperature of 6,000 to 7,500 kelvins and is larger,...
, υ Cygni, ζ Cygni
Zeta Cygni
Zeta Cygni and CCDM J21129+3014B form a binary star system in the constellation Cygnus, approximately 151 light-years away from Earth....
and ε Cygni
Epsilon Cygni
Epsilon Cygni is a star in the constellation Cygnus . It is also called Gienah, a traditional name it shares with Gamma Corvi...
. Consequently, δ Cygni itself is known as
Features
Delta Cygni is a triple star; the system lies at a distance of about 170 light years and consists of two stars quite close together and one much farther out. This sort of common configuration lends stability.The bright naked-eye star is a blue-white subgiant of spectral class B9.5, with a temperature of 9,800 kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
s. It is nearing the end of its main-sequence life stage with a luminosity
Luminosity
Luminosity 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...
180 times that of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, a radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
of 4.7 solar radii, and a mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
approximately 3.15 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
es. Like many hot stars, it spins rapidly, at least 135 kilometers per second at the equator, about 60 times that of the Sun. Its close companion is a yellow-white class F of the sixth magnitude (6.33) with a luminosity about 6 times that of the sun, and a mass about 1.5 times that of the sun. The much more distant third companion is an orange (class K) twelfth magnitude star, being only 38% as luminous as the sun, and only 70% as massive as the sun. As seen from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, the entire triple star system of Delta Cygni shines at a combined apparent 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...
of 2.86.
'North star'
It is one of eight bright stars in the northern hemisphereNorthern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
that lay claim to the position of "North Star" over the course of Earth's 26,000-year precession
Precession
Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...
cycle.
The other seven stars are
- Tau Herculis (of HerculesHercules (constellation)Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today...
), - VegaVegaVega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...
(of Lyra), - Alpha CepheiAlpha CepheiAlpha Cephei is a second magnitude star in the constellation of Cepheus that is relatively close to Earth at only 49 light years...
(of CepheusCepheus (constellation)Cepheus is a constellation in the northern sky. It is named after Cepheus, King of Aethiopia in Greek mythology. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations.-Stars:...
), - Gamma CepheiGamma CepheiGamma Cephei , traditionally named Errai, Er Rai, and or Alrai, is a binary star system approximately 45 light-years away in the constellation of Cepheus. Gamma Cephei contains an apparent magnitude of 3.22. The visible part of the system is a stellar class K1III-IV orange subgiant star on its...
(of CepheusCepheus (constellation)Cepheus is a constellation in the northern sky. It is named after Cepheus, King of Aethiopia in Greek mythology. It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations.-Stars:...
), - PolarisPolarisPolaris |Alpha]] Ursae Minoris, commonly North Star or Pole Star, also Lodestar) is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star....
(of Ursa Minor), - Kappa DraconisKappa DraconisKappa Draconis is a blue giant star located in the constellation Draco. At an apparent magnitude of 3.88, it is barely visible to the naked eye when artificial lighting from cities is present. Nevertheless, it is a powerful star, approximately five time as massive as the Sun...
(of DracoDraco (constellation)Draco is a constellation in the far northern sky. Its name is Latin for dragon. Draco is circumpolar for many observers in the northern hemisphere...
), and - Alpha DraconisThubanThuban also known by its Bayer designation Alpha Draconis is a star in the constellation of Draco. A relatively inconspicuous star in the night sky of the Northern Hemisphere, it is historically significant as having been the north pole star in ancient times...
(of Draco).
External links
- Marshall "Roc" Burns, My Nickname: The Mythological Roc - TheRoc.net
- James B. "Jim" Kaler, DELTA CYG (Delta Cygni) - STARS
- Alan M. MacRobert, Understanding Celestial Coordinates - Sky & Telescope
- Richard Powell, The Brightest Stars - An Atlas of The Universe