Deneb
Overview
 
Deneb is the brightest star
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...

 and one of the vertices of the Summer Triangle
Summer Triangle
The Summer Triangle is an astronomical asterism involving an imaginary triangle drawn on the northern hemisphere's celestial sphere, with its defining vertices at Altair, Deneb, and Vega, being the brightest stars in the three constellations of Aquila, Cygnus, and Lyra.The English term was...

. It is the 19th brightest star in the night sky, with an 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 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars. Other names include Arided and Aridif, but these have fallen out of use.
Deneb's absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...

 is approximately −7.0, placing it among the most luminous stars known, with an estimated luminosity nearly 60,000 times that of our 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...

.

Deneb's exact distance from the Earth is uncertain, which makes determining many of Deneb's other properties similarly imprecise.
Encyclopedia
Deneb is the brightest star
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...

 and one of the vertices of the Summer Triangle
Summer Triangle
The Summer Triangle is an astronomical asterism involving an imaginary triangle drawn on the northern hemisphere's celestial sphere, with its defining vertices at Altair, Deneb, and Vega, being the brightest stars in the three constellations of Aquila, Cygnus, and Lyra.The English term was...

. It is the 19th brightest star in the night sky, with an 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 1.25. A blue-white supergiant, Deneb is also one of the most luminous nearby stars. Other names include Arided and Aridif, but these have fallen out of use.

Distance and physical characteristics

Deneb's absolute magnitude
Absolute magnitude
Absolute magnitude is the measure of a celestial object's intrinsic brightness. it is also the apparent magnitude a star would have if it were 32.6 light years away from Earth...

 is approximately −7.0, placing it among the most luminous stars known, with an estimated luminosity nearly 60,000 times that of our 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...

.

Deneb's exact distance from the Earth is uncertain, which makes determining many of Deneb's other properties similarly imprecise. However, the uncertainty was dramatically reduced upon analysis of the New Hipparcos
Hipparcos
Hipparcos was a scientific mission of the European Space Agency , launched in 1989 and operated between 1989 and 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky...

 Data Reduction in 2007. One 2008 study puts the most likely distance at 1,550 light-years, with an uncertainty of approxmiately 10%. The reduced parallax
Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

 uncertainties do not rule out a distance as close as 1,340 light-years or as far as 1,840 light-years. It is the farthest-known first-magnitude star from Earth.

Based on its temperature and luminosity, and also on direct measurements of its tiny angular diameter
Angular diameter
The angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. In the vision sciences it is called the visual angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its...

 (a mere 0.002 second of arc), Deneb appears to have a diameter of about 110 times that of the Sun; if placed at the center of our Solar System, Deneb would extend halfway out to the orbit of the Earth. It is one of the largest white stars known.

Deneb is a bluish-white star of spectral type
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...

 A2Ia, with a surface temperature of 8,400 kelvin. It is the prototype of a class of 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...

s known as Alpha Cygni variable
Alpha Cygni variable
Alpha Cygni variables are variable stars which exhibit non-radial pulsations, meaning that some portions of the stellar surface are contracting at the same time others parts expand. They are supergiant stars of spectral types B or A...

s. Its surface undergoes non-radial fluctuations which cause its brightness and spectral type to change slightly.

Deneb's mass is estimated at 20 solar masses. As a blue-white supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...

, its high mass and temperature mean that the star will have a short lifespan and will probably go supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...

 within a few million years. It has already stopped fusing hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 in its core. The star was probably an O class star during its main sequence lifetime and is now probably expanding into a red supergiant like Mu Cephei
Mu Cephei
Mu Cephei , also known as Herschel's Garnet Star, is a red supergiant star in the constellation Cepheus. It is one of the largest and most luminous stars known in the Milky Way...

. As it expands, it will go through the F, G, K and M spectral types.

Deneb's solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

 causes it to lose mass at a rate of 0.8 millionth of a solar mass per year, a hundred thousand times the flow rate from the Sun.

Etymology and cultural significance

The name Deneb is derived from dhaneb, the Arabic for "tail", from the phrase ذنب الدجاجة Dhanab ad-Dajājah, or "tail of the hen". Similar names were given to at least seven different stars, most notably Deneb Kaitos
Deneb Kaitos
Deneb Kaitos can refer to the following stars in the constellation Cetus Deneb Kaitos can refer to the following stars in the constellation Cetus Deneb Kaitos can refer to the following stars in the constellation Cetus (the name derives from the Arabic Dhanab Qaiṭus meaning "the Sea Monster's...

, the brightest star in the constellation Cetus
Cetus
Cetus is a constellation. Its name refers to Cetus, a sea monster in Greek mythology, although it is often called 'the whale' today. Cetus is located in the region of the sky that contains other water-related constellations such as Aquarius, Pisces, and Eridanus.-Ecliptic:Although Cetus is not...

; Deneb Algedi
Delta Capricorni
Delta Capricorni , also traditionally named Deneb Algedi and Scheddi, is a quaternary star system approximately 39 light-years away in the constellation of Capricornus . The primary star in the system is a white giant star and the combined light of its four members makes it the brightest "single"...

, the brightest star in Capricornus
Capricornus
Capricornus is one of the constellations of the zodiac; it is often called Capricorn, especially when referring to the corresponding astrological sign. Its name is Latin for "horned male goat" or "goat horn", and it is commonly represented in the form of a sea-goat: a mythical creature that is half...

; and Denebola
Denebola
Denebola is the second brightest star in the constellation Leo. It is an A-class star that is about distant from earth, and has a luminosity about twelve times that of the sun. Its apparent magnitude is 2.14...

, the second brightest star in Leo
Leo (constellation)
Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:...

. All these stars are referring to the tail of the animals that their respective constellations represent.

Less contracted names include Deneb Adige, Denebadigege, and Denebedigege. Arided was used in the Alfonsine Tables
Alfonsine tables
The Alfonsine tables provided data for computing the position of the Sun, Moon and planets relative to the fixed stars....

, this latter name derived from Al Ridhādh, a name for the constellation. Johann Bayer
Johann Bayer
Johann Bayer was a German lawyer and uranographer . He was born in Rain, Bavaria, in 1572. He began his study of philosophy in Ingolstadt in 1592, and moved later to Augsburg to begin work as a lawyer. He grew interested in astronomy during his time in Augsburg...

 called it Arrioph, derived from Aridf and Al Ridf, 'the hindmost' or Gallina. Caesius
Caesius
The gens Caesia was a plebeian family at Rome during the late Republic, and through imperial times. The first member of the gens to achieve prominence was Marcus Caesius, praetor in 75 BC...

 termed it Os rosae, or Rosemund in German, or Uropygium – the parson's nose.

In Chinese, , 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 Deneb, γ Cygni
Gamma Cygni
Gamma Cygni is a star in the constellation Cygnus. It has the traditional name Sadr ....

, δ Cygni
Delta Cygni
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....

, 30 Cygni, 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, Deneb itself is known as .

In the Chinese love story of Qi Xi
Qi Xi
Qixi Festival , also known as Magpie Festival, falls on the seventh day of the seventh lunar month on the Chinese calendar; thus its name. It inspired Tanabata in Japan, Chilseok in Korea, and Thất Tịch in Vietnam...

, Deneb marks the magpie
Magpie
Magpies are passerine birds of the crow family, Corvidae.In Europe, "magpie" is often used by English speakers as a synonym for the European Magpie, as there are no other magpies in Europe outside Iberia...

 bridge across the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...

, which allows the separated lovers Niu Lang (Altair) and Zhi Nü (Vega
Vega
Vega 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...

) to be reunited on one special night of the year in late summer. In other versions of the story Deneb is a fairy who acts as chaperone when the lovers meet.

Deneb is the north pole star of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

.

Namesakes

USS Arided (AK-73)
USS Arided (AK-73)
USS Arided , a Crater-class cargo ship, is the only ship of the United States Navy to have this name. She was named after Arided, the other name of Deneb, the alpha star of constellation Cygnus....

 was a United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 Crater class cargo ship
Crater class cargo ship
Crater-class cargo ship is a category of freighter that was constructed for use by the United States Navy during World War II under Maritime Commission EC2-S-C1 type....

named after the star.
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