Deneb (α Cyg, α Cygni, Alpha Cygni) 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. However, its exact distance (and hence luminosity) has been difficult to calculate, so it is anywhere between 54,000 and 196,000 times as luminous as the sun. Other names include Arided and Aridif, but these have fallen out of use.

Deneb's absolute magnitude is currently estimated as −8.4, placing it among the most luminous stars known, with an estimated luminosity nearly 200,000 times that of our Sun.4 This is towards the upper end of various published values over the last few decades.

Deneb's exact distance from the Earth is still rather uncertain. The currently accepted distance of around 2,600 light-years (and the associated physical data shown in the starbox) is derived by a variety of methods, including spectral luminosity classes, atmospheric modelling, stellar evolution models, assumed membership of the Cyg OB7 association, and direct measurements of angular diameter. The original rather inaccurate Hipparcos parallax measurement was not inconsistent with this distance, but the more recent re-analysis gives a much larger parallax and a distance barely half the widely accepted value. One 2008 calculation using the Hipparcos data puts the most likely distance at 1,550 light-years, with an uncertainty of only around 10%, although parallax measurements of asymmetric, pulsating stars embedded within shells is known to be unreliable. The controversy over whether the direct Hipparcos measurements can be ignored in favour of a wide range of indirect stellar models and interstellar distance scales is similar to the better known situation with the Pleiades. The Gaia satellite should provide distance measurements at least two orders of magnitude more reliable than Hipparcos and resolve many such questions, although it will not measure Deneb itself.

Even assuming the lowest estimates of distance and luminosity, Deneb is the brightest and most distant of the stars with apparent magnitude brighter than 1.5, and the most distant (by a factor of almost 2) of the 30 brightest stars. Based on its temperature and luminosity, and also on direct measurements of its tiny angular diameter (a mere 0.002 second of arc), Deneb appears to have a diameter of 100-200 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 A2Ia, with a surface temperature of 8,500 kelvin. Since 1943, its spectrum has served as one of the stable anchor points by which other stars are classified. It is the prototype of a class of variable stars known as Alpha Cygni variables. 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, its high mass and temperature mean that it will have a short lifespan and will probably go supernova within a few million years. It has already stopped fusing hydrogen in its core. It was probably an O class star during its main-sequence lifetime and is now probably expanding into a red supergiant. As it expands, it will go through the F, G, K and M spectral types.

Deneb's solar wind 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.

Deneb in Space Opera

  • Hyperion (1989), first novel in the Hyperion Cantos series by Dan Simmons. Deneb Drei (Deneb III, in German) and Deneb Vier (Deneb IV) are inhabited planets in the Deneb system, just two of dozens of richly detailed planets featured in the single novel that by itself would make Dan Simmons one of the half-dozen central science fiction figures of the 1980s.
  • Honor Harrington (1993- ), series of novels written by David Weber. The Deneb star system is where the Honorverse's rules of war, the Deneb Accords (similar to the Geneva Conventions) were negotiated under the sponsorship of the Solarian League.
  • "Where No Man Has Gone Before" (1966), second pilot episode of Star Trek: The Original Series written by Samuel A. Peeples. The powerful—and dangerous—newly minted telepath Gary Mitchell reminisces with his old friend Captain Kirk about a wild shore leave they once spent together on Deneb IV, a planet of paranormal adepts, where he had already displayed high psychic potential.
  • "I, Mudd" (1967), episode of Star Trek: The Original Series written by Gene Roddenberry and David Gerrold (uncredited). The USS Enterprise is hijacked by a mysterious android and taken to an unnamed planet, populated by hundreds of thousands of his fellows, and by one Harcourt Fenton Mudd, a hapless con-man known to Captain Kirk. The androids, assisted by Harry Mudd, plot to commandeer the Enterprise, take over the galaxy, and control—and serve—humanity forever in a sort of cosmic nanny state. The crew of the Enterprise overcome their robotic captors by using the classic ruse of beguiling them with paradoxes, but not before Mr. Spock has occasion to remind Mudd of the penalty for fraud on Deneb V: capital punishment, with the means freely chosen by the condemned.
  • "The Trouble With Tribbles (1967), episode of Star Trek: The Original Series written by David Gerrold. The USS Enterprise pulls into Deep Space Station K7 where trouble immediately starts with the crew of a Klingon battle cruiser on shore leave, and the Enterprise suffers an infestation of tribbles, adorable balls of fluff that multiply without bound and eat everything in sight. Things go from bad to worse, as Korax, the Klingon first officer, calls Captain Kirk a Denebian slime devil and the tribbles all die of an unknown cause—later revealed to be the unintended consequence of a Klingon plot.
  • "Encounter at Farpoint" (1987), two-hour pilot episode of Star Trek: The Next Generation written by Gene Roddenberry and directed by Corey Allen. Captain Picard and the crew of the newly built USS Enterprise-D examine the mysterious Farpoint Station in orbit around Deneb IV, which the enigmatic Bandi are offering to the Federation—all as he labors under the judgmental gaze of a powerful alien entity that calls itself Q. At Farpoint, Picard wants to fire on a mysterious hostile craft, but is warned off by Q, so he sends an away team instead.
  • Blake's 7 (1978-1981), television series created and mostly written by Terry Nation. Roj Blake, a political dissident is arrested, tried and convicted on false charges and deported to the prison planet Cygnus Alpha (see graphic). He and two fellow prisoners commandeer an abandoned alien spacecraft, rescue two more prisoners and are joined by an alien guerrilla with telepathic abilities. The group conducts an ineffectual campaign against the totalitarian Terran Federation.
  • Babylon 5 (1993–1998), television series developed and written by J. Michael Straczynski. Deneb IV is a large Earth settlement and the largest colony market in its part of the galaxy. It is one of 23 colonies in the Earth Alliance, one of the galaxy's major powers (although not the most powerful) in the Babylon 5 universe, and a hotbed of prophecies, religious zealotry, racial tensions, social pressures and political rivalries.
  • Traveller (1977), role-playing game developed and published by the Game Designers' Workshop. The Domain of Deneb is a region of the Imperium in the universe of Traveller game. It includes the Deneb Sector, whose capital is at Deneb itself. In the Traveller universe, Deneb is closer to Earth and shines with less intrinsic brightness than the actual star.
  • Descent: FreeSpace – The Great War (1998), computer game developed by Volition, Inc. and published by Interplay Entertainment. Deneb is the location of two major battles fought by the Galactic Terran-Vasudan Alliance. The first Battle of Deneb occurs in 2335 between the Shivan Super Destroyer Lucifer with its fleet and a joint Terran-Vasudan force; during the melee the Lucifer disappears, slips through subspace, and launches a devastating surprise attack on Vasuda Prime. The second Battle of Deneb occurs in 2367 between the Galactic Terran-Vasudan Alliance and the Neo-Terran Front in a 72-hour long fight for control of the system. The planets of Deneb include Cygnus Prime, Deneb II, and Deneb III.
  • Earth & Beyond (2002), online role-playing game developed by Westwood Studios and published by Electronic Arts. The Deneb system lurks in the outskirts of the inhabited universe.
  • Vendetta Online (2004), online role-playing game developed and published by Guild Software. Two of the three great factions in the Vendetta Online universe are the Itani Nation, reputed for their advanced science and light maneuverable ships, and the Serco Dominion, a warrior culture with slow, heavily armored vessels. In the year 4063 a Sercan invasion of Itani space culminates at Deneb, the last bastion before the Itani home system of Eo. The Sercan navy is carrying the day, and just beginning to destroy the last Itani remnants among the icy boulders of Aeron's Icefield, when suddenly the Akanese Obsidian Armada drops into normal space to succor them and turn the tide. The Serco retreat, their invasion stalled. Deneb remains the boundary between the factions' territories.

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