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Deneb (Alpha Cygni) - HD197345 - HIP102098 - HR7924

Deneb (Alpha Cygni) is a blue pulsating very luminous supergiant star that can be located in the constellation of Cygnus. Deneb is the 20th brightest star in the night sky and is the brightest star in Cygnus based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Alpha Cygni is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR7924. HIP102098 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD197345.

Deneb has alternative name(s), 50 Cygni , alf_Cyg, 50 Cyg. In Arabic, it is known as Dhanab ad-Dulfin.

Location of Deneb

The location of the star in the galaxy is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the star is compared to the celestial equator and is expressed in degrees. For Deneb, the location is 20h 41m 25.91 and +45d16`49.2 .

Proper Motion of Deneb

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving 1.85 ± 0.25 miliarcseconds/year towards the north and 2.01 ± 0.32 miliarcseconds/year east if we saw them in the horizon.

Deneb Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 40000.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of Deneb

Deneb has a spectral type of A2Ia. This means the star is a blue supergiant star. The star is 7370.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24038.2384528000000000s. The star has a B-V Colour Index of 0.09 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,573 Kelvin.

Deneb Radius has been calculated as being 235.90 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 164,137,528.53.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 102.97. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is 0.15 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Deneb Apparent and Absolute Magnitudes

Deneb has an apparent magnitude of 1.25 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of -8.73 If you used the 2007 Parallax value, you would get an absolute magnitude of -6.93. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Distance to Deneb

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.01 which gave the calculated distance to Deneb as 3229.34 light years away from Earth or 990.10 parsecs. It would take a spaceship travelling at the speed of light, 3229.34 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 2.31 which put Deneb at a distance of 1411.96 light years or 432.90 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

The star's Galacto-Centric Distance is 7,370.00 Parsecs or 24,038.24 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Deneb

The star is a pulsating Alpha Cygnus variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. Deneb brightness ranges from a magnitude of 1.000 to a magnitude of 1.000 over its variable period. The smaller the magnitude, the brighter the star.

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Deneb Facts

Alternative Names

Traditional/Proper NameDeneb
Short Namealf Cyg, 50 Cyg
Arabic NameDhanab ad-Dulfin
English MeaningTail of the Dolphin
Bayer DesignationAlpha Cygni
Alternative Name(s)50 Cygni
Hipparcos Library I.D.102098
Yale Bright Star Catalogue (HR) Id7924
Bonner DurchmusterungBDD+44 3541
Henry Draper Designation197345

Visual Facts

Star Typesupergiant star
Absolute Magnitude-8.73 / -6.93
Visual / Apparent Magnitude1.25
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 41m 25.91
Declination (Dec.)+45d16`49.2
Galactic Latitude2.00 degrees
Galactic Longitude84.28 degrees
1997 Distance from Earth1.01 Parallax (milliarcseconds)
 3229.34 Light Years
 990.10 Parsecs
2007 Revised Distance from Earth2.31 Parallax (milliarcseconds)
 1411.96 Light Years
 432.90 Parsecs
Galacto-Centric Distance24,038.24 Light Years / 7,370.00 Parsecs
Proper Motion Dec.1.85 ± 0.25 milliarcseconds/year
Proper Motion RA.2.01 ± 0.32 milliarcseconds/year
B-V Index0.09
Radial Velocity-4.90 ± 0.30 km/s
Iron Abundance0.15 ± 9.99 Fe/H
Spectral TypeA2Ia
Brightest in Night Sky20th
Colour(A) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeAlpha Cygnus

Estimated Facts

Luminosity (x the Sun)40,000.0000000
Calculated Effective Temperature8,573 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
197345+44 3541.0A1.300001.000005.00000A2White
B11.700001879

Location of Deneb in Cygnus


Deneb (Alpha Cygni) Location in Cygnus

The map was generated using Night Vision, an awesome free application by Brian Simpson.


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