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47 Cygni (47 Cygni A) Star Facts

47 Cygni Facts

47 Cygni's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR7866. HIP101474 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD196094.

47 Cygni has alternative name(s) :- , V2125 Cyg.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 47 Cygni A with it shortened to 47 Cyg A.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+34 4079.

More details on objects' alternative names can be found at Star Names .

Location of 47 Cygni

The location of the supergiant star in the night sky 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 object is compared to the celestial equator and is expressed in degrees. For 47 Cygni, the location is 20h 33m 54.19 and +35° 15` 03.1 .

Radial Velocity and Proper Motion of 47 Cygni

Proper Motion

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 -5.36 ± 0.29 milliarcseconds/year towards the north and -1.58 ± 0.41 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -4.63 km/s with an error of about 0.25 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties (Colour, Temperature) of 47 Cygni

47 Cygni Colour and Temperature

47 Cygni has a spectral type of K2Ib comp. This means the star is a orange to red supergiant star. The star has a B-V Colour Index of 1.59 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,802 Kelvin.

47 Cygni Radius

Radius has been calculated as being 73.27 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 50,978,813.09.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 218.24. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

47 Cygni Apparent and Absolute Magnitudes

47 Cygni has an apparent magnitude of 4.61 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 -2.66 If you used the 2007 Parallax value, you would get an absolute magnitude of -5.03. 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 47 Cygni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.51 which gave the calculated distance to 47 Cygni as 929.24 light years away from Earth or 284.90 parsecs. It would take a spaceship travelling at the speed of light, 929.24 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 1.18 which put 47 Cygni at a distance of 2764.10 light years or 847.46 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.

Using the 2007 distance, the star is roughly 174,799,954.68 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

Variable Type of 47 Cygni

The star is a pulsating Slow Irregular 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. 47 Cygni brightness ranges from a magnitude of 4.775 to a magnitude of 4.669 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 days (variability).

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.

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Additional 47 Cygni Facts and Figures

Visual Facts


Primary / Proper / Traditional Name47 Cygni
Alternative NamesHD 196094, HIP 101474, HR 7866, 47 Cygni A, 47 Cyg A, BD+34 4079, V2125 Cyg
Spectral TypeK2Ib comp
Constellation's Main StarNo
Multiple Star SystemYes
Star Type very luminous Supergiant Star less luminour Supergiant Star
ColourOrange to Red
GalaxyMilky Way
ConstellationCygnus
Absolute Magnitude -2.66 / -5.03
Visual / Apparent Magnitude4.61
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 33m 54.19
Declination (Dec.)+35° 15` 03.1
Galactic Latitude -2.93 degrees
Galactic Longitude75.43 degrees
1997 Distance from Earth3.51 Parallax (milliarcseconds)
 929.24 Light Years
 284.90 Parsecs
2007 Distance from Earth1.18 Parallax (milliarcseconds)
 2764.10 Light Years
 847.46 Parsecs
 174,799,954.68 Astronomical Units
Proper Motion Dec.-5.36 ± 0.29 milliarcseconds/year
Proper Motion RA.-1.58 ± 0.41 milliarcseconds/year
B-V Index1.59
Radial Velocity-4.63 ± 0.25 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.087
Variable Magnitude Range (Brighter - Dimmer)4.669 - 4.775

Estimated Calculated Facts


Radius (x the Sun)218.24
Effective Temperature3,802 Kelvin

Sources and Links


SIMBAD SourceLink

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
196094BA3White1950
C10.40000-19.00000-11.000001880
196093+34 4079.0A4.80000-2.00000-4.00000K5Orange

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