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55 Cygni

55 Cygni Facts

  • 55 Cygni is a pulsating supergiant star that can be located in the constellation of Cygnus. The description is based on the spectral class.
  • 55 Cygni is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (B3Ia) of the star, the star's colour is blue .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 2329.74 light years away from us. Distance

55 Cygni's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR7977. HIP102724 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD198478.

55 Cygni has alternative name(s) :- , V1661 Cyg.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 55 Cygni. The Flamsteed name can be shortened to 55 Cyg.

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+45 3291.

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

Location of 55 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 55 Cygni, the location is 20h 48m 56.29 and +46° 06` 50.9 .

Radial Velocity and Proper Motion of 55 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 -2.84 ± 0.13 milliarcseconds/year towards the north and -2.65 ± 0.17 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 -7.20000 km/s with an error of about 2.80 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 of 55 Cygni

55 Cygni Temperature and Colour

Based on the star's spectral type of B3Ia , 55 Cygni's colour and type is blue supergiant star. The star has a B-V Colour Index of 0.57 which means the star's temperature is about 5,945 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

55 Cygni 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 5,230.10 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

55 Cygni Radius

55 Cygni estimated radius has been calculated as being 66.17 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 46,039,130.52.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 68.650463552446846910247767809. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

55 Cygni Iron Abundance

55 Cygni Iron Abundance is -0.23 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context. The value comes from the Hipparcos Extended Catalog.

55 Cygni Apparent and Absolute Magnitudes

55 Cygni has an apparent magnitude of 4.81 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 -4.38 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.46. 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 55 Cygni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.45000 which gave the calculated distance to 55 Cygni as 2249.40 light years away from Earth or 689.66 parsecs. If you want that in miles, it is about 13,223,379,914,439,212.33, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 1.40000 which put 55 Cygni at a distance of 2329.74 light years or 714.29 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 147,331,861.83 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. The star's Galacto-Centric Distance is 7,382.00 Parsecs or 24,077.38 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to 55 Cygni

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Walking4390,590,596,311.62
Car12013,019,686,543.72
Airbus A3807362,122,774,979.95
Speed of Sound (Mach 1)767.2692,036,264,185.37
Concorde (Mach 2)1,534.541,018,130,765.73
New Horizons Probe33,00047,344,314.70
Speed of Light670,616,629.002,329.74

Variable Type of 55 Cygni

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. 55 Cygni brightness ranges from a magnitude of 4.952 to a magnitude of 4.895 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 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 55 Cygni Facts and Figures

Visual Facts


Primary / Proper / Traditional Name55 Cygni
Alternative NamesHD 198478, HIP 102724, HR 7977, 55 Cyg, BD+45 3291, V1661 Cyg
Spectral TypeB3Ia
Constellation's Main StarNo
Multiple Star SystemYes
Star Type very luminous Supergiant Star
ColourBlue
GalaxyMilky Way
ConstellationCygnus
Absolute Magnitude -4.38 / -4.46
Visual / Apparent Magnitude4.81
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 48m 56.29
Declination (Dec.)+46° 06` 50.9
Galactic Latitude1.49002900 degrees
Galactic Longitude85.75353267 degrees
1997 Distance from Earth1.45000 Parallax (milliarcseconds)
 2249.40 Light Years
 689.66 Parsecs
2007 Distance from Earth1.40000 Parallax (milliarcseconds)
 2329.74 Light Years
 714.29 Parsecs
 147,331,861.83 Astronomical Units
Galacto-Centric Distance24,077.38 Light Years / 7,382.00 Parsecs
Proper Motion Dec.-2.84000 ± 0.13000 milliarcseconds/year
Proper Motion RA.-2.65000 ± 0.17000 milliarcseconds/year
B-V Index0.57
Radial Velocity-7.20000 ± 2.80 km/s
Iron Abundance-0.2300 ± 9.99 Fe/H
Eccentricity0.08260
Semi-Major Axis7980.0000000
Stellar Luminosity (Lsun)5230.1000000

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeAlpha Cygnus
Mean Variability Period in Days0.044
Variable Magnitude Range (Brighter - Dimmer)4.895 - 4.952

Estimated Calculated Facts


Radius (x the Sun)68.65
Effective Temperature5,945 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
198478+45 3291.0A4.900001.000002.00000B2Blue/White
B10.900001.000002.000001934

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