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V2100 Cygni, HD189775, HIP98379

V2100 Cygni is a blue rotating giant star that can be located in the constellation of Cygnus. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

V2100 Cygni's Alternative Names

HIP98379 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD189775.

V2100 Cygni has alternative name(s) :- , V2100 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+51 2728.

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

Location of V2100 Cygni

The location of the 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 star is compared to the celestial equator and is expressed in degrees. For V2100 Cygni, the location is 19h 59m 15.34 and +52° 03` 20.5 .

Proper Motion of V2100 Cygni

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 2.24 ± 0.18 miliarcseconds/year towards the north and 8.77 ± 0.21 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is -16.20000 km/s with an error of about 2.90 km/s .

V2100 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 623.10 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of V2100 Cygni

V2100 Cygni has a spectral type of B5III. This means the star is a blue giant star. The star is 7,388.00 Parsecs from the Galactic Centre or terms of Light Years is 24,096.95 s. The star has a B-V Colour Index of -0.18 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 15,433 Kelvin.

V2100 Cygni Radius has been calculated as being 1.82 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,266,176.32.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 1.85. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

V2100 Cygni Apparent and Absolute Magnitudes

V2100 Cygni has an apparent magnitude of 6.14 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 -0.72 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.75. 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 V2100 Cygni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.24 which gave the calculated distance to V2100 Cygni as 769.25 light years away from Earth or 235.85 parsecs. It would take a spaceship travelling at the speed of light, 769.25 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 4.19 which put V2100 Cygni at a distance of 778.43 light years or 238.66 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 7,388.00 Parsecs or 24,096.95 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 V2100 Cygni

The star is a rotating Alpha2 Canum Venaticorum 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. V2100 Cygni brightness ranges from a magnitude of 6.113 to a magnitude of 6.052 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 2.6 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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V2100 Cygni Facts

Visual Facts


Primary / Proper / Traditional NameV2100 Cygni
Alternative NamesHD 189775, HIP 98379, BD+51 2728, V2100 Cyg
Spectral TypeB5III
Multiple Star SystemNo / Unknown
Star TypeGiant Star
Colour blue
GalaxyMilky Way
ConstellationCygnus
Absolute Magnitude-0.72 / -0.75
Visual / Apparent Magnitude6.14
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)19h 59m 15.34
Declination (Dec.)+52° 03` 20.5
Galactic Latitude11.54 degrees
Galactic Longitude86.04 degrees
1997 Distance from Earth4.24 Parallax (milliarcseconds)
 769.25 Light Years
 235.85 Parsecs
2007 Distance from Earth4.19 Parallax (milliarcseconds)
 778.43 Light Years
 238.66 Parsecs
Galacto-Centric Distance24,096.95 Light Years / 7,388.00 Parsecs
Proper Motion Dec.2.24 ± 0.18 milliarcseconds/year
Proper Motion RA.8.77 ± 0.21 milliarcseconds/year
B-V Index-0.18
Radial Velocity-16.20 ± 2.90 km/s
Eccentricity0.01
Semi-Major Axis7435.00
Stellar Luminosity (Lsun)623.10

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venaticorum
Mean Variability Period in Days2.607
Variable Magnitude Range (Brighter - Dimmer)6.052 - 6.113

Estimated Facts


Calculated Effective Temperature15,433 Kelvin

Sources and Links


SIMBAD SourceLink

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