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Cygnus X-1 - HD226868 - HIP98298

Cygnus X-1 is a blue rotating very luminous supergiant star that can be located in the constellation of Cygnus. HIP98298 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD226868. Cygnus X-1 has alternative name(s), V1357_Cyg.

Cygnus X-1 is the most well known black hole so far discovered if you exclude the supermassive black hole at the centre of the milky way. The black hole is leeching off the nearby star which is whats actually documented on this page. The below is a NASA image and artists impression of what the black hole and star look likes.

Location of Cygnus X-1

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 Cygnus X-1, the location is 19h 58m 21.68 and +35d12`05.8 .

Proper Motion of Cygnus X-1

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 -007.15 ± 000.71 towards the north and -003.37 ± 000.91 east if we saw them in the horizon.

Cygnus X-1 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 320000.0000000 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 Cygnus X-1

Cygnus X-1 has a spectral type of B0Ib. This means the star is a blue supergiant star. The star has a B-V Colour Index of 0.73 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,581 Kelvin.

Cygnus X-1 has been calculated as 29.34 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 20,416,756.92.km.

Cygnus X-1 Apparent and Absolute Magnitudes

Cygnus X-1 has an apparent magnitude of 8.84 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 -2.34 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.03. 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 Cygnus X-1

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.58 which gave the calculated distance to Cygnus X-1 as 5623.51 light years away from Earth or 1724.14 parsecs. It would take a spaceship travelling at the speed of light, 5623.51 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 1.68 which put Cygnus X-1 at a distance of 1941.45 light years or 595.24 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.

Variable Type of Cygnus X-1

The star is a rotating Rotating ellipsoidal and X-Ray 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. Cygnus X-1 brightness ranges from a magnitude of 9.000 to a magnitude of 9.000 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Cygnus X-1 Facts

Alternative Names

Traditional NameCygnus X-1
Short NameV1357 Cyg
Hipparcos Library I.D.98298
Bonner DurchmusterungBD+34 3815
Henry Draper Designation226868

Visual Facts

Star Typesupergiant star
Absolute Magnitude-2.34 / -0.03
Apparent Magnitude8.84
Right Ascension (R.A.)19h 58m 21.68
Declination (Dec.)+35d12`05.8
1997 Distance from Earth0.58 Parallax (milliarcseconds)
 5623.51 Light Years
 1724.14 Parsecs
2007 Revised Distance from Earth1.68 Parallax (milliarcseconds)
 1941.45 Light Years
 595.24 Parsecs
Proper Motion Dec.-7.15 ± 0.71 milliarcseconds/year
Proper Motion RA.-3.37 ± 0.91 milliarcseconds/year
B-V Index0.73
Spectral TypeB0Ib
Colour(B) blue

Variable Star Details

Variable Star ClassRotating
Variable Star TypeRotating ellipsoidal and X-Ray

Estimated Facts

Radius (x the Sun)29.34
Luminosity (x the Sun)320,000.0000000
Calculated Effective Temperature5,581 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars


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