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Cygnus X-1, HD226868, HIP98298

Cygnus X-1 Location in Cygnus

Cygnus X-1 is a blue rotating supergiant star that can be located in the constellation of Cygnus. The description is based on the spectral class. The star can not be seen by the naked eye, you need a telescope to see it.

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.

Cygnus X-1's Alternative Names

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) :- HDE 226868, V1357 Cygni, V1357 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+34 3815.

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

Location of Cygnus X-1

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 Cygnus X-1, the location is 19h 58m 21.68 and +35° 12` 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 -7.15 ± 0.71 miliarcseconds/year towards the north and -3.37 ± 0.91 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 -2.70000 km/s with an error of about 3.20 km/s .

Physical Properties (Colour, Temperature) 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 Radius has been calculated as being 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. 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 10.13. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

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 9.028 to a magnitude of 8.941 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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Cygnus X-1 Facts

Visual Facts

Primary / Proper / Traditional NameCygnus X-1
Alternative NamesHDE 226868, V1357 Cygni, HD 226868, HIP 98298, BD+34 3815, V1357 Cyg
Spectral TypeB0Ib
Multiple Star SystemNo / Unknown
Star Type very luminous Supergiant Star
Colour blue
GalaxyMilky Way
Absolute Magnitude-2.34 / -0.03
Visual / Apparent Magnitude8.84
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)19h 58m 21.68
Declination (Dec.)+35° 12` 05.8
Galactic Latitude3.07 degrees
Galactic Longitude71.34 degrees
1997 Distance from Earth0.58 Parallax (milliarcseconds)
 5623.51 Light Years
 1724.14 Parsecs
2007 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
Radial Velocity-2.70 ± 3.20 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassRotating
Variable Star TypeRotating ellipsoidal and X-Ray
Mean Variability Period in Days0.061
Variable Magnitude Range (Brighter - Dimmer)8.941 - 9.028

Estimated Facts

Calculated Effective Temperature5,581 Kelvin

Sources and Links

SIMBAD SourceLink

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