Universe Guide


AD Capricorni, HD206046, HIP106961

AD Capricorni is a orange to red eclipsing binary system subgiant star that can be located in the constellation of Capricornus. The star can not be seen by the naked eye, you need a telescope to see it.

HIP106961 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD206046.

AD Capricorni has alternative name(s), AD Cap.

Location of AD Capricorni

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 AD Capricorni, the location is 21h 39m 48.89 and -16d00`21.0 .

Proper Motion of AD Capricorni

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 -2.23 ± 1.10 miliarcseconds/year towards the north and 44.60 ± 1.63 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of AD Capricorni

AD Capricorni has a spectral type of K0IV/V. This means the star is a orange to red subgiant star. The star has a B-V Colour Index of 0.88 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,096 Kelvin.

AD Capricorni Radius has been calculated as being 2.61 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,815,083.03.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 4.21. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

AD Capricorni Apparent and Absolute Magnitudes

AD Capricorni has an apparent magnitude of 9.72 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 3.31 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.27. 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 AD Capricorni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.22 which gave the calculated distance to AD Capricorni as 624.83 light years away from Earth or 191.57 parsecs. It would take a spaceship travelling at the speed of light, 624.83 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 3.24 which put AD Capricorni at a distance of 1006.68 light years or 308.64 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 AD Capricorni

The star is a eclipsing binary system Beta Lyrae (Sheliak) 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. AD Capricorni brightness ranges from a magnitude of 10.126 to a magnitude of 9.800 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 3.0 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.

AD Capricorni Facts

Alternative Names

Traditional/Proper NameAD Capricorni
Short NameAD Cap
Hipparcos Library I.D.106961
Bonner DurchmusterungBD-16 5909
Henry Draper Designation206046

Visual Facts

Star Typesubgiant star
Absolute Magnitude3.31 / 2.27
Visual / Apparent Magnitude9.72
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)21h 39m 48.89
Declination (Dec.)-16d00`21.0
Galactic Latitude-44.36 degrees
Galactic Longitude36.82 degrees
1997 Distance from Earth5.22 Parallax (milliarcseconds)
 624.83 Light Years
 191.57 Parsecs
2007 Revised Distance from Earth3.24 Parallax (milliarcseconds)
 1006.68 Light Years
 308.64 Parsecs
Proper Motion Dec.-2.23 ± 1.10 milliarcseconds/year
Proper Motion RA.44.60 ± 1.63 milliarcseconds/year
B-V Index0.88
Radial Velocity9.00 ± 3.00 km/s
Spectral TypeK0IV/V
Colour(K) Orange to Red

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeBeta Lyrae (Sheliak)
Mean Variability Period in Days2.959
Variable Magnitude Range (Brighter - Dimmer)9.800 - 10.126

Estimated Facts

Calculated Effective Temperature5,096 Kelvin

Sources and Links

SIMBAD SourceLink

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