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AB Crucis, HD106871, HIP59935

AB Crucis is a blue eclipsing binary system subgiant star that can be located in the constellation of Crux. 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.

AB Crucis's Alternative Names

HIP59935 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD106871.

AB Crucis has alternative name(s) :- , AB Cru.

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

Location of AB Crucis

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 AB Crucis, the location is 12h 17m 37.14 and -58° 09` 52.4 .

Proper Motion of AB Crucis

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 0.52 ± 0.55 miliarcseconds/year towards the north and -11.27 ± 0.88 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 -0.91000 km/s with an error of about 2.70 km/s .

Physical Properties (Colour, Temperature) of AB Crucis

AB Crucis has a spectral type of B0IVvar. This means the star is a blue subgiant star. The star has a B-V Colour Index of 0.09 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,538 Kelvin.

AB Crucis Radius has been calculated as being 20.81 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 14,478,024.31.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 5.20. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

AB Crucis Apparent and Absolute Magnitudes

AB Crucis has an apparent magnitude of 8.44 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 -3.44 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.43. 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 AB Crucis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.42 which gave the calculated distance to AB Crucis as 7765.79 light years away from Earth or 2380.95 parsecs. It would take a spaceship travelling at the speed of light, 7765.79 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 AB Crucis 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 AB Crucis

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. AB Crucis brightness ranges from a magnitude of 9.205 to a magnitude of 8.449 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 3.4 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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AB Crucis Facts

Visual Facts


Primary / Proper / Traditional NameAB Crucis
Alternative NamesHD 106871, HIP 59935, AB Cru
Spectral TypeB0IVvar
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
Colour blue
GalaxyMilky Way
ConstellationCrux
Absolute Magnitude-3.44 / -0.43
Visual / Apparent Magnitude8.44
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)12h 17m 37.14
Declination (Dec.)-58° 09` 52.4
Galactic Latitude4.41 degrees
Galactic Longitude298.47 degrees
1997 Distance from Earth0.42 Parallax (milliarcseconds)
 7765.79 Light Years
 2380.95 Parsecs
2007 Distance from Earth1.68 Parallax (milliarcseconds)
 1941.45 Light Years
 595.24 Parsecs
Proper Motion Dec.0.52 ± 0.55 milliarcseconds/year
Proper Motion RA.-11.27 ± 0.88 milliarcseconds/year
B-V Index0.09
Radial Velocity-0.91 ± 2.70 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing binary system
Variable Star TypeBeta Lyrae (Sheliak)
Mean Variability Period in Days3.413
Variable Magnitude Range (Brighter - Dimmer)8.449 - 9.205

Estimated Facts


Calculated Effective Temperature8,538 Kelvin

Sources and Links


SIMBAD SourceLink

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