Universe Guide


BG Crucis - HD108968 - HIP61136

BG Crucis is a blue to white pulsating giant star that can be located in the constellation of Crux. HIP61136 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD108968. BG Crucis has alternative name(s), BG_Cru.

Location of BG Crucis

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 BG Crucis, the location is 12h 31m 40.34 and -59d25`26.1 .

Proper Motion of BG 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 -3.39 ± 0.20 miliarcseconds/year towards the north and -12.84 ± 0.29 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of BG Crucis

BG Crucis has a spectral type of F5III. This means the star is a blue to white giant star. The star has a B-V Colour Index of 0.62 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,824 Kelvin.

BG Crucis has been calculated as 37.71 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 26,240,689.20.km.

BG Crucis Apparent and Absolute Magnitudes

BG Crucis has an apparent magnitude of 5.49 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 -3.07 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.67. 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 BG Crucis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.94 which gave the calculated distance to BG Crucis as 1681.25 light years away from Earth or 515.46 parsecs. It would take a spaceship travelling at the speed of light, 1681.25 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 2.33 which put BG Crucis at a distance of 1399.84 light years or 429.18 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 BG Crucis

The star is a pulsating Delta Cepheid 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. BG Crucis brightness ranges from a magnitude of 6.000 to a magnitude of 5.000 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

BG Crucis Facts

Alternative Names

Traditional/Proper NameBG Crucis
Short NameBG Cru
Hipparcos Library I.D.61136
Henry Draper Designation108968

Visual Facts

Star Typegiant star
Absolute Magnitude-3.07 / -2.67
Apparent Magnitude5.49
Right Ascension (R.A.)12h 31m 40.34
Declination (Dec.)-59d25`26.1
1997 Distance from Earth1.94 Parallax (milliarcseconds)
 1681.25 Light Years
 515.46 Parsecs
2007 Revised Distance from Earth2.33 Parallax (milliarcseconds)
 1399.84 Light Years
 429.18 Parsecs
Proper Motion Dec.-3.39 ± 0.20 milliarcseconds/year
Proper Motion RA.-12.84 ± 0.29 milliarcseconds/year
B-V Index0.62
Spectral TypeF5III
Colour(F) blue to white

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Cepheid
Mean Variability Period in Days3.000
Variable Magnitude Range (Brighter - Dimmer)5.000 - 6.000

Estimated Facts

Radius (x the Sun)37.71
Calculated Effective Temperature5,824 Kelvin

Sources and Links

SIMBAD SourceLink

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