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BE Capricorni, HD191639, HIP99457

BE Capricorni is a blue eruptive main sequence dwarf star that can be located in the constellation of Capricornus. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

BE Capricorni's Alternative Names

HIP99457 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD191639.

BE Capricorni has alternative name(s) :- , BE Cap.

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-09 5382.

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

Location of BE 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 BE Capricorni, the location is 20h 11m 10.08 and -08° 50` 32.4 .

Proper Motion of BE 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 -2.17 ± 0.33 miliarcseconds/year towards the north and 0.98 ± 0.44 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 -7.00000 km/s with an error of about 4.30 km/s .

Physical Properties (Colour, Temperature) of BE Capricorni

BE Capricorni has a spectral type of B1V. This means the star is a blue main sequence dwarf star. The star has a B-V Colour Index of -0.13 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 12,762 Kelvin.

BE Capricorni Radius has been calculated as being 335.10 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 233,163,465.91.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 7.20. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.39 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

BE Capricorni Apparent and Absolute Magnitudes

BE Capricorni has an apparent magnitude of 6.39 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 -11.22 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.88. 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 BE Capricorni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.03 which gave the calculated distance to BE Capricorni as 108721.11 light years away from Earth or 33333.33 parsecs. It would take a spaceship travelling at the speed of light, 108721.11 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 1.40 which put BE Capricorni at a distance of 2329.74 light years or 714.29 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 BE Capricorni

The star is a eruptive Gamma Cassiopeiae 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. BE Capricorni brightness ranges from a magnitude of 6.432 to a magnitude of 6.354 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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BE Capricorni Facts

Visual Facts

Alternative NamesHD 191639, HIP 99457, BD-09 5382, BE Cap
Star Type main sequence Dwarf Star
GalaxyMilky Way
Absolute Magnitude-11.22 / -2.88
Visual / Apparent Magnitude6.39
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 11m 10.08
Declination (Dec.)-08° 50` 32.4
Galactic Latitude-21.71 degrees
Galactic Longitude33.97 degrees
1997 Distance from Earth0.03 Parallax (milliarcseconds)
 108721.11 Light Years
 33333.33 Parsecs
2007 Revised Distance from Earth1.40 Parallax (milliarcseconds)
 2329.74 Light Years
 714.29 Parsecs
Proper Motion Dec.-2.17 ± 0.33 milliarcseconds/year
Proper Motion RA.0.98 ± 0.44 milliarcseconds/year
B-V Index-0.13
Radial Velocity-7.00 ± 4.30 km/s
Iron Abundance-0.39 ± 9.99 Fe/H
Spectral TypeB1V
Colour(B) blue

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeGamma Cassiopeiae
Mean Variability Period in Days0.072
Variable Magnitude Range (Brighter - Dimmer)6.354 - 6.432

Estimated Facts

Calculated Effective Temperature12,762 Kelvin

Sources and Links

SIMBAD SourceLink

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