Universe Guide


BW Vulpeculae, HD199140, HIP103191

BW Vulpeculae is a blue pulsating giant star that can be located in the constellation of Vulpecula. BW Vulpeculae is the brightest star in Vulpecula based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP103191 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD199140.

BW Vulpeculae has alternative name(s), BW Vul.

Location of BW Vulpeculae

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 BW Vulpeculae, the location is 20h 54m 22.39 and +28d31`19.2 .

Proper Motion of BW Vulpeculae

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 -5.11 ± 0.26 miliarcseconds/year towards the north and 1.42 ± 0.40 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of BW Vulpeculae

BW Vulpeculae has a spectral type of B2IIIvar. This means the star is a blue giant star. The star is 7315.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23858.8486136000000000s. The star has a B-V Colour Index of -0.14 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 13,196 Kelvin.

BW Vulpeculae Radius has been calculated as being 4.76 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,315,309.88.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.81. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

BW Vulpeculae Apparent and Absolute Magnitudes

BW Vulpeculae has an apparent magnitude of 6.55 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 -2.13 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.98. 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 BW Vulpeculae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.84 which gave the calculated distance to BW Vulpeculae as 1772.63 light years away from Earth or 543.48 parsecs. It would take a spaceship travelling at the speed of light, 1772.63 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 3.12 which put BW Vulpeculae at a distance of 1045.40 light years or 320.51 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.

The star's Galacto-Centric Distance is 7,315.00 Parsecs or 23,858.85 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of BW Vulpeculae

The star is a pulsating Beta Cephei 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. BW Vulpeculae brightness ranges from a magnitude of 6.635 to a magnitude of 6.411 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 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.

BW Vulpeculae Facts

Alternative Names

Traditional/Proper NameBW Vulpeculae
Short NameBW Vul
Hipparcos Library I.D.103191
Bonner DurchmusterungBD+27 3909
Henry Draper Designation199140

Visual Facts

Star Typegiant star
Absolute Magnitude-2.13 / -0.98
Visual / Apparent Magnitude6.55
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)20h 54m 22.39
Declination (Dec.)+28d31`19.2
Galactic Latitude-10.48 degrees
Galactic Longitude72.75 degrees
1997 Distance from Earth1.84 Parallax (milliarcseconds)
 1772.63 Light Years
 543.48 Parsecs
2007 Revised Distance from Earth3.12 Parallax (milliarcseconds)
 1045.40 Light Years
 320.51 Parsecs
Galacto-Centric Distance23,858.85 Light Years / 7,315.00 Parsecs
Proper Motion Dec.-5.11 ± 0.26 milliarcseconds/year
Proper Motion RA.1.42 ± 0.40 milliarcseconds/year
B-V Index-0.14
Radial Velocity-6.10 ± 3.00 km/s
Spectral TypeB2IIIvar
Colour(B) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeBeta Cephei
Mean Variability Period in Days0.201
Variable Magnitude Range (Brighter - Dimmer)6.411 - 6.635

Estimated Facts

Calculated Effective Temperature13,196 Kelvin

Sources and Links

SIMBAD SourceLink

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