Universe Guide

BK Virginis

BK Virginis Facts

BK Virginis's Alternative Names

HIP61022 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD108849.

BK Virginis has alternative name(s) :- , BK Vir.

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+05 2634.

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

Location of BK Virginis

The location of the variable 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 object is compared to the celestial equator and is expressed in degrees. For BK Virginis, the location is 12h 30m 21.04 and +04° 24` 59.4 .

Radial Velocity and Proper Motion of BK Virginis

Proper Motion

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 -26.77 ± 0.40 milliarcseconds/year towards the north and -43.88 ± 0.68 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 16.53 km/s with an error of about 0.35 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

BK Virginis Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 22.87 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of BK Virginis

BK Virginis Colour and Temperature

BK Virginis has a spectral type of M7. This means the star is a red variable star. The star has a B-V Colour Index of 1.19 which means the star's temperature is about 4,586 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu at being .

BK Virginis Radius

Radius has been calculated as being 5.75 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,004,051.03.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 5.92. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

BK Virginis Apparent and Absolute Magnitudes

BK Virginis has an apparent magnitude of 8.28 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 2.05 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.99. 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 BK Virginis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.68 which gave the calculated distance to BK Virginis as 574.23 light years away from Earth or 176.06 parsecs. If you want that in miles, it is 385,088,186,871.

In 2007, Hipparcos data was revised with a new parallax of 5.53 which put BK Virginis at a distance of 589.81 light years or 180.83 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.

Using the 2007 distance, the star is roughly 37,298,605.01 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

The star's Galacto-Centric Distance is 7,379.00 Parsecs or 24,067.59 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to BK Virginis

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A380736537,413,578.74
Speed of Sound (Mach 1)767.269515,512,022.45
Concorde (Mach 2)1,534.54257,755,675.28
New Horizons Probe33,00011,985,951.33
Speed of Light670,616,629.00589.81

Variable Type of BK Virginis

The star is a pulsating Semiregular late- (M 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. BK Virginis brightness ranges from a magnitude of 7.441 to a magnitude of 7.048 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.3 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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Additional BK Virginis Facts and Figures

Visual Facts

Primary / Proper / Traditional NameBK Virginis
Alternative NamesHD 108849, HIP 61022, BD+05 2634, BK Vir
Spectral TypeM7
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
GalaxyMilky Way
Absolute Magnitude 2.05 / 1.99
Visual / Apparent Magnitude8.28
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)12h 30m 21.04
Declination (Dec.)+04° 24` 59.4
Galactic Latitude66.74 degrees
Galactic Longitude289.52 degrees
1997 Distance from Earth5.68 Parallax (milliarcseconds)
 574.23 Light Years
 176.06 Parsecs
2007 Distance from Earth5.53 Parallax (milliarcseconds)
 589.81 Light Years
 180.83 Parsecs
 37,298,605.01 Astronomical Units
Galacto-Centric Distance24,067.59 Light Years / 7,379.00 Parsecs
Proper Motion Dec.-26.77 ± 0.40 milliarcseconds/year
Proper Motion RA.-43.88 ± 0.68 milliarcseconds/year
B-V Index1.19
Radial Velocity16.53 ± 0.35 km/s
Semi-Major Axis5729.00
Stellar Luminosity (Lsun)22.87

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M
Mean Variability Period in Days0.326
Variable Magnitude Range (Brighter - Dimmer)7.048 - 7.441

Estimated Calculated Facts

Radius (x the Sun)5.92
Effective Temperature4,586 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Comments and Questions

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