Universe Guide


BY Draconis - HD234677 - HIP91009

BY Draconis is a orange to red rotating/eruptive main sequence dwarf star that can be located in the constellation of Draco. HIP91009 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD234677. BY Draconis has alternative name(s), BY_Dra.

Location of BY Draconis

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 BY Draconis, the location is 18h 33m 55.60 and +51d43`11.7 .

Proper Motion of BY Draconis

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 -324.69 ± 000.58 towards the north and 186.51 ± 000.68 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of BY Draconis

BY Draconis has a spectral type of K7Vvar. This means the star is a orange to red main sequence dwarf star. The star has a B-V Colour Index of 1.26 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,388 Kelvin.

BY Draconis has been calculated as 0.61 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 423,432.99.km.

BY Draconis Apparent and Absolute Magnitudes

BY Draconis has an apparent magnitude of 8.20 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 7.12 If you used the 2007 Parallax value, you would get an absolute magnitude of 7.13. 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 BY Draconis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 60.90 which gave the calculated distance to BY Draconis as 53.56 light years away from Earth or 16.42 parsecs. It would take a spaceship travelling at the speed of light, 53.56 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 61.15 which put BY Draconis at a distance of 53.34 light years or 16.35 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 BY Draconis

The star is a rotating/eruptive BY Draconis and Eruptive UV Ceti 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. BY Draconis brightness ranges from a magnitude of 8.000 to a magnitude of 8.000 over its variable period. The smaller the magnitude, the brighter the star.

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.

BY Draconis Facts

Alternative Names

Traditional NameBY Draconis
Short NameBY Dra
Hipparcos Library I.D.91009
Bonner DurchmusterungBD+51 2402
Henry Draper Designation234677

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude7.12 / 7.13
Apparent Magnitude8.20
Right Ascension (R.A.)18h 33m 55.60
Declination (Dec.)+51d43`11.7
1997 Distance from Earth60.90 Parallax (milliarcseconds)
 53.56 Light Years
 16.42 Parsecs
2007 Revised Distance from Earth61.15 Parallax (milliarcseconds)
 53.34 Light Years
 16.35 Parsecs
Proper Motion Dec.-324.69 ± 0.58 milliarcseconds/year
Proper Motion RA.186.51 ± 0.68 milliarcseconds/year
B-V Index1.26
Semi-Major Axis3.11
Orbital Period (Days)114.02
Argument Of Periastron0.00
Spectral TypeK7Vvar
Colour(K) Orange to Red

Variable Star Details

Variable Star ClassRotating/Eruptive
Variable Star TypeBY Draconis and Eruptive UV Ceti

Estimated Facts

Radius (x the Sun)0.61
Calculated Effective Temperature4,388 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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