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GT Ursae Majoris

GT Ursae Majoris Facts

GT Ursae Majoris's Alternative Names

HIP51876 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD91543.

GT Ursae Majoris has alternative name(s) :- GT UMa, GT UMa.



Location of GT Ursae Majoris


Radial Velocity and Proper Motion of GT Ursae Majoris

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 -11.59 ± 0.76 miliarcseconds/year towards the north and 19.75 ± 1.18 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 the Sun is -54.60 km/s with an error of about 3.20 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.

GT Ursae Majoris 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 9.85 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 GT Ursae Majoris

GT Ursae Majoris has a spectral type of F2. This means the star is a blue to white variable star. The star is 7,478.00 Parsecs from the Galactic Centre or in terms of Light Years is 24,390.49 s. The star has a B-V Colour Index of 0.44 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,276 Kelvin.

GT Ursae Majoris Radius has been calculated as being 2.34 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,629,281.18.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 2.79. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

GT Ursae Majoris Apparent and Absolute Magnitudes

GT Ursae Majoris has an apparent magnitude of 8.08 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 2.64 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.26. 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 GT Ursae Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.18 which gave the calculated distance to GT Ursae Majoris as 398.73 light years away from Earth or 122.25 parsecs. It would take a spaceship travelling at the speed of light, 398.73 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 6.86 which put GT Ursae Majoris at a distance of 475.46 light years or 145.77 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 30,067,011.30 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.


Variable Type of GT Ursae Majoris

The star is a eclipsing binary sys Beta Lyrae (Sheliak) 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. GT Ursae Majoris brightness ranges from a magnitude of 8.440 to a magnitude of 8.150 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 1.2 days (variability).

Source of Information


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Additional GT Ursae Majoris Facts and Figures

Visual Facts

Primary / Proper / Traditional NameGT Ursae Majoris
Alternative NamesGT UMa, HD 91543, HIP 51876, BD+64 795, GT UMa
Spectral TypeF2
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeVariable Star
ColourYellow - White
GalaxyMilky Way
ConstellationUrsa Major
Absolute Magnitude 2.64 / 2.26
Visual / Apparent Magnitude8.08
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)10h 35m 55.64
Declination (Dec.)+63° 35` 32.5
Galactic Latitude47.48 degrees
Galactic Longitude144.45 degrees
1997 Distance from Earth8.18 Parallax (milliarcseconds)
 398.73 Light Years
 122.25 Parsecs
2007 Distance from Earth6.86 Parallax (milliarcseconds)
 475.46 Light Years
 145.77 Parsecs
 30,067,011.30 Astronomical Units
Galacto-Centric Distance24,390.49 Light Years / 7,478.00 Parsecs
Proper Motion Dec.-11.59 ± 0.76 milliarcseconds/year
Proper Motion RA.19.75 ± 1.18 milliarcseconds/year
B-V Index0.44
Radial Velocity-54.60 ± 3.20 km/s
Semi-Major Axis7238.00
Stellar Luminosity (Lsun)9.85

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEclipsing binary sys
Variable Star TypeBeta Lyrae (Sheliak)
Mean Variability Period in Days1.165
Variable Magnitude Range (Brighter - Dimmer)8.150 - 8.440

Estimated Calculated Facts

Radius (x the Sun)2.79
Effective Temperature6,276 Kelvin

Sources and Links

SIMBAD SourceLink

Multi-Star System


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
91543+64 795.0A8.4000029.00000-19.00000F2Yellow/White

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