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U Ursae Minoris, HD125556, HIP69816

U Ursae Minoris is a red pulsating star that can be located in the constellation of UrsaMinor. The star can not be seen by the naked eye, you need a telescope to see it.

HIP69816 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD125556.

U Ursae Minoris has alternative name(s), U UMi.

Location of U Ursae Minoris

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 U Ursae Minoris, the location is 14h 17m 19.90 and +66d 47` 39.1 .

Proper Motion of U Ursae Minoris

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 8.70 ± 0.97 miliarcseconds/year towards the north and -2.19 ± 1.07 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 -26.30000 km/s with an error of about 3.20 km/s .

Physical Properties (Colour, Temperature, Radius) of U Ursae Minoris

U Ursae Minoris has a spectral type of M6e-M8e. This means the star is a red star. The star has a B-V Colour Index of 1.14 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,683 Kelvin.

U Ursae Minoris Radius has been calculated as being 6.42 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,470,155.48.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 5.94. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

U Ursae Minoris Apparent and Absolute Magnitudes

U Ursae Minoris has an apparent magnitude of 8.99 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 1.72 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.89. 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 U Ursae Minoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.51 which gave the calculated distance to U Ursae Minoris as 929.24 light years away from Earth or 284.90 parsecs. It would take a spaceship travelling at the speed of light, 929.24 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 3.80 which put U Ursae Minoris at a distance of 858.32 light years or 263.16 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 U Ursae Minoris

The star is a pulsating Omicron 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. U Ursae Minoris brightness ranges from a magnitude of 10.176 to a magnitude of 7.662 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 321.4 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.

U Ursae Minoris Facts

Alternative Names

Traditional/Proper NameU Ursae Minoris
Short NameU UMi
Hipparcos Library I.D.69816
Henry Draper Designation125556

Visual Facts

Star Type star
ConstellationUrsa Minor
Absolute Magnitude1.72 / 1.89
Visual / Apparent Magnitude8.99
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)14h 17m 19.90
Declination (Dec.)+66d 47` 39.1
Galactic Latitude48.20 degrees
Galactic Longitude110.43 degrees
1997 Distance from Earth3.51 Parallax (milliarcseconds)
 929.24 Light Years
 284.90 Parsecs
2007 Revised Distance from Earth3.80 Parallax (milliarcseconds)
 858.32 Light Years
 263.16 Parsecs
Proper Motion Dec.8.70 ± 0.97 milliarcseconds/year
Proper Motion RA.-2.19 ± 1.07 milliarcseconds/year
B-V Index1.14
Radial Velocity-26.30 ± 3.20 km/s
Spectral TypeM6e-M8e
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeOmicron Ceti
Mean Variability Period in Days321.400
Variable Magnitude Range (Brighter - Dimmer)7.662 - 10.176

Estimated Facts

Calculated Effective Temperature4,683 Kelvin

Sources and Links

SIMBAD SourceLink

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