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31 Ursae Majoris, HD85795, HIP48682

31 Ursae Majoris is a blue giant star that can be located in the constellation of UrsaMajor. 31 Ursae Majoris is the brightest star in Ursa Major based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

HIP48682 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD85795.

Location of 31 Ursae Majoris

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 31 Ursae Majoris, the location is 09h 55m 43.01 and +49d49`11.3 .

Proper Motion of 31 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 20.31 ± 0.12 miliarcseconds/year towards the north and -4.57 ± 0.22 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 31 Ursae Majoris

31 Ursae Majoris has a spectral type of A3III. This means the star is a blue giant star. The star is 7440.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24266.5527936000000000s. The star has a B-V Colour Index of 0.08 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,626 Kelvin.

31 Ursae Majoris Radius has been calculated as being 2.52 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,752,903.96.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.35. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

31 Ursae Majoris Apparent and Absolute Magnitudes

31 Ursae Majoris has an apparent magnitude of 5.27 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 1.10 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.25. 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 31 Ursae Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 14.65 which gave the calculated distance to 31 Ursae Majoris as 222.64 light years away from Earth or 68.26 parsecs. It would take a spaceship travelling at the speed of light, 222.64 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 15.68 which put 31 Ursae Majoris at a distance of 208.01 light years or 63.78 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 7,440.00 Parsecs or 24,266.55 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

31 Ursae Majoris Facts

Alternative Names

Traditional/Proper Name31 Ursae Majoris
Flamsteed Name31 Ursae Majoris
Flamsteed Short Name31 UMa
Hipparcos Library I.D.48682
Bonner DurchmusterungBD+50 1698
Henry Draper Designation85795

Visual Facts

Star Typegiant star
Absolute Magnitude1.10 / 1.25
Visual / Apparent Magnitude5.27
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)09h 55m 43.01
Declination (Dec.)+49d49`11.3
Galactic Latitude49.63 degrees
Galactic Longitude166.65 degrees
1997 Distance from Earth14.65 Parallax (milliarcseconds)
 222.64 Light Years
 68.26 Parsecs
2007 Revised Distance from Earth15.68 Parallax (milliarcseconds)
 208.01 Light Years
 63.78 Parsecs
Galacto-Centric Distance24,266.55 Light Years / 7,440.00 Parsecs
Proper Motion Dec.20.31 ± 0.12 milliarcseconds/year
Proper Motion RA.-4.57 ± 0.22 milliarcseconds/year
B-V Index0.08
Radial Velocity-9.00 ± 1.70 km/s
Spectral TypeA3III
Colour(A) blue

Estimated Facts

Calculated Effective Temperature8,626 Kelvin

Sources and Links

SIMBAD SourceLink

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