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23 Ursae Majoris - HD81937 - HIP46733

23 Ursae Majoris is a blue to white subgiant star that can be located in the constellation of UrsaMajor. HIP46733 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD81937. 23 Ursae Majoris has alternative name(s), 23 Ursae Majoris , 23 UMa.

Location of 23 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 23 Ursae Majoris, the location is 09h 31m 31.57 and +63d03`42.5 .

Proper Motion of 23 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 027.15 ± 000.10 towards the north and 107.99 ± 000.16 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 23 Ursae Majoris

23 Ursae Majoris has a spectral type of F0IV. This means the star is a blue to white subgiant star. The star has a B-V Colour Index of 0.36 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,918 Kelvin.

23 Ursae Majoris has been calculated as 2.80 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,947,191.88.km.

23 Ursae Majoris Apparent and Absolute Magnitudes

23 Ursae Majoris has an apparent magnitude of 3.65 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 1.83 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.77. 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 23 Ursae Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 43.20 which gave the calculated distance to 23 Ursae Majoris as 75.50 light years away from Earth or 23.15 parsecs. It would take a spaceship travelling at the speed of light, 75.50 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 41.99 which put 23 Ursae Majoris at a distance of 77.68 light years or 23.82 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.

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.

23 Ursae Majoris Facts

Alternative Names

Traditional Name23 Ursae Majoris
Short Name23 UMa
Alternative Name(s)23 Ursae Majoris
Hipparcos Library I.D.46733
Bonner DurchmusterungBD+63 845
Henry Draper Designation81937

Visual Facts

Star Typesubgiant star
Absolute Magnitude1.83 / 1.77
Apparent Magnitude3.65
Right Ascension (R.A.)09h 31m 31.57
Declination (Dec.)+63d03`42.5
1997 Distance from Earth43.20 Parallax (milliarcseconds)
 75.50 Light Years
 23.15 Parsecs
2007 Revised Distance from Earth41.99 Parallax (milliarcseconds)
 77.68 Light Years
 23.82 Parsecs
Proper Motion Dec.27.15 ± 0.10 milliarcseconds/year
Proper Motion RA.107.99 ± 0.16 milliarcseconds/year
B-V Index0.36
Spectral TypeF0IV
Colour(F) blue to white

Estimated Facts

Radius (x the Sun)2.80
Calculated Effective Temperature6,918 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
81937+63 845.0A3.80000108.0000026.00000F0Yellow/White
B9.0000081.0000028.000001830
C10.500001957

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