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Tau Ursae Majoris - HD78362 - HIP45075

Tau Ursae Majoris is a blue star that can be located in the constellation of UrsaMajor. It is calculated at being 5.000 Billion Years old. This information comes from ExoPlanet. Tau Ursae Majoris is the Bayer Classification for the star. HIP45075 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD78362. Tau Ursae Majoris has alternative name(s), 14 Ursae Majoris , 14 UMa.

Location of Tau 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 Tau Ursae Majoris, the location is 09h 10m 54.93 and +63d30`49.6 .

Proper Motion of Tau 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 -063.55 ± 000.29 towards the north and 102.37 ± 000.54 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Age, Mass, Radius) of Tau Ursae Majoris

Tau Ursae Majoris has a spectral type of Am. This means the star is a blue star. The star has a B-V Colour Index of 0.38 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,465 Kelvin.

Tau Ursae Majoris has been calculated as 3.23 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,250,261.56.km. The star's solar mass is 1.00 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

The star's metallicity is -0.250000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

The star is believed to be about 5.00 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.

Tau Ursae Majoris Apparent and Absolute Magnitudes

Tau Ursae Majoris has an apparent magnitude of 4.67 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 1.81 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.73. 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 Tau Ursae Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 26.79 which gave the calculated distance to Tau Ursae Majoris as 121.75 light years away from Earth or 37.33 parsecs. It would take a spaceship travelling at the speed of light, 121.75 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 25.82 which put Tau Ursae Majoris at a distance of 126.32 light years or 38.73 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.

Tau Ursae Majoris Facts

Alternative Names

Short Name14 UMa
Bayer DesignationTau Ursae Majoris
Alternative Name(s)14 Ursae Majoris
Hipparcos Library I.D.45075
Bonner DurchmusterungBD+64 723
Henry Draper Designation78362

Visual Facts

Star Type star
Age5.000 Billions of Years
Absolute Magnitude1.81 / 1.73
Apparent Magnitude4.67
Right Ascension (R.A.)09h 10m 54.93
Declination (Dec.)+63d30`49.6
1997 Distance from Earth26.79 Parallax (milliarcseconds)
 121.75 Light Years
 37.33 Parsecs
2007 Revised Distance from Earth25.82 Parallax (milliarcseconds)
 126.32 Light Years
 38.73 Parsecs
Proper Motion Dec.-63.55 ± 0.29 milliarcseconds/year
Proper Motion RA.102.37 ± 0.54 milliarcseconds/year
B-V Index0.38
Eccentricity0.48
Inclination67.09
Semi-Major Axis11.27
Orbital Period (Days)1062.40
Argument Of Periastron349.35
Spectral TypeAm
Colour(A) blue

Estimated Facts

Radius (x the Sun)3.23
Calculated Effective Temperature6,465 Kelvin
Mass Compared to the Sun1.00
Metallicity-0.25000

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
78362+64 723.0A4.7000095.00000-56.00000F5Yellow/White
B10.300001899

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