Universe Guide

HomeFactsConstellationsUrsa Minor

Pi Ursae Minoris - HD139777 - HIP75809

Pi Ursae Minoris is a white to yellow subgiant 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. The star has an estimated age of 12.30 Billion of Years but could be as young as 7.80 to 16.40 according to Hipparcos.

Pi Ursae Minoris is the Bayer Classification for the star. HIP75809 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD139777.

Location of Pi 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 Pi Ursae Minoris, the location is 15h 29m 11.97 and +80d26`54.0 .

Proper Motion of Pi 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 108.19 ± 0.33 miliarcseconds/year towards the north and -224.25 ± 0.37 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Age, Radius) of Pi Ursae Minoris

Pi Ursae Minoris has a spectral type of G8IV-V+.... This means the star is a white to yellow subgiant star. The star is 7408.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24162.1805235200000000s. The star has a B-V Colour Index of 0.66 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,689 Kelvin.

Pi Ursae Minoris Radius has been calculated as being 1.03 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 716,586.05.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.02. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is 0.01 with an error value of 0.02 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 12.30 Billion years old but could be between 7.80 and 16.40 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old. The reported age is older than the widely recognised age of the Universe so a little scepticism about the age is warranted.

Pi Ursae Minoris Apparent and Absolute Magnitudes

Pi Ursae Minoris has an apparent magnitude of 6.57 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 4.85 If you used the 2007 Parallax value, you would get an absolute magnitude of 4.87. 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 Pi Ursae Minoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 45.32 which gave the calculated distance to Pi Ursae Minoris as 71.97 light years away from Earth or 22.07 parsecs. It would take a spaceship travelling at the speed of light, 71.97 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 45.77 which put Pi Ursae Minoris at a distance of 71.26 light years or 21.85 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 7,408.00 Parsecs or 24,162.18 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.

Pi Ursae Minoris Facts

Alternative Names

Bayer DesignationPi Ursae Minoris
Hipparcos Library I.D.75809
Bonner DurchmusterungBDD+80 480
Henry Draper Designation139777

Visual Facts

Star Typesubgiant star
Age12.30 Billion Years Old
Age Range7.80 - 16.40 Billion Years Old
Absolute Magnitude4.85 / 4.87
Visual / Apparent Magnitude6.57
Naked Eye VisibleRequires a 7x50 Binoculars - Ref: Wiki
Right Ascension (R.A.)15h 29m 11.97
Declination (Dec.)+80d26`54.0
Galactic Latitude34.31 degrees
Galactic Longitude115.60 degrees
1997 Distance from Earth45.32 Parallax (milliarcseconds)
 71.97 Light Years
 22.07 Parsecs
2007 Revised Distance from Earth45.77 Parallax (milliarcseconds)
 71.26 Light Years
 21.85 Parsecs
Galacto-Centric Distance24,162.18 Light Years / 7,408.00 Parsecs
Proper Motion Dec.108.19 ± 0.33 milliarcseconds/year
Proper Motion RA.-224.25 ± 0.37 milliarcseconds/year
B-V Index0.66
Radial Velocity-16.27 ± 0.09 km/s
Iron Abundance0.01 ± 0.02 Fe/H
Spectral TypeG8IV-V+...
Colour(G) White to Yellow

Estimated Facts

Calculated Effective Temperature5,689 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars


Add a Comment


Name:
Email: (Optional)
Comment: