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IO Ursae Majoris, HD115268, HIP64636

IO Ursae Majoris is a blue eclipsing binary system variable star that can be located in the constellation of Ursa Major. The description is based on the spectral class. The star can not be seen by the naked eye, you need a telescope to see it.

IO Ursae Majoris's Alternative Names

HIP64636 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD115268.

IO Ursae Majoris has alternative name(s) :- , IO UMa.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+60 1456.

More details on star alternative names can be found at Star Names .

Location of IO Ursae Majoris

The location of the star in the night sky 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 IO Ursae Majoris, the location is 13h 14m 54.52 and +59° 17` 44.2 .

Radial Velocity and Proper Motion of IO 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 22.44 ± 0.56 miliarcseconds/year towards the north and -51.71 ± 0.67 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 the Sun is 9.60 km/s with an error of about 3.20 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties (Colour, Temperature) of IO Ursae Majoris

IO Ursae Majoris has a spectral type of A3. This means the star is a blue variable star. The star has a B-V Colour Index of 0.24 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,120 Kelvin.

IO Ursae Majoris Radius has been calculated as being 4.00 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,782,394.54.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 4.32. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

IO Ursae Majoris Apparent and Absolute Magnitudes

IO Ursae Majoris has an apparent magnitude of 8.18 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 0.93 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.76. 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 IO Ursae Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.55 which gave the calculated distance to IO Ursae Majoris as 918.77 light years away from Earth or 281.69 parsecs. It would take a spaceship travelling at the speed of light, 918.77 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 3.28 which put IO Ursae Majoris at a distance of 994.40 light years or 304.88 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 IO Ursae Majoris

The star is a eclipsing binary system Beta Persei (Algol) 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. IO Ursae Majoris brightness ranges from a magnitude of 8.790 to a magnitude of 8.190 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 5.5 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.

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IO Ursae Majoris Facts

Visual Facts


Primary / Proper / Traditional NameIO Ursae Majoris
Alternative NamesHD 115268, HIP 64636, BD+60 1456, IO UMa
Spectral TypeA3
Multiple Star SystemNo / Unknown
Star TypeVariable Star
Colour blue
GalaxyMilky Way
ConstellationUrsa Major
Absolute Magnitude0.93 / 0.76
Visual / Apparent Magnitude8.18
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)13h 14m 54.52
Declination (Dec.)+59° 17` 44.2
Galactic Latitude57.58 degrees
Galactic Longitude117.34 degrees
1997 Distance from Earth3.55 Parallax (milliarcseconds)
 918.77 Light Years
 281.69 Parsecs
2007 Distance from Earth3.28 Parallax (milliarcseconds)
 994.40 Light Years
 304.88 Parsecs
Proper Motion Dec.22.44 ± 0.56 milliarcseconds/year
Proper Motion RA.-51.71 ± 0.67 milliarcseconds/year
B-V Index0.24
Radial Velocity9.60 ± 3.20 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing binary system
Variable Star TypeBeta Persei (Algol)
Mean Variability Period in Days5.520
Variable Magnitude Range (Brighter - Dimmer)8.190 - 8.790

Estimated Facts


Calculated Effective Temperature7,120 Kelvin

Sources and Links


SIMBAD SourceLink

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