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24 Ursae Majoris, HD82210, HIP46977

24 Ursae Majoris is a white to yellow eclipsing binary system subgiant star that can be located in the constellation of UrsaMajor. 24 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. It is calculated at being 4.604 Billion Years old. This information comes from ExoPlanet.

HIP46977 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD82210. The Gliese ID of the star is Gliese GL355.1. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

24 Ursae Majoris has alternative name(s), DK UMa.

Location of 24 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 24 Ursae Majoris, the location is 09h 34m 28.97 and +69d49`48.6 .

Proper Motion of 24 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 77.25 ± 0.13 miliarcseconds/year towards the north and -63.84 ± 0.19 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Age, Mass, Radius) of 24 Ursae Majoris

24 Ursae Majoris has a spectral type of G4III-IV. This means the star is a white to yellow subgiant star. The star is 7420.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24201.3201248000000000s. The star has a B-V Colour Index of 0.78 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,337 Kelvin.

24 Ursae Majoris Radius has been calculated as being 4.37 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,039,302.22.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 4.31. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 1.23 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 4.60 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.

24 Ursae Majoris Apparent and Absolute Magnitudes

24 Ursae Majoris has an apparent magnitude of 4.54 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 1.99 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.02. 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 24 Ursae Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 30.89 which gave the calculated distance to 24 Ursae Majoris as 105.59 light years away from Earth or 32.37 parsecs. It would take a spaceship travelling at the speed of light, 105.59 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 31.32 which put 24 Ursae Majoris at a distance of 104.14 light years or 31.93 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 7,420.00 Parsecs or 24,201.32 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of 24 Ursae Majoris

The star is a eclipsing binary system RS Canum Venaticorum 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. 24 Ursae Majoris brightness ranges from a magnitude of 4.717 to a magnitude of 4.672 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 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.

24 Ursae Majoris Facts

Alternative Names

Traditional/Proper Name24 Ursae Majoris
Flamsteed Name24 Ursae Majoris
Flamsteed Short Name24 UMa
Short NameDK UMa
Hipparcos Library I.D.46977
Bonner DurchmusterungBD+70 565
Gliese ID355.1
Henry Draper Designation82210

Visual Facts

Star Typesubgiant star
Age4.60 Billion Years Old
Absolute Magnitude1.99 / 2.02
Visual / Apparent Magnitude4.54
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)09h 34m 28.97
Declination (Dec.)+69d49`48.6
Galactic Latitude38.93 degrees
Galactic Longitude142.55 degrees
1997 Distance from Earth30.89 Parallax (milliarcseconds)
 105.59 Light Years
 32.37 Parsecs
2007 Revised Distance from Earth31.32 Parallax (milliarcseconds)
 104.14 Light Years
 31.93 Parsecs
Galacto-Centric Distance24,201.32 Light Years / 7,420.00 Parsecs
Proper Motion Dec.77.25 ± 0.13 milliarcseconds/year
Proper Motion RA.-63.84 ± 0.19 milliarcseconds/year
B-V Index0.78
Radial Velocity-27.00 ± 0.20 km/s
Iron Abundance-0.25 ± 9.99 Fe/H
Spectral TypeG4III-IV
Colour(G) White to Yellow

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeRS Canum Venaticorum
Mean Variability Period in Days0.034
Variable Magnitude Range (Brighter - Dimmer)4.672 - 4.717

Estimated Facts

Calculated Effective Temperature5,337 Kelvin
Mass Compared to the Sun1.23
Metallicity-0.25000

Sources and Links

SIMBAD SourceLink

Related Stars


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