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Megrez, Delta Ursae Majoris, 69 Ursae Majoris, HD106591, HIP59774, HR4660

Megrez (Delta Ursae Majoris) is a blue main sequence dwarf star that can be located in the constellation of UrsaMajor. Megrez 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.

Delta Ursae Majoris is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR4660. HIP59774 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD106591. The Gliese ID of the star is Gliese GL459. 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.

Location of Megrez

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 Megrez, the location is 12h 15m 25.45 and +57d01`57.4 .

Proper Motion of Megrez

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 7.30 ± 0.11 miliarcseconds/year towards the north and 104.11 ± 0.15 miliarcseconds/year east if we saw them in the horizon.

Megrez Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 14.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of Megrez

Megrez has a spectral type of A3Vvar. This means the star is a blue main sequence dwarf star. The star is 7409.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24165.4421569600000000s. The star has a B-V Colour Index of 0.07 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,718 Kelvin.

Megrez Radius has been calculated as being 2.22 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,543,622.30.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.19. 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 -0.35 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Megrez Apparent and Absolute Magnitudes

Megrez has an apparent magnitude of 3.32 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 1.33 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.36. 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 Megrez

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 40.05 which gave the calculated distance to Megrez as 81.44 light years away from Earth or 24.97 parsecs. It would take a spaceship travelling at the speed of light, 81.44 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 40.51 which put Megrez at a distance of 80.51 light years or 24.69 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 7,409.00 Parsecs or 24,165.44 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.

Megrez Facts

Alternative Names

Traditional/Proper NameMegrez
Flamsteed Name69 Ursae Majoris
Flamsteed Short Name69 UMa
Bayer DesignationDelta Ursae Majoris
Hipparcos Library I.D.59774
Yale Bright Star Catalogue (HR) Id4660
Bonner DurchmusterungBD+57 1363
Gliese ID459
Henry Draper Designation106591

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude1.33 / 1.36
Visual / Apparent Magnitude3.32
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)12h 15m 25.45
Declination (Dec.)+57d01`57.4
Galactic Latitude59.42 degrees
Galactic Longitude132.57 degrees
1997 Distance from Earth40.05 Parallax (milliarcseconds)
 81.44 Light Years
 24.97 Parsecs
2007 Revised Distance from Earth40.51 Parallax (milliarcseconds)
 80.51 Light Years
 24.69 Parsecs
Galacto-Centric Distance24,165.44 Light Years / 7,409.00 Parsecs
Proper Motion Dec.7.30 ± 0.11 milliarcseconds/year
Proper Motion RA.104.11 ± 0.15 milliarcseconds/year
B-V Index0.07
Radial Velocity-15.30 ± 0.50 km/s
Iron Abundance-0.35 ± 9.99 Fe/H
Spectral TypeA3Vvar
Colour(A) blue

Estimated Facts

Luminosity (x the Sun)14.0000000
Calculated Effective Temperature8,718 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
106591+57 1363.0A3.40000101.000004.00000A2White

Location of Megrez in Ursa Major

Megrez (Delta Ursae Majoris) Location in Ursa Major

The map was generated using Night Vision, an awesome free application by Brian Simpson.

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William CreedThursday, 2nd March 2017 5:58:14 AM
When I was a kid in around 1955 to 1969 that star was very visible in the night. Why has it seemed to fade over the 20 some years.