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Adhara, Epsilon Canis Majoris, 21 Canis Majoris, HD52089, HIP33579, HR2618

Adhara (Epsilon Canis Majoris) Location in Canis Major

Adhara (Epsilon Canis Majoris) is a blue luminous giant star that can be located in the constellation of Canis Major. The description is based on the spectral class. Adhara is a main star of the constellation.

Adhara is the 22nd brightest star in the night sky and the 2nd brightest star in Canis 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.

Adhara's Alternative Names

Epsilon Canis Majoris (Eps Cma) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR2618. HIP33579 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD52089.

Adhara has alternative name(s) :- adara. In Arabic, it is known as Al-'Adhara.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 21 Canis Majoris with it shortened to 21 CMa.

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

Location of Adhara

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 Adhara, the location is 06h 58m 37.55 and -28° 58` 19.5 .

Radial Velocity and Proper Motion of Adhara

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 1.33 ± 0.11 miliarcseconds/year towards the north and 3.24 ± 0.14 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 27.30 km/s with an error of about 0.40 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.

Adhara 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 16,783.91 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of Adhara

Adhara has a spectral type of B2II. This means the star is a blue luminous giant star. The star is 7,462.00 Parsecs from the Galactic Centre or terms of Light Years is 24,338.31 s. The star has a B-V Colour Index of -0.21 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 22,579 Kelvin.

Adhara Radius has been calculated as being 4.03 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,805,554.28.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 3.80. 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 -0.75 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Adhara Apparent and Absolute Magnitudes

Adhara has an apparent magnitude of 1.50 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 -4.10 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.97. 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 Adhara

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 7.57 which gave the calculated distance to Adhara as 430.86 light years away from Earth or 132.10 parsecs. It would take a spaceship travelling at the speed of light, 430.86 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 8.05 which put Adhara at a distance of 405.17 light years or 124.22 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.

Using the 2007 distance, the star is roughly 25,622,035.70 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

The star's Galacto-Centric Distance is 7,462.00 Parsecs or 24,338.31 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.

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Adhara Facts

Visual Facts

Primary / Proper / Traditional NameAdhara
Alternative NamesEpsilon Canis Majoris, Eps Cma, adara, Al-'Adhara, HD 52089, HIP 33579, HR 2618, 21 Canis Majoris, 21 CMa
Spectral TypeB2II
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeLuminous Giant Star
Colour blue
GalaxyMilky Way
ConstellationCanis Major
Absolute Magnitude -4.10 / -3.97
Visual / Apparent Magnitude1.50
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 58m 37.55
Declination (Dec.)-28° 58` 19.5
Galactic Latitude-11.33 degrees
Galactic Longitude239.83 degrees
1997 Distance from Earth7.57 Parallax (milliarcseconds)
 430.86 Light Years
 132.10 Parsecs
2007 Distance from Earth8.05 Parallax (milliarcseconds)
 405.17 Light Years
 124.22 Parsecs
 25,622,035.70 Astronomical Units
Galacto-Centric Distance24,338.31 Light Years / 7,462.00 Parsecs
Proper Motion Dec.1.33 ± 0.11 milliarcseconds/year
Proper Motion RA.3.24 ± 0.14 milliarcseconds/year
B-V Index-0.21
Radial Velocity27.30 ± 0.40 km/s
Iron Abundance-0.75 ± 9.99 Fe/H
Semi-Major Axis6919.00
Stellar Luminosity (Lsun)16,783.91
Brightest in Night Sky22nd

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Facts

Calculated Effective Temperature22,579 Kelvin

Sources and Links

SIMBAD SourceLink

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
52089-28 3666.2A1.600002.000002.00000B1Blue/White

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