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Alphecca, Alpha Coronae Borealis, 5 Coronae Borealis, HD139006, HIP76267, HR5793

Alphecca (Alpha Coronae Borealis) is a blue eclipsing binary system star that can be located in the constellation of CoronaBorealis. Alphecca is the 66th brightest star in the night sky and is the brightest star in Corona Borealis 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.

Alpha Coronae Borealis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR5793. HIP76267 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD139006.

Alphecca has alternative name(s), alf CrB. In Arabic, it is known as Al-Fakkah.

Location of Alphecca

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 Alphecca, the location is 15h 34m 41.19 and +26d 42` 53.7 .

Proper Motion of Alphecca

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 -89.58 ± 0.17 miliarcseconds/year towards the north and 120.27 ± 0.28 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 us is 1.40000 km/s with an error of about 1.78 km/s .

Alphecca 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 24.0000000 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 Alphecca

Alphecca has a spectral type of A0V. This means the star is a blue star. The star is 7390.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24103.4711216000000000s. The star has a B-V Colour Index of 0.03 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 9,140 Kelvin.

Alphecca Radius has been calculated as being 3.07 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,135,459.38.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.08. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Alphecca Apparent and Absolute Magnitudes

Alphecca has an apparent magnitude of 2.22 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 0.42 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.41. 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 Alphecca

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 43.65 which gave the calculated distance to Alphecca as 74.72 light years away from Earth or 22.91 parsecs. It would take a spaceship travelling at the speed of light, 74.72 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 43.46 which put Alphecca at a distance of 75.05 light years or 23.01 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 7,390.00 Parsecs or 24,103.47 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 Alphecca

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. Alphecca brightness ranges from a magnitude of 2.290 to a magnitude of 2.213 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.

Alphecca Facts

Alternative Names

Traditional/Proper NameAlphecca
Flamsteed Name5 Coronae Borealis
Flamsteed Short Name5 CrB
Short Namealf CrB
Arabic NameAl-Fakkah
English Meaning'The broken' ring of stars
Bayer DesignationAlpha Coronae Borealis
Hipparcos Library I.D.76267
Yale Bright Star Catalogue (HR) Id5793
Bonner DurchmusterungBD+27 2512
Henry Draper Designation139006

Visual Facts

Star Type star
ConstellationCorona Borealis
Absolute Magnitude0.42 / 0.41
Visual / Apparent Magnitude2.22
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)15h 34m 41.19
Declination (Dec.)+26d 42` 53.7
Galactic Latitude53.77 degrees
Galactic Longitude41.87 degrees
1997 Distance from Earth43.65 Parallax (milliarcseconds)
 74.72 Light Years
 22.91 Parsecs
2007 Revised Distance from Earth43.46 Parallax (milliarcseconds)
 75.05 Light Years
 23.01 Parsecs
Galacto-Centric Distance24,103.47 Light Years / 7,390.00 Parsecs
Proper Motion Dec.-89.58 ± 0.17 milliarcseconds/year
Proper Motion RA.120.27 ± 0.28 milliarcseconds/year
B-V Index0.03
Radial Velocity1.40 ± 1.78 km/s
Semi-Major Axis1.75
Orbital Period (Days)17.36
Argument Of Periastron311.00
Spectral TypeA0V
Brightest in Night Sky66th
Colour(A) blue

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeBeta Persei (Algol)
Mean Variability Period in Days0.016
Variable Magnitude Range (Brighter - Dimmer)2.213 - 2.290

Estimated Facts

Luminosity (x the Sun)24.0000000
Calculated Effective Temperature9,140 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Alphecca in Corona Borealis

Alphecca (Alpha Coronae Borealis) Location in Corona Borealis

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

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