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Algiedi Prima (Alpha Capricorni) - HD192876 - HIP100027

Algiedi Prima (Alpha Capricorni) is a white to yellow very luminous supergiant star that can be located in the constellation of Capricornus. Algiedi Prima is the brightest star in Capricornus 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 Capricorni is the Bayer Classification for the star. HIP100027 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD192876.

Algiedi Prima has alternative name(s), 5 Capricorni , 5 Cap. Algiedi Prima is a multiple star system with 2 stars orbiting in its solar system.

Location of Algiedi Prima

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 Algiedi Prima, the location is 20h 17m 38.86 and -12d30`29.6 .

Proper Motion of Algiedi Prima

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 1.28 ± 0.14 miliarcseconds/year towards the north and 22.98 ± 0.33 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Algiedi Prima

Algiedi Prima has a spectral type of G3Ib. This means the star is a white to yellow supergiant star. The star is 7266.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23699.0285750400000000s. The star has a B-V Colour Index of 0.92 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,150 Kelvin.

Algiedi Prima Radius has been calculated as being 34.14 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 23,757,248.96.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 28.27. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Algiedi Prima Apparent and Absolute Magnitudes

Algiedi Prima has an apparent magnitude of 4.30 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 -2.32 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.91. 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 Algiedi Prima

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.75 which gave the calculated distance to Algiedi Prima as 686.66 light years away from Earth or 210.53 parsecs. It would take a spaceship travelling at the speed of light, 686.66 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 5.73 which put Algiedi Prima at a distance of 569.22 light years or 174.52 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 7,266.00 Parsecs or 23,699.03 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Meteor Showers Radiating from near Algiedi Prima

The Alpha Capricornids Meteor Shower radiants from a point near this star. The meteor shower runs typically between Jul 03 - Aug 15 with a peak date of Jul 30. The speed of a meteor in the shower is 23 Km/s. The amount of meteors predicted to be seen per hour (Zenith Hourly Rate) is 23.

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.

Algiedi Prima Facts

Alternative Names

Traditional/Proper NameAlgiedi Prima
Short Name5 Cap
Bayer DesignationAlpha Capricorni
Alternative Name(s)5 Capricorni
Hipparcos Library I.D.100027
Bonner DurchmusterungBDD-12 5683
Henry Draper Designation192876

Visual Facts

Star Typesupergiant star
Absolute Magnitude-2.32 / -1.91
Visual / Apparent Magnitude4.30
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 17m 38.86
Declination (Dec.)-12d30`29.6
Galactic Latitude-24.70 degrees
Galactic Longitude31.09 degrees
1997 Distance from Earth4.75 Parallax (milliarcseconds)
 686.66 Light Years
 210.53 Parsecs
2007 Revised Distance from Earth5.73 Parallax (milliarcseconds)
 569.22 Light Years
 174.52 Parsecs
Galacto-Centric Distance23,699.03 Light Years / 7,266.00 Parsecs
Proper Motion Dec.1.28 ± 0.14 milliarcseconds/year
Proper Motion RA.22.98 ± 0.33 milliarcseconds/year
B-V Index0.92
Radial Velocity-26.70 ± 0.40 km/s
Spectral TypeG3Ib
Colour(G) White to Yellow
Stars in Solar System2

Estimated Facts

Calculated Effective Temperature5,150 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
192876-12 5683.0A4.6000070.000000.00000G0Yellow
B14.100001960
-12 5682.0C9.6000020.0000025.000001932
CD14.300001905

Location of Algiedi Prima in Capricornus


Algiedi Prima (Alpha Capricorni) Location in Capricornus

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


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