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Algedi, Alpha2 Capricorni, 6 Capricorni, HD192947, HIP100064, HR7754

Algedi (Alpha2 Capricorni) is a white to yellow star that can be located in the constellation of Capricornus. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Alpha2 Capricorni is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR7754. HIP100064 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD192947.

Algedi has alternative name(s), Algedi Secunda, Secunda Giedi , .

Location of Algedi

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 Algedi, the location is 20h 18m 03.22 and -12d 32` 41.5 .

Proper Motion of Algedi

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 2.66 ± 0.08 miliarcseconds/year towards the north and 62.63 ± 0.19 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 0.70000 km/s with an error of about 0.40 km/s .

Physical Properties (Colour, Temperature, Radius) of Algedi

Algedi has a spectral type of G6/G8III. This means the star is a white to yellow star. The star is 7375.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24054.5466200000000000s. The star has a B-V Colour Index of 0.88 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,096 Kelvin.

Algedi Radius has been calculated as being 7.66 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 5,332,360.08.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 7.49. 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 -0.10 with an error value of 0.04 Fe/H with the Sun has a value of 1 to put it into context.

Algedi Apparent and Absolute Magnitudes

Algedi has an apparent magnitude of 3.58 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 0.97 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.02. 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 Algedi

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 30.01 which gave the calculated distance to Algedi as 108.68 light years away from Earth or 33.32 parsecs. It would take a spaceship travelling at the speed of light, 108.68 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 30.82 which put Algedi at a distance of 105.83 light years or 32.45 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 7,375.00 Parsecs or 24,054.55 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.

Algedi Facts

Alternative Names

Traditional/Proper NameAlgedi
Flamsteed Name6 Capricorni
Flamsteed Short Name6 Cap
Bayer DesignationAlpha2 Capricorni
Alternative Name(s)Algedi Secunda, Secunda Giedi
Hipparcos Library I.D.100064
Yale Bright Star Catalogue (HR) Id7754
Bonner DurchmusterungBD-12 5685
Henry Draper Designation192947

Visual Facts

Star Type star
Absolute Magnitude0.97 / 1.02
Visual / Apparent Magnitude3.58
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 18m 03.22
Declination (Dec.)-12d 32` 41.5
Galactic Latitude-24.81 degrees
Galactic Longitude31.10 degrees
1997 Distance from Earth30.01 Parallax (milliarcseconds)
 108.68 Light Years
 33.32 Parsecs
2007 Revised Distance from Earth30.82 Parallax (milliarcseconds)
 105.83 Light Years
 32.45 Parsecs
Galacto-Centric Distance24,054.55 Light Years / 7,375.00 Parsecs
Proper Motion Dec.2.66 ± 0.08 milliarcseconds/year
Proper Motion RA.62.63 ± 0.19 milliarcseconds/year
B-V Index0.88
Radial Velocity0.70 ± 0.40 km/s
Iron Abundance-0.10 ± 0.04 Fe/H
Spectral TypeG6/G8III
Associated / Clustered StarsAlgiedi Prima
Colour(G) White to Yellow

Estimated Facts

Calculated Effective Temperature5,096 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
192947-12 5685.0A3.8000061.000005.00000G5Yellow

Location of Algedi in Capricornus

Algedi (Alpha2 Capricorni) Location in Capricornus

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

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