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Ras Algethi (Alpha Herculis) - HD156014 - HIP84345 - HR6406

Ras Algethi (Alpha Herculis) is a red pulsating luminous giant star that can be located in the constellation of Hercules. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Alpha Herculis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR6406. HIP84345 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD156014.

Ras Algethi has alternative name(s), 64 Herculis , alf_Her, 64 Her. Ras Algethi is a multiple star system with 2 stars orbiting in its solar system.

Location of Ras Algethi

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 Ras Algethi, the location is 17h 14m 38.86 and +14d23`24.9 .

Proper Motion of Ras Algethi

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 36.07 ± 0.88 miliarcseconds/year towards the north and -7.32 ± 1.32 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Ras Algethi

Ras Algethi has a spectral type of M5IIvar. This means the star is a red luminous giant star. The star is 7323.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23884.9416811200000000s. The star has a B-V Colour Index of 1.16 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,644 Kelvin.

Ras Algethi Radius has been calculated as being 47.11 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 32,781,486.20.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 44.17. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Ras Algethi Apparent and Absolute Magnitudes

Ras Algethi has an apparent magnitude of 2.78 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 -2.57 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.43. 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 Ras Algethi

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.53 which gave the calculated distance to Ras Algethi as 382.37 light years away from Earth or 117.23 parsecs. It would take a spaceship travelling at the speed of light, 382.37 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 9.07 which put Ras Algethi at a distance of 359.61 light years or 110.25 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 7,323.00 Parsecs or 23,884.94 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 Ras Algethi

The star is a pulsating Semiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep) 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. Ras Algethi brightness ranges from a magnitude of 3.000 to a magnitude of 3.000 over its variable period. The smaller the magnitude, the brighter the star.

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.

Ras Algethi Facts

Alternative Names

Traditional/Proper NameRas Algethi
Short Namealf Her, 64 Her
Bayer DesignationAlpha Herculis
Alternative Name(s)64 Herculis
Hipparcos Library I.D.84345
Yale Bright Star Catalogue (HR) Id6406
Bonner DurchmusterungBDD+14 3207
Henry Draper Designation156014

Visual Facts

Star Typeluminous giant star
Absolute Magnitude-2.57 / -2.43
Visual / Apparent Magnitude2.78
Naked Eye VisibleYes - Ref: Wiki
Right Ascension (R.A.)17h 14m 38.86
Declination (Dec.)+14d23`24.9
Galactic Latitude27.82 degrees
Galactic Longitude35.53 degrees
1997 Distance from Earth8.53 Parallax (milliarcseconds)
 382.37 Light Years
 117.23 Parsecs
2007 Revised Distance from Earth9.07 Parallax (milliarcseconds)
 359.61 Light Years
 110.25 Parsecs
Galacto-Centric Distance23,884.94 Light Years / 7,323.00 Parsecs
Proper Motion Dec.36.07 ± 0.88 milliarcseconds/year
Proper Motion RA.-7.32 ± 1.32 milliarcseconds/year
B-V Index1.16
Radial Velocity-32.09 ± 0.22 km/s
Spectral TypeM5IIvar
Colour(M) Red
Stars in Solar System2

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep)

Estimated Facts

Calculated Effective Temperature4,644 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
156014+14 3207.0A3.50000-8.0000033.00000M2Red
156015B5.40000-6.0000044.00000M2Red1957
C15.500001934
D11.100001960

Location of Ras Algethi in Hercules


Ras Algethi (Alpha Herculis) Location in Hercules

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


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