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Almaaz, Epsilon Aurigae, 7 Aurigae, HD31964, HIP23416, HR1605

Almaaz (Epsilon Aurigae) Location in Auriga

Almaaz (Epsilon Aurigae) is a blue to white eclipsing supergiant star that can be located in the constellation of Auriga. The description is based on the spectral class. Almaaz is a main star of the constellation.

The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Almaaz's Alternative Names

Epsilon Aurigae (Eps Aur) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR1605. HIP23416 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD31964.

Almaaz has alternative name(s) :- Al Anz, Haldus, eps Aur.

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 7 Aurigae with it shortened to 7 Aur.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+43 1166.

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

Location of Almaaz

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 Almaaz, the location is 05h 01m 58.13 and +43° 49` 23.9 .

Radial Velocity and Proper Motion of Almaaz

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 ± 0.63 miliarcseconds/year towards the north and -0.86 ± 1.29 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 -10.40 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.

Physical Properties (Colour, Temperature) of Almaaz

Almaaz has a spectral type of F0Ia. This means the star is a blue to white supergiant star. The star has a B-V Colour Index of 0.53 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,040 Kelvin.

Almaaz Radius has been calculated as being 132.10 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 91,912,031.93.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 138.32. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Almaaz Apparent and Absolute Magnitudes

Almaaz has an apparent magnitude of 3.03 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 -5.95 If you used the 2007 Parallax value, you would get an absolute magnitude of -6.05. 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 Almaaz

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.60 which gave the calculated distance to Almaaz as 2038.52 light years away from Earth or 625 parsecs. It would take a spaceship travelling at the speed of light, 2038.52 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 1.53 which put Almaaz at a distance of 2131.79 light years or 653.59 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 134,811,675.33 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.

Variable Type of Almaaz

The star is a eclipsing 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. Almaaz brightness ranges from a magnitude of 3.197 to a magnitude of 3.052 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.

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Almaaz Facts

Visual Facts


Primary / Proper / Traditional NameAlmaaz
Alternative NamesEpsilon Aurigae, Eps Aur, Al Anz, Haldus, HD 31964, HIP 23416, HR 1605, 7 Aurigae, 7 Aur, BD+43 1166, eps Aur
Spectral TypeF0Ia
Constellation's Main StarYes
Multiple Star SystemYes
Star Type very luminous Supergiant Star
Colour blue to white
GalaxyMilky Way
ConstellationAuriga
Absolute Magnitude -5.95 / -6.05
Visual / Apparent Magnitude3.03
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)05h 01m 58.13
Declination (Dec.)+43° 49` 23.9
Galactic Latitude1.18 degrees
Galactic Longitude162.79 degrees
1997 Distance from Earth1.60 Parallax (milliarcseconds)
 2038.52 Light Years
 625 Parsecs
2007 Distance from Earth1.53 Parallax (milliarcseconds)
 2131.79 Light Years
 653.59 Parsecs
 134,811,675.33 Astronomical Units
Proper Motion Dec.-2.66 ± 0.63 milliarcseconds/year
Proper Motion RA.-0.86 ± 1.29 milliarcseconds/year
B-V Index0.53
Radial Velocity-10.40 ± 0.40 km/s
Eccentricity0.07
Inclination87.00
Orbital Period (Days)9887.00
Argument Of Periastron0.00

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing
Variable Star TypeBeta Persei (Algol)/
Variable Magnitude Range (Brighter - Dimmer)3.052 - 3.197

Estimated Facts


Calculated Effective Temperature6,040 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
31964+43 1166.0A1.00000-4.00000F5Yellow/White
B14.000001878
C11.700001878
D12.000001879
+43 1168.0E9.2000010.000002.000001913

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