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Deneb el Okab (Epsilon Aquilae) - HD176411 - HIP93244

Deneb el Okab (Epsilon Aquilae) is a orange to red giant star that can be located in the constellation of Aquila. Epsilon Aquilae is the Bayer Classification for the star. HIP93244 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD176411. Deneb el Okab has alternative name(s), 13 Aquilae , 13 Aql.

The name is shared between this star and Zeta Aquilae which is in the same constellation as this one.

Location of Deneb el Okab

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 Deneb el Okab, the location is 18h 59m 37.39 and +15d04`06.5 .

Proper Motion of Deneb el Okab

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 -72.36 ± 0.48 miliarcseconds/year towards the north and -50.75 ± 0.70 miliarcseconds/year east if we saw them in the horizon.

Deneb el Okab 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 70.0000000 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 Deneb el Okab

Deneb el Okab has a spectral type of K2III. This means the star is a orange to red giant star. The star has a B-V Colour Index of 1.08 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,700 Kelvin.

Deneb el Okab has been calculated as 10.44 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 7,264,165.55.km.

Deneb el Okab Apparent and Absolute Magnitudes

Deneb el Okab has an apparent magnitude of 4.02 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 0.65 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.64. 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 Deneb el Okab

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 21.22 which gave the calculated distance to Deneb el Okab as 153.71 light years away from Earth or 47.13 parsecs. It would take a spaceship travelling at the speed of light, 153.71 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 21.05 which put Deneb el Okab at a distance of 154.95 light years or 47.51 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.

Meteor Showers Radiating from near Deneb el Okab

The Epsilon Aquilids Meteor Shower radiants from a point near this star. The meteor shower runs typically between May 4-27 with a peak date of May17/18. The speed of a meteor in the shower is 32 Km/s.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Deneb el Okab Facts

Alternative Names

Traditional/Proper NameDeneb el Okab
Short Name13 Aql
Bayer DesignationEpsilon Aquilae
Alternative Name(s)13 Aquilae
Hipparcos Library I.D.93244
Bonner DurchmusterungBD+14 3736
Henry Draper Designation176411

Visual Facts

Star Typegiant star
Absolute Magnitude0.65 / 0.64
Apparent Magnitude4.02
Right Ascension (R.A.)18h 59m 37.39
Declination (Dec.)+15d04`06.5
1997 Distance from Earth21.22 Parallax (milliarcseconds)
 153.71 Light Years
 47.13 Parsecs
2007 Revised Distance from Earth21.05 Parallax (milliarcseconds)
 154.95 Light Years
 47.51 Parsecs
Proper Motion Dec.-72.36 ± 0.48 milliarcseconds/year
Proper Motion RA.-50.75 ± 0.70 milliarcseconds/year
B-V Index1.08
Eccentricity0.27
Inclination87.52
Semi-Major Axis13.69
Orbital Period (Days)1270.60
Argument Of Periastron82.00
Spectral TypeK2III
Colour(K) Orange to Red

Estimated Facts

Radius (x the Sun)10.44
Luminosity (x the Sun)70.0000000
Calculated Effective Temperature4,700 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
176411+14 3736.0A4.20000-52.00000-73.00000K0Orange
B10.100001909
C10.200001887

Location of Deneb el Okab in Aquila


Deneb el Okab (Epsilon Aquilae) Location in Aquila

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


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