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Epsilon Lyrae (Epsilon1 Lyrae) - HD173582 - HIP91919

Epsilon Lyrae (Epsilon1 Lyrae) is a blue to white main sequence dwarf star that can be located in the constellation of Lyra. Epsilon1 Lyrae is the Bayer Classification for the star. HIP91919 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD173582. Epsilon Lyrae has alternative name(s), 4 Lyrae , 4 Lyr. Epsilon Lyrae is a multiple star system with 2 stars orbiting in its solar system.

Epsilon Lyrae is a double star, the primary one being this one. This page details the star that is better known as Epsilon1 Lyrae with the other is known as Epsilon2 Lyrae. Unlike other mutli-star systems, both components of the star system were studied by the Hipparcos satellite which is where are there two pages for the star.

Location of Epsilon Lyrae

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 Epsilon Lyrae, the location is 18h 44m 20.34 and +39d40`11.9 .

Proper Motion of Epsilon Lyrae

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 061.39 ± 000.61 towards the north and 011.09 ± 000.78 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Epsilon Lyrae

Epsilon Lyrae has a spectral type of F1V. This means the star is a blue to white main sequence dwarf star. The star has a B-V Colour Index of 0.17 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,952 Kelvin.

Epsilon Lyrae has been calculated as 2.84 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,978,897.98.km.

Epsilon Lyrae Apparent and Absolute Magnitudes

Epsilon Lyrae has an apparent magnitude of 4.67 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 1.19 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.18. 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 Epsilon Lyrae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 20.10 which gave the calculated distance to Epsilon Lyrae as 162.27 light years away from Earth or 49.75 parsecs. It would take a spaceship travelling at the speed of light, 162.27 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 20.09 which put Epsilon Lyrae at a distance of 162.35 light years or 49.78 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.

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.

Epsilon Lyrae Facts

Alternative Names

Traditional NameEpsilon Lyrae
Short Name4 Lyr
Bayer DesignationEpsilon1 Lyrae
Alternative Name(s)4 Lyrae
Hipparcos Library I.D.91919
Bonner DurchmusterungBD+39 3509
Henry Draper Designation173582

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude1.19 / 1.18
Apparent Magnitude4.67
Right Ascension (R.A.)18h 44m 20.34
Declination (Dec.)+39d40`11.9
1997 Distance from Earth20.10 Parallax (milliarcseconds)
 162.27 Light Years
 49.75 Parsecs
2007 Revised Distance from Earth20.09 Parallax (milliarcseconds)
 162.35 Light Years
 49.78 Parsecs
Proper Motion Dec.61.39 ± 0.61 milliarcseconds/year
Proper Motion RA.11.09 ± 0.78 milliarcseconds/year
B-V Index0.17
Spectral TypeF1V
Colour(F) blue to white
Stars in Solar System2

Estimated Facts

Radius (x the Sun)2.84
Calculated Effective Temperature7,952 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
173582+39 3509.0A5.1000012.0000060.00000A3White
173583B6.10000-2.0000061.000001959

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