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Delta2 Lyrae, 12 Lyrae, HD175588, HIP92791, HR7139

Delta2 Lyrae is a red pulsating luminous giant star that can be located in the constellation of Lyra. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Delta2 Lyrae's Alternative Names

Delta2 Lyrae (Del02 Lyr) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR7139. HIP92791 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD175588.

Delta2 Lyrae has alternative name(s) :- , del02 Lyr.

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 12 Lyrae with it shortened to 12 Lyr.

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+36 3319.

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

Location of Delta2 Lyrae

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 Delta2 Lyrae, the location is 18h 54m 30.29 and +36° 53` 55.0 .

Proper Motion of Delta2 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 4.06 ± 0.16 miliarcseconds/year towards the north and -7.36 ± 0.18 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 -25.55000 km/s with an error of about 0.84 km/s .

Delta2 Lyrae 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 4,335.24 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of Delta2 Lyrae

Delta2 Lyrae has a spectral type of M4IIvar. This means the star is a red luminous giant star. The star is 7,305.00 Parsecs from the Galactic Centre or terms of Light Years is 23,826.23 s. The star has a B-V Colour Index of 1.57 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,854 Kelvin.

Delta2 Lyrae Radius has been calculated as being 82.62 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 57,490,179.66.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 67.78. 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 -0.04 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Delta2 Lyrae Apparent and Absolute Magnitudes

Delta2 Lyrae has an apparent magnitude of 4.22 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 -2.98 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.55. 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 Delta2 Lyrae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.63 which gave the calculated distance to Delta2 Lyrae as 898.52 light years away from Earth or 275.48 parsecs. It would take a spaceship travelling at the speed of light, 898.52 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 4.43 which put Delta2 Lyrae at a distance of 736.26 light years or 225.73 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 7,305.00 Parsecs or 23,826.23 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 Delta2 Lyrae

The star is a pulsating Semi-Regular Star which are giants or supergiants of intermediate and late spectral 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. Delta2 Lyrae brightness ranges from a magnitude of 4.309 to a magnitude of 4.130 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 days (variability).

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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Delta2 Lyrae Facts

Visual Facts


Primary / Proper / Traditional NameDelta2 Lyrae
Alternative NamesDel02 Lyr, HD 175588, HIP 92791, HR 7139, 12 Lyrae, 12 Lyr, BD+36 3319, del02 Lyr
Spectral TypeM4IIvar
Multiple Star SystemYes
Star TypeLuminous Giant Star
Colour red
GalaxyMilky Way
ConstellationLyra
Absolute Magnitude-2.98 / -2.55
Visual / Apparent Magnitude4.22
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)18h 54m 30.29
Declination (Dec.)+36° 53` 55.0
Galactic Latitude15.32 degrees
Galactic Longitude66.93 degrees
1997 Distance from Earth3.63 Parallax (milliarcseconds)
 898.52 Light Years
 275.48 Parsecs
2007 Distance from Earth4.43 Parallax (milliarcseconds)
 736.26 Light Years
 225.73 Parsecs
Galacto-Centric Distance23,826.23 Light Years / 7,305.00 Parsecs
Proper Motion Dec.4.06 ± 0.16 milliarcseconds/year
Proper Motion RA.-7.36 ± 0.18 milliarcseconds/year
B-V Index1.57
Radial Velocity-25.55 ± 0.84 km/s
Iron Abundance-0.04 ± 9.99 Fe/H
Eccentricity0.11
Semi-Major Axis6558.00
Stellar Luminosity (Lsun)4,335.24
Associated / Clustered StarsDelta1 Lyrae

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star which are giants or supergiants of intermediate and late spectral
Mean Variability Period in Days0.151
Variable Magnitude Range (Brighter - Dimmer)4.130 - 4.309

Estimated Facts


Calculated Effective Temperature3,854 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
175588+36 3319.0A4.50000-14.0000012.00000M2Red
B11.200001923
BC11.600001923

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