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RR Lyrae, HD182989, HIP95497

RR Lyrae is a blue pulsating star that can be located in the constellation of Lyra. RR Lyrae is the brightest star in Lyra based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP95497 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD182989.

RR Lyrae has alternative name(s), RR Lyr.

Location of RR 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 RR Lyrae, the location is 19h 25m 28.00 and +42d 47` 05.4 .

Proper Motion of RR 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 -195.75 ± 0.55 miliarcseconds/year towards the north and -109.68 ± 0.64 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 -72.20000 km/s with an error of about 0.80 km/s .

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

RR Lyrae has a spectral type of A5.0-F7.0. This means the star is a blue star. The star is 7335.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23924.0812824000000000s. The star has a B-V Colour Index of 0.43 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,305 Kelvin.

RR Lyrae Radius has been calculated as being 4.65 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,235,985.41.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 5.88. 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 -1.35 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

RR Lyrae Apparent and Absolute Magnitudes

RR Lyrae has an apparent magnitude of 7.92 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 1.13 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.62. 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 RR Lyrae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.38 which gave the calculated distance to RR Lyrae as 744.67 light years away from Earth or 228.31 parsecs. It would take a spaceship travelling at the speed of light, 744.67 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 3.46 which put RR Lyrae at a distance of 942.67 light years or 289.02 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 7,335.00 Parsecs or 23,924.08 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 RR Lyrae

The star is a pulsating RR Lyrae type with asymmetric light curves 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. RR Lyrae brightness ranges from a magnitude of 8.157 to a magnitude of 7.448 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.6 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.

RR Lyrae Facts

Alternative Names

Traditional/Proper NameRR Lyrae
Short NameRR Lyr
Hipparcos Library I.D.95497
Bonner DurchmusterungBD+42 3338
Henry Draper Designation182989

Visual Facts

Star Type star
Absolute Magnitude1.13 / 0.62
Visual / Apparent Magnitude7.92
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)19h 25m 28.00
Declination (Dec.)+42d 47` 05.4
Galactic Latitude12.30 degrees
Galactic Longitude74.95 degrees
1997 Distance from Earth4.38 Parallax (milliarcseconds)
 744.67 Light Years
 228.31 Parsecs
2007 Revised Distance from Earth3.46 Parallax (milliarcseconds)
 942.67 Light Years
 289.02 Parsecs
Galacto-Centric Distance23,924.08 Light Years / 7,335.00 Parsecs
Proper Motion Dec.-195.75 ± 0.55 milliarcseconds/year
Proper Motion RA.-109.68 ± 0.64 milliarcseconds/year
B-V Index0.43
Radial Velocity-72.20 ± 0.80 km/s
Iron Abundance-1.35 ± 9.99 Fe/H
Spectral TypeA5.0-F7.0
Colour(A) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeRR Lyrae type with asymmetric light curves
Mean Variability Period in Days0.567
Variable Magnitude Range (Brighter - Dimmer)7.448 - 8.157

Estimated Facts

Calculated Effective Temperature6,305 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of RR Lyrae in Lyra

RR Lyrae Location in Lyra

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

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