HK Lyrae is a pulsating luminous giant star that can be located in the constellation of Lyra. HK 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.
HIP91774 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD173291.
HK Lyrae has alternative name(s), HK Lyr.
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 HK Lyrae, the location is 18h 42m 50.00 and +36d57`30.9 .
HK Lyrae has a spectral type of C5II. This means the star is a luminous giant star. The star has a B-V Colour Index of 3.08 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 0 Kelvin. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.
HK Lyrae has an apparent magnitude of 7.97 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 -2.71 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.73 which gave the calculated distance to HK Lyrae as 4467.99 light years away from Earth or 1369.86 parsecs. It would take a spaceship travelling at the speed of light, 4467.99 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.
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. HK Lyrae brightness ranges from a magnitude of 8.068 to a magnitude of 7.749 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 186.0 days (variability).
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.
|Traditional/Proper Name||HK Lyrae|
|Short Name||HK Lyr|
|Hipparcos Library I.D.||91774|
|Bonner Durchmusterung||BD+36 3243|
|Henry Draper Designation||173291|
|Star Type||luminous giant star|
|Visual / Apparent Magnitude||7.97|
|Naked Eye Visible||Requires a 7x50 Binoculars - Magnitudes|
|Right Ascension (R.A.)||18h 42m 50.00|
|Galactic Latitude||17.51 degrees|
|Galactic Longitude||66.08 degrees|
|1997 Distance from Earth||0.73 Parallax (milliarcseconds)|
|4467.99 Light Years|
|Radial Velocity||-5.00 ± 3.10 km/s|
|Variable Star Class||Pulsating|
|Variable Star Type||Semi-Regular Star which are giants or supergiants of intermediate and late spectral|
|Mean Variability Period in Days||186.000|
|Variable Magnitude Range (Brighter - Dimmer)||7.749 - 8.068|