AC Hercules is a blue to white pulsating very luminous supergiant star that can be located in the constellation of Hercules. The star can not be seen by the naked eye, you need a telescope to see it.
HIP90697 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD170756.
AC Hercules has alternative name(s), AC Her.
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 AC Hercules, the location is 18h 30m 16.24 and +21d52`00.6 .
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 -0.18 ± 0.86 miliarcseconds/year towards the north and -2.82 ± 1.40 miliarcseconds/year east if we saw them in the horizon.
AC Hercules has a spectral type of F4Ibpvar. This means the star is a blue to white supergiant star. The star has a B-V Colour Index of 0.72 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,603 Kelvin.
AC Hercules Radius has been calculated as being 43.26 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 30,100,797.45.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 57.29. 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 -1.16 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.
AC Hercules has an apparent magnitude of 7.57 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 -3.20 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.81. 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 0.70 which gave the calculated distance to AC Hercules as 4659.48 light years away from Earth or 1428.57 parsecs. It would take a spaceship travelling at the speed of light, 4659.48 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 0.53 which put AC Hercules at a distance of 6154.03 light years or 1886.79 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 is a pulsating RV Tauri 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. AC Hercules brightness ranges from a magnitude of 8.501 to a magnitude of 7.318 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 75.3 days (variability).
|Traditional/Proper Name||AC Hercules|
|Short Name||AC Her|
|Hipparcos Library I.D.||90697|
|Bonner Durchmusterung||BD+21 3459|
|Henry Draper Designation||170756|
|Star Type||supergiant star|
|Absolute Magnitude||-3.20 / -3.81|
|Visual / Apparent Magnitude||7.57|
|Naked Eye Visible||Requires a 7x50 Binoculars - Magnitudes|
|Right Ascension (R.A.)||18h 30m 16.24|
|Galactic Latitude||14.24 degrees|
|Galactic Longitude||50.49 degrees|
|1997 Distance from Earth||0.70 Parallax (milliarcseconds)|
|4659.48 Light Years|
|2007 Revised Distance from Earth||0.53 Parallax (milliarcseconds)|
|6154.03 Light Years|
|Proper Motion Dec.||-0.18 ± 0.86 milliarcseconds/year|
|Proper Motion RA.||-2.82 ± 1.40 milliarcseconds/year|
|Radial Velocity||-30.00 ± 3.10 km/s|
|Iron Abundance||-1.16 ± 9.99 Fe/H|
|Colour||(F) blue to white|
|Variable Star Class||Pulsating|
|Variable Star Type||RV Tauri|
|Mean Variability Period in Days||75.300|
|Variable Magnitude Range (Brighter - Dimmer)||7.318 - 8.501|
|Calculated Effective Temperature||5,603 Kelvin|