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AC Coronae Borealis

AC Coronae Borealis Facts

AC Coronae Borealis's Alternative Names

HIP78844 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD144620.

AC Coronae Borealis has alternative name(s) :- , AC CrB.

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+31 2815.

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

Location of AC Coronae Borealis

The location of the variable 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 object is compared to the celestial equator and is expressed in degrees. For AC Coronae Borealis, the location is 16h 05m 40.42 and +30° 55` 01.4 .

Proper Motion of AC Coronae Borealis

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 -12.26 ± 0.58 miliarcseconds/year towards the north and 12.92 ± 0.81 miliarcseconds/year east if we saw them in the horizon. . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties (Colour, Temperature) of AC Coronae Borealis

AC Coronae Borealis has a spectral type of M.... This means the star is a red variable star. The star has a B-V Colour Index of 1.53 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,949 Kelvin.

AC Coronae Borealis Radius has been calculated as being 16.59 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 11,545,417.33.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 16.75. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

AC Coronae Borealis Apparent and Absolute Magnitudes

AC Coronae Borealis has an apparent magnitude of 8.28 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 0.40 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.38. 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 AC Coronae Borealis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.65 which gave the calculated distance to AC Coronae Borealis as 1230.81 light years away from Earth or 377.36 parsecs. It would take a spaceship travelling at the speed of light, 1230.81 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 2.63 which put AC Coronae Borealis at a distance of 1240.16 light years or 380.23 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.

Using the 2007 distance, the star is roughly 78,427,520.79 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. AC Coronae Borealis brightness ranges from a magnitude of 8.356 to a magnitude of 8.235 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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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Additional AC Coronae Borealis Facts and Figures

Visual Facts


Primary / Proper / Traditional NameAC Coronae Borealis
Alternative NamesHD 144620, HIP 78844, BD+31 2815, AC CrB
Spectral TypeM...
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
ColourRed
GalaxyMilky Way
ConstellationCorona Borealis
Absolute Magnitude 0.40 / 0.38
Visual / Apparent Magnitude8.28
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)16h 05m 40.42
Declination (Dec.)+30° 55` 01.4
Galactic Latitude47.70 degrees
Galactic Longitude50.07 degrees
1997 Distance from Earth2.65 Parallax (milliarcseconds)
 1230.81 Light Years
 377.36 Parsecs
2007 Distance from Earth2.63 Parallax (milliarcseconds)
 1240.16 Light Years
 380.23 Parsecs
 78,427,520.79 Astronomical Units
Proper Motion Dec.-12.26 ± 0.58 milliarcseconds/year
Proper Motion RA.12.92 ± 0.81 milliarcseconds/year
B-V Index1.53

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Mean Variability Period in Days0.090
Variable Magnitude Range (Brighter - Dimmer)8.235 - 8.356

Estimated Calculated Facts


Radius (x the Sun)16.75
Effective Temperature3,949 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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