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Nu1 Coronae Borealis (20 Coronae Borealis) Star Facts

Nu1 Coronae Borealis Facts

Nu1 Coronae Borealis's Alternative Names

Nu1 Coronae Borealis (Nu.01 Crb) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in the early nineteenth century. The brightest star in the constellation is normally given the Alpha designation although there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR6107. HIP80197 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD147749.

Nu1 Coronae Borealis has alternative name(s) :- , NSV 07676.

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 20 Coronae Borealis with it shortened to 20 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+34 2773.

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

Location of Nu1 Coronae Borealis

The location of the giant 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 Nu1 Coronae Borealis, the location is 16h 22m 21.42 and +33° 47` 56.9 .

Radial Velocity and Proper Motion of Nu1 Coronae Borealis

Proper Motion

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 -37.92 ± 0.18 milliarcseconds/year towards the north and 4.97 ± 0.22 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -13.17 km/s with an error of about 0.35 km/s . 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 Nu1 Coronae Borealis

Nu1 Coronae Borealis Colour and Temperature

Nu1 Coronae Borealis has a spectral type of M2III. This means the star is a red giant star. The star has a B-V Colour Index of 1.63 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,700 Kelvin.

Nu1 Coronae Borealis Radius

Radius has been calculated as being 35.36 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 24,603,325.19.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 40.79. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Nu1 Coronae Borealis Apparent and Absolute Magnitudes

Nu1 Coronae Borealis has an apparent magnitude of 5.20 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 -0.96 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.27. 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 Nu1 Coronae Borealis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.87 which gave the calculated distance to Nu1 Coronae Borealis as 555.64 light years away from Earth or 170.36 parsecs. It would take a spaceship travelling at the speed of light, 555.64 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 5.09 which put Nu1 Coronae Borealis at a distance of 640.79 light years or 196.46 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 40,522,501.47 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.

The star's Galacto-Centric Distance is 7,322.00 Parsecs or 23,881.68 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*. Nu1 Coronae Borealis brightness ranges from a magnitude of 5.314 to a magnitude of 5.258 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 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 Nu1 Coronae Borealis Facts and Figures

Visual Facts


Primary / Proper / Traditional NameNu1 Coronae Borealis
Alternative NamesNu.01 Crb, HD 147749, HIP 80197, HR 6107, 20 Coronae Borealis, 20 Crb, BD+34 2773, NSV 07676
Spectral TypeM2III
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeGiant Star
ColourRed
GalaxyMilky Way
ConstellationCorona Borealis
Absolute Magnitude -0.96 / -1.27
Visual / Apparent Magnitude5.20
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)16h 22m 21.42
Declination (Dec.)+33° 47` 56.9
Galactic Latitude44.55 degrees
Galactic Longitude54.82 degrees
1997 Distance from Earth5.87 Parallax (milliarcseconds)
 555.64 Light Years
 170.36 Parsecs
2007 Distance from Earth5.09 Parallax (milliarcseconds)
 640.79 Light Years
 196.46 Parsecs
 40,522,501.47 Astronomical Units
Galacto-Centric Distance23,881.68 Light Years / 7,322.00 Parsecs
Proper Motion Dec.-37.92 ± 0.18 milliarcseconds/year
Proper Motion RA.4.97 ± 0.22 milliarcseconds/year
B-V Index1.63
Radial Velocity-13.17 ± 0.35 km/s
Eccentricity0.19
Semi-Major Axis6869.00

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Mean Variability Period in Days0.043
Variable Magnitude Range (Brighter - Dimmer)5.258 - 5.314

Estimated Calculated Facts


Radius (x the Sun)40.79
Effective Temperature3,700 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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