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Copernicus (Rho01 Cancri, 55 Cancri)

Copernicus Facts

Copernicus's Alternative Names

Rho01 Cancri (Rho01 Cnc) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR3522. HIP43587 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD75732. The Gliese ID of the star is GL 324A. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

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 55 Cancri with it shortened to 55 Cnc.



Location of Copernicus


Radial Velocity and Proper Motion of Copernicus

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 -234.05 ± 0.40 miliarcseconds/year towards the north and -485.80 ± 0.75 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 the Sun is 27.58 km/s with an error of about 0.07 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.

Copernicus Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 0.66 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Metallicity, Age, Mass) of Copernicus

Copernicus has a spectral type of G8V. This means the star is a white to yellow main sequence star. The star is 7,409.00 Parsecs from the Galactic Centre or in terms of Light Years is 24,165.44 s. The star has a B-V Colour Index of 0.86 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,141 Kelvin.

Copernicus Radius has been calculated as being 0.95 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 659,536.63.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 0.93. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 0.91 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.


The star is believed to be about 10.20 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.

Copernicus Apparent and Absolute Magnitudes

Copernicus has an apparent magnitude of 5.96 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 5.47 If you used the 2007 Parallax value, you would get an absolute magnitude of 5.50. 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 Copernicus

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 79.80 which gave the calculated distance to Copernicus as 40.87 light years away from Earth or 12.53 parsecs. It would take a spaceship travelling at the speed of light, 40.87 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 81.03 which put Copernicus at a distance of 40.25 light years or 12.34 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 2,545,289.97 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.


Source of Information


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Additional Copernicus Facts and Figures

Visual Facts

Primary / Proper / Traditional NameCopernicus
Alternative NamesRho01 Cancri, Rho01 Cnc, HD 75732, HIP 43587, HR 3522, 55 Cancri, 55 Cnc, BD+28 1660, Gliese 324A
Spectral TypeG8V
Constellation's Main StarNo
Multiple Star SystemYes
Star Type main sequence Dwarf Star
ColourWhite to Yellow
GalaxyMilky Way
Age10.20 Billion Years Old
Absolute Magnitude 5.47 / 5.50
Visual / Apparent Magnitude5.96
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)08h 52m 36.13
Declination (Dec.)+28° 19` 53.0
Galactic Latitude37.70 degrees
Galactic Longitude196.79 degrees
1997 Distance from Earth79.80 Parallax (milliarcseconds)
 40.87 Light Years
 12.53 Parsecs
2007 Distance from Earth81.03 Parallax (milliarcseconds)
 40.25 Light Years
 12.34 Parsecs
 2,545,289.97 Astronomical Units
Galacto-Centric Distance24,165.44 Light Years / 7,409.00 Parsecs
Proper Motion Dec.-234.05 ± 0.40 milliarcseconds/year
Proper Motion RA.-485.80 ± 0.75 milliarcseconds/year
B-V Index0.86
Radial Velocity27.58 ± 0.07 km/s
Iron Abundance0.35 ± 0.00 Fe/H
Semi-Major Axis7227.00
Stellar Luminosity (Lsun)0.66

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count5

Estimated Calculated Facts

Radius (x the Sun)0.93
Effective Temperature5,141 Kelvin
Mass Compared to the Sun0.91

Sources and Links

SIMBAD SourceLink

Multi-Star System


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
75732+28 1660.0A6.00000-476.00000-227.00000G8Yellow

List of Extrasolar Planets orbiting Copernicus

55 Cnc bConfirmed0.03114.6530.002319960.11339110.00089.730
55 Cnc cConfirmed0.007844.3730.07220020.23735356.000
55 Cnc dConfirmed0.154867.0000.026920025.446254.000
55 Cnc eConfirmed0.00081050.7370.02820040.015439170.00090.360
55 Cnc fConfirmed0.0093260.9100.0820070.7733139.000

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