R Cancri is a red pulsating star that can be located in the constellation of Cancer. HIP40534 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD69243. R Cancri has alternative name(s), R_Cnc.
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 R Cancri, the location is 08h 16m 33.83 and +11 d 43`34.6 .
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 -012.58 ± 000.43 towards the north and 004.31 ± 001.43 east if we saw them in the horizon.
R Cancri has a spectral type of M6e-M9e. This means the star is a red star. The star has a B-V Colour Index of 1.03 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,908 Kelvin.
R Cancri has an apparent magnitude of 7.04 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 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.97. 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 0.00 which gave the calculated distance to R Cancri as -1 light years away from Earth or -1 parsecs. It would take a spaceship travelling at the speed of light, -1 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 1.58 which put R Cancri at a distance of 2064.32 light years or 632.91 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 Omicron Ceti 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. R Cancri brightness ranges from a magnitude of 10.000 to a magnitude of 6.000 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 356.0 days (variability).
|Traditional Name||R Cancri|
|Short Name||R Cnc|
|Hipparcos Library I.D.||40534|
|Bonner Durchmusterung||BD+12 1803|
|Henry Draper Designation||69243|
|Right Ascension (R.A.)||08h 16m 33.83|
|Declination (Dec.)||+11 d 43`34.6|
|1997 Distance from Earth||0.00 Parallax (milliarcseconds)|
|-1 Light Years|
|2007 Revised Distance from Earth||1.58 Parallax (milliarcseconds)|
|2064.32 Light Years|
|Proper Motion Dec.||-12.58 ± 0.43 milliarcseconds/year|
|Proper Motion RA.||4.31 ± 1.43 milliarcseconds/year|
|Variable Star Class||Pulsating|
|Variable Star Type||Omicron Ceti|
|Mean Variability Period in Days||356.000|
|Variable Magnitude Range (Brighter - Dimmer)||6.000 - 10.000|
|Calculated Effective Temperature||4,908 Kelvin|