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RS Cancri, HD78712, HIP45058, HR3639

RS Cancri is a red pulsating star that can be located in the constellation of Cancer. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

The Id of the star in the Yale Bright Star Catalogue is HR3639. HIP45058 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD78712.

RS Cancri has alternative name(s), RS Cnc.

Location of RS Cancri

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 RS Cancri, the location is 09h 10m 38.81 and +30d 57` 47.6 .

Proper Motion of RS Cancri

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 -33.42 ± 0.30 miliarcseconds/year towards the north and -11.12 ± 0.52 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 us is 13.72000 km/s with an error of about 0.42 km/s .

Physical Properties (Colour, Temperature, Radius) of RS Cancri

RS Cancri has a spectral type of M6S. This means the star is a red star. The star is 7503.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24472.0357003200000000s. The star has a B-V Colour Index of 1.37 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,262 Kelvin.

RS Cancri Radius has been calculated as being 12.93 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 8,998,185.68.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 15.19. 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 -1.00 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

RS Cancri Apparent and Absolute Magnitudes

RS Cancri has an apparent magnitude of 6.04 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 0.61 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.26. 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 RS Cancri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.21 which gave the calculated distance to RS Cancri as 397.28 light years away from Earth or 121.80 parsecs. It would take a spaceship travelling at the speed of light, 397.28 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 6.97 which put RS Cancri at a distance of 467.95 light years or 143.47 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's Galacto-Centric Distance is 7,503.00 Parsecs or 24,472.04 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of RS Cancri

The star is a pulsating Semiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep) 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. This is a some uncertainty as to the type but the type mentioned is the current variable star classification for this star. RS Cancri brightness ranges from a magnitude of 6.108 to a magnitude of 5.177 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.9 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.

RS Cancri Facts

Alternative Names

Traditional/Proper NameRS Cancri
Short NameRS Cnc
Hipparcos Library I.D.45058
Yale Bright Star Catalogue (HR) Id3639
Bonner DurchmusterungBD+31 1946
Henry Draper Designation78712

Visual Facts

Star Type star
Absolute Magnitude0.61 / 0.26
Visual / Apparent Magnitude6.04
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)09h 10m 38.81
Declination (Dec.)+30d 57` 47.6
Galactic Latitude42.08 degrees
Galactic Longitude194.50 degrees
1997 Distance from Earth8.21 Parallax (milliarcseconds)
 397.28 Light Years
 121.80 Parsecs
2007 Revised Distance from Earth6.97 Parallax (milliarcseconds)
 467.95 Light Years
 143.47 Parsecs
Galacto-Centric Distance24,472.04 Light Years / 7,503.00 Parsecs
Proper Motion Dec.-33.42 ± 0.30 milliarcseconds/year
Proper Motion RA.-11.12 ± 0.52 milliarcseconds/year
B-V Index1.37
Radial Velocity13.72 ± 0.42 km/s
Iron Abundance-1.00 ± 9.99 Fe/H
Spectral TypeM6S
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep) probably
Mean Variability Period in Days0.866
Variable Magnitude Range (Brighter - Dimmer)5.177 - 6.108

Estimated Facts

Calculated Effective Temperature4,262 Kelvin

Sources and Links

SIMBAD SourceLink

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