Tau Persei is a white to yellow giant star that can be located in the constellation of Perseus. Tau Persei is the Bayer Classification for the star. HIP13531 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD17878. Tau Persei has alternative name(s), 18 Persei , 18 Per.
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 Tau Persei, the location is 02h 54m 15.46 and +52d45`45.0 .
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 -004.37 ± 000.22 towards the north and -001.26 ± 000.36 east if we saw them in the horizon.
Tau Persei has a spectral type of G4III.... This means the star is a white to yellow giant star. The star has a B-V Colour Index of 0.75 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,418 Kelvin.
Tau Persei has been calculated as 13.22 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 9,198,447.65.km.
Tau Persei has an apparent magnitude of 3.93 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 -0.48 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.53. 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 13.15 which gave the calculated distance to Tau Persei as 248.03 light years away from Earth or 76.05 parsecs. It would take a spaceship travelling at the speed of light, 248.03 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 12.83 which put Tau Persei at a distance of 254.22 light years or 77.94 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.
|Short Name||18 Per|
|Bayer Designation||Tau Persei|
|Alternative Name(s)||18 Persei|
|Hipparcos Library I.D.||13531|
|Bonner Durchmusterung||BD+52 641|
|Henry Draper Designation||17878|
|Star Type||giant star|
|Absolute Magnitude||-0.48 / -0.53|
|Right Ascension (R.A.)||02h 54m 15.46|
|1997 Distance from Earth||13.15 Parallax (milliarcseconds)|
|248.03 Light Years|
|2007 Revised Distance from Earth||12.83 Parallax (milliarcseconds)|
|254.22 Light Years|
|Proper Motion Dec.||-4.37 ± 0.22 milliarcseconds/year|
|Proper Motion RA.||-1.26 ± 0.36 milliarcseconds/year|
|Orbital Period (Days)||1515.60|
|Argument Of Periastron||234.60|
|Colour||(G) White to Yellow|
|Radius (x the Sun)||13.22|
|Calculated Effective Temperature||5,418 Kelvin|
The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.
|Proper Motion mas/yr|
|H.D. Id||B.D. Id||Star Code||Magnitude||R.A.||Dec.||Spectrum||Colour||Year|