Universe Guide

HomeFactsConstellationsCetus

21 Ceti - HD5268 - HIP4257

21 Ceti is a white to yellow subgiant star that can be located in the constellation of Cetus. HIP4257 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD5268. The Id of the star in the Gould Star Catalogue is 92. Stars in the southern hemisphere are more likely to have a Gould Id than the northern hemisphere. For example, there are no Gould classified stars in Ursa Major. 21 Ceti has alternative name(s), 21 Ceti , 21 Cet.

Location of 21 Ceti

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 21 Ceti, the location is 00h 54m 17.58 and -08d44`26.0 .

Proper Motion of 21 Ceti

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 -048.21 ± 000.35 towards the north and 016.70 ± 000.47 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 21 Ceti

21 Ceti has a spectral type of G5IV. This means the star is a white to yellow subgiant star. The star has a B-V Colour Index of 0.91 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,031 Kelvin.

21 Ceti has been calculated as 8.43 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 5,862,341.92.km.

21 Ceti Apparent and Absolute Magnitudes

21 Ceti has an apparent magnitude of 6.15 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 0.82 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.56. 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 21 Ceti

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.60 which gave the calculated distance to 21 Ceti as 379.26 light years away from Earth or 116.28 parsecs. It would take a spaceship travelling at the speed of light, 379.26 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 7.61 which put 21 Ceti at a distance of 428.60 light years or 131.41 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.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

21 Ceti Facts

Alternative Names

Traditional Name21 Ceti
Short Name21 Cet
Alternative Name(s)21 Ceti
Hipparcos Library I.D.4257
Bonner DurchmusterungBD-09 181
Gould I.D.92
Henry Draper Designation5268

Visual Facts

Star Typesubgiant star
Absolute Magnitude0.82 / 0.56
Apparent Magnitude6.15
Right Ascension (R.A.)00h 54m 17.58
Declination (Dec.)-08d44`26.0
1997 Distance from Earth8.60 Parallax (milliarcseconds)
 379.26 Light Years
 116.28 Parsecs
2007 Revised Distance from Earth7.61 Parallax (milliarcseconds)
 428.60 Light Years
 131.41 Parsecs
Proper Motion Dec.-48.21 ± 0.35 milliarcseconds/year
Proper Motion RA.16.70 ± 0.47 milliarcseconds/year
B-V Index0.91
Spectral TypeG5IV
Colour(G) White to Yellow

Estimated Facts

Radius (x the Sun)8.43
Calculated Effective Temperature5,031 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars


Add a Comment


Name:
Email: (Optional)
Comment: