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39 G. Cet, HD2268, HIP2086

39 G. Cet is a red pulsating giant star that can be located in the constellation of Cetus. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

HIP2086 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD2268. The Id of the star in the Gould Star Catalogue is 39. 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.

Location of 39 G. Cet

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 39 G. Cet, the location is 00h 26m 21.74 and -18d41`37.0 .

Proper Motion of 39 G. Cet

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 -12.12 ± 0.37 miliarcseconds/year towards the north and 21.70 ± 0.66 miliarcseconds/year east if we saw them in the horizon.

39 G. Cet 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 13.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of 39 G. Cet

39 G. Cet has a spectral type of M1III. This means the star is a red giant star. The star has a B-V Colour Index of 1.6 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,779 Kelvin.

39 G. Cet Radius has been calculated as being 28.59 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 19,890,231.54.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 59.45. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

39 G. Cet Apparent and Absolute Magnitudes

39 G. Cet has an apparent magnitude of 6.24 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 -0.59 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.18. 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 39 G. Cet

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.30 which gave the calculated distance to 39 G. Cet as 758.52 light years away from Earth or 232.56 parsecs. It would take a spaceship travelling at the speed of light, 758.52 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 2.07 which put 39 G. Cet at a distance of 1575.67 light years or 483.09 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.

Variable Type of 39 G. Cet

The star is a pulsating Semi-Regular Star which are giants or supergiants of intermediate and late spectral 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. 39 G. Cet brightness ranges from a magnitude of 6.366 to a magnitude of 6.285 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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.

39 G. Cet Facts

Alternative Names

Traditional/Proper Name39 G. Cet
Hipparcos Library I.D.2086
Bonner DurchmusterungBD-19 58
Gould I.D.39
Henry Draper Designation2268

Visual Facts

Star Typegiant star
Absolute Magnitude-0.59 / -2.18
Visual / Apparent Magnitude6.24
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)00h 26m 21.74
Declination (Dec.)-18d41`37.0
Galactic Latitude-79.78 degrees
Galactic Longitude87.26 degrees
1997 Distance from Earth4.30 Parallax (milliarcseconds)
 758.52 Light Years
 232.56 Parsecs
2007 Revised Distance from Earth2.07 Parallax (milliarcseconds)
 1575.67 Light Years
 483.09 Parsecs
Proper Motion Dec.-12.12 ± 0.37 milliarcseconds/year
Proper Motion RA.21.70 ± 0.66 milliarcseconds/year
B-V Index1.60
Radial Velocity-0.30 ± 1.20 km/s
Spectral TypeM1III
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star which are giants or supergiants of intermediate and late spectral
Mean Variability Period in Days0.052
Variable Magnitude Range (Brighter - Dimmer)6.285 - 6.366

Estimated Facts

Luminosity (x the Sun)13.0000000
Calculated Effective Temperature3,779 Kelvin

Sources and Links

SIMBAD SourceLink

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