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18 Ceti, HD4307, HIP3559, HR203

18 Ceti is a white to yellow main sequence dwarf star that can be located in the constellation of Cetus. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. The star has an estimated age of 7.70 Billion of Years but could be as young as 7.00 to 8.30 according to Hipparcos.

18 Ceti's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR203. HIP3559 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD4307. The Gliese ID of the star is GJ 1020. The star was added to the Gliese catalogue in 1970 by Richard van der Riet Woolley hence the GJ prefix rather than GL prefix.Star Names.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 18 Ceti with it shortened to 18 Cet.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 75 G. Ceti. There are no stars with a Gould designation in Ursa Major for example.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD-13 128.

More details on star alternative names can be found at Star Names .

Location of 18 Ceti

The location of the star in the night sky 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 18 Ceti, the location is 00h 45m 28.71 and -12° 52` 49.1 .

Proper Motion of 18 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 -205.65 ± 0.25 miliarcseconds/year towards the north and -32.32 ± 0.44 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 -10.31000 km/s with an error of about 0.09 km/s .

18 Ceti 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 3.01 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Age) of 18 Ceti

18 Ceti has a spectral type of G2V. This means the star is a white to yellow main sequence dwarf star. The star is 7,404.00 Parsecs from the Galactic Centre or terms of Light Years is 24,149.13 s. The star has a B-V Colour Index of 0.6 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,895 Kelvin.

18 Ceti Radius has been calculated as being 1.68 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,170,535.46.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.64. 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 -0.22 with an error value of 0.01 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 7.70 Billion years old but could be between 7.00 and 8.30 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

18 Ceti Apparent and Absolute Magnitudes

18 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 3.63 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.69. 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 18 Ceti

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 31.39 which gave the calculated distance to 18 Ceti as 103.91 light years away from Earth or 31.86 parsecs. It would take a spaceship travelling at the speed of light, 103.91 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 32.26 which put 18 Ceti at a distance of 101.10 light years or 31.00 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 7,404.00 Parsecs or 24,149.13 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

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18 Ceti Facts

Visual Facts


Primary / Proper / Traditional Name18 Ceti
Alternative NamesHD 4307, HIP 3559, HR 203, 75 G. Ceti, 18 Cet, BD-13 128, Gliese 1020
Spectral TypeG2V
Multiple Star SystemYes
Star Type main sequence Dwarf Star
Colour white to yellow
GalaxyMilky Way
ConstellationCetus
Age7.70 Billion Years Old
Age Range7.00 - 8.30 Billion Years Old
Absolute Magnitude3.63 / 3.69
Visual / Apparent Magnitude6.15
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)00h 45m 28.71
Declination (Dec.)-12° 52` 49.1
Galactic Latitude-75.68 degrees
Galactic Longitude117.05 degrees
1997 Distance from Earth31.39 Parallax (milliarcseconds)
 103.91 Light Years
 31.86 Parsecs
2007 Distance from Earth32.26 Parallax (milliarcseconds)
 101.10 Light Years
 31.00 Parsecs
Galacto-Centric Distance24,149.13 Light Years / 7,404.00 Parsecs
Proper Motion Dec.-205.65 ± 0.25 milliarcseconds/year
Proper Motion RA.-32.32 ± 0.44 milliarcseconds/year
B-V Index0.60
Radial Velocity-10.31 ± 0.09 km/s
Iron Abundance-0.22 ± 0.01 Fe/H
Eccentricity0.18
Semi-Major Axis6865.00
Stellar Luminosity (Lsun)3.01

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature5,895 Kelvin

Sources and Links


SIMBAD SourceLink

Multi-Star System

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. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
4307-13 128.0A6.10000-34.00000-198.00000G0Yellow
B12.400001959

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