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242 G. Centauri, HD118520, HIP66575

242 G. Centauri is a white to yellow supergiant star that can be located in the constellation of Centaurus. 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.

242 G. Centauri's Alternative Names

HIP66575 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD118520.

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 242 G. Centauri. There are no stars with a Gould designation in Ursa Major for example.

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

Location of 242 G. Centauri

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 242 G. Centauri, the location is 13h 38m 48.96 and -57° 37` 21.7 .

Proper Motion of 242 G. Centauri

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 -5.34 ± 0.34 miliarcseconds/year towards the north and -10.28 ± 0.49 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 -9.60000 km/s with an error of about 0.30 km/s .

Physical Properties (Colour, Temperature) of 242 G. Centauri

242 G. Centauri has a spectral type of G5Ib. This means the star is a white to yellow supergiant star. The star has a B-V Colour Index of 1.13 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,702 Kelvin.

242 G. Centauri Radius has been calculated as being 33.60 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 23,379,818.52.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 105.77. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

242 G. Centauri Apparent and Absolute Magnitudes

242 G. Centauri has an apparent magnitude of 6.00 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 -1.89 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.38. 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 242 G. Centauri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.64 which gave the calculated distance to 242 G. Centauri as 1235.47 light years away from Earth or 378.79 parsecs. It would take a spaceship travelling at the speed of light, 1235.47 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 0.84 which put 242 G. Centauri at a distance of 3882.90 light years or 1190.48 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 Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

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242 G. Centauri Facts

Visual Facts


Primary / Proper / Traditional Name242 G. Centauri
Alternative NamesHD 118520, HIP 66575
Spectral TypeG5Ib
Multiple Star SystemYes
Star Type very luminous Supergiant Star
Colour white to yellow
GalaxyMilky Way
ConstellationCentaurus
Absolute Magnitude-1.89 / -4.38
Visual / Apparent Magnitude6.00
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)13h 38m 48.96
Declination (Dec.)-57° 37` 21.7
Galactic Latitude4.67 degrees
Galactic Longitude309.26 degrees
1997 Distance from Earth2.64 Parallax (milliarcseconds)
 1235.47 Light Years
 378.79 Parsecs
2007 Distance from Earth0.84 Parallax (milliarcseconds)
 3882.90 Light Years
 1190.48 Parsecs
Proper Motion Dec.-5.34 ± 0.34 milliarcseconds/year
Proper Motion RA.-10.28 ± 0.49 milliarcseconds/year
B-V Index1.13
Radial Velocity-9.60 ± 0.30 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature4,702 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
118520-56 5856.4A6.80000-4.00000-17.00000K0Orange
B6.800001957

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