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WR 18, HD89358, HIP50368

WR 18 is a Wolf-Rayet star that can be located in the constellation of Carina. The star can not be seen by the naked eye, you need a telescope to see it.

HIP50368 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD89358.

WR 18 has alternative name(s), V500 Car.

Location of WR 18

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 WR 18, the location is 10h 17m 02.28 and -57d 54` 46.9 .

Wolf-Rayet Star

The star is a Wolf-Rayet, a rare type of star of which not many are known. These stars are extremely luminous and large compared to our Sun. They live fast and die hard in a matter of millions not billions of years like our Sun. They exhaust their hydrogen supplies, turning to other gasses and expand outwards with massive solar winds, moving a step closer in the stellar evolution towards their death in a super or hypernova explosion.

Proper Motion of WR 18

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 5.18 ± 1.30 miliarcseconds/year towards the north and -5.41 ± 1.61 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Temperature, Radius) of WR 18

WR 18 has a spectral type of WN5. This means the star is a Wolf-Rayet star. The star has a B-V Colour Index of 0.49 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,140 Kelvin.

WR 18 Radius has been calculated as being 6.62 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,603,057.24.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 11.82. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

WR 18 Apparent and Absolute Magnitudes

WR 18 has an apparent magnitude of 10.64 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 -0.78. 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 WR 18

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.93 which gave the calculated distance to WR 18 as 3507.13 light years away from Earth or 1075.27 parsecs. It would take a spaceship travelling at the speed of light, 3507.13 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 0.52 which put WR 18 at a distance of 6272.37 light years or 1923.08 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. WR 18 brightness ranges from a magnitude of 10.815 to a magnitude of 10.613 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 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.

WR 18 Facts

Alternative Names

Traditional/Proper NameWR 18
Short NameV500 Car
Hipparcos Library I.D.50368
Henry Draper Designation89358
Wolf-Rayet Id18

Visual Facts

Star Type Wolf-Rayet star
Absolute Magnitude0.48 / -0.78
Visual / Apparent Magnitude10.64
Naked Eye VisibleRequires a 4.5 - 6 Inch Telescope - Magnitudes
Right Ascension (R.A.)10h 17m 02.28
Declination (Dec.)-57d 54` 46.9
Galactic Latitude-0.97 degrees
Galactic Longitude283.57 degrees
1997 Distance from Earth0.93 Parallax (milliarcseconds)
 3507.13 Light Years
 1075.27 Parsecs
2007 Revised Distance from Earth0.52 Parallax (milliarcseconds)
 6272.37 Light Years
 1923.08 Parsecs
Proper Motion Dec.5.18 ± 1.30 milliarcseconds/year
Proper Motion RA.-5.41 ± 1.61 milliarcseconds/year
B-V Index0.49
Spectral TypeWN5

Variable Star Details

Mean Variability Period in Days0.152
Variable Magnitude Range (Brighter - Dimmer)10.613 - 10.815

Estimated Facts

Calculated Effective Temperature6,140 Kelvin

Sources and Links

SIMBAD SourceLink

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