Universe Guide

122 G. Oph - HD156826 - HIP84801

122 G. Oph is a white to yellow main sequence dwarf star that can be located in the constellation of Ophiuchus. HIP84801 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD156826. The Id of the star in the Gould Star Catalogue is 122. 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 122 G. Oph

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 from celestial equator. The Declination is how up or down compared to the celestial equator and is expressed in degrees. For 122 G. Oph, the location is 17h 19m 59.53 and -05 d 55`01.3 .

Proper Motion of 122 G. Oph

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 -192.00 ± 000.00 towards the north and 042.00 ± 001.00 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 122 G. Oph

122 G. Oph has a spectral type of G9V. This means the star is a white to yellow coloured main sequence dwarf star. The star has a B-V Colour Index of 0.85 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,164 Kelvin.

122 G. Oph has been calculated as 3.36 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,340,932.31.km.

122 G. Oph Apparent and Absolute Magnitudes

122 G. Oph has an apparent magnitude of 6.31 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 2.70 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.82. 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 122 G. Oph

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 19.00 which gave the calculated distance to 122 G. Oph as 171.66 light years away from us or 52.63 parsecs. In 2007, Hipparcos data was revised with a new parallax of 20.00 which put 122 G. Oph at a distance of 163.08 light years or 50 parsecs.

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.

122 G. Oph Facts


Traditional Name122 G. Oph
Hipparcos Library I.D.84801
Gould I.D.122
Henry Draper Designation156826
Celestial TypeStar
Absolute Magnitude2.70 / 2.82
Apparent Magnitude6.31
Right Ascension (R.A.)17h 19m 59.53
Declination (Dec.)-05 d 55`01.3
1997 Distance19.00 Parallax (milliarcseconds)
 171.66 Light Years
 52.63 Parsecs
2007 Distance20.00 Parallax (milliarcseconds)
 163.08 Light Years
 50 Parsecs
Proper Motion Dec.-192.00 ± 0.00 milliarcseconds/year
Proper Motion RA.42.00 ± 1.00 milliarcseconds/year
B-V Index0.85
Spectral TypeG9V
Colour(G) White to Yellow
Star Typemain sequence dwarf star
Radius (x the Sun)3.36
Calculated Effective Temperature5,164 Kelvin


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