Universe Guide

121 G. Sagittarii - HD175794 - HIP93134

121 G. Sagittarii is an orange to red giant star that can be located in the constellation of Sagittarius. HIP93134 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD175794. The Id of the star in the Gould Star Catalogue is 121. 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 121 G. Sagittarii

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 121 G. Sagittarii, the location is 18h 58m 21.31 and -31 d 02`09.1 .

Proper Motion of 121 G. Sagittarii

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 -050.00 ± 000.00 towards the north and -046.00 ± 001.00 east if we saw them in the horizon.

121 G. Sagittarii 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 58.0000000 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 121 G. Sagittarii

121 G. Sagittarii has a spectral type of K3III. This means the star is an orange to red coloured giant star. The star has a B-V Colour Index of 1.34 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,257 Kelvin.

121 G. Sagittarii has been calculated as 14.81 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 10,308,070.69.km.

121 G. Sagittarii Apparent and Absolute Magnitudes

121 G. Sagittarii has an apparent magnitude of 6.09 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 0.32 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.32. 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 121 G. Sagittarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 7.00 which gave the calculated distance to 121 G. Sagittarii as 465.95 light years away from Earth or 142.86 parsecs. In 2007, Hipparcos data was revised with a new parallax of 7.00 which put 121 G. Sagittarii at a distance of 465.95 light years or 142.86 parsecs.

It would take a spaceship travelling at the speed of light, 465.95 years using the 1997 distance to get there. We don't have the technology or spaceship that can carry people over that distance yet.

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.

121 G. Sagittarii Facts


Traditional Name121 G. Sagittarii
Hipparcos Library I.D.93134
Gould I.D.121
Henry Draper Designation175794
Celestial TypeStar
Absolute Magnitude0.32 / 0.32
Apparent Magnitude6.09
Right Ascension (R.A.)18h 58m 21.31
Declination (Dec.)-31 d 02`09.1
1997 Distance from Earth7.00 Parallax (milliarcseconds)
 465.95 Light Years
 142.86 Parsecs
2007 Distance from Earth7.00 Parallax (milliarcseconds)
 465.95 Light Years
 142.86 Parsecs
Proper Motion Dec.-50.00 ± 0.00 milliarcseconds/year
Proper Motion RA.-46.00 ± 1.00 milliarcseconds/year
B-V Index1.34
Spectral TypeK3III
Colour(K) Orange to Red
Star Typegiant star
Radius (x the Sun)14.81
Luminosity (x the Sun)58.0000000
Calculated Effective Temperature4,257 Kelvin


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