Universe Guide

142 G. Hya - HD81809 - HIP46404

142 G. Hya is a white to yellow main sequence dwarf star that can be located in the constellation of Hydra. HIP46404 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD81809. The Id of the star in the Gould Star Catalogue is 142. 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 142 G. Hya

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 142 G. Hya, the location is 09h 27m 46.92 and -06 d 04`15.7 .

Proper Motion of 142 G. Hya

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 -066.00 ± 000.00 towards the north and -234.00 ± 001.00 east if we saw them in the horizon.

142 G. Hya 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 1.0000000 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 142 G. Hya

142 G. Hya has a spectral type of G2V. This means the star is a white to yellow coloured main sequence dwarf star. The star has a B-V Colour Index of 0.64 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,755 Kelvin.

142 G. Hya has been calculated as 2.46 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,711,073.26.km.

142 G. Hya Apparent and Absolute Magnitudes

142 G. Hya has an apparent magnitude of 5.38 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 2.91 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.97. 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 142 G. Hya

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 32.00 which gave the calculated distance to 142 G. Hya as 101.93 light years away from us or 31.25 parsecs. In 2007, Hipparcos data was revised with a new parallax of 33.00 which put 142 G. Hya at a distance of 98.84 light years or 30.30 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.

142 G. Hya Facts


Traditional Name142 G. Hya
Hipparcos Library I.D.46404
Gould I.D.142
Henry Draper Designation81809
Celestial TypeStar
Absolute Magnitude2.91 / 2.97
Apparent Magnitude5.38
Right Ascension (R.A.)09h 27m 46.92
Declination (Dec.)-06 d 04`15.7
1997 Distance32.00 Parallax (milliarcseconds)
 101.93 Light Years
 31.25 Parsecs
2007 Distance33.00 Parallax (milliarcseconds)
 98.84 Light Years
 30.30 Parsecs
Proper Motion Dec.-66.00 ± 0.00 milliarcseconds/year
Proper Motion RA.-234.00 ± 1.00 milliarcseconds/year
B-V Index0.64
Spectral TypeG2V
Colour(G) White to Yellow
Star Typemain sequence dwarf star
Radius (x the Sun)2.46
Luminosity (x the Sun)1.0000000
Calculated Effective Temperature5,755 Kelvin


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