Universe Guide


Gamma Reticuli, HD25705, HIP18744

Gamma Reticuli is a red eruptive giant star that can be located in the constellation of Reticulum. Gamma Reticuli is the brightest star in Reticulum based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Gamma Reticuli is the Bayer Classification for the star. HIP18744 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD25705.

Gamma Reticuli has alternative name(s), gam Ret.

Location of Gamma Reticuli

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 Gamma Reticuli, the location is 04h 00m 53.81 and -62d09`33.7 .

Proper Motion of Gamma Reticuli

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 34.67 ± 0.11 miliarcseconds/year towards the north and 3.03 ± 0.11 miliarcseconds/year east if we saw them in the horizon.

Gamma Reticuli 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 7.0000000 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 Gamma Reticuli

Gamma Reticuli has a spectral type of M4III. This means the star is a red giant star. The star is 7392.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24109.9943884800000000s. The star has a B-V Colour Index of 1.5 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,989 Kelvin.

Gamma Reticuli Radius has been calculated as being 37.43 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 26,041,955.97.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 35.74. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Gamma Reticuli Apparent and Absolute Magnitudes

Gamma Reticuli has an apparent magnitude of 4.48 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 -1.41 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.31. 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 Gamma Reticuli

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.65 which gave the calculated distance to Gamma Reticuli as 490.47 light years away from Earth or 150.38 parsecs. It would take a spaceship travelling at the speed of light, 490.47 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 6.95 which put Gamma Reticuli at a distance of 469.30 light years or 143.88 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.

The star's Galacto-Centric Distance is 7,392.00 Parsecs or 24,109.99 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Gamma Reticuli

The star is a eruptive Irregular variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. Gamma Reticuli brightness ranges from a magnitude of 4.621 to a magnitude of 4.427 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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.

Gamma Reticuli Facts

Alternative Names

Short Namegam Ret
Bayer DesignationGamma Reticuli
Hipparcos Library I.D.18744
Henry Draper Designation25705

Visual Facts

Star Typegiant star
Absolute Magnitude-1.41 / -1.31
Visual / Apparent Magnitude4.48
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)04h 00m 53.81
Declination (Dec.)-62d09`33.7
Galactic Latitude-43.21 degrees
Galactic Longitude274.81 degrees
1997 Distance from Earth6.65 Parallax (milliarcseconds)
 490.47 Light Years
 150.38 Parsecs
2007 Revised Distance from Earth6.95 Parallax (milliarcseconds)
 469.30 Light Years
 143.88 Parsecs
Galacto-Centric Distance24,109.99 Light Years / 7,392.00 Parsecs
Proper Motion Dec.34.67 ± 0.11 milliarcseconds/year
Proper Motion RA.3.03 ± 0.11 milliarcseconds/year
B-V Index1.50
Radial Velocity-7.00 ± 2.70 km/s
Spectral TypeM4III
Colour(M) Red

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeIrregular
Mean Variability Period in Days0.147
Variable Magnitude Range (Brighter - Dimmer)4.427 - 4.621

Estimated Facts

Luminosity (x the Sun)7.0000000
Calculated Effective Temperature3,989 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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