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GU Eridani, HD26326, HIP19398

GU Eridani is a blue pulsating subgiant star that can be located in the constellation of Eridanus. GU Eridani is the brightest star in Eridanus 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.

HIP19398 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD26326. The Id of the star in the Gould Star Catalogue is 181. 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.

GU Eridani has alternative name(s), GU Eri.

Location of GU Eridani

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 GU Eridani, the location is 04h 09m 17.84 and -16d23`09.2 .

Proper Motion of GU Eridani

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 0.63 ± 0.19 miliarcseconds/year towards the north and -0.87 ± 0.28 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of GU Eridani

GU Eridani has a spectral type of B5IV. This means the star is a blue subgiant star. The star is 7527.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24550.3149028800000000s. The star has a B-V Colour Index of -0.14 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 13,196 Kelvin.

GU Eridani Radius has been calculated as being 3.24 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,251,727.76.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.91. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

GU Eridani Apparent and Absolute Magnitudes

GU Eridani has an apparent magnitude of 5.45 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 -1.29 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.06. 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 GU Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.49 which gave the calculated distance to GU Eridani as 726.42 light years away from Earth or 222.72 parsecs. It would take a spaceship travelling at the speed of light, 726.42 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 5.00 which put GU Eridani at a distance of 652.33 light years or 200 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 7,527.00 Parsecs or 24,550.31 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 GU Eridani

The star is a pulsating Slow Pulsating B- star 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. GU Eridani brightness ranges from a magnitude of 5.417 to a magnitude of 5.385 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 1.9 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.

GU Eridani Facts

Alternative Names

Traditional/Proper NameGU Eridani
Short NameGU Eri
Hipparcos Library I.D.19398
Bonner DurchmusterungBD-16 796
Gould I.D.181
Henry Draper Designation26326

Visual Facts

Star Typesubgiant star
Absolute Magnitude-1.29 / -1.06
Visual / Apparent Magnitude5.45
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)04h 09m 17.84
Declination (Dec.)-16d23`09.2
Galactic Latitude-43.12 degrees
Galactic Longitude210.32 degrees
1997 Distance from Earth4.49 Parallax (milliarcseconds)
 726.42 Light Years
 222.72 Parsecs
2007 Revised Distance from Earth5.00 Parallax (milliarcseconds)
 652.33 Light Years
 200 Parsecs
Galacto-Centric Distance24,550.31 Light Years / 7,527.00 Parsecs
Proper Motion Dec.0.63 ± 0.19 milliarcseconds/year
Proper Motion RA.-0.87 ± 0.28 milliarcseconds/year
B-V Index-0.14
Radial Velocity17.40 ± 0.80 km/s
Spectral TypeB5IV
Colour(B) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSlow Pulsating B- star
Mean Variability Period in Days1.873
Variable Magnitude Range (Brighter - Dimmer)5.385 - 5.417

Estimated Facts

Calculated Effective Temperature13,196 Kelvin

Sources and Links

SIMBAD SourceLink

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