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22 Eridani, HD22920, HIP17167

22 Eridani is a blue rotating giant star that can be located in the constellation of Eridanus. 22 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.

HIP17167 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD22920. The Id of the star in the Gould Star Catalogue is 115. 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.

22 Eridani has alternative name(s), FY Eri.

Location of 22 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 22 Eridani, the location is 03h 40m 38.33 and -05d12`38.5 .

Proper Motion of 22 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 -5.19 ± 0.31 miliarcseconds/year towards the north and 1.09 ± 0.47 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 22 Eridani

22 Eridani has a spectral type of B9IIIp Si. This means the star is a blue giant star. The star is 7507.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24485.0822340800000000s. 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.

22 Eridani Radius has been calculated as being 3.18 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,210,627.09.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.13. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is 0.30 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

22 Eridani Apparent and Absolute Magnitudes

22 Eridani has an apparent magnitude of 5.53 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 -1.25 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.38. 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 22 Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.41 which gave the calculated distance to 22 Eridani as 739.60 light years away from Earth or 226.76 parsecs. It would take a spaceship travelling at the speed of light, 739.60 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 6.57 which put 22 Eridani at a distance of 496.44 light years or 152.21 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 7,507.00 Parsecs or 24,485.08 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 22 Eridani

The star is a rotating Alpha2 Canum Venaticorum 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. 22 Eridani brightness ranges from a magnitude of 5.511 to a magnitude of 5.471 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 3.9 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.

22 Eridani Facts

Alternative Names

Traditional/Proper Name22 Eridani
Flamsteed Name22 Eridani
Flamsteed Short Name22 Eri
Short NameFY Eri
Hipparcos Library I.D.17167
Bonner DurchmusterungBD-05 715
Gould I.D.115
Henry Draper Designation22920

Visual Facts

Star Typegiant star
Absolute Magnitude-1.25 / -0.38
Visual / Apparent Magnitude5.53
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)03h 40m 38.33
Declination (Dec.)-05d12`38.5
Galactic Latitude-44.18 degrees
Galactic Longitude192.10 degrees
1997 Distance from Earth4.41 Parallax (milliarcseconds)
 739.60 Light Years
 226.76 Parsecs
2007 Revised Distance from Earth6.57 Parallax (milliarcseconds)
 496.44 Light Years
 152.21 Parsecs
Galacto-Centric Distance24,485.08 Light Years / 7,507.00 Parsecs
Proper Motion Dec.-5.19 ± 0.31 milliarcseconds/year
Proper Motion RA.1.09 ± 0.47 milliarcseconds/year
B-V Index-0.14
Radial Velocity17.20 ± 0.70 km/s
Iron Abundance0.30 ± 9.99 Fe/H
Spectral TypeB9IIIp Si
Colour(B) blue

Variable Star Details

Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venaticorum
Mean Variability Period in Days3.947
Variable Magnitude Range (Brighter - Dimmer)5.471 - 5.511

Estimated Facts

Calculated Effective Temperature13,196 Kelvin

Sources and Links

SIMBAD SourceLink

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