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Chi Eridani, HD11937, HIP9007, HR566

Chi Eridani is a white to yellow subgiant star that can be located in the constellation of Eridanus. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Chi Eridani's Alternative Names

Chi Eridani (Chi Eri) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR566. HIP9007 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD11937. The Gliese ID of the star is GL 81A. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

Chi Eridani has alternative name(s) :- , NSV 00671.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 7 G. Eridani. There are no stars with a Gould designation in Ursa Major for example.

More details on star alternative names can be found at Star Names .

Location of Chi Eridani

The location of the star in the night sky 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 Chi Eridani, the location is 01h 55m 56.83 and -51° 36` 34.5 .

Proper Motion of Chi 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 283.46 ± 0.29 miliarcseconds/year towards the north and 680.92 ± 0.38 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is -6.30000 km/s with an error of about 0.70 km/s .

Chi Eridani 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 11.28 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of Chi Eridani

Chi Eridani has a spectral type of G5IV. This means the star is a white to yellow subgiant star. The star is 7,398.00 Parsecs from the Galactic Centre or terms of Light Years is 24,129.56 s. The star has a B-V Colour Index of 0.84 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,188 Kelvin.

Chi Eridani Radius has been calculated as being 3.69 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,566,631.66.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 3.77. 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 -0.07 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Chi Eridani Apparent and Absolute Magnitudes

Chi Eridani has an apparent magnitude of 3.69 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 2.48 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.43. 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 Chi Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 57.19 which gave the calculated distance to Chi Eridani as 57.03 light years away from Earth or 17.49 parsecs. It would take a spaceship travelling at the speed of light, 57.03 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 56.02 which put Chi Eridani at a distance of 58.22 light years or 17.85 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 7,398.00 Parsecs or 24,129.56 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*. Chi Eridani brightness ranges from a magnitude of 3.881 to a magnitude of 3.840 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 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.

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Chi Eridani Facts

Visual Facts

Primary / Proper / Traditional NameChi Eridani
Alternative NamesChi Eri, HD 11937, HIP 9007, HR 566, 7 G. Eridani, Gliese 81A, NSV 00671
Spectral TypeG5IV
Multiple Star SystemYes
Star TypeSubgiant Star
Colour white to yellow
GalaxyMilky Way
Absolute Magnitude2.48 / 2.43
Visual / Apparent Magnitude3.69
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)01h 55m 56.83
Declination (Dec.)-51° 36` 34.5
Galactic Latitude-62.67 degrees
Galactic Longitude280.87 degrees
1997 Distance from Earth57.19 Parallax (milliarcseconds)
 57.03 Light Years
 17.49 Parsecs
2007 Distance from Earth56.02 Parallax (milliarcseconds)
 58.22 Light Years
 17.85 Parsecs
Galacto-Centric Distance24,129.56 Light Years / 7,398.00 Parsecs
Proper Motion Dec.283.46 ± 0.29 milliarcseconds/year
Proper Motion RA.680.92 ± 0.38 milliarcseconds/year
B-V Index0.84
Radial Velocity-6.30 ± 0.70 km/s
Iron Abundance-0.07 ± 9.99 Fe/H
Semi-Major Axis7422.00
Stellar Luminosity (Lsun)11.28

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Mean Variability Period in Days0.040
Variable Magnitude Range (Brighter - Dimmer)3.840 - 3.881

Estimated Facts

Calculated Effective Temperature5,188 Kelvin

Sources and Links

SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.

Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
11937-52 241.4A3.70000676.00000299.00000G5Yellow

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