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Chi Aurigae (25 Aurigae)

Primary Facts on Chi Aurigae

Chi Aurigae's Alternative Names

Chi Aurigae (Chi Aur) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR1843. HIP25984 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD36371.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 25 Aurigae with it shortened to 25 Aur.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+32 1024.

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

Location of Chi Aurigae

The location of the supergiant 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 object is compared to the celestial equator and is expressed in degrees. For Chi Aurigae, the location is 05h 32m 43.67 and +32° 11` 31.3 .

Radial Velocity and Proper Motion of Chi Aurigae

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 -4.33 ± 0.15 miliarcseconds/year towards the north and -1.52 ± 0.23 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 the Sun is -0.20 km/s with an error of about 7.40 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties (Colour, Temperature) of Chi Aurigae

Chi Aurigae has a spectral type of B5Iab. This means the star is a blue supergiant star. The star has a B-V Colour Index of 0.28 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,889 Kelvin.

Chi Aurigae Radius has been calculated as being 93.46 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 65,032,748.31.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 7494.47. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Chi Aurigae Apparent and Absolute Magnitudes

Chi Aurigae has an apparent magnitude of 4.71 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 -5.77 If you used the 2007 Parallax value, you would get an absolute magnitude of -15.29. 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 Aurigae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.80 which gave the calculated distance to Chi Aurigae as 4077.04 light years away from Earth or 1250 parsecs. It would take a spaceship travelling at the speed of light, 4077.04 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 0.01 which put Chi Aurigae at a distance of 326163.34 light years or 100000 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.

Using the 2007 distance, the star is roughly 20,626,336,898.40 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. Chi Aurigae brightness ranges from a magnitude of 4.820 to a magnitude of 4.769 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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Additional Chi Aurigae Facts and Figures

Visual Facts


Primary / Proper / Traditional Name Chi Aurigae
Alternative NamesChi Aur, HD 36371, HIP 25984, HR 1843, 25 Aurigae, 25 Aur, BD+32 1024
Spectral TypeB5Iab
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type very luminous Supergiant Star
Colour blue
GalaxyMilky Way
ConstellationAuriga
Absolute Magnitude -5.77 / -15.29
Visual / Apparent Magnitude4.71
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)05h 32m 43.67
Declination (Dec.)+32° 11` 31.3
Galactic Latitude-0.61 degrees
Galactic Longitude175.77 degrees
1997 Distance from Earth0.80 Parallax (milliarcseconds)
 4077.04 Light Years
 1250 Parsecs
2007 Distance from Earth0.01 Parallax (milliarcseconds)
 326163.34 Light Years
 100000 Parsecs
 20,626,336,898.40 Astronomical Units
Proper Motion Dec.-4.33 ± 0.15 milliarcseconds/year
Proper Motion RA.-1.52 ± 0.23 milliarcseconds/year
B-V Index0.28
Radial Velocity-0.20 ± 7.40 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Mean Variability Period in Days0.045
Variable Magnitude Range (Brighter - Dimmer)4.769 - 4.820

Estimated Calculated Facts


Radius (x the Sun)7,494.47
Effective Temperature6,889 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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