Universe Guide


Sadira (Epsilon Eridani) - HD22049 - HIP16537 - HR1084

Sadira (Epsilon Eridani) is a orange to red main sequence dwarf star that can be located in the constellation of Eridanus. Epsilon Eridani is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR1084. HIP16537 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD22049. The Id of the star in the Gould Star Catalogue is 101. 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. Sadira has alternative name(s), 18 Eridani , 18 Eri. Sadira has at least 2 Extrasolar Planets believed to be in orbit around the star.

Whilst Sadira is referenced as being a name for Epsilon Eridani on the net, it would seem its not accepted by the powers that be at IAU which named it Ran, after a Norse God. Ran was a sea Goddess who stirred up the waves and captured sailors with her net. Epsilon Eridani b was named AEgir which is the name of Ran`s husband.

The star is well known for having a number of planets as well as an asteroid belt. The star is relatively close to us compared to other stars in the milky way

Location of Sadira

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 Sadira, the location is 03h 32m 56.42 and -09d27`29.9 .

Proper Motion of Sadira

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 019.49 ± 000.11 towards the north and -975.17 ± 000.16 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Sadira

Sadira has a spectral type of K2V. This means the star is a orange to red main sequence dwarf star. The star has a B-V Colour Index of 0.88 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,096 Kelvin.

Sadira has been calculated as 0.70 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 484,025.59.km.

Sadira Apparent and Absolute Magnitudes

Sadira has an apparent magnitude of 3.72 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 6.18 If you used the 2007 Parallax value, you would get an absolute magnitude of 6.18. 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 Sadira

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 310.75 which gave the calculated distance to Sadira as 10.50 light years away from Earth or 3.22 parsecs. It would take a spaceship travelling at the speed of light, 10.50 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 310.94 which put Sadira at a distance of 10.49 light years or 3.22 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.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Sadira Facts

Alternative Names

Traditional NameSadira
Short Name18 Eri
Bayer DesignationEpsilon Eridani
Alternative Name(s)18 Eridani
Hipparcos Library I.D.16537
Yale Bright Star Catalogue (HR) Id1084
Bonner DurchmusterungBD-09 697
Gould I.D.101
Henry Draper Designation22049

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude6.18 / 6.18
Apparent Magnitude3.72
Right Ascension (R.A.)03h 32m 56.42
Declination (Dec.)-09d27`29.9
1997 Distance from Earth310.75 Parallax (milliarcseconds)
 10.50 Light Years
 3.22 Parsecs
2007 Revised Distance from Earth310.94 Parallax (milliarcseconds)
 10.49 Light Years
 3.22 Parsecs
Proper Motion Dec.19.49 ± 0.11 milliarcseconds/year
Proper Motion RA.-975.17 ± 0.16 milliarcseconds/year
B-V Index0.88
Spectral TypeK2V
Colour(K) Orange to Red

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count2

Estimated Facts

Radius (x the Sun)0.70
Calculated Effective Temperature5,096 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

List of Extrasolar Planets orbiting Sadira

NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronInclination
Eps Eridani BConfirmed3.092502.0000.70220003.3947.00030.000
Eps Eridani CUnconfirmed0.1102270.0000.340

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