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Sadira, Epsilon Eridani, 18 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. Sadira 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.

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. The Gliese ID of the star is Gliese GL144. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names. 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 19.49 ± 0.11 miliarcseconds/year towards the north and -975.17 ± 0.16 miliarcseconds/year 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 is 7402.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24142.6107228800000000s. 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 Radius has been calculated as being 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. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 0.70. 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 -0.06 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

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.

The star's Galacto-Centric Distance is 7,402.00 Parsecs or 24,142.61 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

Sadira Facts

Alternative Names

Traditional/Proper NameSadira
Flamsteed Name18 Eridani
Flamsteed Short Name18 Eri
Bayer DesignationEpsilon Eridani
Hipparcos Library I.D.16537
Yale Bright Star Catalogue (HR) Id1084
Bonner DurchmusterungBD-09 697
Gould I.D.101
Gliese ID144
Henry Draper Designation22049

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude6.18 / 6.18
Visual / Apparent Magnitude3.72
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)03h 32m 56.42
Declination (Dec.)-09d27`29.9
Galactic Latitude-48.05 degrees
Galactic Longitude195.85 degrees
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
Galacto-Centric Distance24,142.61 Light Years / 7,402.00 Parsecs
Proper Motion Dec.19.49 ± 0.11 milliarcseconds/year
Proper Motion RA.-975.17 ± 0.16 milliarcseconds/year
B-V Index0.88
Radial Velocity16.43 ± 0.09 km/s
Iron Abundance-0.06 ± 9.99 Fe/H
Spectral TypeK2V
Colour(K) Orange to Red

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count2

Estimated Facts

Calculated Effective Temperature5,096 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Sadira in Eridanus


Sadira (Epsilon Eridani) Location in Eridanus

The map was generated using Night Vision, an awesome free application by Brian Simpson.


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

Sadira Solar System


This is a N.A.S.A. impression of what the solar system might look like. If the star is not on display, its because its so small compared to the orbits of the outer planets. The green area denotes the habital zone which if the planet is within that area, life could exist. The habital zone might not appear on the picture because its outside the area for the picture. Our planets show the orbit of the planet if its was in our solar system. For more information about the planet and other exoplanetary stuff, visit N.A.S.A.

Sadira Solar System

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