Universe Guide

EI Eridani

EI Eridani Facts

  • EI Eridani is a eclipsing binary sys variable star that can be located in the constellation of Eridanus. The description is based on the spectral class.
  • EI Eridani is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (G0) of the star, the star's colour is yellow .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • The star has an estimated age of 7.50 Billion of Years but could be as young as 6.50 to 8.70 according to Hipparcos.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 165.73 light years away from us. Distance

EI Eridani's Alternative Names

HIP19431 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD26337.

EI Eridani has alternative name(s) :- , EI Eri.

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-08 801.

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

Location of EI Eridani

The location of the variable 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 EI Eridani, the location is 04h 09m 40.87 and -07° 53` 35.2 .

Radial Velocity and Proper Motion of EI Eridani

Proper Motion

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 104.38 ± 1.10 milliarcseconds/year towards the north and 34.67 ± 1.06 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 17.60000 km/s with an error of about 0.20 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 of EI Eridani

EI Eridani Temperature and Colour

Based on the star's spectral type of G0 , EI Eridani's colour and type is yellow variable star. The star has a B-V Colour Index of 0.71 which means the star's temperature is about 5,626 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

EI 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 3.82 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

EI Eridani Radius

EI Eridani estimated radius has been calculated as being 2.17 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,509,927.77.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 1.9609638553343954717172008091. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

EI Eridani Iron Abundance

EI Eridani Iron Abundance is -0.36 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context. The value comes from the Hipparcos Extended Catalog.

EI Eridani Estimated Age

The stars age according to Hipparcos data files put the star at an age of about 7.50 Billion years old but could be between 6.50 and 8.70 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

EI Eridani Apparent and Absolute Magnitudes

EI Eridani has an apparent magnitude of 7.03 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 3.28 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.50. 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 EI Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 17.80000 which gave the calculated distance to EI Eridani as 183.24 light years away from Earth or 56.18 parsecs. If you want that in miles, it is about 1,077,199,313,382,164.70, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 19.68000 which put EI Eridani at a distance of 165.73 light years or 50.81 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 10,480,241.78 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. The star's Galacto-Centric Distance is 7,437.00 Parsecs or 24,256.77 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to EI Eridani

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A380736151,007,192.83
Speed of Sound (Mach 1)767.269144,853,100.96
Concorde (Mach 2)1,534.5472,426,456.09
New Horizons Probe33,0003,367,918.00
Speed of Light670,616,629.00165.73

Variable Type of EI Eridani

The star is a eclipsing binary sys RS 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. EI Eridani brightness ranges from a magnitude of 7.236 to a magnitude of 7.140 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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 EI Eridani Facts and Figures

Visual Facts

Primary / Proper / Traditional NameEI Eridani
Alternative NamesHD 26337, HIP 19431, BD-08 801, EI Eri
Spectral TypeG0
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
GalaxyMilky Way
Age7.50 Billion Years Old
Age Range6.50 - 8.70 Billion Years Old
Absolute Magnitude 3.28 / 3.50
Visual / Apparent Magnitude7.03
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)04h 09m 40.87
Declination (Dec.)-07° 53` 35.2
Galactic Latitude-39.37781347 degrees
Galactic Longitude200.17014556 degrees
1997 Distance from Earth17.80000 Parallax (milliarcseconds)
 183.24 Light Years
 56.18 Parsecs
2007 Distance from Earth19.68000 Parallax (milliarcseconds)
 165.73 Light Years
 50.81 Parsecs
 10,480,241.78 Astronomical Units
Galacto-Centric Distance24,256.77 Light Years / 7,437.00 Parsecs
Proper Motion Dec.104.38000 ± 1.10000 milliarcseconds/year
Proper Motion RA.34.67000 ± 1.06000 milliarcseconds/year
B-V Index0.71
Radial Velocity17.60000 ± 0.20 km/s
Iron Abundance-0.3600 ± 9.99 Fe/H
Semi-Major Axis9473.0000000
Stellar Luminosity (Lsun)3.8200000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEclipsing binary sys
Variable Star TypeRS Canum Venaticorum
Mean Variability Period in Days0.081
Variable Magnitude Range (Brighter - Dimmer)7.140 - 7.236

Estimated Calculated Facts

Radius (x the Sun)1.96
Effective Temperature5,626 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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