Universe Guide

EQ Eridani

EQ Eridani Facts

  • EQ Eridani is a pulsating giant star that can be located in the constellation of Eridanus. The description is based on the spectral class.
  • EQ Eridani is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (F2III) of the star, the star's colour is yellow to white .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 549.10 light years away from us. Distance

EQ Eridani's Alternative Names

HIP20979 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD28665.

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

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

Location of EQ Eridani

The location of the giant 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 EQ Eridani, the location is 04h 29m 57.61 and -28° 52` 46.7 .

Proper Motion of EQ 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 6.19 ± 0.64 milliarcseconds/year towards the north and 11.05 ± 0.80 milliarcseconds/year east if we saw them in the horizon. . 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 EQ Eridani

EQ Eridani Colour and Temperature

Based on the star's spectral type of F2III , EQ Eridani's colour and type is yellow to white giant star. The star has a B-V Colour Index of 0.29 which means the star's temperature is about 7,270 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

EQ 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 18.52 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

EQ Eridani Radius

EQ Eridani estimated radius has been calculated as being 3.15 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,189,301.91.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 2.8432763482814139235318206640. 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.

EQ Eridani Apparent and Absolute Magnitudes

EQ Eridani has an apparent magnitude of 7.71 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 1.36 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.58. 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 EQ Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.37000 which gave the calculated distance to EQ Eridani as 607.38 light years away from Earth or 186.22 parsecs. If you want that in miles, it is about 3,570,559,479,164,261.04, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 5.94000 which put EQ Eridani at a distance of 549.10 light years or 168.35 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 34,724,438.17 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 7,482.00 Parsecs or 24,403.54 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 EQ 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 A380736500,320,096.45
Speed of Sound (Mach 1)767.269479,930,234.36
Concorde (Mach 2)1,534.54239,964,804.43
New Horizons Probe33,00011,158,654.27
Speed of Light670,616,629.00549.10

Variable Type of EQ Eridani

The star is a pulsating Delta Scuti 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. EQ Eridani brightness ranges from a magnitude of 7.857 to a magnitude of 7.738 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 EQ Eridani Facts and Figures

Visual Facts

Primary / Proper / Traditional NameEQ Eridani
Alternative NamesHD 28665, HIP 20979, EQ Eri
Spectral TypeF2III
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeGiant Star
ColourYellow - White
GalaxyMilky Way
Absolute Magnitude 1.36 / 1.58
Visual / Apparent Magnitude7.71
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)04h 29m 57.61
Declination (Dec.)-28° 52` 46.7
Galactic Latitude-42.16944488 degrees
Galactic Longitude228.48425705 degrees
1997 Distance from Earth5.37000 Parallax (milliarcseconds)
 607.38 Light Years
 186.22 Parsecs
2007 Distance from Earth5.94000 Parallax (milliarcseconds)
 549.10 Light Years
 168.35 Parsecs
 34,724,438.17 Astronomical Units
Galacto-Centric Distance24,403.54 Light Years / 7,482.00 Parsecs
Proper Motion Dec.6.19000 ± 0.64000 milliarcseconds/year
Proper Motion RA.11.05000 ± 0.80000 milliarcseconds/year
B-V Index0.29
Stellar Luminosity (Lsun)18.5200000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Scuti
Mean Variability Period in Days0.093
Variable Magnitude Range (Brighter - Dimmer)7.738 - 7.857

Estimated Calculated Facts

Radius (x the Sun)2.84
Effective Temperature7,270 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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