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CT Eridani

CT Eridani Facts

  • CT Eridani is a eclipsing variable star that can be located in the constellation of Eridanus. The description is based on the spectral class.
  • CT Eridani is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (F0) 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 1418.10 light years away from us. Distance

CT Eridani's Alternative Names

HIP20943 is the reference name for the star in the Hipparcos Star Catalogue.

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

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

Location of CT 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 CT Eridani, the location is 04h 29m 24.79 and -33° 34` 34.3 .

Radial Velocity and Proper Motion of CT 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 -0.47 ± 1.41 milliarcseconds/year towards the north and 8.86 ± 1.69 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 3.40000 km/s with an error of about 11.10 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 CT Eridani

CT Eridani Temperature and Colour

Based on the star's spectral type of F0 , CT Eridani's colour and type is yellow to white variable star. Based on the star's spectral, the stars temperature is between 6,000.00 and 7,500.00 degrees kelvin.

CT Eridani Radius

CT Eridani Apparent and Absolute Magnitudes

CT Eridani has an apparent magnitude of 10.07 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 1.63 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.88. 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 CT Eridani

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.05000 which gave the calculated distance to CT Eridani as 1591.04 light years away from Earth or 487.80 parsecs. If you want that in miles, it is about 9,353,128,113,750,050.85, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 2.30000 which put CT Eridani at a distance of 1418.10 light years or 434.78 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 89,679,187.57 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.

Travel Time to CT 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)
Walking4237,750,360,396.23
Car1207,925,012,013.21
Airbus A3807361,292,121,523.89
Speed of Sound (Mach 1)767.2691,239,462,876.23
Concorde (Mach 2)1,534.54619,730,630.41
New Horizons Probe33,00028,818,225.50
Speed of Light670,616,629.001,418.10

Variable Type of CT Eridani

The star is a eclipsing W Ursae Majoris/Cont 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. CT Eridani brightness ranges from a magnitude of 10.551 to a magnitude of 10.062 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.6 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 CT Eridani Facts and Figures

Visual Facts


Primary / Proper / Traditional NameCT Eridani
Alternative NamesCT Eri, HIP 20943, CT Eri
Spectral TypeF0
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeVariable Star
ColourYellow - White
GalaxyMilky Way
ConstellationEridanus
Absolute Magnitude 1.63 / 1.88
Visual / Apparent Magnitude10.07
Naked Eye VisibleRequires a 4.5 - 6 Inch Telescope - Magnitudes
Right Ascension (R.A.)04h 29m 24.79
Declination (Dec.)-33° 34` 34.3
Galactic Latitude-43.06542912 degrees
Galactic Longitude234.75284394 degrees
1997 Distance from Earth2.05000 Parallax (milliarcseconds)
 1591.04 Light Years
 487.80 Parsecs
2007 Distance from Earth2.30000 Parallax (milliarcseconds)
 1418.10 Light Years
 434.78 Parsecs
 89,679,187.57 Astronomical Units
Proper Motion Dec.-0.47000 ± 1.41000 milliarcseconds/year
Proper Motion RA.8.86000 ± 1.69000 milliarcseconds/year
B-V Index-99
Radial Velocity3.40000 ± 11.10 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing
Variable Star TypeW Ursae Majoris/Cont
Mean Variability Period in Days0.634
Variable Magnitude Range (Brighter - Dimmer)10.062 - 10.551

Estimated Calculated Facts


Calculated Temperature Range6,000.00 - 7,500.00

Sources and Links


SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
-33 1755.2A10.00000-21.000006.00000F0Yellow/White
B12.600001918

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