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CP Hydri

CP Hydri Facts

CP Hydri's Alternative Names

HIP13999 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD19733.

CP Hydri has alternative name(s) :- CP Hyi, CP Hyi.

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

Location of CP Hydri

The location of the main sequence 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 CP Hydri, the location is 03h 00m 13.45 and -81° 05` 19.1 .

Proper Motion of CP Hydri

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 62.12 ± 0.55 milliarcseconds/year towards the north and 74.35 ± 0.53 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.

CP Hydri 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 7.88 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Age) of CP Hydri

CP Hydri Colour and Temperature

CP Hydri has a spectral type of F0V. This means the star is a yellow to white main sequence star. The star has a B-V Colour Index of 0.34 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,016 Kelvin.

CP Hydri Radius

Radius has been calculated as being 2.04 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,416,395.44.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 1.95. 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 -0.19 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 1.80 Billion years old but could be between 1.70 and 1.90 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

CP Hydri Apparent and Absolute Magnitudes

CP Hydri has an apparent magnitude of 7.84 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 2.46 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.55. 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 CP Hydri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.38 which gave the calculated distance to CP Hydri as 389.22 light years away from Earth or 119.33 parsecs. It would take a spaceship travelling at the speed of light, 389.22 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 8.74 which put CP Hydri at a distance of 373.18 light years or 114.42 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 23,600,654.68 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 7,358.00 Parsecs or 23,999.10 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of CP Hydri

The star is a eclipsing binary sys W Ursae Majoris 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. CP Hydri brightness ranges from a magnitude of 8.039 to a magnitude of 7.898 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.5 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 CP Hydri Facts and Figures

Visual Facts


Primary / Proper / Traditional NameCP Hydri
Alternative NamesCP Hyi, HD 19733, HIP 13999, CP Hyi
Spectral TypeF0V
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type Main Sequence Dwarf Star
ColourYellow - White
GalaxyMilky Way
ConstellationHydrus
Age1.80 Billion Years Old
Age Range1.70 - 1.90 Billion Years Old
Absolute Magnitude 2.46 / 2.55
Visual / Apparent Magnitude7.84
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)03h 00m 13.45
Declination (Dec.)-81° 05` 19.1
Galactic Latitude-34.55 degrees
Galactic Longitude297.18 degrees
1997 Distance from Earth8.38 Parallax (milliarcseconds)
 389.22 Light Years
 119.33 Parsecs
2007 Distance from Earth8.74 Parallax (milliarcseconds)
 373.18 Light Years
 114.42 Parsecs
 23,600,654.68 Astronomical Units
Galacto-Centric Distance23,999.10 Light Years / 7,358.00 Parsecs
Proper Motion Dec.62.12 ± 0.55 milliarcseconds/year
Proper Motion RA.74.35 ± 0.53 milliarcseconds/year
B-V Index0.34
Iron Abundance-0.19 ± 9.99 Fe/H
Stellar Luminosity (Lsun)7.88

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing binary sys
Variable Star TypeW Ursae Majoris
Mean Variability Period in Days0.479
Variable Magnitude Range (Brighter - Dimmer)7.898 - 8.039

Estimated Calculated Facts


Radius (x the Sun)1.95
Effective Temperature7,016 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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