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CU Hydri

CU Hydri Facts

  • CU Hydri is a pulsating main sequence star that can be located in the constellation of Hydrus. The description is based on the spectral class.
  • CU Hydri is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (G6V) 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.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 675.29 light years away from us. Distance

CU Hydri's Alternative Names

HIP20015 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD27867.

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

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

Location of CU 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 CU Hydri, the location is 04h 17m 35.48 and -71° 58` 39.1 .

Proper Motion of CU 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 -10.83 ± 0.81 milliarcseconds/year towards the north and 26.00 ± 0.89 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 CU Hydri

CU Hydri Colour and Temperature

Based on the star's spectral type of G6V , CU Hydri's colour and type is yellow main sequence star. The star has a B-V Colour Index of 0.96 which means the star's temperature is about 4,927 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

CU 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 9.96 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

CU Hydri Radius

CU Hydri estimated radius has been calculated as being 4.81 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,343,503.59.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 3.8878800174776271654418217226. 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.

CU Hydri Apparent and Absolute Magnitudes

CU Hydri has an apparent magnitude of 9.17 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 2.13 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.59. 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 CU Hydri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.91000 which gave the calculated distance to CU Hydri as 834.18 light years away from Earth or 255.75 parsecs. If you want that in miles, it is about 4,903,831,713,802,303.79, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 4.83000 which put CU Hydri at a distance of 675.29 light years or 207.04 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 42,704,767.91 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 7,361.00 Parsecs or 24,008.88 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 CU Hydri

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)
Walking4113,215,175,849.35
Car1203,773,839,194.98
Airbus A380736615,299,868.75
Speed of Sound (Mach 1)767.269590,224,163.10
Concorde (Mach 2)1,534.54295,111,696.92
New Horizons Probe33,00013,723,051.62
Speed of Light670,616,629.00675.29

Variable Type of CU Hydri

The star is a pulsating Semi-Regular Star w 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. CU Hydri brightness ranges from a magnitude of 9.439 to a magnitude of 9.201 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 15.6 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 CU Hydri Facts and Figures

Visual Facts


Primary / Proper / Traditional NameCU Hydri
Alternative NamesCU Hyi, HD 27867, HIP 20015, CU Hyi
Spectral TypeG6V
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type Main Sequence Dwarf Star
ColourYellow
GalaxyMilky Way
ConstellationHydrus
Absolute Magnitude 2.13 / 2.59
Visual / Apparent Magnitude9.17
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)04h 17m 35.48
Declination (Dec.)-71° 58` 39.1
Galactic Latitude-37.22009022 degrees
Galactic Longitude285.22035807 degrees
1997 Distance from Earth3.91000 Parallax (milliarcseconds)
 834.18 Light Years
 255.75 Parsecs
2007 Distance from Earth4.83000 Parallax (milliarcseconds)
 675.29 Light Years
 207.04 Parsecs
 42,704,767.91 Astronomical Units
Galacto-Centric Distance24,008.88 Light Years / 7,361.00 Parsecs
Proper Motion Dec.-10.83000 ± 0.81000 milliarcseconds/year
Proper Motion RA.26.00000 ± 0.89000 milliarcseconds/year
B-V Index0.96
Stellar Luminosity (Lsun)9.9600000

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star w
Mean Variability Period in Days15.615
Variable Magnitude Range (Brighter - Dimmer)9.201 - 9.439

Estimated Calculated Facts


Radius (x the Sun)3.89
Effective Temperature4,927 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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