Universe Guide

GK Hydrae

GK Hydrae Facts

GK Hydrae's Alternative Names

HIP41751 is the reference name for the star in the Hipparcos Star Catalogue.

GK Hydrae has alternative name(s) :- GK Hya, GK Hya.

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+02 1993.

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

Location of GK Hydrae

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 GK Hydrae, the location is 08h 30m 49.33 and +02° 16` 26.5 .

Radial Velocity and Proper Motion of GK Hydrae

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 9.85 ± 0.76 milliarcseconds/year towards the north and -46.78 ± 1.45 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 32.00 km/s with an error of about 2.00 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 (Colour, Temperature) of GK Hydrae

GK Hydrae Colour and Temperature

GK Hydrae has a spectral type of G4V. This means the star is a yellow main sequence star. The star has a B-V Colour Index of 0.72 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,503 Kelvin.

GK Hydrae Radius

Radius has been calculated as being 3.40 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,366,820.07.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 3.96. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

GK Hydrae Apparent and Absolute Magnitudes

GK Hydrae has an apparent magnitude of 9.33 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 2.40 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.07. 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 GK Hydrae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.11 which gave the calculated distance to GK Hydrae as 793.58 light years away from Earth or 243.31 parsecs. If you want that in miles, it is 5,416,389,060,090,173.53.

In 2007, Hipparcos data was revised with a new parallax of 3.54 which put GK Hydrae at a distance of 921.37 light years or 282.49 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 58,267,339.10 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.

Time to Travel to GK Hydrae

A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

If you were to drive there at about 120 m.p.h. in a car with an infinity engine so you didn't have to pull over for petrol, it would take you 38,876,329,363,758.68 hours or 4,437,937,141.98 years.

At the time of writing, the fastest probe so far created is the New Horizon probe which is travelling at a speed of 33,000 m.p.h. If the probe was travelling to GK Hydrae then it would take 141,368,470,413.67 hours / 16,137,953.24 years to get there. Speed Ref: N.A.S.A.

It would to take a spaceship journey travelling at the speed of light, 793.58 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

Variable Type of GK Hydrae

The star is a eclipsing Beta Persei (Algol)/ 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. GK Hydrae brightness ranges from a magnitude of 9.950 to a magnitude of 9.360 over its variable period. The smaller the magnitude, the brighter the star.

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 GK Hydrae Facts and Figures

Visual Facts

Primary / Proper / Traditional NameGK Hydrae
Alternative NamesGK Hya, HIP 41751, BD+02 1993, GK Hya
Spectral TypeG4V
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type Main Sequence Dwarf Star
GalaxyMilky Way
Absolute Magnitude 2.40 / 2.07
Visual / Apparent Magnitude9.33
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)08h 30m 49.33
Declination (Dec.)+02° 16` 26.5
Galactic Latitude23.06 degrees
Galactic Longitude222.70 degrees
1997 Distance from Earth4.11 Parallax (milliarcseconds)
 793.58 Light Years
 243.31 Parsecs
2007 Distance from Earth3.54 Parallax (milliarcseconds)
 921.37 Light Years
 282.49 Parsecs
 58,267,339.10 Astronomical Units
Proper Motion Dec.9.85 ± 0.76 milliarcseconds/year
Proper Motion RA.-46.78 ± 1.45 milliarcseconds/year
B-V Index0.72
Radial Velocity32.00 ± 2.00 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEclipsing
Variable Star TypeBeta Persei (Algol)/
Variable Magnitude Range (Brighter - Dimmer)9.360 - 9.950

Estimated Calculated Facts

Radius (x the Sun)3.96
Effective Temperature5,503 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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