II Hydrae is a red pulsating giant star that can be located in the constellation of Hydra. HIP57613 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD102620. The Id of the star in the Gould Star Catalogue is 298. Stars in the southern hemisphere are more likely to have a Gould Id than the northern hemisphere. For example, there are no Gould classified stars in Ursa Major. II Hydrae has alternative name(s), II_Hya.
The location of the star in the galaxy 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 star is compared to the celestial equator and is expressed in degrees. For II Hydrae, the location is 11h 48m 45.11 and -26d44`59.1 .
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 -010.36 ± 000.17 towards the north and -034.13 ± 000.27 east if we saw them in the horizon.
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 7.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.
II Hydrae has a spectral type of M4III. This means the star is a red giant star. The star has a B-V Colour Index of 1.59 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,804 Kelvin.
II Hydrae has been calculated as 29.95 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 20,840,775.83.km.
II Hydrae has an apparent magnitude of 5.10 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 -0.72 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.02. 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.84 which gave the calculated distance to II Hydrae as 476.85 light years away from Earth or 146.20 parsecs. It would take a spaceship travelling at the speed of light, 476.85 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 5.98 which put II Hydrae at a distance of 545.42 light years or 167.22 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.
The star is a pulsating Semiregular s, which are giants or supergiants of intermediate and late spectral 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. II Hydrae brightness ranges from a magnitude of 5.000 to a magnitude of 5.000 over its variable period. The smaller the magnitude, the brighter the star.
|Traditional Name||II Hydrae|
|Short Name||II Hya|
|Hipparcos Library I.D.||57613|
|Henry Draper Designation||102620|
|Star Type||giant star|
|Absolute Magnitude||-0.72 / -1.02|
|Right Ascension (R.A.)||11h 48m 45.11|
|1997 Distance from Earth||6.84 Parallax (milliarcseconds)|
|476.85 Light Years|
|2007 Revised Distance from Earth||5.98 Parallax (milliarcseconds)|
|545.42 Light Years|
|Proper Motion Dec.||-10.36 ± 0.17 milliarcseconds/year|
|Proper Motion RA.||-34.13 ± 0.27 milliarcseconds/year|
|Variable Star Class||Pulsating|
|Variable Star Type||Semiregular s, which are giants or supergiants of intermediate and late spectral|
|Radius (x the Sun)||29.95|
|Luminosity (x the Sun)||7.0000000|
|Calculated Effective Temperature||3,804 Kelvin|