Universe Guide


Head of Hydrus (Alpha Hydri) - HD12311 - HIP9236

Head of Hydrus (Alpha Hydri) is a blue to white main sequence dwarf star that can be located in the constellation of Hydrus. Alpha Hydri is the Bayer Classification for the star. HIP9236 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD12311.

Location of Head of Hydrus

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 Head of Hydrus, the location is 01h 58m 45.87 and -61d34`11.7 .

Proper Motion of Head of Hydrus

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 26.77 ± 0.38 miliarcseconds/year towards the north and 263.66 ± 0.44 miliarcseconds/year east if we saw them in the horizon.

Head of Hydrus 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 5.0000000 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.

Physical Properties (Colour, Temperature, Radius) of Head of Hydrus

Head of Hydrus has a spectral type of F0V. This means the star is a blue to white main sequence dwarf star. The star has a B-V Colour Index of 0.29 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,270 Kelvin.

Head of Hydrus has been calculated as 3.45 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,400,532.67.km.

Head of Hydrus Apparent and Absolute Magnitudes

Head of Hydrus has an apparent magnitude of 2.86 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 1.16 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.15. 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 Head of Hydrus

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 45.74 which gave the calculated distance to Head of Hydrus as 71.31 light years away from Earth or 21.86 parsecs. It would take a spaceship travelling at the speed of light, 71.31 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 45.43 which put Head of Hydrus at a distance of 71.79 light years or 22.01 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.

Meteor Showers Radiating from near Head of Hydrus

The Alpha Hydrids Meteor Shower radiants from a point near this star. The meteor shower runs typically between 15-30 Jan with a peak date of 20/21 Jan. The speed of a meteor in the shower is 43 Km/s.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Head of Hydrus Facts

Alternative Names

Traditional/Proper NameHead of Hydrus
Bayer DesignationAlpha Hydri
Hipparcos Library I.D.9236
Henry Draper Designation12311

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude1.16 / 1.15
Apparent Magnitude2.86
Right Ascension (R.A.)01h 58m 45.87
Declination (Dec.)-61d34`11.7
1997 Distance from Earth45.74 Parallax (milliarcseconds)
 71.31 Light Years
 21.86 Parsecs
2007 Revised Distance from Earth45.43 Parallax (milliarcseconds)
 71.79 Light Years
 22.01 Parsecs
Proper Motion Dec.26.77 ± 0.38 milliarcseconds/year
Proper Motion RA.263.66 ± 0.44 milliarcseconds/year
B-V Index0.29
Semi-Major Axis21.66
Orbital Period (Days)605.96
Argument Of Periastron233.96
Spectral TypeF0V
Colour(F) blue to white

Estimated Facts

Radius (x the Sun)3.45
Luminosity (x the Sun)5.0000000
Calculated Effective Temperature7,270 Kelvin

Sources and Links

SIMBAD SourceLink

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