Universe Guide


Hydrobius, Zeta Hydrae, 16 Hydrae, HD76294, HIP43813

Hydrobius (Zeta Hydrae) is a white to yellow subgiant star that can be located in the constellation of Hydra. Hydrobius is the brightest star in Hydra based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Zeta Hydrae is the Bayer Classification for the star. HIP43813 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD76294. The Id of the star in the Gould Star Catalogue is 77. 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.

Location of Hydrobius

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 Hydrobius, the location is 08h 55m 23.68 and +05d56`43.9 .

Proper Motion of Hydrobius

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 15.46 ± 0.10 miliarcseconds/year towards the north and -100.06 ± 0.18 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Hydrobius

Hydrobius has a spectral type of G8III-IV. This means the star is a white to yellow subgiant star. The star is 7433.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24243.7213595200000000s. The star has a B-V Colour Index of 0.97 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,907 Kelvin.

Hydrobius Radius has been calculated as being 14.23 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 9,902,794.71.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 15.82. 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 -0.08 with an error value of 0.03 Fe/H with the Sun has a value of 1 to put it into context.

Hydrobius Apparent and Absolute Magnitudes

Hydrobius has an apparent magnitude of 3.11 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 -0.21 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.44. 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 Hydrobius

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 21.64 which gave the calculated distance to Hydrobius as 150.72 light years away from Earth or 46.21 parsecs. It would take a spaceship travelling at the speed of light, 150.72 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 19.51 which put Hydrobius at a distance of 167.18 light years or 51.26 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's Galacto-Centric Distance is 7,433.00 Parsecs or 24,243.72 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

Hydrobius Facts

Alternative Names

Traditional/Proper NameHydrobius
Flamsteed Name16 Hydrae
Flamsteed Short Name16 Hya
Bayer DesignationZeta Hydrae
Hipparcos Library I.D.43813
Bonner DurchmusterungBD+06 2060
Gould I.D.77
Henry Draper Designation76294

Visual Facts

Star Typesubgiant star
Absolute Magnitude-0.21 / -0.44
Visual / Apparent Magnitude3.11
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)08h 55m 23.68
Declination (Dec.)+05d56`43.9
Galactic Latitude30.20 degrees
Galactic Longitude222.34 degrees
1997 Distance from Earth21.64 Parallax (milliarcseconds)
 150.72 Light Years
 46.21 Parsecs
2007 Revised Distance from Earth19.51 Parallax (milliarcseconds)
 167.18 Light Years
 51.26 Parsecs
Galacto-Centric Distance24,243.72 Light Years / 7,433.00 Parsecs
Proper Motion Dec.15.46 ± 0.10 milliarcseconds/year
Proper Motion RA.-100.06 ± 0.18 milliarcseconds/year
B-V Index0.97
Radial Velocity22.30 ± 0.30 km/s
Iron Abundance-0.08 ± 0.03 Fe/H
Spectral TypeG8III-IV
Colour(G) White to Yellow

Estimated Facts

Calculated Effective Temperature4,907 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Hydrobius in Hydra

Hydrobius (Zeta Hydrae) Location in Hydra

The map was generated using Night Vision, an awesome free application by Brian Simpson.

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