Universe Guide


Iota Hydri, HD21024, HIP15201

Iota Hydri is a blue to white giant star that can be located in the constellation of Hydrus. Iota Hydri is the brightest star in Hydrus 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. The star has an estimated age of 1.80 Billion of Years but could be as young as 1.60 to 2.10 according to Hipparcos.

Iota Hydri is the Bayer Classification for the star. HIP15201 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD21024.

Location of Iota Hydri

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 Iota Hydri, the location is 03h 15m 57.36 and -77d23`19.0 .

Proper Motion of Iota 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 62.10 ± 0.23 miliarcseconds/year towards the north and 113.72 ± 0.24 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Age, Radius) of Iota Hydri

Iota Hydri has a spectral type of F4III. This means the star is a blue to white giant star. The star is 7390.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24103.4711216000000000s. The star has a B-V Colour Index of 0.43 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,590 Kelvin.

Iota Hydri Radius has been calculated as being 1.66 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,157,672.93.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.68. 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 0.05 with an error value of 0.08 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 1.80 Billion years old but could be between 1.60 and 2.10 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Iota Hydri Apparent and Absolute Magnitudes

Iota Hydri has an apparent magnitude of 5.51 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 3.17 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.15. 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 Iota Hydri

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 34.02 which gave the calculated distance to Iota Hydri as 95.87 light years away from Earth or 29.39 parsecs. It would take a spaceship travelling at the speed of light, 95.87 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 33.66 which put Iota Hydri at a distance of 96.90 light years or 29.71 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 7,390.00 Parsecs or 24,103.47 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.

Iota Hydri Facts

Alternative Names

Bayer DesignationIota Hydri
Hipparcos Library I.D.15201
Henry Draper Designation21024

Visual Facts

Star Typegiant star
Age1.80 Billion Years Old
Age Range1.60 - 2.10 Billion Years Old
Absolute Magnitude3.17 / 3.15
Visual / Apparent Magnitude5.51
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)03h 15m 57.36
Declination (Dec.)-77d23`19.0
Galactic Latitude-37.01 degrees
Galactic Longitude293.65 degrees
1997 Distance from Earth34.02 Parallax (milliarcseconds)
 95.87 Light Years
 29.39 Parsecs
2007 Revised Distance from Earth33.66 Parallax (milliarcseconds)
 96.90 Light Years
 29.71 Parsecs
Galacto-Centric Distance24,103.47 Light Years / 7,390.00 Parsecs
Proper Motion Dec.62.10 ± 0.23 milliarcseconds/year
Proper Motion RA.113.72 ± 0.24 milliarcseconds/year
B-V Index0.43
Radial Velocity19.40 ± 2.90 km/s
Iron Abundance0.05 ± 0.08 Fe/H
Spectral TypeF4III
Colour(F) blue to white

Estimated Facts

Calculated Effective Temperature6,590 Kelvin

Sources and Links

SIMBAD SourceLink

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