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108 Aquarii, HD223640, HIP117629, HR9031

108 Aquarii is a blue rotating star that can be located in the constellation of Aquarius. 108 Aquarii is the brightest star in Aquarius 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 Id of the star in the Yale Bright Star Catalogue is HR9031. HIP117629 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD223640. The Id of the star in the Gould Star Catalogue is 270. 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.

108 Aquarii has alternative name(s), ET Aqr.

Location of 108 Aquarii

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 108 Aquarii, the location is 23h 51m 21.32 and -18d 54` 33.0 .

Proper Motion of 108 Aquarii

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 -4.27 ± 0.23 miliarcseconds/year towards the north and 26.82 ± 0.31 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 108 Aquarii

108 Aquarii has a spectral type of Ap Si. This means the star is a blue star. The star is 7387.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24093.6862212800000000s. The star has a B-V Colour Index of -0.12 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 14,942 Kelvin.

108 Aquarii Radius has been calculated as being 1.27 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 884,236.43.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.26. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

108 Aquarii Apparent and Absolute Magnitudes

108 Aquarii has an apparent magnitude of 5.17 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 0.20 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.22. 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 108 Aquarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 10.16 which gave the calculated distance to 108 Aquarii as 321.03 light years away from Earth or 98.43 parsecs. It would take a spaceship travelling at the speed of light, 321.03 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 10.23 which put 108 Aquarii at a distance of 318.83 light years or 97.75 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 7,387.00 Parsecs or 24,093.69 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of 108 Aquarii

The star is a rotating Alpha2 Canum Venaticorum 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. 108 Aquarii brightness ranges from a magnitude of 5.162 to a magnitude of 5.122 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 3.7 days (variability).

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.

108 Aquarii Facts

Alternative Names

Traditional/Proper Name108 Aquarii
Flamsteed Name108 Aquarii
Flamsteed Short Name108 Aqr
Short NameET Aqr
Hipparcos Library I.D.117629
Yale Bright Star Catalogue (HR) Id9031
Bonner DurchmusterungBD-19 6522
Gould I.D.270
Henry Draper Designation223640

Visual Facts

Star Type star
Absolute Magnitude0.20 / 0.22
Visual / Apparent Magnitude5.17
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)23h 51m 21.32
Declination (Dec.)-18d 54` 33.0
Galactic Latitude-73.94 degrees
Galactic Longitude60.54 degrees
1997 Distance from Earth10.16 Parallax (milliarcseconds)
 321.03 Light Years
 98.43 Parsecs
2007 Revised Distance from Earth10.23 Parallax (milliarcseconds)
 318.83 Light Years
 97.75 Parsecs
Galacto-Centric Distance24,093.69 Light Years / 7,387.00 Parsecs
Proper Motion Dec.-4.27 ± 0.23 milliarcseconds/year
Proper Motion RA.26.82 ± 0.31 milliarcseconds/year
B-V Index-0.12
Radial Velocity12.70 ± 2.80 km/s
Spectral TypeAp Si
Colour(A) blue

Variable Star Details

Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venaticorum
Mean Variability Period in Days3.735
Variable Magnitude Range (Brighter - Dimmer)5.122 - 5.162

Estimated Facts

Calculated Effective Temperature14,942 Kelvin

Sources and Links

SIMBAD SourceLink

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