Universe Guide

108 Aquarii - HD223640 - HIP117629

108 Aquarii is a blue rotating that can be located in the constellation of Aquarius. 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), 108 Aquarii , ET_Aqr, 108 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 -18 d 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 -004.00 ± 000.00 towards the north and 027.00 ± 000.00 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 coloured . 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 has been calculated as 1.29 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 896,537.99.km.

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 0.17 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.17. 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 10.00 which gave the calculated distance to 108 Aquarii as 326.16 light years away from Earth or 100 parsecs. In 2007, Hipparcos data was revised with a new parallax of 10.00 which put 108 Aquarii at a distance of 326.16 light years or 100 parsecs.

It would take a spaceship travelling at the speed of light, 326.16 years using the 1997 distance to get there. We don't have the technology or spaceship that can carry people over that distance yet.

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 5.000 to a magnitude of 5.000 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 4.0 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

108 Aquarii Facts


Traditional Name108 Aquarii
Short NameET Aqr, 108 Aqr
Alternative Name(s)108 Aquarii
Hipparcos Library I.D.117629
Bonner DurchmusterungBD-19 6522
Gould I.D.270
Henry Draper Designation223640
Celestial TypeStar
Absolute Magnitude0.17 / 0.17
Apparent Magnitude5.17
Right Ascension (R.A.)23h 51m 21.32
Declination (Dec.)-18 d 54`33.0
1997 Distance from Earth10.00 Parallax (milliarcseconds)
 326.16 Light Years
 100 Parsecs
2007 Distance from Earth10.00 Parallax (milliarcseconds)
 326.16 Light Years
 100 Parsecs
Proper Motion Dec.-4.00 ± 0.00 milliarcseconds/year
Proper Motion RA.27.00 ± 0.00 milliarcseconds/year
B-V Index-0.12
Spectral TypeAp Si
Colour(A) blue
Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venaticorum
Mean Variability Period in Days4.000
Radius (x the Sun)1.29
Calculated Effective Temperature14,942 Kelvin


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