Universe Guide

108 Aquarii

108 Aquarii Facts

  • 108 Aquarii is a rotating variable star that can be located in the constellation of Aquarius. The description is based on the spectral class.
  • 108 Aquarii is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (Ap Si) of the star, the star's colour is blue - white .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 318.83 light years away from us. Distance

108 Aquarii's Alternative Names

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.

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

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 108 Aquarii. The Flamsteed name can be shortened to 108 Aqr.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 270 G. Aquarii. There are no stars with a Gould designation in Ursa Major for example.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD-19 6522.

More details on objects' alternative names can be found at Star Names .

Location of 108 Aquarii

The location of the variable star in the night sky 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 object is compared to the celestial equator and is expressed in degrees. For 108 Aquarii, the location is 23h 51m 21.32 and -18° 54` 33.0 .

Radial Velocity and Proper Motion of 108 Aquarii

Proper Motion

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 milliarcseconds/year towards the north and 26.82 ± 0.31 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 12.70000 km/s with an error of about 2.80 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of 108 Aquarii

108 Aquarii Colour and Temperature

Based on the star's spectral type of Ap Si , 108 Aquarii's colour and type is blue - white variable star. The star has a B-V Colour Index of -0.12 which means the star's temperature is about 14,942 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

108 Aquarii 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 150.97 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

108 Aquarii Radius

108 Aquarii estimated 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. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.2591683004838248231502269498. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It 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 10.16000 which gave the calculated distance to 108 Aquarii as 321.03 light years away from Earth or 98.43 parsecs. If you want that in miles, it is about 1,887,215,103,553,134.32, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 10.23000 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.

Using the 2007 distance, the star is roughly 20,162,244.32 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. 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*.

Travel Time to 108 Aquarii

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A380736290,506,385.63
Speed of Sound (Mach 1)767.269278,667,194.72
Concorde (Mach 2)1,534.54139,333,415.76
New Horizons Probe33,0006,479,172.72
Speed of Light670,616,629.00318.83

Variable Type of 108 Aquarii

The star is a rotating Alpha2 Canum Venatic 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.

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Additional 108 Aquarii Facts and Figures

Visual Facts

Primary / Proper / Traditional Name108 Aquarii
Alternative NamesI03 Aqr, ET Aqr, ET Aquarii, HD 223640, HIP 117629, HR 9031, 270 G. Aquarii, 108 Aqr, BD-19 6522, ET Aqr
Spectral TypeAp Si
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
GalaxyMilky Way
Absolute Magnitude 0.20 / 0.22
Visual / Apparent Magnitude5.17
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)23h 51m 21.32
Declination (Dec.)-18° 54` 33.0
Galactic Latitude-73.93762326 degrees
Galactic Longitude60.53970424 degrees
1997 Distance from Earth10.16000 Parallax (milliarcseconds)
 321.03 Light Years
 98.43 Parsecs
2007 Distance from Earth10.23000 Parallax (milliarcseconds)
 318.83 Light Years
  97.75 Parsecs
 20,162,244.32 Astronomical Units
Galacto-Centric Distance24,093.69 Light Years / 7,387.00 Parsecs
Proper Motion Dec.-4.27000 ± 0.23000 milliarcseconds/year
Proper Motion RA.26.82000 ± 0.31000 milliarcseconds/year
B-V Index-0.12
Radial Velocity12.70000 ± 2.80 km/s
Semi-Major Axis8200.0000000
Stellar Luminosity (Lsun)150.9700000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

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

Estimated Calculated Facts

Radius (x the Sun)1.26
Effective Temperature14,942 Kelvin

Sources and Links

SIMBAD SourceLink

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