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VX Sagittarii - HD165674 - HIP88838

VX Sagittarii is a red pulsating giant star that can be located in the constellation of Sagittarius. HIP88838 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD165674. VX Sagittarii has alternative name(s), VX_Sgr.

Although it shares the start of its name with a deadly gas, it is nothing to do with the nerve gas. The VX is probably from the names of the people who first discovered the large pulsating star. It is located towards the Galactic Centre where there are other large stars such as UY Scuti. VX is one of the largest stars to have been discovered, it is probably named after the discoverers. Its been calculated to pulsate between 1,350 to 1,940 times the radius of the Sun. ref: Wiki

Location of VX Sagittarii

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 VX Sagittarii, the location is 18h 08m 04.05 and -22d13`26.6 .

Proper Motion of VX Sagittarii

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 -006.71 ± 001.51 towards the north and 003.20 ± 002.73 east if we saw them in the horizon.

VX Sagittarii 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 5.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of VX Sagittarii

VX Sagittarii has a spectral type of M5/M6III:. This means the star is a red giant star. The star has a B-V Colour Index of 2.77 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 0 Kelvin.

VX Sagittarii Apparent and Absolute Magnitudes

VX Sagittarii has an apparent magnitude of 8.82 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 1.23 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.73. 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 VX Sagittarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.03 which gave the calculated distance to VX Sagittarii as 1076.45 light years away from Earth or 330.03 parsecs. It would take a spaceship travelling at the speed of light, 1076.45 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 3.82 which put VX Sagittarii at a distance of 853.83 light years or 261.78 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.

Variable Type of VX Sagittarii

The star is a pulsating Semiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep) 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. VX Sagittarii brightness ranges from a magnitude of 9.000 to a magnitude of 8.000 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 737.0 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.

VX Sagittarii Facts

Alternative Names

Traditional NameVX Sagittarii
Short NameVX Sgr
Hipparcos Library I.D.88838
Bonner DurchmusterungBD-22 4575
Henry Draper Designation165674

Visual Facts

Star Typegiant star
Absolute Magnitude1.23 / 1.73
Apparent Magnitude8.82
Right Ascension (R.A.)18h 08m 04.05
Declination (Dec.)-22d13`26.6
1997 Distance from Earth3.03 Parallax (milliarcseconds)
 1076.45 Light Years
 330.03 Parsecs
2007 Revised Distance from Earth3.82 Parallax (milliarcseconds)
 853.83 Light Years
 261.78 Parsecs
Proper Motion Dec.-6.71 ± 1.51 milliarcseconds/year
Proper Motion RA.3.20 ± 2.73 milliarcseconds/year
B-V Index2.77
Spectral TypeM5/M6III:
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep)
Mean Variability Period in Days737.000
Variable Magnitude Range (Brighter - Dimmer)8.000 - 9.000

Estimated Facts

Luminosity (x the Sun)5.0000000

Sources and Links

SIMBAD SourceLink

Related Stars

Location of VX Sagittarii in Sagittarius


VX Sagittarii Location in Sagittarius

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


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