Universe Guide

VX Sagittarii (Supergiant Star) Star Facts

VX Sagittarii Facts

Information on VX Sagittarii

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

VX Sagittarii's Alternative Names

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, VX Sgr.

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-22 4575.

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

Location of VX Sagittarii

The location of the giant 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 VX Sagittarii, the location is 18h 08m 04.05 and -22° 13` 26.6 .

Radial Velocity and Proper Motion of VX Sagittarii

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 -6.71 ± 1.51 milliarcseconds/year towards the north and 3.20 ± 2.73 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 3.00 km/s with an error of about 4.20 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 (Colour, Temperature, Radius) of VX Sagittarii

VX Sagittarii Colour and Temperature

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 Radius

VX Sagittarii has been calculated as 1,120.00 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 779,296,000.00.km. If you need the diameter of the star, you just need to multiple the radius by 2.

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.

Using the 2007 distance, the star is roughly 53,995,624.73 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.

Variable Type of VX Sagittarii

The star is a pulsating Semiregular late- (M 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 9.349 to a magnitude of 7.859 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 Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

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Additional VX Sagittarii Facts and Figures

Visual Facts

Primary / Proper / Traditional NameVX Sagittarii
Alternative NamesVX Sgr, HD 165674, HIP 88838, BD-22 4575, VX Sgr
Spectral TypeM5/M6III:
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude 1.23 / 1.73
Visual / Apparent Magnitude8.82
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)18h 08m 04.05
Declination (Dec.)-22° 13` 26.6
Galactic Latitude-1.00 degrees
Galactic Longitude8.34 degrees
1997 Distance from Earth3.03 Parallax (milliarcseconds)
 1076.45 Light Years
 330.03 Parsecs
2007 Distance from Earth3.82 Parallax (milliarcseconds)
 853.83 Light Years
 261.78 Parsecs
 53,995,624.73 Astronomical Units
Proper Motion Dec.-6.71 ± 1.51 milliarcseconds/year
Proper Motion RA.3.20 ± 2.73 milliarcseconds/year
B-V Index2.77
Radial Velocity3.00 ± 4.20 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M
Mean Variability Period in Days737.000
Variable Magnitude Range (Brighter - Dimmer)7.859 - 9.349

Estimated Calculated Facts

Radius (x the Sun)1,120.00 - 1,550.00

Sources and Links

SIMBAD SourceLink

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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