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V3879 Sagittarii, HD172816, HIP91781

V3879 Sagittarii is a red pulsating star that can be located in the constellation of Sagittarius. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

HIP91781 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD172816. The Id of the star in the Gould Star Catalogue is 89. 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.

V3879 Sagittarii has alternative name(s), V3879 Sgr.

Location of V3879 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 V3879 Sagittarii, the location is 18h 42m 55.11 and -19d 17` 02.9 .

Proper Motion of V3879 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 -34.46 ± 0.25 miliarcseconds/year towards the north and -10.29 ± 0.44 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is -32.40000 km/s with an error of about 0.60 km/s .

V3879 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 7.0000000 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 V3879 Sagittarii

V3879 Sagittarii has a spectral type of M4III. This means the star is a red star. The star is 7109.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23186.9521249600000000s. The star has a B-V Colour Index of 1.59 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,804 Kelvin.

V3879 Sagittarii Radius has been calculated as being 43.90 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 30,543,727.11.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 36.34. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.44 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

V3879 Sagittarii Apparent and Absolute Magnitudes

V3879 Sagittarii has an apparent magnitude of 6.32 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 -1.55 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.14. 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 V3879 Sagittarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.67 which gave the calculated distance to V3879 Sagittarii as 1221.59 light years away from Earth or 374.53 parsecs. It would take a spaceship travelling at the speed of light, 1221.59 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 3.22 which put V3879 Sagittarii at a distance of 1012.93 light years or 310.56 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 7,109.00 Parsecs or 23,186.95 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 V3879 Sagittarii

The star is a pulsating Semiregular late- (M, C, S or Me, Ce, Se) giants with poorly defined periodicity 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. V3879 Sagittarii brightness ranges from a magnitude of 6.286 to a magnitude of 5.901 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.3 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.

V3879 Sagittarii Facts

Alternative Names

Traditional/Proper NameV3879 Sagittarii
Short NameV3879 Sgr
Hipparcos Library I.D.91781
Bonner DurchmusterungBD-19 5134
Gould I.D.89
Henry Draper Designation172816

Visual Facts

Star Type star
Absolute Magnitude-1.55 / -1.14
Visual / Apparent Magnitude6.32
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)18h 42m 55.11
Declination (Dec.)-19d 17` 02.9
Galactic Latitude-6.86 degrees
Galactic Longitude14.74 degrees
1997 Distance from Earth2.67 Parallax (milliarcseconds)
 1221.59 Light Years
 374.53 Parsecs
2007 Revised Distance from Earth3.22 Parallax (milliarcseconds)
 1012.93 Light Years
 310.56 Parsecs
Galacto-Centric Distance23,186.95 Light Years / 7,109.00 Parsecs
Proper Motion Dec.-34.46 ± 0.25 milliarcseconds/year
Proper Motion RA.-10.29 ± 0.44 milliarcseconds/year
B-V Index1.59
Radial Velocity-32.40 ± 0.60 km/s
Iron Abundance-0.44 ± 9.99 Fe/H
Spectral TypeM4III
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M, C, S or Me, Ce, Se) giants with poorly defined periodicity
Mean Variability Period in Days0.347
Variable Magnitude Range (Brighter - Dimmer)5.901 - 6.286

Estimated Facts

Luminosity (x the Sun)7.0000000
Calculated Effective Temperature3,804 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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