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RS Sagittarii, HD167647, HIP89637

RS Sagittarii is a blue eclipsing binary system subgiant 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.

HIP89637 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD167647. The Id of the star in the Gould Star Catalogue is 47. 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.

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

Location of RS 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 RS Sagittarii, the location is 18h 17m 36.25 and -34d06`26.0 .

Proper Motion of RS 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 -9.77 ± 0.27 miliarcseconds/year towards the north and -5.14 ± 0.45 miliarcseconds/year east if we saw them in the horizon.

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

RS Sagittarii has a spectral type of B3/B4IV/V. This means the star is a blue subgiant star. The star is 7072.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23066.2716876800000000s. The star has a B-V Colour Index of -0.09 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 11,375 Kelvin.

RS Sagittarii Radius has been calculated as being 4.05 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,815,114.82.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 5.12. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

RS Sagittarii Apparent and Absolute Magnitudes

RS Sagittarii has an apparent magnitude of 6.03 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 -1.13 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.64. 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 RS Sagittarii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.70 which gave the calculated distance to RS Sagittarii as 881.52 light years away from Earth or 270.27 parsecs. It would take a spaceship travelling at the speed of light, 881.52 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 2.93 which put RS Sagittarii at a distance of 1113.19 light years or 341.30 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 7,072.00 Parsecs or 23,066.27 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 RS Sagittarii

The star is a eclipsing binary system Beta Lyrae (Sheliak) 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. RS Sagittarii brightness ranges from a magnitude of 6.320 to a magnitude of 5.995 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 2.4 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.

RS Sagittarii Facts

Alternative Names

Traditional/Proper NameRS Sagittarii
Short NameRS Sgr
Hipparcos Library I.D.89637
Gould I.D.47
Henry Draper Designation167647

Visual Facts

Star Typesubgiant star
Absolute Magnitude-1.13 / -1.64
Visual / Apparent Magnitude6.03
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)18h 17m 36.25
Declination (Dec.)-34d06`26.0
Galactic Latitude-8.47 degrees
Galactic Longitude358.83 degrees
1997 Distance from Earth3.70 Parallax (milliarcseconds)
 881.52 Light Years
 270.27 Parsecs
2007 Revised Distance from Earth2.93 Parallax (milliarcseconds)
 1113.19 Light Years
 341.30 Parsecs
Galacto-Centric Distance23,066.27 Light Years / 7,072.00 Parsecs
Proper Motion Dec.-9.77 ± 0.27 milliarcseconds/year
Proper Motion RA.-5.14 ± 0.45 milliarcseconds/year
B-V Index-0.09
Radial Velocity10.10 ± 4.30 km/s
Spectral TypeB3/B4IV/V
Colour(B) blue

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeBeta Lyrae (Sheliak)
Mean Variability Period in Days2.416
Variable Magnitude Range (Brighter - Dimmer)5.995 - 6.320

Estimated Facts

Calculated Effective Temperature11,375 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
167647-3412673.2A-58.00000-47.00000B5Blue/White
B9.700001890
167669-3412675.2C8.70000-34.00000-4.00000A0White1890
CD10.200001919

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