RY Sagittarii is a carbon red eruptive variable star that can be located in the constellation of Sagittarius. The description is based on the spectral class. The star can not be seen by the naked eye, you need a telescope to see it.
The Id of the star in the Yale Bright Star Catalogue is HR7296. HIP94730 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD180093.
RY Sagittarii has alternative name(s) :- , RY Sgr.
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 156 G. Sagittarii. There are no stars with a Gould designation in Ursa Major for example.
More details on star alternative names can be found at Star Names .
The location of the 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 star is compared to the celestial equator and is expressed in degrees. For RY Sagittarii, the location is 19h 16m 32.76 and -33° 31` 20.3 .
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 -0.32 ± 0.45 miliarcseconds/year towards the north and 10.00 ± 0.82 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 -21.00000 km/s with an error of about 2.00 km/s .
RY Sagittarii has a spectral type of Cp. This means the star is a carbon red variable star. The star has a B-V Colour Index of 0.69 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,671 Kelvin.
RY Sagittarii Radius has been calculated as being 129.91 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 90,390,732.65.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 36.28. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.
RY Sagittarii has an apparent magnitude of 6.58 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 -5.64 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.87. 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.36 which gave the calculated distance to RY Sagittarii as 9060.09 light years away from Earth or 2777.78 parsecs. It would take a spaceship travelling at the speed of light, 9060.09 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 1.29 which put RY Sagittarii at a distance of 2528.40 light years or 775.19 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 is a eruptive R Coronae Borealis 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. RY Sagittarii brightness ranges from a magnitude of 7.991 to a magnitude of 6.253 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 2.3 days (variability).
|Primary / Proper / Traditional Name||RY Sagittarii|
|Alternative Names||Ry Sgr, HD 180093, HIP 94730, HR 7296, 156 G. Sagittarii, RY Sgr|
|Multiple Star System||No / Unknown|
|Star Type||Variable Star|
|Absolute Magnitude||-5.64 / -2.87|
|Visual / Apparent Magnitude||6.58|
|Naked Eye Visible||Requires a 7x50 Binoculars - Magnitudes|
|Right Ascension (R.A.)||19h 16m 32.76|
|Declination (Dec.)||-33° 31` 20.3|
|Galactic Latitude||-19.45 degrees|
|Galactic Longitude||4.43 degrees|
|1997 Distance from Earth||0.36 Parallax (milliarcseconds)|
|9060.09 Light Years|
|2007 Distance from Earth||1.29 Parallax (milliarcseconds)|
|2528.40 Light Years|
|Proper Motion Dec.||-0.32 ± 0.45 milliarcseconds/year|
|Proper Motion RA.||10.00 ± 0.82 milliarcseconds/year|
|Radial Velocity||-21.00 ± 2.00 km/s|
|Variable Star Class||Eruptive|
|Variable Star Type||R Coronae Borealis|
|Mean Variability Period in Days||2.321|
|Variable Magnitude Range (Brighter - Dimmer)||6.253 - 7.991|
|Calculated Effective Temperature||5,671 Kelvin|