Universe Guide


RY Sagittarii, HD180093, HIP94730

RY Sagittarii is a eruptive star that can be located in the constellation of Sagittarius. The star can not be seen by the naked eye, you need a telescope to see it.

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. The Id of the star in the Gould Star Catalogue is 156. 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.

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

Location of RY 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 RY Sagittarii, the location is 19h 16m 32.76 and -33d31`20.3 .

Proper Motion of RY 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 -0.32 ± 0.45 miliarcseconds/year towards the north and 10.00 ± 0.82 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Temperature, Radius) of RY Sagittarii

RY Sagittarii has a spectral type of Cp. This means the star is a 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. 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 Apparent and Absolute Magnitudes

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.

Distance to RY Sagittarii

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.

Variable Type of RY Sagittarii

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).

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.

RY Sagittarii Facts

Alternative Names

Traditional/Proper NameRY Sagittarii
Short NameRY Sgr
Hipparcos Library I.D.94730
Gould I.D.156
Henry Draper Designation180093

Visual Facts

Star Type star
Absolute Magnitude-5.64 / -2.87
Visual / Apparent Magnitude6.58
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)19h 16m 32.76
Declination (Dec.)-33d31`20.3
Galactic Latitude-19.45 degrees
Galactic Longitude4.43 degrees
1997 Distance from Earth0.36 Parallax (milliarcseconds)
 9060.09 Light Years
 2777.78 Parsecs
2007 Revised Distance from Earth1.29 Parallax (milliarcseconds)
 2528.40 Light Years
 775.19 Parsecs
Proper Motion Dec.-0.32 ± 0.45 milliarcseconds/year
Proper Motion RA.10.00 ± 0.82 milliarcseconds/year
B-V Index0.69
Radial Velocity-21.00 ± 2.00 km/s
Spectral TypeCp

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeR Coronae Borealis
Mean Variability Period in Days2.321
Variable Magnitude Range (Brighter - Dimmer)6.253 - 7.991

Estimated Facts

Calculated Effective Temperature5,671 Kelvin

Sources and Links

SIMBAD SourceLink

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