Universe Guide


RT Cygni, HD186686, HIP97068

RT Cygni is a red pulsating very luminous supergiant star that can be located in the constellation of Cygnus. The star can not be seen by the naked eye, you need a telescope to see it.

HIP97068 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD186686.

RT Cygni has alternative name(s), RT Cyg.

Location of RT Cygni

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 RT Cygni, the location is 19h 43m 37.78 and +48d46`41.2 .

RT Cygni 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 53000.0000000 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 RT Cygni

RT Cygni has a spectral type of M2e-M8.8Ibe. This means the star is a red supergiant star. The star has a B-V Colour Index of 1.27 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,440 Kelvin. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

RT Cygni Apparent and Absolute Magnitudes

RT Cygni has an apparent magnitude of 8.44 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 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 RT Cygni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as -0.87 which gave the calculated distance to RT Cygni as -3749.00 light years away from Earth or -1149.43 parsecs. It would take a spaceship travelling at the speed of light, -3749.00 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

Variable Type of RT Cygni

The star is a pulsating Omicron Ceti 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. RT Cygni brightness ranges from a magnitude of 11.036 to a magnitude of 7.355 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 189.7 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.

RT Cygni Facts

Alternative Names

Traditional/Proper NameRT Cygni
Short NameRT Cyg
Hipparcos Library I.D.97068
Bonner DurchmusterungBD+48 2942
Henry Draper Designation186686

Visual Facts

Star Typesupergiant star
Visual / Apparent Magnitude8.44
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)19h 43m 37.78
Declination (Dec.)+48d46`41.2
Galactic Latitude12.16 degrees
Galactic Longitude81.88 degrees
1997 Distance from Earth-0.87 Parallax (milliarcseconds)
 -3749.00 Light Years
 -1149.43 Parsecs
B-V Index1.27
Radial Velocity-116.00 ± 4.50 km/s
Spectral TypeM2e-M8.8Ibe
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeOmicron Ceti
Mean Variability Period in Days189.700
Variable Magnitude Range (Brighter - Dimmer)7.355 - 11.036

Estimated Facts

Luminosity (x the Sun)53,000.0000000
Calculated Effective Temperature4,440 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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