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R Doradus, HD29712, HIP21479, HR1492

R Doradus is a red pulsating variable star that can be located in the constellation of Dorado. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

R Doradus's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR1492. HIP21479 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD29712.

R Doradus has alternative name(s) :- , R Dor.

More details on star alternative names can be found at Star Names .

Location of R Doradus

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 R Doradus, the location is 04h 36m 45.68 and -62° 04` 37.1 .

Proper Motion of R Doradus

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 -75.78 ± 0.94 miliarcseconds/year towards the north and -69.36 ± 0.99 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 26.10000 km/s with an error of about 2.90 km/s .

R Doradus 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 55.30 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of R Doradus

R Doradus has a spectral type of M8e. This means the star is a red variable star. The star is 7,398.00 Parsecs from the Galactic Centre or terms of Light Years is 24,129.56 s. The star has a B-V Colour Index of 1.5 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,014 Kelvin.

R Doradus Radius has been calculated as being 9.20 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 6,400,549.90.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 8.05. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

R Doradus Apparent and Absolute Magnitudes

R Doradus has an apparent magnitude of 5.59 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 1.61 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.90. 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 R Doradus

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 16.02 which gave the calculated distance to R Doradus as 203.60 light years away from Earth or 62.42 parsecs. It would take a spaceship travelling at the speed of light, 203.60 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 18.31 which put R Doradus at a distance of 178.13 light years or 54.61 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 7,398.00 Parsecs or 24,129.56 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 R Doradus

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. R Doradus brightness ranges from a magnitude of 4.941 to a magnitude of 4.177 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.6 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.

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R Doradus Facts

Visual Facts

 R Doradus
Alternative NamesR Dor, HD 29712, HIP 21479, HR 1492, R Dor
Spectral TypeM8e
Multiple Star SystemYes
Star TypeVariable Star
Colour red
GalaxyMilky Way
Absolute Magnitude1.61 / 1.90
Visual / Apparent Magnitude5.59
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)04h 36m 45.68
Declination (Dec.)-62° 04` 37.1
Galactic Latitude-39.34 degrees
Galactic Longitude272.67 degrees
1997 Distance from Earth16.02 Parallax (milliarcseconds)
 203.60 Light Years
 62.42 Parsecs
2007 Distance from Earth18.31 Parallax (milliarcseconds)
 178.13 Light Years
 54.61 Parsecs
Galacto-Centric Distance24,129.56 Light Years / 7,398.00 Parsecs
Proper Motion Dec.-75.78 ± 0.94 milliarcseconds/year
Proper Motion RA.-69.36 ± 0.99 milliarcseconds/year
B-V Index1.50
Radial Velocity26.10 ± 2.90 km/s
Semi-Major Axis7882.00
Stellar Luminosity (Lsun)55.30

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

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 Days0.610
Variable Magnitude Range (Brighter - Dimmer)4.177 - 4.941

Estimated Facts

Calculated Effective Temperature4,014 Kelvin

Sources and Links

SIMBAD SourceLink

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
29712-62 372.4A-59.00000-79.00000M7Red

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