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RZ Scorpii, HD144018, HIP78746

RZ Scorpii is a red pulsating giant star that can be located in the constellation of Scorpius. 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.

RZ Scorpii's Alternative Names

HIP78746 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD144018.

RZ Scorpii has alternative name(s) :- , RZ Sco.

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

Location of RZ Scorpii

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 RZ Scorpii, the location is 16h 04m 36.14 and -24° 06` 00.5 .

Proper Motion of RZ Scorpii

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 -19.16 ± 0.99 miliarcseconds/year towards the north and -13.85 ± 1.55 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 -174.00000 km/s with an error of about 4.60 km/s .

Physical Properties (Colour, Temperature) of RZ Scorpii

RZ Scorpii has a spectral type of M1III. This means the star is a red giant star. The star has a B-V Colour Index of 1.79 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,006 Kelvin.

RZ Scorpii Radius has been calculated as being 21.52 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 14,976,139.05.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 246.02. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

RZ Scorpii Apparent and Absolute Magnitudes

RZ Scorpii has an apparent magnitude of 9.12 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 1.02 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.27. 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 RZ Scorpii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.40 which gave the calculated distance to RZ Scorpii as 1359.01 light years away from Earth or 416.67 parsecs. It would take a spaceship travelling at the speed of light, 1359.01 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 0.21 which put RZ Scorpii at a distance of 15531.59 light years or 4761.90 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 RZ Scorpii

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. RZ Scorpii brightness ranges from a magnitude of 10.567 to a magnitude of 8.637 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 162.0 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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RZ Scorpii Facts

Visual Facts


 RZ Scorpii
Alternative NamesHD 144018, HIP 78746, RZ Sco
Spectral TypeM1III
Multiple Star SystemNo / Unknown
Star TypeGiant Star
Colour red
GalaxyMilky Way
ConstellationScorpius
Absolute Magnitude1.02 / -4.27
Visual / Apparent Magnitude9.12
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)16h 04m 36.14
Declination (Dec.)-24° 06` 00.5
Galactic Latitude20.75 degrees
Galactic Longitude349.71 degrees
1997 Distance from Earth2.40 Parallax (milliarcseconds)
 1359.01 Light Years
 416.67 Parsecs
2007 Distance from Earth0.21 Parallax (milliarcseconds)
 15531.59 Light Years
 4761.90 Parsecs
Proper Motion Dec.-19.16 ± 0.99 milliarcseconds/year
Proper Motion RA.-13.85 ± 1.55 milliarcseconds/year
B-V Index1.79
Radial Velocity-174.00 ± 4.60 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeOmicron Ceti
Mean Variability Period in Days162.000
Variable Magnitude Range (Brighter - Dimmer)8.637 - 10.567

Estimated Facts


Calculated Effective Temperature3,006 Kelvin

Sources and Links


SIMBAD SourceLink

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