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Theta Coronae Australis, HD170845, HIP90982

Theta Coronae Australis is a white to yellow giant star that can be located in the constellation of CoronaAustralis. Theta Coronae Australis is the brightest star in Corona Australis based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Theta Coronae Australis is the Bayer Classification for the star. HIP90982 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD170845.

Location of Theta Coronae Australis

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 Theta Coronae Australis, the location is 18h 33m 30.16 and -42d18`44.9 .

Proper Motion of Theta Coronae Australis

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 -20.72 ± 0.17 miliarcseconds/year towards the north and 33.27 ± 0.27 miliarcseconds/year east if we saw them in the horizon.

Theta Coronae Australis 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 127.0000000 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 Theta Coronae Australis

Theta Coronae Australis has a spectral type of G5III. This means the star is a white to yellow giant star. The star is 7237.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23604.4412052800000000s. The star has a B-V Colour Index of 0.99 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,868 Kelvin.

Theta Coronae Australis Radius has been calculated as being 41.52 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 28,887,584.90.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 26.68. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Theta Coronae Australis Apparent and Absolute Magnitudes

Theta Coronae Australis has an apparent magnitude of 4.62 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 -2.50 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.54. 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 Theta Coronae Australis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.76 which gave the calculated distance to Theta Coronae Australis as 867.46 light years away from Earth or 265.96 parsecs. It would take a spaceship travelling at the speed of light, 867.46 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 5.85 which put Theta Coronae Australis at a distance of 557.54 light years or 170.94 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 7,237.00 Parsecs or 23,604.44 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

Theta Coronae Australis Facts

Alternative Names

Bayer DesignationTheta Coronae Australis
Hipparcos Library I.D.90982
Henry Draper Designation170845

Visual Facts

Star Typegiant star
Absolute Magnitude-2.50 / -1.54
Visual / Apparent Magnitude4.62
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)18h 33m 30.16
Declination (Dec.)-42d18`44.9
Galactic Latitude-14.80 degrees
Galactic Longitude352.62 degrees
1997 Distance from Earth3.76 Parallax (milliarcseconds)
 867.46 Light Years
 265.96 Parsecs
2007 Revised Distance from Earth5.85 Parallax (milliarcseconds)
 557.54 Light Years
 170.94 Parsecs
Galacto-Centric Distance23,604.44 Light Years / 7,237.00 Parsecs
Proper Motion Dec.-20.72 ± 0.17 milliarcseconds/year
Proper Motion RA.33.27 ± 0.27 milliarcseconds/year
B-V Index0.99
Radial Velocity-2.10 ± 2.80 km/s
Spectral TypeG5III
Colour(G) White to Yellow

Estimated Facts

Luminosity (x the Sun)127.0000000
Calculated Effective Temperature4,868 Kelvin

Sources and Links

SIMBAD SourceLink

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