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Theta Gruis, HD218227, HIP114131, HR8787

Theta Gruis is a blue to white star that can be located in the constellation of Grus. Theta Gruis is the brightest star in Grus 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 Gruis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR8787. HIP114131 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD218227.

Location of Theta Gruis

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 Gruis, the location is 23h 06m 52.77 and -43d 31` 13.2 .

Proper Motion of Theta Gruis

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 -13.49 ± 0.33 miliarcseconds/year towards the north and -47.17 ± 0.45 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 11.00000 km/s with an error of about 1.70 km/s .

Physical Properties (Colour, Temperature, Radius) of Theta Gruis

Theta Gruis has a spectral type of F5me.... This means the star is a blue to white star. The star is 7382.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24077.3780540800000000s. The star has a B-V Colour Index of 0.42 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,335 Kelvin.

Theta Gruis Radius has been calculated as being 4.40 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,061,135.23.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 4.36. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Theta Gruis Apparent and Absolute Magnitudes

Theta Gruis has an apparent magnitude of 4.28 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 1.23 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.25. 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 Gruis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 24.51 which gave the calculated distance to Theta Gruis as 133.07 light years away from Earth or 40.80 parsecs. It would take a spaceship travelling at the speed of light, 133.07 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 24.73 which put Theta Gruis at a distance of 131.89 light years or 40.44 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 7,382.00 Parsecs or 24,077.38 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 Gruis Facts

Alternative Names

Bayer DesignationTheta Gruis
Hipparcos Library I.D.114131
Yale Bright Star Catalogue (HR) Id8787
Henry Draper Designation218227

Visual Facts

Star Type star
Absolute Magnitude1.23 / 1.25
Visual / Apparent Magnitude4.28
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)23h 06m 52.77
Declination (Dec.)-43d 31` 13.2
Galactic Latitude-63.30 degrees
Galactic Longitude348.24 degrees
1997 Distance from Earth24.51 Parallax (milliarcseconds)
 133.07 Light Years
 40.80 Parsecs
2007 Revised Distance from Earth24.73 Parallax (milliarcseconds)
 131.89 Light Years
 40.44 Parsecs
Galacto-Centric Distance24,077.38 Light Years / 7,382.00 Parsecs
Proper Motion Dec.-13.49 ± 0.33 milliarcseconds/year
Proper Motion RA.-47.17 ± 0.45 milliarcseconds/year
B-V Index0.42
Radial Velocity11.00 ± 1.70 km/s
Spectral TypeF5me...
Colour(F) blue to white

Estimated Facts

Calculated Effective Temperature6,335 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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

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