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Theta Tucanae, HD3112, HIP2629, HR139

Theta Tucanae is a blue pulsating subgiant star that can be located in the constellation of Tucana. 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.

Theta Tucanae's Alternative Names

Theta Tucanae (The Tuc) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR139. HIP2629 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD3112.

Theta Tucanae has alternative name(s) :- , the Tuc.

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

Location of Theta Tucanae

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 Theta Tucanae, the location is 00h 33m 23.23 and -71° 15` 58.4 .

Proper Motion of Theta Tucanae

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 -13.42 ± 0.21 miliarcseconds/year towards the north and 73.40 ± 0.22 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 2.30000 km/s with an error of about 2.90 km/s .

Theta Tucanae 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 50.27 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 Theta Tucanae

Theta Tucanae has a spectral type of A7IV. This means the star is a blue subgiant star. The star is 7,349.00 Parsecs from the Galactic Centre or terms of Light Years is 23,969.74 s. The star has a B-V Colour Index of 0.2 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,767 Kelvin.

Theta Tucanae Radius has been calculated as being 4.66 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,242,493.10.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 4.02. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Theta Tucanae Apparent and Absolute Magnitudes

Theta Tucanae has an apparent magnitude of 6.11 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 0.22 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.54. 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 Tucanae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.65 which gave the calculated distance to Theta Tucanae as 490.47 light years away from Earth or 150.38 parsecs. It would take a spaceship travelling at the speed of light, 490.47 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 7.69 which put Theta Tucanae at a distance of 424.14 light years or 130.04 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 7,349.00 Parsecs or 23,969.74 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 Theta Tucanae

The star is a pulsating Delta Scuti 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. Theta Tucanae brightness ranges from a magnitude of 6.215 to a magnitude of 6.165 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 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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Theta Tucanae Facts

Visual Facts


Primary / Proper / Traditional NameTheta Tucanae
Alternative NamesThe Tuc, HD 3112, HIP 2629, HR 139, the Tuc
Spectral TypeA7IV
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
Colour blue
GalaxyMilky Way
ConstellationTucana
Absolute Magnitude0.22 / 0.54
Visual / Apparent Magnitude6.11
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)00h 33m 23.23
Declination (Dec.)-71° 15` 58.4
Galactic Latitude-45.79 degrees
Galactic Longitude305.01 degrees
1997 Distance from Earth6.65 Parallax (milliarcseconds)
 490.47 Light Years
 150.38 Parsecs
2007 Distance from Earth7.69 Parallax (milliarcseconds)
 424.14 Light Years
 130.04 Parsecs
Galacto-Centric Distance23,969.74 Light Years / 7,349.00 Parsecs
Proper Motion Dec.-13.42 ± 0.21 milliarcseconds/year
Proper Motion RA.73.40 ± 0.22 milliarcseconds/year
B-V Index0.20
Radial Velocity2.30 ± 2.90 km/s
Eccentricity0.16
Semi-Major Axis6395.00
Stellar Luminosity (Lsun)50.27

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeDelta Scuti
Mean Variability Period in Days0.046
Variable Magnitude Range (Brighter - Dimmer)6.165 - 6.215

Estimated Facts


Calculated Effective Temperature7,767 Kelvin

Sources and Links


SIMBAD SourceLink

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