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Iota Trianguli Australis, HD147787, HIP80645

Iota Trianguli Australis is a blue to white subgiant star that can be located in the constellation of TriangulumAustrale. Iota Trianguli Australis is the brightest star in Triangulum Australe 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. The star has an estimated age of 1.70 Billion of Years but could be as young as 1.60 to 1.80 according to Hipparcos.

Iota Trianguli Australis is the Bayer Classification for the star. HIP80645 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD147787.

Location of Iota Trianguli 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 Iota Trianguli Australis, the location is 16h 27m 57.27 and -64d03`28.8 .

Proper Motion of Iota Trianguli 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 25.45 ± 0.35 miliarcseconds/year towards the north and 53.12 ± 0.51 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Age, Radius) of Iota Trianguli Australis

Iota Trianguli Australis has a spectral type of F4IV. This means the star is a blue to white subgiant star. The star is 7369.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24034.9768193600000000s. The star has a B-V Colour Index of 0.38 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,822 Kelvin.

Iota Trianguli Australis Radius has been calculated as being 2.37 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,650,221.76.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.28. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.11 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 1.70 Billion years old but could be between 1.60 and 1.80 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Iota Trianguli Australis Apparent and Absolute Magnitudes

Iota Trianguli Australis has an apparent magnitude of 5.28 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 2.25 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.34. 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 Iota Trianguli Australis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 24.75 which gave the calculated distance to Iota Trianguli Australis as 131.78 light years away from Earth or 40.40 parsecs. It would take a spaceship travelling at the speed of light, 131.78 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 25.77 which put Iota Trianguli Australis at a distance of 126.57 light years or 38.80 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 7,369.00 Parsecs or 24,034.98 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*. Iota Trianguli Australis brightness ranges from a magnitude of 5.396 to a magnitude of 5.332 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 1.5 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.

Iota Trianguli Australis Facts

Alternative Names

Bayer DesignationIota Trianguli Australis
Hipparcos Library I.D.80645
Henry Draper Designation147787

Visual Facts

Star Typesubgiant star
Age1.70 Billion Years Old
Age Range1.60 - 1.80 Billion Years Old
Absolute Magnitude2.25 / 2.34
Visual / Apparent Magnitude5.28
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)16h 27m 57.27
Declination (Dec.)-64d03`28.8
Galactic Latitude-10.48 degrees
Galactic Longitude324.06 degrees
1997 Distance from Earth24.75 Parallax (milliarcseconds)
 131.78 Light Years
 40.40 Parsecs
2007 Revised Distance from Earth25.77 Parallax (milliarcseconds)
 126.57 Light Years
 38.80 Parsecs
Galacto-Centric Distance24,034.98 Light Years / 7,369.00 Parsecs
Proper Motion Dec.25.45 ± 0.35 milliarcseconds/year
Proper Motion RA.53.12 ± 0.51 milliarcseconds/year
B-V Index0.38
Radial Velocity-5.60 ± 4.20 km/s
Iron Abundance-0.11 ± 9.99 Fe/H
Spectral TypeF4IV
Colour(F) blue to white

Variable Star Details

Mean Variability Period in Days1.456
Variable Magnitude Range (Brighter - Dimmer)5.332 - 5.396

Estimated Facts

Calculated Effective Temperature6,822 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
147787-63 3923.4A5.3000055.0000025.00000F3Yellow/White
B10.300000.00000-23.000001918

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