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TT Aquilae, HD178359, HIP93990

TT Aquilae is a blue to white pulsating subgiant star that can be located in the constellation of Aquila. The star can not be seen by the naked eye, you need a telescope to see it.

TT Aquilae's Alternative Names

HIP93990 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD178359.

TT Aquilae has alternative name(s) :- , TT Aql.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+01 3899.

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

Location of TT Aquilae

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 TT Aquilae, the location is 19h 08m 13.75 and +01° 17` 55.2 .

Proper Motion of TT Aquilae

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 -3.33 ± 0.78 miliarcseconds/year towards the north and 1.17 ± 1.26 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 3.00000 km/s with an error of about 0.30 km/s .

Physical Properties (Colour, Temperature) of TT Aquilae

TT Aquilae has a spectral type of F5IV. This means the star is a blue to white subgiant star. The star has a B-V Colour Index of 1.27 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,372 Kelvin.

TT Aquilae Radius has been calculated as being 151.91 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 105,700,036.85.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 344.83. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

TT Aquilae Apparent and Absolute Magnitudes

TT Aquilae has an apparent magnitude of 7.09 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 -4.85 If you used the 2007 Parallax value, you would get an absolute magnitude of -6.63. 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 TT Aquilae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.41 which gave the calculated distance to TT Aquilae as 7955.20 light years away from Earth or 2439.02 parsecs. It would take a spaceship travelling at the speed of light, 7955.20 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 0.18 which put TT Aquilae at a distance of 18120.19 light years or 5555.56 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 TT Aquilae

The star is a pulsating Delta Cepheid 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. TT Aquilae brightness ranges from a magnitude of 7.774 to a magnitude of 6.814 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 13.8 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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TT Aquilae Facts

Visual Facts

Alternative NamesHD 178359, HIP 93990, BD+01 3899, TT Aql
Star TypeSubgiant Star
GalaxyMilky Way
Absolute Magnitude-4.85 / -6.63
Visual / Apparent Magnitude7.09
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)19h 08m 13.75
Declination (Dec.)+01° 17` 55.2
Galactic Latitude-3.14 degrees
Galactic Longitude36.01 degrees
1997 Distance from Earth0.41 Parallax (milliarcseconds)
 7955.20 Light Years
 2439.02 Parsecs
2007 Revised Distance from Earth0.18 Parallax (milliarcseconds)
 18120.19 Light Years
 5555.56 Parsecs
Proper Motion Dec.-3.33 ± 0.78 milliarcseconds/year
Proper Motion RA.1.17 ± 1.26 milliarcseconds/year
B-V Index1.27
Radial Velocity3.00 ± 0.30 km/s
Spectral TypeF5IV
Colour (F) blue to white

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Cepheid
Mean Variability Period in Days13.753
Variable Magnitude Range (Brighter - Dimmer)6.814 - 7.774

Estimated Facts

Calculated Effective Temperature4,372 Kelvin

Sources and Links

SIMBAD SourceLink

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