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Theta Delphini, 8 Delphini, HD196725, HIP101882, HR7892

Theta Delphini is a orange to red very luminous supergiant star that can be located in the constellation of Delphinus. Theta Delphini is the brightest star in Delphinus 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 Delphini is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR7892. HIP101882 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD196725.

Location of Theta Delphini

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 Delphini, the location is 20h 38m 43.98 and +13d 18` 54.5 .

Proper Motion of Theta Delphini

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 -0.47 ± 0.25 miliarcseconds/year towards the north and 3.53 ± 0.40 miliarcseconds/year east if we saw them in the horizon.

Theta Delphini 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 17000.0000000 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 Delphini

Theta Delphini has a spectral type of K3Ib. This means the star is a orange to red supergiant star. The star has a B-V Colour Index of 1.5 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,014 Kelvin.

Theta Delphini Radius has been calculated as being 56.20 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 39,107,123.30.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 86.65. 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 0.22 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Theta Delphini Apparent and Absolute Magnitudes

Theta Delphini has an apparent magnitude of 5.69 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 -2.32 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.26. 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 Delphini

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.50 which gave the calculated distance to Theta Delphini as 1304.65 light years away from Earth or 400 parsecs. It would take a spaceship travelling at the speed of light, 1304.65 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 1.62 which put Theta Delphini at a distance of 2013.35 light years or 617.28 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.

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 Delphini Facts

Alternative Names

Flamsteed Name8 Delphini
Flamsteed Short Name8 Del
Bayer DesignationTheta Delphini
Hipparcos Library I.D.101882
Yale Bright Star Catalogue (HR) Id7892
Bonner DurchmusterungBD+12 4411
Henry Draper Designation196725

Visual Facts

Star Typesupergiant star
Absolute Magnitude-2.32 / -3.26
Visual / Apparent Magnitude5.69
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 38m 43.98
Declination (Dec.)+13d 18` 54.5
Galactic Latitude-16.61 degrees
Galactic Longitude57.95 degrees
1997 Distance from Earth2.50 Parallax (milliarcseconds)
 1304.65 Light Years
 400 Parsecs
2007 Revised Distance from Earth1.62 Parallax (milliarcseconds)
 2013.35 Light Years
 617.28 Parsecs
Proper Motion Dec.-0.47 ± 0.25 milliarcseconds/year
Proper Motion RA.3.53 ± 0.40 milliarcseconds/year
B-V Index1.50
Radial Velocity-15.09 ± 0.13 km/s
Iron Abundance0.22 ± 9.99 Fe/H
Spectral TypeK3Ib
Colour(K) Orange to Red

Estimated Facts

Luminosity (x the Sun)17,000.0000000
Calculated Effective Temperature4,014 Kelvin

Sources and Links

SIMBAD SourceLink

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