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Delta Delphini - HD197461 - HIP102281

Delta Delphini is a blue pulsating giant star that can be located in the constellation of Delphinus. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Delta Delphini is the Bayer Classification for the star. HIP102281 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD197461.

Delta Delphini has alternative name(s), 11 Delphini , del_Del, 11 Del.

Location of Delta 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 Delta Delphini, the location is 20h 43m 27.55 and +15d04`28.9 .

Proper Motion of Delta 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 -43.33 ± 0.13 miliarcseconds/year towards the north and -20.44 ± 0.20 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Delta Delphini

Delta Delphini has a spectral type of A7IIIp d Del. This means the star is a blue giant star. The star is 7368.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24031.7151859200000000s. The star has a B-V Colour Index of 0.3 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,218 Kelvin.

Delta Delphini Radius has been calculated as being 4.85 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,377,144.60.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 5.32. 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 -0.20 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Delta Delphini Apparent and Absolute Magnitudes

Delta Delphini has an apparent magnitude of 4.43 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 0.45 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.25. 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 Delta Delphini

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 16.03 which gave the calculated distance to Delta Delphini as 203.47 light years away from Earth or 62.38 parsecs. It would take a spaceship travelling at the speed of light, 203.47 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 14.61 which put Delta Delphini at a distance of 223.25 light years or 68.45 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 7,368.00 Parsecs or 24,031.72 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 Delta Delphini

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. Delta Delphini brightness ranges from a magnitude of 5.000 to a magnitude of 4.000 over its variable period. The smaller the magnitude, the brighter the star.

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.

Delta Delphini Facts

Alternative Names

Short Namedel Del, 11 Del
Bayer DesignationDelta Delphini
Alternative Name(s)11 Delphini
Hipparcos Library I.D.102281
Bonner DurchmusterungBDD+14 4403
Henry Draper Designation197461

Visual Facts

Star Typegiant star
Absolute Magnitude0.45 / 0.25
Visual / Apparent Magnitude4.43
Naked Eye VisibleYes - Ref: Wiki
Right Ascension (R.A.)20h 43m 27.55
Declination (Dec.)+15d04`28.9
Galactic Latitude-16.55 degrees
Galactic Longitude60.14 degrees
1997 Distance from Earth16.03 Parallax (milliarcseconds)
 203.47 Light Years
 62.38 Parsecs
2007 Revised Distance from Earth14.61 Parallax (milliarcseconds)
 223.25 Light Years
 68.45 Parsecs
Galacto-Centric Distance24,031.72 Light Years / 7,368.00 Parsecs
Proper Motion Dec.-43.33 ± 0.13 milliarcseconds/year
Proper Motion RA.-20.44 ± 0.20 milliarcseconds/year
B-V Index0.30
Radial Velocity9.30 ± 0.90 km/s
Iron Abundance-0.20 ± 9.99 Fe/H
Spectral TypeA7IIIp d Del
Colour(A) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Scuti
Variable Magnitude Range (Brighter - Dimmer)4.000 - 5.000

Estimated Facts

Calculated Effective Temperature7,218 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Delta Delphini in Delphinus


Delta Delphini (Delta Delphini) Location in Delphinus

The map was generated using Night Vision, an awesome free application by Brian Simpson.


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