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15 Cephei

15 Cephei Facts

15 Cephei's Alternative Names

HIP108925 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD209744.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 15 Cephei with it shortened to 15 Cep.

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+59 2456.

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

Location of 15 Cephei

The location of the main sequence 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 object is compared to the celestial equator and is expressed in degrees. For 15 Cephei, the location is 22h 03m 53.86 and +59° 48` 52.5 .

Radial Velocity and Proper Motion of 15 Cephei

Proper Motion

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 -1.61 ± 0.44 milliarcseconds/year towards the north and -3.28 ± 0.58 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -17.40 km/s with an error of about 3.00 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties (Colour, Temperature) of 15 Cephei

15 Cephei Colour and Temperature

15 Cephei has a spectral type of B1V. This means the star is a blue main sequence star. The star has a B-V Colour Index of 0.17 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,952 Kelvin.

15 Cephei Radius

Radius has been calculated as being 9.51 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 6,613,770.59.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 10.19. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

15 Cephei Apparent and Absolute Magnitudes

15 Cephei has an apparent magnitude of 6.69 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 -1.43 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.58. 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 15 Cephei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.38 which gave the calculated distance to 15 Cephei as 1370.43 light years away from Earth or 420.17 parsecs. It would take a spaceship travelling at the speed of light, 1370.43 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 2.22 which put 15 Cephei at a distance of 1469.20 light years or 450.45 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.

Using the 2007 distance, the star is roughly 92,911,334.56 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

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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Additional 15 Cephei Facts and Figures

Visual Facts

Primary / Proper / Traditional Name15 Cephei
Alternative NamesHD 209744, HIP 108925, 15 Cep, BD+59 2456
Spectral TypeB1V
Constellation's Main StarNo
Multiple Star SystemYes
Star Type Main Sequence Dwarf Star
GalaxyMilky Way
Absolute Magnitude -1.43 / -1.58
Visual / Apparent Magnitude6.69
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)22h 03m 53.86
Declination (Dec.)+59° 48` 52.5
Galactic Latitude3.50 degrees
Galactic Longitude103.28 degrees
1997 Distance from Earth2.38 Parallax (milliarcseconds)
 1370.43 Light Years
 420.17 Parsecs
2007 Distance from Earth2.22 Parallax (milliarcseconds)
 1469.20 Light Years
 450.45 Parsecs
 92,911,334.56 Astronomical Units
Proper Motion Dec.-1.61 ± 0.44 milliarcseconds/year
Proper Motion RA.-3.28 ± 0.58 milliarcseconds/year
B-V Index0.17
Radial Velocity-17.40 ± 3.00 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)10.19
Effective Temperature7,952 Kelvin

Sources and Links

SIMBAD SourceLink

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
209744+59 2456.0A6.70000-30.0000026.00000B5Blue/White
+59 2457.0C9.7000010.00000-8.000001876
209810+59 2461.0D7.900003.0000017.00000AWhite1876

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