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YZ Capricorni, HD358431, HIP105285

YZ Capricorni is a blue pulsating variable star that can be located in the constellation of Capricornus. The description is based on the spectral class. YZ Capricorni is not part of the constellation but is within the borders of the constellation.

The star can not be seen by the naked eye, you need a telescope to see it.

YZ Capricorni's Alternative Names

HIP105285 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD358431.

YZ Capricorni has alternative name(s) :- , YZ Cap.

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-15 5948.

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

Location of YZ Capricorni

The location of the 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 star is compared to the celestial equator and is expressed in degrees. For YZ Capricorni, the location is 21h 19m 32.42 and -15° 07` 01.0 .

Radial Velocity and Proper Motion of YZ Capricorni

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 -20.73 ± 1.24 miliarcseconds/year towards the north and -18.19 ± 2.39 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 the Sun is -106.50 km/s with an error of about 2.80 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 YZ Capricorni

YZ Capricorni has a spectral type of A6. This means the star is a blue variable star. The star has a B-V Colour Index of 0.12 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,178 Kelvin.

YZ Capricorni Radius has been calculated as being 0.83 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 578,171.79.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 0.60. 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 -1.03 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

YZ Capricorni Apparent and Absolute Magnitudes

YZ Capricorni has an apparent magnitude of 11.38 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 3.74 If you used the 2007 Parallax value, you would get an absolute magnitude of 4.45. 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 YZ Capricorni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.97 which gave the calculated distance to YZ Capricorni as 1098.19 light years away from Earth or 336.70 parsecs. It would take a spaceship travelling at the speed of light, 1098.19 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 4.11 which put YZ Capricorni at a distance of 793.58 light years or 243.31 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 50,185,940.31 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.

Variable Type of YZ Capricorni

The star is a pulsating RR Lyrae type with n 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. YZ Capricorni brightness ranges from a magnitude of 11.632 to a magnitude of 11.129 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.3 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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YZ Capricorni Facts

Visual Facts


Primary / Proper / Traditional NameYZ Capricorni
Alternative NamesHD 358431, HIP 105285, BD-15 5948, YZ Cap
Spectral TypeA6
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
Colour blue
GalaxyMilky Way
ConstellationCapricornus
Absolute Magnitude 3.74 / 4.45
Visual / Apparent Magnitude11.38
Naked Eye VisibleRequires a 4.5 - 6 Inch Telescope - Magnitudes
Right Ascension (R.A.)21h 19m 32.42
Declination (Dec.)-15° 07` 01.0
Galactic Latitude-39.52 degrees
Galactic Longitude35.38 degrees
1997 Distance from Earth2.97 Parallax (milliarcseconds)
 1098.19 Light Years
 336.70 Parsecs
2007 Distance from Earth4.11 Parallax (milliarcseconds)
 793.58 Light Years
 243.31 Parsecs
 50,185,940.31 Astronomical Units
Proper Motion Dec.-20.73 ± 1.24 milliarcseconds/year
Proper Motion RA.-18.19 ± 2.39 milliarcseconds/year
B-V Index0.12
Radial Velocity-106.50 ± 2.80 km/s
Iron Abundance-1.03 ± 9.99 Fe/H

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeRR Lyrae type with n
Mean Variability Period in Days0.274
Variable Magnitude Range (Brighter - Dimmer)11.129 - 11.632

Estimated Facts


Calculated Effective Temperature8,178 Kelvin

Sources and Links


SIMBAD SourceLink

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