Universe Guide


SY Equulei, HD203664, HIP105614

SY Equulei is a blue pulsating giant star that can be located in the constellation of Equuleus. SY Equulei is the brightest star in Equuleus based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP105614 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD203664.

SY Equulei has alternative name(s), SY Equ.

Location of SY Equulei

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 SY Equulei, the location is 21h 23m 28.81 and +09d55`55.0 .

Proper Motion of SY Equulei

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 -8.27 ± 0.67 miliarcseconds/year towards the north and 0.41 ± 0.89 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of SY Equulei

SY Equulei has a spectral type of B0.5IIIn. This means the star is a blue giant star. The star has a B-V Colour Index of -0.2 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 16,954 Kelvin.

SY Equulei Radius has been calculated as being 0.94 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 652,890.62.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.68. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

SY Equulei Apparent and Absolute Magnitudes

SY Equulei has an apparent magnitude of 8.57 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 0.31 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.97. 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 SY Equulei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.23 which gave the calculated distance to SY Equulei as 1462.62 light years away from Earth or 448.43 parsecs. It would take a spaceship travelling at the speed of light, 1462.62 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 0.78 which put SY Equulei at a distance of 4181.58 light years or 1282.05 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 SY Equulei

The star is a pulsating Beta Cephei 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. SY Equulei brightness ranges from a magnitude of 8.535 to a magnitude of 8.470 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 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.

SY Equulei Facts

Alternative Names

Traditional/Proper NameSY Equulei
Short NameSY Equ
Hipparcos Library I.D.105614
Bonner DurchmusterungBD+09 4793
Henry Draper Designation203664

Visual Facts

Star Typegiant star
Absolute Magnitude0.31 / -1.97
Visual / Apparent Magnitude8.57
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)21h 23m 28.81
Declination (Dec.)+09d55`55.0
Galactic Latitude-27.46 degrees
Galactic Longitude61.93 degrees
1997 Distance from Earth2.23 Parallax (milliarcseconds)
 1462.62 Light Years
 448.43 Parsecs
2007 Revised Distance from Earth0.78 Parallax (milliarcseconds)
 4181.58 Light Years
 1282.05 Parsecs
Proper Motion Dec.-8.27 ± 0.67 milliarcseconds/year
Proper Motion RA.0.41 ± 0.89 milliarcseconds/year
B-V Index-0.20
Radial Velocity48.00 ± 5.50 km/s
Spectral TypeB0.5IIIn
Colour(B) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeBeta Cephei
Mean Variability Period in Days0.166
Variable Magnitude Range (Brighter - Dimmer)8.470 - 8.535

Estimated Facts

Calculated Effective Temperature16,954 Kelvin

Sources and Links

SIMBAD SourceLink

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