Universe Guide


EY Orionis, HD36412, HIP25863

EY Orionis is a blue eclipsing/detached system main sequence dwarf star that can be located in the constellation of Orion. The star can not be seen by the naked eye, you need a telescope to see it.

HIP25863 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD36412.

EY Orionis has alternative name(s), EY Ori.

Location of EY Orionis

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 EY Orionis, the location is 05h 31m 18.41 and -05d42`13.5 .

Proper Motion of EY Orionis

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 -1.55 ± 0.85 miliarcseconds/year towards the north and 0.72 ± 1.64 miliarcseconds/year east if we saw them in the horizon.

EY Orionis 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 9.0000000 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 EY Orionis

EY Orionis has a spectral type of A7V. This means the star is a blue main sequence dwarf star. The star is 7686.00000000 Parsecs from the Galactic Centre or terms of Light Years is 25068.9146198400000000s. The star has a B-V Colour Index of 0.74 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,446 Kelvin.

EY Orionis Radius has been calculated as being 5.69 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,955,664.95.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 13.45. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

EY Orionis Apparent and Absolute Magnitudes

EY Orionis has an apparent magnitude of 9.46 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 1.33 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.54. 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 EY Orionis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.37 which gave the calculated distance to EY Orionis as 1376.22 light years away from Earth or 421.94 parsecs. It would take a spaceship travelling at the speed of light, 1376.22 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 1.00 which put EY Orionis at a distance of 3261.63 light years or 1000 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 7,686.00 Parsecs or 25,068.91 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 EY Orionis

The star is a eclipsing/detached system Beta Persei (Algol)/Detached Systems (subtype) 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. EY Orionis brightness ranges from a magnitude of 10.160 to a magnitude of 9.550 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.

EY Orionis Facts

Alternative Names

Traditional/Proper NameEY Orionis
Short NameEY Ori
Hipparcos Library I.D.25863
Bonner DurchmusterungBD-05 1281
Henry Draper Designation36412

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude1.33 / -0.54
Visual / Apparent Magnitude9.46
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)05h 31m 18.41
Declination (Dec.)-05d42`13.5
Galactic Latitude-20.41 degrees
Galactic Longitude208.83 degrees
1997 Distance from Earth2.37 Parallax (milliarcseconds)
 1376.22 Light Years
 421.94 Parsecs
2007 Revised Distance from Earth1.00 Parallax (milliarcseconds)
 3261.63 Light Years
 1000 Parsecs
Galacto-Centric Distance25,068.91 Light Years / 7,686.00 Parsecs
Proper Motion Dec.-1.55 ± 0.85 milliarcseconds/year
Proper Motion RA.0.72 ± 1.64 milliarcseconds/year
B-V Index0.74
Radial Velocity28.60 ± 7.40 km/s
Spectral TypeA7V
Colour(A) blue

Variable Star Details

Variable Star ClassEclipsing/Detached System
Variable Star TypeBeta Persei (Algol)/Detached Systems (subtype)
Variable Magnitude Range (Brighter - Dimmer)9.550 - 10.160

Estimated Facts

Luminosity (x the Sun)9.0000000
Calculated Effective Temperature5,446 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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