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Sabik (Eta Ophiuchi) - HD155125 - HIP84012 - HR6378

Sabik (Eta Ophiuchi) is a blue main sequence dwarf star that can be located in the constellation of Ophiuchus. It is the 86th brightest star in the night sky. Eta Ophiuchi is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR6378. HIP84012 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD155125. The Id of the star in the Gould Star Catalogue is 90. Stars in the southern hemisphere are more likely to have a Gould Id than the northern hemisphere. For example, there are no Gould classified stars in Ursa Major. Sabik has alternative name(s), 35 Ophiuchi , 35 Oph. In Arabic, it is known as As-Sabiq. Sabik is a multiple star system with 2 stars orbiting in its solar system.

Location of Sabik

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 Sabik, the location is 17h 10m 22.66 and -15d43`30.5 .

Proper Motion of Sabik

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 099.17 ± 000.37 towards the north and 040.13 ± 000.80 east if we saw them in the horizon.

Sabik 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 17.0000000 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 Sabik

Sabik has a spectral type of A2.5Va. This means the star is a blue main sequence dwarf star. The star has a B-V Colour Index of 0.05 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,917 Kelvin.

Sabik has been calculated as 3.30 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,295,866.68.km.

Sabik Apparent and Absolute Magnitudes

Sabik has an apparent magnitude of 2.43 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 0.37 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.27. 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 Sabik

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 38.77 which gave the calculated distance to Sabik as 84.13 light years away from Earth or 25.79 parsecs. It would take a spaceship travelling at the speed of light, 84.13 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 36.91 which put Sabik at a distance of 88.37 light years or 27.09 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.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Sabik Facts

Alternative Names

Traditional NameSabik
Short Name35 Oph
Arabic NameAs-Sabiq
English MeaningThe preceding
Bayer DesignationEta Ophiuchi
Alternative Name(s)35 Ophiuchi
Hipparcos Library I.D.84012
Yale Bright Star Catalogue (HR) Id6378
Bonner DurchmusterungBD-15 4467
Gould I.D.90
Henry Draper Designation155125

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude0.37 / 0.27
Apparent Magnitude2.43
Right Ascension (R.A.)17h 10m 22.66
Declination (Dec.)-15d43`30.5
1997 Distance from Earth38.77 Parallax (milliarcseconds)
 84.13 Light Years
 25.79 Parsecs
2007 Revised Distance from Earth36.91 Parallax (milliarcseconds)
 88.37 Light Years
 27.09 Parsecs
Proper Motion Dec.99.17 ± 0.37 milliarcseconds/year
Proper Motion RA.40.13 ± 0.80 milliarcseconds/year
B-V Index0.05
Spectral TypeA2.5Va
Brightest in Night Sky86th
Colour(A) blue
Stars in Solar System2

Estimated Facts

Radius (x the Sun)3.30
Luminosity (x the Sun)17.0000000
Calculated Effective Temperature8,917 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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
155125-15 4467.0A3.1000036.0000092.00000A2White
B3.600001889
C12.200001911
D10.700001898

Location of Sabik in Ophiuchus


Sabik (Eta Ophiuchi) Location in Ophiuchus

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


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