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Omicron Ophiuchi B, 39 Ophiuchi, HD156350, HIP84625, HR6425

Omicron Ophiuchi B is a white to yellow luminous giant star that can be located in the constellation of Ophiuchus. The description is based on the spectral class. Omicron Ophiuchi B 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. The star has an estimated age of 1.30 Billion of Years but could be as young as 1.20 to 1.40 according to Hipparcos.

Omicron Ophiuchi B's Alternative Names

Omicron Ophiuchi B (Omi Oph) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR6425. HIP84625 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD156350.

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 39 Ophiuchi with it shortened to 39 Oph.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 113 G. Ophiuchi. There are no stars with a Gould designation in Ursa Major for example.

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

Location of Omicron Ophiuchi B

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 Omicron Ophiuchi B, the location is 17h 18m 00.64 and -24° 17` 02.7 .

Radial Velocity and Proper Motion of Omicron Ophiuchi B

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 -8.10 ± 0.63 miliarcseconds/year towards the north and -57.47 ± 1.09 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 -29.90 km/s with an error of about 0.30 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.

Omicron Ophiuchi B 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 18.84 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Age) of Omicron Ophiuchi B

Omicron Ophiuchi B has a spectral type of G8/K0II. This means the star is a white to yellow luminous giant star. The star is 7,304.00 Parsecs from the Galactic Centre or terms of Light Years is 23,822.97 s. The star has a B-V Colour Index of 0.51 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,089 Kelvin.

Omicron Ophiuchi B Radius has been calculated as being 5.94 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,133,219.97.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 3.96. 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 0.23 with an error value of 0.08 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 1.30 Billion years old but could be between 1.20 and 1.40 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Omicron Ophiuchi B Apparent and Absolute Magnitudes

Omicron Ophiuchi B has an apparent magnitude of 6.59 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 0.75 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.63. 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 Omicron Ophiuchi B

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.78 which gave the calculated distance to Omicron Ophiuchi B as 481.07 light years away from Earth or 147.49 parsecs. It would take a spaceship travelling at the speed of light, 481.07 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 10.18 which put Omicron Ophiuchi B at a distance of 320.40 light years or 98.23 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 20,261,250.74 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.

The star's Galacto-Centric Distance is 7,304.00 Parsecs or 23,822.97 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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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Omicron Ophiuchi B Facts

Visual Facts


Primary / Proper / Traditional NameOmicron Ophiuchi B
Alternative NamesOmi Oph, HD 156350, HIP 84625, HR 6425, 113 G. Ophiuchi, 39 Ophiuchi, 39 Oph
Spectral TypeG8/K0II
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeLuminous Giant Star
Colour white to yellow
GalaxyMilky Way
ConstellationOphiuchus
Age1.30 Billion Years Old
Age Range1.20 - 1.40 Billion Years Old
Absolute Magnitude 0.75 / 1.63
Visual / Apparent Magnitude6.59
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)17h 18m 00.64
Declination (Dec.)-24° 17` 02.7
Galactic Latitude7.71 degrees
Galactic Longitude0.54 degrees
1997 Distance from Earth6.78 Parallax (milliarcseconds)
 481.07 Light Years
 147.49 Parsecs
2007 Distance from Earth10.18 Parallax (milliarcseconds)
 320.40 Light Years
 98.23 Parsecs
 20,261,250.74 Astronomical Units
Galacto-Centric Distance23,822.97 Light Years / 7,304.00 Parsecs
Proper Motion Dec.-8.10 ± 0.63 milliarcseconds/year
Proper Motion RA.-57.47 ± 1.09 milliarcseconds/year
B-V Index0.51
Radial Velocity -29.90 ± 0.30 km/s
Iron Abundance0.23 ± 0.08 Fe/H
Eccentricity0.18
Semi-Major Axis6176.00
Stellar Luminosity (Lsun)18.84
Associated / Clustered StarsOmicron Ophiuchi

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature6,089 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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