Sigma Ophiuchi is a orange to red luminous giant star that can be located in the constellation of Ophiuchus. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
Sigma Ophiuchi is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR6498. HIP85355 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD157999.
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 49 Ophiuchi with it shortened to 49 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 143 G. Ophiuchi. There are no stars with a Gould designation in Ursa Major for example.
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+04 3422.
More details on star alternative names can be found at Star Names.
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 Sigma Ophiuchi, the location is 17h 26m 30.88 and +04° 08` 25.2 .
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 7.03 ± 0.16 miliarcseconds/year towards the north and 0.72 ± 0.29 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 us is -27.81000 km/s with an error of about 0.35 km/s .
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 3238.3200000 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.
Sigma Ophiuchi has a spectral type of K3IIvar. This means the star is a orange to red luminous giant star. The star is 7173.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23395.6966651200000000s. The star has a B-V Colour Index of 1.48 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,056 Kelvin.
Sigma Ophiuchi Radius has been calculated as being 92.20 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 64,154,291.02.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 70.91. 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 -0.05 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.
Sigma Ophiuchi has an apparent magnitude of 4.34 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 -3.44 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.87. 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.78 which gave the calculated distance to Sigma Ophiuchi as 1173.25 light years away from Earth or 359.71 parsecs. It would take a spaceship travelling at the speed of light, 1173.25 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 3.62 which put Sigma Ophiuchi at a distance of 901.00 light years or 276.24 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 7,173.00 Parsecs or 23,395.70 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.
|Alternative Names||HD 157999, HIP 85355, HR 6498, 143 G. Ophiuchi, 49 Ophiuchi, 49 Oph, BD+04 3422|
|Star Type||Luminous Giant Star|
|Absolute Magnitude||-3.44 / -2.87|
|Visual / Apparent Magnitude||4.34|
|Naked Eye Visible||Yes - Magnitudes|
|Right Ascension (R.A.)||17h 26m 30.88|
|Declination (Dec.)||+04° 08` 25.2|
|Galactic Latitude||20.75 degrees|
|Galactic Longitude||26.77 degrees|
|1997 Distance from Earth||2.78 Parallax (milliarcseconds)|
|1173.25 Light Years|
|2007 Revised Distance from Earth||3.62 Parallax (milliarcseconds)|
|901.00 Light Years|
|Galacto-Centric Distance||23,395.70 Light Years / 7,173.00 Parsecs|
|Proper Motion Dec.||7.03 ± 0.16 milliarcseconds/year|
|Proper Motion RA.||0.72 ± 0.29 milliarcseconds/year|
|Radial Velocity||-27.81 ± 0.35 km/s|
|Iron Abundance||-0.05 ± 9.99 Fe/H|
|Stellar Luminosity (Lsun)||3,238.32|
|Colour||(K) Orange to Red|
|Calculated Effective Temperature||4,056 Kelvin|