Universe Guide


77 G. Oph, HD154204, HIP83567

77 G. Oph is a blue subgiant 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.

HIP83567 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD154204. The Id of the star in the Gould Star Catalogue is 77. 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.

Location of 77 G. Oph

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 77 G. Oph, the location is 17h 04m 45.33 and -20d29`40.7 .

Proper Motion of 77 G. Oph

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 -24.27 ± 0.28 miliarcseconds/year towards the north and -5.17 ± 0.51 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of 77 G. Oph

77 G. Oph has a spectral type of B7IV/V. This means the star is a blue subgiant star. The star is 7260.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23679.4587744000000000s. The star has a B-V Colour Index of -0.03 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 10,010 Kelvin.

77 G. Oph Radius has been calculated as being 2.09 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,453,821.99.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.48. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

77 G. Oph Apparent and Absolute Magnitudes

77 G. Oph has an apparent magnitude of 6.29 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 0.86 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.49. 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 77 G. Oph

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.21 which gave the calculated distance to 77 G. Oph as 397.28 light years away from Earth or 121.80 parsecs. It would take a spaceship travelling at the speed of light, 397.28 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 6.91 which put 77 G. Oph at a distance of 472.02 light years or 144.72 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 7,260.00 Parsecs or 23,679.46 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.

77 G. Oph Facts

Alternative Names

Traditional/Proper Name77 G. Oph
Hipparcos Library I.D.83567
Bonner DurchmusterungBD-20 4627
Gould I.D.77
Henry Draper Designation154204

Visual Facts

Star Typesubgiant star
Absolute Magnitude0.86 / 0.49
Visual / Apparent Magnitude6.29
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)17h 04m 45.33
Declination (Dec.)-20d29`40.7
Galactic Latitude12.39 degrees
Galactic Longitude1.91 degrees
1997 Distance from Earth8.21 Parallax (milliarcseconds)
 397.28 Light Years
 121.80 Parsecs
2007 Revised Distance from Earth6.91 Parallax (milliarcseconds)
 472.02 Light Years
 144.72 Parsecs
Galacto-Centric Distance23,679.46 Light Years / 7,260.00 Parsecs
Proper Motion Dec.-24.27 ± 0.28 milliarcseconds/year
Proper Motion RA.-5.17 ± 0.51 milliarcseconds/year
B-V Index-0.03
Radial Velocity-11.00 ± 4.30 km/s
Spectral TypeB7IV/V
Colour(B) blue

Estimated Facts

Calculated Effective Temperature10,010 Kelvin

Sources and Links

SIMBAD SourceLink

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