Universe Guide


20 G. Oph, HD148515, HIP80719

20 G. Oph is a blue to white main sequence dwarf 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. The star has an estimated age of 1.70 Billion of Years but could be as young as 1.40 to 1.90 according to Hipparcos.

HIP80719 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD148515. The Id of the star in the Gould Star Catalogue is 20. 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 20 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 20 G. Oph, the location is 16h 28m 48.99 and -08d07`43.2 .

Proper Motion of 20 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 -71.27 ± 0.49 miliarcseconds/year towards the north and -53.99 ± 0.80 miliarcseconds/year east if we saw them in the horizon.

20 G. Oph 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 4.0000000 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, Age, Radius) of 20 G. Oph

20 G. Oph has a spectral type of F2V. This means the star is a blue to white main sequence dwarf star. The star is 7355.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23989.3139512000000000s. The star has a B-V Colour Index of 0.41 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,681 Kelvin.

20 G. Oph Radius has been calculated as being 1.63 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,131,550.30.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.79. 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 0.01 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 1.70 Billion years old but could be between 1.40 and 1.90 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

20 G. Oph Apparent and Absolute Magnitudes

20 G. Oph has an apparent magnitude of 6.49 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 3.16 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.95. 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 20 G. Oph

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 21.55 which gave the calculated distance to 20 G. Oph as 151.35 light years away from Earth or 46.40 parsecs. It would take a spaceship travelling at the speed of light, 151.35 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 19.63 which put 20 G. Oph at a distance of 166.16 light years or 50.94 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 7,355.00 Parsecs or 23,989.31 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.

20 G. Oph Facts

Alternative Names

Traditional/Proper Name20 G. Oph
Hipparcos Library I.D.80719
Bonner DurchmusterungBD-07 4299
Gould I.D.20
Henry Draper Designation148515

Visual Facts

Star Typemain sequence dwarf star
Age1.70 Billion Years Old
Age Range1.40 - 1.90 Billion Years Old
Absolute Magnitude3.16 / 2.95
Visual / Apparent Magnitude6.49
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)16h 28m 48.99
Declination (Dec.)-08d07`43.2
Galactic Latitude26.69 degrees
Galactic Longitude7.13 degrees
1997 Distance from Earth21.55 Parallax (milliarcseconds)
 151.35 Light Years
 46.40 Parsecs
2007 Revised Distance from Earth19.63 Parallax (milliarcseconds)
 166.16 Light Years
 50.94 Parsecs
Galacto-Centric Distance23,989.31 Light Years / 7,355.00 Parsecs
Proper Motion Dec.-71.27 ± 0.49 milliarcseconds/year
Proper Motion RA.-53.99 ± 0.80 milliarcseconds/year
B-V Index0.41
Radial Velocity0.30 ± 1.40 km/s
Iron Abundance0.01 ± 0.08 Fe/H
Spectral TypeF2V
Colour(F) blue to white

Estimated Facts

Luminosity (x the Sun)4.0000000
Calculated Effective Temperature6,681 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
148515-07 4299.0A6.50000-60.00000-77.00000F0Yellow/White

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