Universe Guide


Gliese 818, HD200779, HIP104092

Gliese 818 is a orange to red star that can be located in the constellation of Equuleus. Gliese 818 is the brightest star in Equuleus based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP104092 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD200779. The Gliese ID of the star is Gliese GL818. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

Location of Gliese 818

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 Gliese 818, the location is 21h 05m 19.70 and +07d04`14.4 .

Proper Motion of Gliese 818

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 -563.11 ± 0.75 miliarcseconds/year towards the north and 77.22 ± 0.95 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Gliese 818

Gliese 818 has a spectral type of K5. This means the star is a orange to red star. The star is 7392.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24109.9943884800000000s. The star has a B-V Colour Index of 1.11 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,742 Kelvin.

Gliese 818 Radius has been calculated as being 0.46 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 317,242.95.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 0.46. 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 0.04 with an error value of 0.02 Fe/H with the Sun has a value of 1 to put it into context.

Gliese 818 Apparent and Absolute Magnitudes

Gliese 818 has an apparent magnitude of 8.27 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 7.41 If you used the 2007 Parallax value, you would get an absolute magnitude of 7.38. 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 Gliese 818

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 67.38 which gave the calculated distance to Gliese 818 as 48.41 light years away from Earth or 14.84 parsecs. It would take a spaceship travelling at the speed of light, 48.41 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 66.41 which put Gliese 818 at a distance of 49.11 light years or 15.06 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 7,392.00 Parsecs or 24,109.99 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.

Gliese 818 Facts

Alternative Names

Traditional/Proper NameGliese 818
Hipparcos Library I.D.104092
Bonner DurchmusterungBD+06 4741
Gliese ID818
Henry Draper Designation200779

Visual Facts

Star Type star
Absolute Magnitude7.41 / 7.38
Visual / Apparent Magnitude8.27
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)21h 05m 19.70
Declination (Dec.)+07d04`14.4
Galactic Latitude-25.53 degrees
Galactic Longitude56.38 degrees
1997 Distance from Earth67.38 Parallax (milliarcseconds)
 48.41 Light Years
 14.84 Parsecs
2007 Revised Distance from Earth66.41 Parallax (milliarcseconds)
 49.11 Light Years
 15.06 Parsecs
Galacto-Centric Distance24,109.99 Light Years / 7,392.00 Parsecs
Proper Motion Dec.-563.11 ± 0.75 milliarcseconds/year
Proper Motion RA.77.22 ± 0.95 milliarcseconds/year
B-V Index1.11
Radial Velocity-66.94 ± 0.18 km/s
Iron Abundance0.04 ± 0.02 Fe/H
Spectral TypeK5
Colour(K) Orange to Red

Estimated Facts

Calculated Effective Temperature4,742 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
200779+06 4741.0A9.0000072.00000-576.00000K5Orange
200806+06 4742.0C9.90000-15.00000-6.00000F0Yellow/White1908

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