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HD 102117, HIP57291

HD 102117 is a white to yellow main sequence dwarf star that can be located in the constellation of Centaurus. The description is based on the spectral class. The star can not be seen by the naked eye, you need a telescope to see it. The star has an estimated age of 13.00 Billion of Years but could be as young as 11.10 to 14.50 according to Hipparcos. HD 102117 has at least 1 Extrasolar Planets believed to be in orbit around the star.

HD 102117's Alternative Names

HIP57291 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD102117.

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

Location of HD 102117

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 HD 102117, the location is 11h 44m 50.53 and -58° 42` 12.7 .

Proper Motion of HD 102117

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 -70.76 ± 0.43 miliarcseconds/year towards the north and -63.74 ± 0.61 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 49.59000 km/s with an error of about 0.00 km/s .

HD 102117 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 1.56 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, Metallicity, Age, Mass) of HD 102117

HD 102117 has a spectral type of G6V. This means the star is a white to yellow main sequence dwarf star. The star is 7,384.00 Parsecs from the Galactic Centre or terms of Light Years is 24,083.90 s. The star has a B-V Colour Index of 0.72 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,503 Kelvin.

HD 102117 Radius has been calculated as being 1.39 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 964,153.31.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 1.31. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 1.03 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

The star's metallicity is 0.300000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

The stars age according to Hipparcos data files put the star at an age of about 13.00 Billion years old but could be between 11.10 and 14.50 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old. The reported age is older than the widely recognised age of the Universe so a little scepticism about the age is warranted.

HD 102117 Apparent and Absolute Magnitudes

HD 102117 has an apparent magnitude of 7.47 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 4.35 If you used the 2007 Parallax value, you would get an absolute magnitude of 4.48. 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 HD 102117

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 23.81 which gave the calculated distance to HD 102117 as 136.99 light years away from Earth or 42.00 parsecs. It would take a spaceship travelling at the speed of light, 136.99 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 25.19 which put HD 102117 at a distance of 129.48 light years or 39.70 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 7,384.00 Parsecs or 24,083.90 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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HD 102117 Facts

Visual Facts


Primary / Proper / Traditional NameHD 102117
Alternative NamesHD 102117, HIP 57291
Spectral TypeG6V
Multiple Star SystemNo / Unknown
Star Type main sequence Dwarf Star
Colour white to yellow
GalaxyMilky Way
ConstellationCentaurus
Age13.00 Billion Years Old
Age Range11.10 - 14.50 Billion Years Old
Metalicity0.3000
Absolute Magnitude4.35 / 4.48
Visual / Apparent Magnitude7.47
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)11h 44m 50.53
Declination (Dec.)-58° 42` 12.7
Galactic Latitude3.06 degrees
Galactic Longitude294.36 degrees
1997 Distance from Earth23.81 Parallax (milliarcseconds)
 136.99 Light Years
 42.00 Parsecs
2007 Distance from Earth25.19 Parallax (milliarcseconds)
 129.48 Light Years
 39.70 Parsecs
Galacto-Centric Distance24,083.90 Light Years / 7,384.00 Parsecs
Proper Motion Dec.-70.76 ± 0.43 milliarcseconds/year
Proper Motion RA.-63.74 ± 0.61 milliarcseconds/year
B-V Index0.72
Radial Velocity49.59 ± 0.00 km/s
Iron Abundance0.27 ± 0.02 Fe/H
Eccentricity0.32
Semi-Major Axis5434.00
Stellar Luminosity (Lsun)1.56

Companions (Multi-Star and Exoplanets) Facts


Exoplanet Count1

Estimated Facts


Calculated Effective Temperature5,503 Kelvin
Mass Compared to the Sun1.03

Sources and Links


SIMBAD SourceLink

List of Extrasolar Planets orbiting HD 102117


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronInclination
HD 102117 bConfirmed0.01820.6700.10620040.1532283.0002004.000

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