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HR 8799 - HD218396 - HIP114189

HR 8799 is a blue main sequence dwarf star that can be located in the constellation of Pegasus. HIP114189 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD218396. HR 8799 has alternative name(s), V342_Peg. HR 8799 has at least 4 Extrasolar Planets believed to be in orbit around the star.

Location of HR 8799

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 HR 8799, the location is 23h 07m 28.65 and +21d08`03.7 .

Proper Motion of HR 8799

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 -049.63 ± 000.45 towards the north and 107.93 ± 000.70 east if we saw them in the horizon.

HR 8799 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 11.0000000 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, Mass, Radius) of HR 8799

HR 8799 has a spectral type of A5V. This means the star is a blue main sequence dwarf star. The star has a B-V Colour Index of 0.25 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,483 Kelvin.

HR 8799 has been calculated as 1.42 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 989,025.02.km. The star's solar mass is 2.00 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 -0.470000, 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.

HR 8799 Apparent and Absolute Magnitudes

HR 8799 has an apparent magnitude of 5.97 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 2.96 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.99. 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 HR 8799

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 25.04 which gave the calculated distance to HR 8799 as 130.26 light years away from Earth or 39.94 parsecs. It would take a spaceship travelling at the speed of light, 130.26 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 25.38 which put HR 8799 at a distance of 128.51 light years or 39.40 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. HR 8799 brightness ranges from a magnitude of 6.000 to a magnitude of 6.000 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 1.0 days (variability).

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

HR 8799 Facts

Alternative Names

Traditional NameHR 8799
Short NameV342 Peg
Hipparcos Library I.D.114189
Bonner DurchmusterungBD+20 5278
Henry Draper Designation218396

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude2.96 / 2.99
Apparent Magnitude5.97
Right Ascension (R.A.)23h 07m 28.65
Declination (Dec.)+21d08`03.7
1997 Distance from Earth25.04 Parallax (milliarcseconds)
 130.26 Light Years
 39.94 Parsecs
2007 Revised Distance from Earth25.38 Parallax (milliarcseconds)
 128.51 Light Years
 39.40 Parsecs
Proper Motion Dec.-49.63 ± 0.45 milliarcseconds/year
Proper Motion RA.107.93 ± 0.70 milliarcseconds/year
B-V Index0.25
Spectral TypeA5V
Colour(A) blue

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count4

Variable Star Details

Mean Variability Period in Days1.000

Estimated Facts

Radius (x the Sun)1.42
Luminosity (x the Sun)11.0000000
Calculated Effective Temperature7,483 Kelvin
Mass Compared to the Sun2.00
Metallicity-0.47000

Sources and Links

SIMBAD SourceLink

Related Stars


List of Extrasolar Planets orbiting HR 8799


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronInclination
Hr 8799 BConfirmed7164250.000020086828.000
Hr 8799 CConfirmed1082145.0000200842.928.000
Hr 8799 DConfirmed1041054.0000.120082780.00028.000
Hr 8799 EConfirmed918000.000201014.5

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