Universe Guide


9 Geminorum, HD43384, HIP29840

9 Geminorum is a blue pulsating very luminous supergiant star that can be located in the constellation of Gemini. 9 Geminorum is the brightest star in Gemini based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

HIP29840 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD43384.

9 Geminorum has alternative name(s), PX Gem.

Location of 9 Geminorum

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 9 Geminorum, the location is 06h 16m 58.71 and +23d44`27.3 .

9 Geminorum 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 180000.0000000 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, Radius) of 9 Geminorum

9 Geminorum has a spectral type of B3Ia. This means the star is a blue supergiant star. The star has a B-V Colour Index of 0.44 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,276 Kelvin.

9 Geminorum Radius has been calculated as being 28.55 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 19,863,206.21.km. 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 -0.14 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

9 Geminorum Apparent and Absolute Magnitudes

9 Geminorum has an apparent magnitude of 6.24 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 -2.79 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 9 Geminorum

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.56 which gave the calculated distance to 9 Geminorum as 2090.79 light years away from Earth or 641.03 parsecs. It would take a spaceship travelling at the speed of light, 2090.79 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

Variable Type of 9 Geminorum

The star is a pulsating Alpha Cygnus variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. 9 Geminorum brightness ranges from a magnitude of 6.388 to a magnitude of 6.333 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 13.7 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 Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

9 Geminorum Facts

Alternative Names

Traditional/Proper Name9 Geminorum
Flamsteed Name9 Geminorum
Flamsteed Short Name9 Gem
Short NamePX Gem
Hipparcos Library I.D.29840
Bonner DurchmusterungBD+23 1275
Henry Draper Designation43384

Visual Facts

Star Typesupergiant star
Visual / Apparent Magnitude6.24
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 16m 58.71
Declination (Dec.)+23d44`27.3
Galactic Latitude3.53 degrees
Galactic Longitude187.99 degrees
1997 Distance from Earth1.56 Parallax (milliarcseconds)
 2090.79 Light Years
 641.03 Parsecs
B-V Index0.44
Radial Velocity13.20 ± 2.90 km/s
Iron Abundance-0.14 ± 9.99 Fe/H
Spectral TypeB3Ia
Colour(B) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeAlpha Cygnus
Mean Variability Period in Days13.700
Variable Magnitude Range (Brighter - Dimmer)6.333 - 6.388

Estimated Facts

Luminosity (x the Sun)180,000.0000000
Calculated Effective Temperature6,276 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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