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11 Geminorum, HD43818, HIP30046

11 Geminorum is a blue pulsating luminous giant star that can be located in the constellation of Gemini. The description is based on the spectral class. 11 Geminorum is not part of the constellation but is within the borders of the constellation.

The star can not be seen by the naked eye, you need a telescope to see it.

11 Geminorum's Alternative Names

HIP30046 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD43818.

11 Geminorum has alternative name(s) :- , LU Gem.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 11 Geminorum with it shortened to 11 Gem.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+23 1300.

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

Location of 11 Geminorum

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 11 Geminorum, the location is 06h 19m 19.30 and +23° 28` 09.9 .

Radial Velocity and Proper Motion of 11 Geminorum

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 -1.57 ± 0.39 miliarcseconds/year towards the north and -0.61 ± 0.67 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 the Sun is 18.20 km/s with an error of about 3.00 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties (Colour, Temperature) of 11 Geminorum

11 Geminorum has a spectral type of B0II. This means the star is a blue luminous giant 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 7,058 Kelvin.

11 Geminorum Radius has been calculated as being 17.85 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 12,417,864.20.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 25.68. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

11 Geminorum Apparent and Absolute Magnitudes

11 Geminorum has an apparent magnitude of 6.91 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 -2.28 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.07. 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 11 Geminorum

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.45 which gave the calculated distance to 11 Geminorum as 2249.40 light years away from Earth or 689.66 parsecs. It would take a spaceship travelling at the speed of light, 2249.40 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 1.01 which put 11 Geminorum at a distance of 3229.34 light years or 990.10 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.

Using the 2007 distance, the star is roughly 204,221,361.63 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

Variable Type of 11 Geminorum

The star is a pulsating Beta Cephei 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. 11 Geminorum brightness ranges from a magnitude of 7.004 to a magnitude of 6.958 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.0 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 Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

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11 Geminorum Facts

Visual Facts


Primary / Proper / Traditional Name11 Geminorum
Alternative NamesHD 43818, HIP 30046, 11 Gem, BD+23 1300, LU Gem
Spectral TypeB0II
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeLuminous Giant Star
Colour blue
GalaxyMilky Way
ConstellationGemini
Absolute Magnitude -2.28 / -3.07
Visual / Apparent Magnitude6.91
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)06h 19m 19.30
Declination (Dec.)+23° 28` 09.9
Galactic Latitude3.87 degrees
Galactic Longitude188.49 degrees
1997 Distance from Earth1.45 Parallax (milliarcseconds)
 2249.40 Light Years
 689.66 Parsecs
2007 Distance from Earth1.01 Parallax (milliarcseconds)
 3229.34 Light Years
 990.10 Parsecs
 204,221,361.63 Astronomical Units
Proper Motion Dec.-1.57 ± 0.39 milliarcseconds/year
Proper Motion RA.-0.61 ± 0.67 milliarcseconds/year
B-V Index0.25
Radial Velocity18.20 ± 3.00 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeBeta Cephei
Mean Variability Period in Days0.029
Variable Magnitude Range (Brighter - Dimmer)6.958 - 7.004

Estimated Facts


Calculated Effective Temperature7,058 Kelvin

Sources and Links


SIMBAD SourceLink

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