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25 Geminorum, HD47731, HIP32019, HR2453

25 Geminorum is a white to yellow supergiant star that can be located in the constellation of Gemini. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

25 Geminorum's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR2453. HIP32019 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD47731.

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 25 Geminorum with it shortened to 25 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+28 1207.

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

Location of 25 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 25 Geminorum, the location is 06h 41m 20.90 and +28° 11` 47.9 .

Proper Motion of 25 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 -3.02 ± 0.29 miliarcseconds/year towards the north and -0.01 ± 0.53 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 -3.10000 km/s with an error of about 0.50 km/s .

Physical Properties (Colour, Temperature) of 25 Geminorum

25 Geminorum has a spectral type of G5Ib. This means the star is a white to yellow supergiant star. The star has a B-V Colour Index of 1.09 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,783 Kelvin.

25 Geminorum Radius has been calculated as being 30.17 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 20,989,594.71.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 44.21. 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 -0.06 with an error value of 0.04 Fe/H with the Sun has a value of 1 to put it into context.

25 Geminorum Apparent and Absolute Magnitudes

25 Geminorum has an apparent magnitude of 6.45 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 -1.73 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.56. 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 25 Geminorum

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.31 which gave the calculated distance to 25 Geminorum as 1411.96 light years away from Earth or 432.90 parsecs. It would take a spaceship travelling at the speed of light, 1411.96 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 1.58 which put 25 Geminorum at a distance of 2064.32 light years or 632.91 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.

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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25 Geminorum Facts

Visual Facts


Primary / Proper / Traditional Name25 Geminorum
Alternative NamesHD 47731, HIP 32019, HR 2453, 25 Gem, BD+28 1207
Spectral TypeG5Ib
Multiple Star SystemYes
Star Type very luminous Supergiant Star
Colour white to yellow
GalaxyMilky Way
ConstellationGemini
Absolute Magnitude-1.73 / -2.56
Visual / Apparent Magnitude6.45
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 41m 20.90
Declination (Dec.)+28° 11` 47.9
Galactic Latitude10.42 degrees
Galactic Longitude186.47 degrees
1997 Distance from Earth2.31 Parallax (milliarcseconds)
 1411.96 Light Years
 432.90 Parsecs
2007 Distance from Earth1.58 Parallax (milliarcseconds)
 2064.32 Light Years
 632.91 Parsecs
Proper Motion Dec.-3.02 ± 0.29 milliarcseconds/year
Proper Motion RA.-0.01 ± 0.53 milliarcseconds/year
B-V Index1.09
Radial Velocity-3.10 ± 0.50 km/s
Iron Abundance-0.06 ± 0.04 Fe/H

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature4,783 Kelvin

Sources and Links


SIMBAD SourceLink

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
C10.400001878
47731+28 1207.0A6.50000-1.000002.00000K0Orange
B11.700001904

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