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25 Geminorum

25 Geminorum Facts

  • 25 Geminorum is a supergiant star that can be located in the constellation of Gemini. The description is based on the spectral class.
  • 25 Geminorum is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (G5Ib) of the star, the star's colour is yellow .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 2064.32 light years away from us. Distance

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 named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 25 Geminorum. The Flamsteed name can be 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 objects' alternative names can be found at Star Names .

Location of 25 Geminorum

The location of the supergiant 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 object 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 .

Radial Velocity and Proper Motion of 25 Geminorum

Proper Motion

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 milliarcseconds/year towards the north and -0.01 ± 0.53 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -3.10000 km/s with an error of about 0.50 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 of 25 Geminorum

25 Geminorum Temperature and Colour

Based on the star's spectral type of G5Ib , 25 Geminorum's colour and type is yellow supergiant star. The star has a B-V Colour Index of 1.09 which means the star's temperature is about 4,783 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

25 Geminorum Radius

25 Geminorum estimated 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 44.210739262337081904766079644. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

25 Geminorum Iron Abundance

25 Geminorum 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. The value comes from the Hipparcos Extended Catalog.

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 2.31000 which gave the calculated distance to 25 Geminorum as 1411.96 light years away from Earth or 432.90 parsecs. If you want that in miles, it is about 8,300,383,881,920,329.98, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 1.58000 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.

Using the 2007 distance, the star is roughly 130,546,148.86 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.

Travel Time to 25 Geminorum

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Walking4346,091,829,894.32
Car12011,536,394,329.81
Airbus A3807361,880,933,858.12
Speed of Sound (Mach 1)767.2691,804,278,968.10
Concorde (Mach 2)1,534.54902,138,308.27
New Horizons Probe33,00041,950,524.84
Speed of Light670,616,629.002,064.32

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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Additional 25 Geminorum Facts and Figures

Visual Facts


Primary / Proper / Traditional Name25 Geminorum
Alternative NamesHD 47731, HIP 32019, HR 2453, 25 Gem, BD+28 1207
Spectral TypeG5Ib
Constellation's Main StarNo
Multiple Star SystemYes
Star Type very luminous Supergiant Star less luminour Supergiant Star
ColourYellow
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 Latitude10.42402564 degrees
Galactic Longitude186.47282968 degrees
1997 Distance from Earth2.31000 Parallax (milliarcseconds)
 1411.96 Light Years
 432.90 Parsecs
2007 Distance from Earth1.58000 Parallax (milliarcseconds)
 2064.32 Light Years
 632.91 Parsecs
 130,546,148.86 Astronomical Units
Proper Motion Dec.-3.02000 ± 0.29000 milliarcseconds/year
Proper Motion RA.-0.01000 ± 0.53000 milliarcseconds/year
B-V Index1.09
Radial Velocity-3.10000 ± 0.50 km/s
Iron Abundance-0.0600 ± 0.04 Fe/H

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Calculated Facts


Radius (x the Sun)44.21
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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