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WY Geminorum, HD42474, HIP29425

WY Geminorum is a red pulsating supergiant star that can be located in the constellation of Gemini. The description is based on the spectral class. WY 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.

WY Geminorum's Alternative Names

HIP29425 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD42474.

WY Geminorum has alternative name(s) :- , WY 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 1243.

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

Location of WY 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 WY Geminorum, the location is 06h 11m 56.25 and +23° 12` 25.4 .

Radial Velocity and Proper Motion of WY 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 -1.87 ± 0.42 miliarcseconds/year towards the north and -1.46 ± 0.81 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 24.07 km/s with an error of about 1.20 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 WY Geminorum

WY Geminorum has a spectral type of M2Iabpe comp. This means the star is a red supergiant star. The star has a B-V Colour Index of 1.51 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,993 Kelvin. The star's Iron Abundance is -0.36 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

WY Geminorum Apparent and Absolute Magnitudes

WY Geminorum has an apparent magnitude of 7.17 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 If you used the 2007 Parallax value, you would get an absolute magnitude of -7.43. 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 WY Geminorum

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as -0.17 which gave the calculated distance to WY Geminorum as -19186.08 light years away from Earth or -5882.35 parsecs. It would take a spaceship travelling at the speed of light, -19186.08 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 0.12 which put WY Geminorum at a distance of 27180.28 light years or 8333.33 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.

Variable Type of WY Geminorum

The star is a pulsating Slow Irregular 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. WY Geminorum brightness ranges from a magnitude of 7.281 to a magnitude of 7.101 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 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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WY Geminorum Facts

Visual Facts


Primary / Proper / Traditional NameWY Geminorum
Alternative NamesHD 42474, HIP 29425, BD+23 1243, WY Gem
Spectral TypeM2Iabpe comp
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type very luminous Supergiant Star
Colour red
GalaxyMilky Way
ConstellationGemini
Visual / Apparent Magnitude7.17
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)06h 11m 56.25
Declination (Dec.)+23° 12` 25.4
Galactic Latitude2.26 degrees
Galactic Longitude187.91 degrees
1997 Distance from Earth-0.17 Parallax (milliarcseconds)
 -19186.08 Light Years
 -5882.35 Parsecs
2007 Distance from Earth0.12 Parallax (milliarcseconds)
 27180.28 Light Years
 8333.33 Parsecs
Proper Motion Dec.-1.87 ± 0.42 milliarcseconds/year
Proper Motion RA.-1.46 ± 0.81 milliarcseconds/year
B-V Index1.51
Radial Velocity24.07 ± 1.20 km/s
Iron Abundance-0.36 ± 9.99 Fe/H

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.198
Variable Magnitude Range (Brighter - Dimmer)7.101 - 7.281

Estimated Facts


Calculated Effective Temperature3,993 Kelvin

Sources and Links


SIMBAD SourceLink

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