Universe Guide


TV Geminorum, HD42475, HIP29416

TV Geminorum is a red pulsating very luminous supergiant star that can be located in the constellation of Gemini. The star can not be seen by the naked eye, you need a telescope to see it.

HIP29416 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD42475.

TV Geminorum has alternative name(s), TV Gem.

Location of TV 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 TV Geminorum, the location is 06h 11m 51.41 and +21d52`05.7 .

Proper Motion of TV 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 -2.41 ± 0.34 miliarcseconds/year towards the north and 0.29 ± 0.58 miliarcseconds/year east if we saw them in the horizon.

TV 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 52000.0000000 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 TV Geminorum

TV Geminorum has a spectral type of M1:Iavar. This means the star is a red supergiant star. The star has a B-V Colour Index of 2.14 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 945 Kelvin. 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 0.18 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

TV Geminorum Apparent and Absolute Magnitudes

TV Geminorum has an apparent magnitude of 6.93 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 -2.96. 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 TV Geminorum

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as -0.67 which gave the calculated distance to TV Geminorum as -4868.11 light years away from Earth or -1492.54 parsecs. It would take a spaceship travelling at the speed of light, -4868.11 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 1.05 which put TV Geminorum at a distance of 3106.32 light years or 952.38 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 TV Geminorum

The star is a pulsating Semiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep) 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. TV Geminorum brightness ranges from a magnitude of 6.873 to a magnitude of 6.258 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.6 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.

TV Geminorum Facts

Alternative Names

Traditional/Proper NameTV Geminorum
Short NameTV Gem
Hipparcos Library I.D.29416
Bonner DurchmusterungBD+21 1146
Henry Draper Designation42475

Visual Facts

Star Typesupergiant star
Visual / Apparent Magnitude6.93
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)06h 11m 51.41
Declination (Dec.)+21d52`05.7
Galactic Latitude1.60 degrees
Galactic Longitude189.08 degrees
1997 Distance from Earth-0.67 Parallax (milliarcseconds)
 -4868.11 Light Years
 -1492.54 Parsecs
2007 Revised Distance from Earth1.05 Parallax (milliarcseconds)
 3106.32 Light Years
 952.38 Parsecs
Proper Motion Dec.-2.41 ± 0.34 milliarcseconds/year
Proper Motion RA.0.29 ± 0.58 milliarcseconds/year
B-V Index2.14
Radial Velocity20.42 ± 1.06 km/s
Iron Abundance0.18 ± 9.99 Fe/H
Spectral TypeM1:Iavar
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M, C, S or Me, Ce, Se) supergiants (Mu Cep)
Mean Variability Period in Days0.638
Variable Magnitude Range (Brighter - Dimmer)6.258 - 6.873

Estimated Facts

Luminosity (x the Sun)52,000.0000000
Calculated Effective Temperature945 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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