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Pollux, Beta Geminorum, 78 Geminorum, HD62509, HIP37826, HR2990

Pollux (Beta Geminorum) Location in Gemini

Pollux (Beta Geminorum) is a orange to red giant star that can be located in the constellation of Gemini. The description is based on the spectral class. Pollux is a main star of the constellation.

Pollux is the 17th brightest star in the night sky and is the brightest star in Gemini based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. Pollux has at least 1 Extrasolar Planets believed to be in orbit around the star.

Pollux is the star that is the head of the left twin in the Geminiconstellation. The other head is the star Castor. It is one of a few number of stars with common names that have Extrasolar planet orbiting around it. The reason for this most other stars with Common names are giants and are at the ends of their lives such as Betelgeuse in the constellation of Orion.

Although it is growing in size, having used up its hydrogen supplies, its solar system is still able to host a planet orbiting it. The planet is believed to be a gas giant that is about 2.3 times the size of Jupiter and orbits round Pollux about 590 days. ref:space.

Pollux's Alternative Names

Beta Geminorum (Bet Gem) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR2990. HIP37826 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD62509. The Gliese ID of the star is GL 286. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

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 78 Geminorum with it shortened to 78 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 1463.

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

Location of Pollux

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 Pollux, the location is 07h 45m 19.36 and +28° 01` 34.7 .

Radial Velocity and Proper Motion of Pollux

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 -45.80 ± 0.14 miliarcseconds/year towards the north and -626.55 ± 0.27 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 3.23 km/s with an error of about 0.02 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.

Pollux 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 44.40 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Metallicity, Mass) of Pollux

Pollux has a spectral type of K0IIIvar. This means the star is a orange to red giant star. The star is 7,409.00 Parsecs from the Galactic Centre or terms of Light Years is 24,165.44 s. The star has a B-V Colour Index of 0.99 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,868 Kelvin.

Pollux Radius has been calculated as being 7.95 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 5,529,374.30.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 7.98. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 1.47 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

The star's metallicity is 0.190000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

Pollux Apparent and Absolute Magnitudes

Pollux has an apparent magnitude of 1.16 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 1.09 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.08. 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 Pollux

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 96.74 which gave the calculated distance to Pollux as 33.72 light years away from Earth or 10.34 parsecs. It would take a spaceship travelling at the speed of light, 33.72 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 96.54 which put Pollux at a distance of 33.79 light years or 10.36 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 2,136,888.50 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.

The star's Galacto-Centric Distance is 7,409.00 Parsecs or 24,165.44 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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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Pollux Facts

Visual Facts


Primary / Proper / Traditional NamePollux
Alternative NamesBeta Geminorum, Bet Gem, HD 62509, HIP 37826, HR 2990, 78 Geminorum, 78 Gem, BD+28 1463, Gliese 286
Spectral TypeK0IIIvar
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
Colour orange to red
GalaxyMilky Way
ConstellationGemini
Metalicity0.1900
Absolute Magnitude 1.09 / 1.08
Visual / Apparent Magnitude1.16
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)07h 45m 19.36
Declination (Dec.)+28° 01` 34.7
Galactic Latitude23.41 degrees
Galactic Longitude192.23 degrees
1997 Distance from Earth96.74 Parallax (milliarcseconds)
 33.72 Light Years
 10.34 Parsecs
2007 Distance from Earth96.54 Parallax (milliarcseconds)
 33.79 Light Years
 10.36 Parsecs
 2,136,888.50 Astronomical Units
Galacto-Centric Distance 24,165.44 Light Years / 7,409.00 Parsecs
Proper Motion Dec.-45.80 ± 0.14 milliarcseconds/year
Proper Motion RA.-626.55 ± 0.27 milliarcseconds/year
B-V Index0.99
Radial Velocity3.23 ± 0.02 km/s
Iron Abundance0.08 ± 9.99 Fe/H
Eccentricity0.20
Semi-Major Axis9100.00
Stellar Luminosity (Lsun)44.40
Brightest in Night Sky17th

Companions (Multi-Star and Exoplanets) Facts


Exoplanet Count1

Estimated Facts


Calculated Effective Temperature4,868 Kelvin
Mass Compared to the Sun1.47

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
62509+28 1463.0A1.20000-626.00000-51.00000K0Orange
B13.700001900
C8.900001922
CD11.700001922
E9.700001924
+28 1465.0F10.400001924
G1924

List of Extrasolar Planets orbiting Pollux


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
HD 62509 bConfirmed0.1589.6400.0220061.69354.580

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