Sol Region Sight-Seeing Tour #2 – Pollux

2nd in a series of posts inspired by Elite Dangerous, a space video-game that I’ve been playing; full of images, cool astronomy & science facts, and associated sci-fi & pop culture trivia.

Sol Region Sight-Seeing Tour – Stop #2:
Pollux / β Geminorum


Pollux to Sun Comparison

Pollux is 34 lightyears from Sol, and the closest giant star to our sun. Pollux is 18 ly from Stop 1 on our tour, it’s “twin” Castor. Pollux is the 18th brightest star as seen from Earth (including the Sun) and the brightest star in constellation Gemini. Pollux is an orange-hued “evolved giant” star in a special spectral class, called Class KO-III. Earlier in its life it would have been a Class A (hot white or blue/white dwarf star), but Pollux has exhausted the hydrogen in its core, and expanded and cooled as a result. As such the star has moved off the line of main sequence or “adult” stars and entered it’s old age “giant” phase, and is estimated to be about 724 million years old. It is about two times the mass, and almost NINE times the radius of our Sun.


History & Trivia, Real and Fictional:

  • Reality: 
    • Known Exo-Planet:  Since 1993 Pollux was suspected of having a extrasolar planet due to measured radial velocity oscillations. Pollux b was confirmed in 2006, and officially named Thestias in 2015. Thestias was the father of Leda, the mother of Castor & Pollux in Greek Myth (see below). With some astronomical bodies already named for her, her patronym was chosen instead.
    • Star & Constellation names from Greek Myth: As mentioned in Tour Stop 1, the Constellation Gemini is named for “The Twins” of Greek mythology, Castor and Pollux. The two brothers were fraternal twins, born of their mother, Leda, but inseminated by separate fathers. The brightest star in the constellation is the “head” of the twin Pollux, son of the god Zuess, who seduced the queen in the guise of a swan. The 2nd brightest star in the constellation forms the “head” of the other twin, Castor, fathered by her husband Tyndareus, King of Sparta.
    • Chinese Star & Constellation Name: In the Chinese Constellation of the “North River” Běi Hé, (which consists of the stars western society named Castor, Pollux and ρ Geminorum), Pollux is known as Běi Hé sān or “Third Star of North River”.
    • Castor Crater: name of a crater on Epimetheus, the 11th moon of Saturn.
  • Fictional References:
    • Pollux in Star Trek: In S2E2 of the original series, the Enterprise has entered the Pollux system and approaches Pollux IV on a survey mission when a huge energy field in the shape of a glowing hand materializes and seizes the ship. An apparition appears on the bridge claiming to be the god Apollo. Other planets in the Pollux system also make appearances in various Star Trek novels and comics.
    • Frontier games: Ironically, wikipedia’s disambiguation page for the Pollux references ED, stating that a single permanent settlement engaged in mining and refining was located @ Pollux in the 2nd & 3rd installments of the series that would become Elite Dangerous. Namely Frontier: Elite II, and Frontier: First Encounters. As you will see, it still has a small population and is still involved in extraction, but it is starting to be mined out.

      System Details:

      Pollux has a long established human presence compared to our first tour stop. Obviously most of this is fictional (though possible for the star type). I’ll highlight some of the most interesting differences between game and reality details below.

      A quiet extraction system in the Federation of just over 51,000 people, this is the home of the Daedalus Consortium, formed at the turn of the 4th Millennium, (a reference to its history in previous versions of the game franchise). While still a faction there, currently the system is primarily in the control of the Earth Defense Fleet minor faction.

      The system consists of 4 large gas giant planets, 9 rocky moons, and a couple of metal rich planetary rings. It’s remarkably devoid of icy bodies often found around outer system gas giants. There are 2 starports, and 27 minor settlements spread around the 8 landable moons in the system. The stats of some of the most prominent bodies follow.

      • Pollux: Class G Star (same class as the sun, white-yellow dwarf stars), 0.8 to 1.2 solar mass in size, ~6,000°K temp. [NOTE: Note this does not match reality for some reason. As shown above, Pollux is Class K0-III (orange evolved giant)]
        • Age: 130 Million years [actually 724Myrs]
        • Solar Mass (w/ 1 being our sun): 0.9844 [actually 1.91 solar mass]
        • Solar Radius (w/ 1 being our sun): 9.3084 [weirdly close to actual 9.06 solar radius considering how far the other stars are. It’s like they only partially updated it with the factual data.]
        • Surface Temp: 4,487K [again pretty close to actual 4,586K]
        • Controlling Facton: Earth Defense Fleet
        • Government: Corporate
        • State: Boom, Expansion
        • Allegiance: Federation
        • Population: 51,053
        • Security: Low
      • Pollux 1: Class III gas giant (common giant planets that have primarily hydrogen & helium atmospheres without distinctive cloud layers). Surface temp 300-800K. Primarily blue in color because of optical scattering in atmosphere – with the chance of wispy cloud layers from sulphides & chlorides. [This planet is close enough to the actually discovered ExoPlanet Thestias in the few known details. Frontier may have updated their data to match, or its a darn lucky coincidence. (The algorithms they use to simulate these systems though is strongly based on science so that while skewed to provide lots of stuff to explore, they are all in the realm of possibility.)]
        • Earth Masses (with 1 being Earth): 874.3555 [Good match. Thestias has been estimated to be at least 2x mass of Jupiter which would be over 636 Earth masses.]
        • Radius: 75,280km
        • Gravity: 6.28G (1G is Earth’s gravity)
        • Surface Temp: 581K
        • Atmosphere: 72.9% Hydrogen, 27.1% Helium
        • Orbit: 589.6 days @ 1.76AU from Pollux (1 AU=dist from Earth to Sun) [matches Thestias orbital period and close to measured axis of 1.64AU]
      • Pollux 2: Class III gas giant
        • Earth Masses: 74.6795
        • Radius: 38,247km
        • Gravity: 2.08G
        • Surface Temp: 376K
        • Atmosphere: 72.9% Hydrogen, 27.1% Helium
        • Orbit: 1,534 days @ 2.48AU from Pollux
        • Moons: 1. Landable.
      • Pollux 2A “Cambridge”: moon of Pollux 2. Rocky body (little to no surface metal). Landable.
        • Earth Masses: 0.0010
        • Radius: 684km
        • Gravity: 0.09G
        • Surface Temp: 378K
        • Volcanism: none
        • Atmosphere: none
        • Composition: 80% rock, 20% metal
        • Orbit: 3.2 days @ 0.01AU from Pollux 2
      • Pollux 3: Class III gas giant
        • Earth Masses: 2,238.4815
        • Radius: 71,607km
        • Gravity: 17.75G
        • Surface Temp: 737K
        • Atmosphere: 72.9% Hydrogen, 27.1% Helium
        • Orbit: 3,498.4 days @ 4.5AU from Pollux
        • Moons: 7 (all rocky bodies, all landable.)
      • Pollux 3C: 3rd moon of Pollux 3. Rocky body. Home to surface starport Naddoddur Survey.
        • Earth Masses: 0.0098
        • Radius: 1,493km
        • Gravity: 0.18G
        • Surface Temp: 336K
        • Volcanism: none
        • Atmosphere: none
        • Composition: 91.1% rock, 8.9% metal
        • Orbit: 6.5 days @ 0.01AU from Pollux 3
      • Pollux 3Ea: 6th moon of Pollux 3. “MoonMoon” of Pollux 3E (the 5th moon of Pollux 3). Rocky body. [Moons of moons are believed to be scientifically possible, but yet to be observed. Most of these would probably be kind of orbiting each other and then orbiting their planet at their combined center of gravity. They are likely fairly uncommon.]
      • Pollux 4: Class II gas giant (rare large planets that have primarily hydrogen & helium atmospheres, but also water vapor in the upper cloud layers gives them a much higher albedo/reflectivity.) Surface temp around 250K.
        • Earth Masses: 31.8943
        • Radius: 23,032km
        • Gravity: 2.43G
        • Surface Temp: 209K
        • Atmosphere: 72.9% Hydrogen, 27.1% Helium
        • Orbit: 8,106.1 days @ 7.88AU from Pollux
        • Moons: 1
        • Rings: 1, metal rich
        • Orbital Starport: 1 “Cook Depot”. Orbital refinery & transport hub for ring mining.
      • Pollux 4a: moon of Pollox 4. Rocky body.
        • Rings: 1, metal rich

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