Polyphemus

Polyphemus
3D Version: red/cyan, cross-eyed
General Information
Galaxy	Milky Way
Star(s)	Alpha Centauri A
Moon(s)	Pandora Cassandra Hades Dante Chaos 9 other unnamed moons
Rotational Period	10.1 - 10.6 hours (depends on the cloud latitudes)
Diameter	123,900 km
Atmosphere	Hydrogen (>72%) Helium (>24%) 4% (Methane, Ammonia, Hydrogen sulfide, and Water vapor)
Behind the Scenes
First seen	James Cameron's Avatar: The Game

Polyphemus (Na'vi name: Naranawm meaning "great eye") is the second of the three gas giants and the fourth planet orbiting the star Alpha Centauri A (ACA by the humans; Tsawke by the Na'vi) in the Alpha Centauri System. Slightly smaller and denser than Jupiter, Polyphemus has no rings and has fourteen moons, the most notable being Pandora.

Polyphemus exerts strong gravitational and magnetic influence on Pandora which contributes to the dramatic geological and morphological elements on Pandora’s surface, called flux concentrations. Features like the Hallelujah Mountains or stone arches would not exist if not for these competing forces at play.

Polyphemus is similar to Saturn, but without its rings. But unlike that planet, which is located in the outer reaches of the Solar System, Polyphemus orbits Alpha Centauri A at a distance comparable to Earth's orbit around the Sun. Because Polyphemus formed in a higher-temperature environment than Saturn, it is composed of a much larger proportion of helium and other heavier elements and has a greater mass for its size. It also has a proportionally larger liquid metallic hydrogen core, an iron central body, and produces a far stronger and more extended planetary magnetic field.

Originally, the planet was named "Crius", after a Titan in Greek mythology, however the name was later changed to its current one.

History

Humanity discovered the gas giant somewhere between 2030 and 2057, using a ground-based telescope named COSTIN.

The ISV Ray Bradbury first discovered ACA after ACB. After discovering the two rocky planets, Odyssey and Ulysses, they discovered the first gas giant Coeus, and then Crius came next. The crew immediately noticed the massive eye-shaped storm, far larger than Jupiter's Great Red Spot. They renamed Crius to Polyphemus, after the Cyclops from Homer's epic "The Odyssey", and the new name was adopted after the crew returned to Earth eight years later.

Physical Description

Polyphemus compared with Jupiter

Visually, Polyphemus resembles a slightly smaller, blue and purple version of Jupiter, with less prominent bands and a larger vortex storm. This large, eye-shaped storm is the source of the planet's name, being that "Polyphemus" is the gigantic, cyclops son of Poseidon and Thoosa in Greek mythology, appearing in Homer's epic "The Odyssey". Unlike other gas giants, Polyphemus has no visible rings and to date, no trace of a ring system has been found.

At 74,000 miles in diameter, Polyphemus is slightly smaller than Saturn and considerably more massive. Its magnetic field, and thus its core, rotates in 9.7 hours. The visible surface features rotate more slowly, ranging from 10.1 to 10.6 hours, depending on latitude. Polyphemus has more prominent banding than Saturn, although not as spectacular as Jupiter. Still, Polyphemus has a vortex storm far exceeding Jupiter's "Great Red Spot" in size and turbulence. It also has an unusual internal structure and complex magnetic interactions with its inner satellites.

Polyphemus appears to be a typical gas giant with a typical composition. Like most planets, it started condensing from the primordial stellar nebula. Alpha Centauri A's system happened to be very rich in the heavier elements, particularly iron. Also, having formed closer to its sun, it has far less hydrogen because the higher temperature increased the speed of the lightest gas atoms preferentially, allowing them to escape the star's vicinity. The stellar wind also contributed to removing the lighter elements, blowing them farther outward.

Auroral activity is near-continuous and intense enough to be visible in daylight. When magnetic flux tubes form and link to various satellites, they too display brilliant auroral bands in the moons' polar regions where the tubes' flux joins the global ones.

As with all gas giants (especially gas giants close to the parent star, as with Polyphemus), this planet is surrounded by a lethal halo of charged particles (the radiation belts around Polyphemus are more energetic than the belts surrounding Jupiter); the innermost moonlets of Polyphemus have reported radiation in excess of 4,500 rem per day (Io receives 3,200 rem per day), which is aggravated due to the higher metallicity in the planets' internal composition. Pandora resides just outside the main radiation belts of Polyphemus, except for a week, when rotating along the night side of Polyphemus. At that time, the planet is shrouded at night in a shimmering aurora and receives a scourge of radiation.

Pandoran life has evolved to not be affected by strong ionizing radiation, but humans on Pandora routinely take iodine supplements and seek protection during radiation storms; even then, incidences of radiation-related sicknesses absorb a significant part of medical treatments for personnel stationed on Pandora.

Polyphemus can be seen in the sky on Pandora. Depending on where the moons are in their orbits, Pandora may also have two or even three moons in its sky at once. Depending on ACA's position, Pandora and the other large moons cast dark shadows on Polyphemus, like beauty marks.

Atmosphere

Because it formed in a higher-temperature environment, Polyphemus has less hydrogen and more helium in its atmosphere than most gas giants: seventy-two percent hydrogen and twenty-four percent helium, compared to Saturn's ninety-one percent and six percent. Since helium is about twice as dense as hydrogen, Polyphemus is much more massive than Saturn and thus has increased gravitational compression sufficient to produce a liquid metallic hydrogen center twice as large. The remaining four percent of the atmosphere is mainly composed of the gasses methane, ammonia, hydrogen sulfide, and water vapor.

There are minor amounts of compounds that are chemically reactive and therefore require a continual renewal mechanism. These compounds include acetylene, carbon monoxide, ethane, germane, methyl acetylene, phosphine, and propane. They are produced by high-temperature chemical reactions deep in the planet's interior, upper atmosphere energetic reactions from stellar ultraviolet photons, high-energy particles from the radiation belts, and atmospheric lightning discharges.

This chemical "stew" is stirred by convection currents and shearing-force winds produced by the planet's rapid rotation. The result is a brilliant display of an ever-changing pattern of colored cloud belts and rotating storms.

Internal Structure

Beneath the liquid droplet clouds that make up its visible "surface", Polyphemus' atmosphere gradually thickens as its temperature and pressure build up from gravitational compression. When the pressure reaches about two megabars (approximately 29,000,000 pounds per square inch, which is almost two million times Earth's sea level atmospheric pressure) and the temperature reaches about 6,000 K (10,340 °F, slightly hotter than the surface of the Sun), hydrogen undergoes a phase change to its metallic form. The size of the liquid metal portion is about three-quarters of the planet's total diameter. This feature is common to all but the smallest gas giants.

Continuing downward, there is a central core of molten iron, surrounded by a thin "jacket" of lighter, rockier material. Large amounts of iron are not commonly found in gas giants as they have mainly rocky cores.

Polyphemus has an intense internal heat source that results from the gravitational energy released during the contracting of the gases from which it is formed. Additionally, as hydrogen and helium were compressed, they changed from gases to liquids. This released their latent heat (also called the "heat of vaporization", which is the amount of energy it takes to evaporate a liquid into a gas). Finally, some of the helium that dissolved in the metallic hydrogen core condensed out & moved downwards, converting its gravitational potential energy into heat via friction processes.

Magnetic Environment

Polyphemus' rotation and its internal heat sources produce circulating convection flows in its liquid center. These flows carry entrained electric currents that generate an extremely powerful magnetic field. The liquid iron core at the center of the liquid metallic hydrogen exerts a synergistic effect and intensifies the magnetic field far beyond those produced by conventional gas giants. This magnetic field rotates with the planet. It serves to trap charged particles (electrons, protons, and ionized atoms and molecules) into various radiation belts that encircle the planet.

The merging of the fields of Pandora and Polyphemus is particularly interesting. The localized magnetic fields of Pandora's unobtanium deposits produce magnetic "hot spots" that can funnel some of Polyphemus' trapped radiation (or radiation emitted from Alpha Centauri A during flares) to the moon's surface (The consequences for anyone caught in the area are highly unpleasant). At certain times, a particular configuration of the two fields can cause a magnetic flux tube to form, linking the polar areas of the planet and satellite with an electrical current flow of millions of amperes. This causes a dramatic increase in electrical activity on both bodies, which results in massive lightning storms and other electromagnetic phenomena.

Satellite System

The moons of Polyphemus.

Polyphemus is said to have fourteen moons. Dante is the innermost moon, followed by Hades. The third and fourth moons are unknown, but the fifth is Pandora.

Cassandra is one known moon, and Chaos orbits beyond Cassandra, although their exact placements are unknown.

The two outer moons are known to orbit in a different direction from all the others.

In addition to the fourteen moons orbiting Polyphemus, there is a large and a small planetoid at the gas giant's L4 and L5 Lagrangian points respectively. These co-orbital asteroids are called Poly-L4 and Poly-L5.

Since Polyphemus' orbit lies in ACA's habitable zone, planet or moon-sized celestial bodies may have liquid surface water and therefore support life, as was the case with Pandora.

Real Life

There is an actual exoplanet candidate discovered in 2021 and possibly spotted again in 2025 where Polyphemus would be around Alpha Centauri A, named Alpha Centauri Ab (also known as "Rigil Kentaurus B" or originally named "Candidate 1") This planet is about the mass of Saturn, which makes it about the same size as Polyphemus is said to be (roughly Saturn-sized). It is also in the habitable zone and could host habitable moons or trojan planets.

Trivia

• In the files of Avatar: Reckoning, it is mentioned about 1 in 200 RDA employees feel extremely uneasy and sick when viewing Polyphemus due to its intense size, inducing feelings of megalophobia, as if one planet is about to be dropped on another.
• There seems to be an error in An Activist Survival Guide claiming Polyphemus was originally named "Coeus". However, there was a Pandorapedia entry in the French version of Avatar: The Game which goes into far more detail, mentioning Coeus and Crius are two separate gas giants, and that it was actually Crius which was re-named Polyphemus. The author of the Survival Guide seems to have made an error while simplifying information. Although neither source is considered canon, this article assumes that The Game is correct until further notice.

Gallery

Diagram in exhibit

Polyphemus with moons from The Game

Seen in Avatar

Seen in Avatar

Polyphemus blocking out Alpha Centauri A in The Way of Water

Seen in Fire and Ash

Seen in Frontiers of Pandora

Seen in The Way of Water - The RDA returns to Pandora; Polyphemus can be seen in the background.

Seen in Avatar: Polyphemus can be seen in the sky with two more moons visible.

Source

• James Cameron's Avatar: An Activist Survival Guide - Page 15
• James Cameron's Avatar: The Game (including French "Planetary Bodies" article from Pandorapedia)