Planets

Alpha Centauri System

 

Distance from earth: Approximately 4.37 light years

Alpha Centauri, the brightest "star" in the constellation of centaurus, when seen through a telescope, is, in fact, three stars orbiting around one another. This triple star system consists of two Sun-like stars, Alpha Centauri A and Alpha Centauri B, and a red dwarf, Alpha Centauri C, or Proxima Centauri.

The three gas giant planets orbiting Alpha Centauri B were discovered by terrestrial observatories. The five rocky planets were found two decades later. Since the arrangement of the planets resembled our own solar system, they were named for their counterparts: Vulcan (inside Mercury's orbit), Hermes (Mercury), Aphrodite (Venus), Gaea (Earth), Ares (Mars), Zeus (Jupiter), Cronus (Saturn), and Poseidon (chosen instead of another name for Uranus, because it occupies the equivalent of Neptune's orbit).

The three gas giants around ACA were not found until after the co-orbiting synchronized telescopic interferometer network (COSTIN) went into full operation. Upon their discovery they were named Oceanus, Coeus, and Crius. Coeus was later renamed, or perhaps nicknamed, Polyphemus .

Alpha Centauri is a trinary star system, and Earth's closest stellar neighbor outside the solar system.

Its largest member, Alpha Centauri A (or "ACA" to astronomers), is about twenty-percent larger than our Sun, but otherwise very similar. ACA would be unremarkable were it not for the fact that it serves as the Sun for Pandora, a large moon that orbits Polyphemus. It was on Pandora that explorers encountered the Na'vi, the only intelligent species yet discovered in outer space. Pandora is also the only known source for Unobtanium, a high temperature superconductor essential for many of Earth's technologies.

more after the jump

Alpha Centauri B (ACB) is about fifteen percent smaller than our Sun, and noticeably orange because it is 500 degrees-K cooler than its neighboring star. Alpha Centauri C (ACC) is a red dwarf, only twenty percent of the size of the Sun and less than half of its temperature. ACC gives off only a dim red glow instead of the bright yellow glare of the Sun and ACA.

The astronomical coordinates for the Centaurus star system are: Right Ascension 14h 39.6m; Declination -60 degrees 50'. Alpha Centauri A and B are located approximately 4.37 light years or 277,600 Astronomical units from Earth. (one AU equals about 93,000,000 miles, the average distance of Earth from the Sun.) Alpha Centauri C (also called "Proxima Centauri" because its the closest of the three stars to Earth) about 0.15 light years closer. 

Polyphemus is the second of three gas giants orbiting Alpha Centauri A (ACA). A little smaller and denser than Saturn, Polyphemus has no rings and fourteen moons, the most notable being Pandora. Originally, its name was Coeus.

Visually Polyphemus resembles a blue/purple version of Jupiter, with both less prominent bands, and a larger vortex storm. This large eye-shaped storm is the source of the planets name; Polyphemus being the gigantic one-eyed son of Poseidon and Thoosa, in Greek mythology.

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. Since Polyphemus' orbit lies in ACA's habitable zone, appropriately sized planets or moons may have liquid surface water, and therefore support life.

Depending on where the moons are in their orbits, Pandora may 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.

Pandora

 Air

Nitrogen, Oxygen, Carbon Dioxide (over 18%), Xenon (5.5%), Ammonia, Methane and Hydrogen Cyanide

Galaxy    -                     Milky Way

Diameter                       11447 km

Mass                              0.72 Earths

Gravity                          0.8 g

Atmospheric density     1.2 Earths

Surface pressure            0.9 atm

Pandora is a moon of the gas giant Polyphemus, (both are figures in Greek mythology) which orbits Alpha Centauri A.  Discovered by the first interstellar expedition twenty-five years ago in 2129, Pandora has been the single most interesting thing to happen to the human race in hundreds of years. The news services love to run clips of the wild scenery on Pandora, and its bizarre flora and fauna.

To the cultures of Earth, which has lost all contact with the natural world, Pandora is mysterious, primal and terrifying.

Pandora's proximity to Polyphemus and the other two closest moons produce tidal heating that helps increase rapid continental drift. This creates intense cvulcanism and fractures large continental landmasses, moderating the moon's weather. /The unique substance "unobtanium" has helped create a myriad of remakrkable geological formations through its superconducting magnetic properties. These include the famouse Hallelujah Mountains and the Stone Arches. Despite Pandora's alien landscape, there are Earth-like vallerys, mountaintops, beaches, and lakes. It's unmarred beauty has sparked the imagination of Terrans everywhere.

Pandora's atmosphere is a poisonous (to humans) brew of nitrogen, oxygen, carbon dioxide, xenon, ammonia, methane, and hydrogen cyanide. Even from orbit the scope of florae present on the surface indicates a planet brimming with life.

Other than the color, the trees resemble those of Earth. They have the familiar trunks and branches and leaves, though, due to the difference in planetary gravity, many of the shapes are strange and the proportions are greater due to the lower gravity. The trees and all plant life of Pandora have formed electrochemical connections between the roots and effectively act as neurons, creating a planet-wide "brain" that has achieved sentience

Pandora, despite being almost the same size as Earth, is only a moon of the gas giant Polyphemus, which has thirteen other moons. However, due to its smaller size, its gravity is lower than Earth's. Depending on the position of the various moons, Pandora can have two or even three moons in its sky at once. Pandora and the other moons cast large black shadows on Polyphemus

Pandora appears like a lush paradise by Earth standards during the day, though at night virtually all life on the planet exhibits bioluminescent qualities in various shades of blue (explaining the Na'vi's blue skin color, which is most likely a better camouflage at night on Pandora).

 Discovery

When astronomers turned a powerful space-based telecope toward the Alpha Centauri system, and one of it's planets, Polyphemus, they were stunned to find a moon that had an atmosphere with the specto-scopic signiture of free oxygen, in a concentration almost equal to earth's. Given the presence of oxygen, scientists believed that the moon could harbor life. Even more intriguing was the splitting of spectrographic lines that indicated the presence of intesne magnetic fields, far stronger thatn any known outside of a star's interior.

This spurred the construction of even larger space telescopes. They revealed Pandora to be a verdant Earth-like world in the star system nearest to our own. A subsequent unmanned mission led to the discovery of a world teeming with plants, animals, and geological oddities. The research craft also discovered the source of the intense magnetic fields, a substance that had the remarkable property of high-temperature superconductivity.

It was this substance, later named unobtanium, that made it financially feasable to launch the manned exploration of Pandora. But it was the image of the Na'vi that empowered the world to come together to embrace the first manned mission to another star system.

Geology

Pandora's phystical construction resemble's Earth's; a liquid iron core, a plastic mantle, and a semirigic crust. Like Earth, it has two internal heat sources; the disintegration of radio-active isotopes, and energy from the gravitational collapse of its initial formation. But there is an additional and much larger energy input from tidal forces; the nearest inner and outer moons pull on it in contest with Polyphemus.

This excess of energy drives continental drit at a much faster rate than on Earth, causing the tectonic plates to fracture more extensively because of the increased stress. This explains the lack of large continents on Pandora, as well as it's vulcanism and geothermal activity.

Though Pandora's land-to-water ratio is greater than Earth's, the land is broken up into a larger number of smaller cotinents, creating more coastline and fewer inland regions than on Earth. The moderating influence of the proximity of the continental interior to the oceans reduces extremes in temperature. Polar ice caps comparable to Earth's exist, but because there are no landmasses in the polar areas, the Pandoran ice caps are currently free-floating.

Pandora is more volcanically active than Earth. There are vents both on the land and under the oceans. Many of the mountains and other surface features are of recent volcanic origin. Numerous hot springs and geysers dot the landscape, and there are several rivers that are almost boiling at the place where they erupt from underground aquifers.

Magnetic Fields

Pandora possesses a liquid iron core, with circulating currents that produce a dipole field similar in structure  to the Earth's, but the presence  of unobtanium deposits deep below the surface magnifies its strength hundreds of times. This enhanced fields shields the surface from cosmic rays of material ejected from Alpha Centrauri A, but unlike Earth, these intense magnetic fields are not as uniform, and concentrated unobtanium deposits produce localized distortions to the worldwide field that can act as magnetic funnels. These anomalies can channel incoming particles ejected from the sun to the moon's surface. Any life-form unlucky enough to be caught in one of these areas during a stellar flare event, or CME (Coronal Mass Ejection) will be quickly irradiated with a lethal dose. Depending of the type and amout of radiation, death can occur instantly as brain tissue is ionized and effectively "shorts out," or be delayed for agonizing days or weeks as the tissue slowly necrotizes.   

Pandora's global field also interacts with Polyphemus's much more extensive one. This can divert radiation trapped in the planet's magnetic field to th emoon's surface - also with unpleasant results. Additionally, the configuration of these two fields produces a "magnetic flux tube" that links the polar areas of the planet and satellite with an electrical current flow of millions of ampeers. This causes a gigantic increase in electrical activity on both bodies, with massive auroral storms and other electromagnetic-phenomena.

Atmosphere

Pandora is NOT Earth, and it's paradise is deceiving. The nitrogen-oxygen atmosphere is 20% denser than our own. It contains so much carbon dioxide (more than 18%) that humans who breathe it directly will rapidly loose conciousness and die. Another gas, hydrogen sulfide, is spewed out by pervasive vulcanism, and is toxic in concentrations far less than 1%. It must be removed by the exopack's mask along with the CO(2). The heavy gas xenon comprises about 5.5% of Pandora's atmosphere, and is responsible for much of the increased air density. Although Pandora's air is denser than Earth's the sea level pressure is about 10% less, in part because of the moon's gravity is only 80% of Earth's
The increased air resistance within the twenty-percent denser atmosphere has a number of effects:

- Lower terminal velocity. combined with Pandora's twenty-percent lower gravity, a freely falling object's maximum speed is significantly less than on earth. A Na'vi who happens to fall from a flying banshee (Ikran) has a good chance of surviving uninjured if they are over a forested area. Even over water, falling spread-eagled can reduce their speed sufficiently to allow an impact with the surface that will not knock them unconscious.

- The increased mass of the denser air means that more force is required to accelerate it as it is moved out of the path of a moving object. Humans on Pandora experience this when they try to run - it feels like there is a wind blowing against them, even though the air is still. They are further hampered by the fact that the reduced gravity causes their boots to slip more readily on paved or smooth surfaces, giving them less traction to force their bodies forward. The Na'vi compensate for this loss of frictional force by curling their large toes into the soft ground, and Pandoran six-legged animals use their many feet to gain a purchase on protruding rocks or small crevices.

- Flying animals can take advantage of both the lower gravity, which reduces the weight of their body, and the increased air density, which requires more force to displace with the downward/rearward stroke of their wings, and thus gives the animals body more impetus with each flap. The downside is that the denser air is harder to move through, and requires highly-efficient streamlining to achieve high flight speeds.

- Plants are subject to greater forces from the wind, since the greater air density means that the moving air carries more kinetic energy and more momentum, and the plants, leaves, stems, branches, and trunks must all have a greater strength and/or flexibility to resist it.

Day-Night Cycle

Pandora receives significant light from Alpha Centauri B (ACB). Because of this, for half the Polyphemian year its nights are never dark, but instead are more like Earthly dusk. At the closest point in its orbit, ACB is about 2,300 times as bright as Earth's full moon; at its farthest, it is still one hundred and seventy times as bright. During the other half of the year, when ACB is in the daytime sky, many Pandoran nights are illuminated both by Polyphemus's huge disk and reflected light from other nearby moons. Truly dark nights are uncommon. Polyphemus occasionally eclipses ACB at night for about one hundred minutes, but the light reflected by the planet still keeps the night from being dark.

When ACB shares the daytime sky with ACA, at its closest it adds about half a percent to the total illumination. When the 2 stars are close together in the sky, the effect of ACB's more orange light is unnoticeable, but as they separate over the years, an orange tint may be seen in areas shadowed from ACA's direct illumination. At its most distant, ACB is about 2,700 times dimmer than ACA and does not produce noticeable lighting effects. However, it still appears as a blindingly-bright tiny orange disk in the sky.

Because of its high axial tilt (29 degrees), Pandora exhibits considerable annual variation in the day-to-night ratio. In addition, its elliptical orbit produces seasonal temperature variations and a range in daytime illumination of about ten percent.

Terrain

The terrain on Pandora differs somewhat from place to place. With each terrain region there is a different clan to go with it. The Humans have settled in the jungle region which is home to the Omaticaya Clan. There are different ecosystems with each region but some wild life are the same such as the banshee. It also appears that floating land masses are not just isolated to the jungle region but are widespread as suggested in Avatar: The Game. The different terrains that are known are jungle, mountains, plains (savanna), and oceans. The jungle appears to be the largest region on Pandora.

 Trivia

The name Pandora refers to Pandora in Greek mythology who was the first woman ever created. She opened a jar (popularized as a box) out of curiosity which was filled with every evil mankind could experience, but managed to close it before releasing Hope, saving it from the destruction caused by the evils.

Polyphemus

 

Polyphemus is the second of three gas giants orbiting Alpha Centauri A (ACA). It is similar to our own Saturn, but unlike that planet with it's rings, Polyphemus orbits Alpha Centauri A at a distance  comparable to Earth's orbit of 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

Polyphemus has more prominent banding than Saturn, alought is bands are not as spectacular as Jupiter's. But Polyphemus has a vortex storm far exceeding Jupiter's Great Red Spot in size and turbulance. This large eye-shaped storm is the source of the planets name; Polyphemus being the gigantic one-eyed son of Poseidon and Thoosa, in Greek mythology. Auroral activity is near-continuous and intense enough to be visible in daylight. The chemical "stew" in its atmosphere is stirred by convection currents and gale-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.When magnetic clux tubes form and link to various satellites they too display brilliant auroral bands in the moon's polar regions, where the tube's flux joins the global ones.

* Polyphemus has 14 satellites, including Pandora. The two outer moons orbit in the opposite direction from all the others.