The Science Behind
James Cameron's Avatar
Voyaging to the Stars
By Adam Hadhazy
[Link no longer available]
In Avatar: For the interstellar journey to Alpha Centauri, humans have constructed spaceships nearly a mile long outfitted with hybrid antimatter fusion engines. These craft can cruise up to seven-tenths of the speed of light, or about 670 million miles per hour; even hurtling at these speeds, however, the voyage to our nearest star neighbor takes about six years.
The Science: As a source of energy for propulsion, you can't top matter and antimatter particles coming into contact and annihilating each other.
"It's the strongest energetic reaction we know of," says NASA's George Schmidt, who has worked on advanced propulsion systems and is now deputy director of the Research and Technology Directorate in Ohio.
The energy unleashed by matter–antimatter destruction could be used directly as a propellant shot out of a nozzle at the rear of a rocket, or the antimatter could induce fission (splitting of atoms) or fusion (building of atoms) reactions in other materials to produce less, though still powerful, thrust.
However, getting enough antimatter for the 26 trillion-mile, one-way trip to Alpha Centauri and storing such a volatile fuel for long periods is prohibitively expensive and difficult.
First off, making the stuff is no easy task: Particle colliders at CERN near Geneva, Switzerland and Fermilab in Chicago have only ever produced around a dozen nanograms of antimatter (though it should be noted that these facilities were not designed to make antimatter in large quantities).
The going rate for antimatter is ballpark $60 billion a microgram, Schmidt says, though a several-billion-dollar, dedicated production facility could crank out the antiparticles for more like $6 million per microgram.
"I am happy that [the Avatar moviemakers] went with a hybrid nuclear process as the energy source," Schmidt says. "This type of concept would require much less antimatter than a pure antimatter rocket." But, Schmidt says, the combo antimatter fusion engine could not likely generate the thrust needed to get up to seven-tenths light speed.
Antimatter storage is the other serious barrier. Electromagnetic fields can store antimatter in so-called Penning traps by keeping the antimatter away from the container's walls.
But this only works for a few months before the antimatter bumps into stray-matter particles in the container's holding area, which cannot yet (or ever) be made into a perfect, matter-free vacuum, says Gerald Smith, professor emeritus of physics at Penn State and founder of Positronics Research, LLC, a Sante Fe–based company looking into applications of antimatter.
All told, an interstellar mission to Alpha Centauri—there and back again—hauling a sizable payload would require thousands of tons of antimatter sequestered in a fuel tank for years, Schmidt says, which clearly presents a major showstopper.
And once that's all worked out, there's the issue of slowing a ship down once it gets to Alpha Centauri. "You're going to be going at a pretty good clip," Schmidt says, and the ship could maybe swing through the stars' gravity wells in a kind of reverse slingshot effect to help decelerate.
Alpha Centauri | Source:
By Toliman, Rigel Kentaurus, Rigil Kentaurus
Alpha Centauri is a star of the southern sky, and is not visible to observers at a latitude greater than about 25° north (roughly the latitude of Florida, Egypt or Taiwan).
For those in the southern hemisphere, though, it is not hard to locate: it sits in the centre of the Milky Way, about fifteen degrees east of Crux.
In fact, a line through the cross-piece of the Southern Cross (from Delta Crucis to Becrux) points the way to Alpha Centauri.
While most of the sky's more famous stars are known by their proper names (Polaris, Sirius, Betelgeuse and so on), Alpha Centauri is unique among these in being better known by its Bayer designation, rather than one of its two proper names, Rigel Kentaurus or Toliman.
Of these, 'Rigel Kentaurus' means 'The Centaur's Foot', and is easy to understand as the name of a star in the southern parts of Centaurus, the constellation of the Centaur.
'Toliman' is a little more obscure: it means 'The Vine-shoot', and refers to the ancient tradition that the Centaur held a rod entwined with vines in his hand.
Its magnitude of -0.01 makes this the fourth brightest star in the sky, but only by a tiny fraction: it is just 0.04 magnitudes brighter than Vega in the northern constellation of Lyra.
In fact, Vega is intrinsically a much more luminous star than Alpha Centauri, but this is balanced by the fact that it is more than five times further away from Earth, so the two stars appear artificially similar in the sky.
Vega is not alone in being further away than Alpha Centauri: there are no stars closer to our own Sun than those in this system.
The Alpha Centauri system seems to have formed somewhat earlier than our own Solar System ('somewhat' in this context is probably of the order of a thousand million years or so).
At its heart, two remarkably Sun-like stars orbit their common centre of gravity roughly once every eighty years. Like our Sun, both stars are relatively stable in nature and, again like our Sun, they are comparatively rich in more complex elements.
Alpha Centauri B is an orange star, rather cooler than the Sun, and slightly less massive. By comparison, yellow Alpha Centauri A is close to a twin of our own star.
Its spectral classification (G2V) is identical, though the star itself is just a little more massive, and hence a little more luminous, than the Sun.
With these two stars, particularly Alpha Centauri A, being so similar to the Sun, it's natural to wonder whether they might host a system of planets, perhaps even terrestrial planets comparable to our own Earth.
At the moment, the technology to find this out for sure is several years in the future - there's simply no way of knowing whether such planets exist or not.
It's perhaps notable that to date not even the more massive planets that we are able to detect have been reported orbiting either of the main Alpha Centauri stars: if such planets are absent, any terrestrial planets within their systems would likely be affected.
Without the gravity of more massive planets to attract interplanetary debris, any inner planets of such a system would probably be at rather more risk of comet or asteroid strikes than our own planet.
Of course, this is no more than speculation - the actual workings of the Alpha Centauri systems, assuming they have any planets at all, is completely unknown at this time.
Beyond the A and B stars, there is a third component in the system: Alpha Centauri C. This is a tiny, faint red dwarf orbiting the two main stars at an immense distance: roughly one fifth of a light year.
This is a Proxima, a star with a faint reddish glow so feeble that it would hardly be visible even from the core the Alpha Centauri system.
It seems to be a late-comer to that system, perhaps a wanderer pulled into orbit by the two older stars, but it has one important distinguishing feature: it is the single closest star to our own Solar System.
For more info and imagery on the Alpha Centauri System, go to
Articles exploring the Alpha Centauri System and traveling there. Some articles contain excerpt highlights, click on the source link for the complete article.
Detecting Volcanos in Alpha Centauri
Scientists at at the Harvard-Smithsonian Center for Astrophysics have said that it is possible for us to detect volcanoes on alien planets. "You would need something truly earthshaking, an eruption that dumped a lot of gases into the atmosphere," said Smithsonian astronomer Lisa Kaltenegger.
"Using the James Webb Space Telescope, we could spot an eruption 10 to 100 times the size of Pinatubo for the closest stars," she added.
In a few cases, scientists have been able to detect exoplanet atmospheres for gas giants known as "hot Jupiters." An eruption sends out fumes and various gases, so volcanic activity on a rocky exoplanet might leave a telltale atmospheric signature.
Kaltenegger, Wade Henning and Dimitar Sasselov found that sulphur dioxide from a very large, explosive eruption is potentially measurable because a lot is produced and it is slow to wash out of the air. The 1991 eruption of Mount Pinatubo in the Philippines spewed about 17 million tons of sulphur dioxide into the stratosphere.
"Once you detected one eruption, you could keep watch for further ones, to learn if frequent eruptions are common on other planets," said Henning. To look for volcanic sulphur dioxide, astronomers would rely on a technique known as the secondary eclipse, which requires the exoplanet to cross behind its star as seen from Earth.
Alpha Centauri for instance, would offer a best-case scenario for a Sun-like star. A super-Earth orbiting a smaller host star close to our own Sun would show the biggest signal. But any Earth-like planet less than 30 light-years away could show faint signs of volcanism when studied with the James Webb Space Telescope.
Traveling from Earth to the Alpha Centauri system
By Larry Klaes | Excerpt: centauri-dreams.org
The starship that transported our hero, a Marine named Jake Sully, to Pandora made only a brief appearance at the beginning of the film. While nothing much was really said about this vessel, it did at least bear a resemblance to a craft that might actually operate in space at least during the next few centuries. This is in opposition to the starships of Star Trek and Star Wars, which often tend to be ’sexy’, sleek to the point of being needlessly aerodynamic in the near vacuum of space.
I do not recall the type of propulsion used by the starship in Avatar, but apparently it could attain high relativistic velocities, as the crew was in suspended animation for just over five years, which would be just about right for traveling from Earth to the Alpha Centauri system. Now whether we will have such a starcraft or any kind of manned starship by the year 2154 when the film takes place is another matter.
Now about the humans in Avatar: It seems that 150 years in the future people haven’t changed all that much, even though they do have some expectedly neat technology. But the people themselves don’t seem all that transformed by it, either physically or socially. This future society does have the means to repair major injuries, apparently – if the one injured can afford the care – and they do have the Avatar Program which allows people to place their minds in a genetically formed body of a Na’vi.
A Realistic Human Future?
My next point is the motives for humans being on Pandora. While the need for resources and land and the removal of any group that happens to be occupying the place where those resources are by a stronger group is an unfortunate but age-old reality on this planet, how plausible will it be once our civilization expands into the galaxy? I was disappointed that Cameron made it seem that most of humanity occupied one planet, the one it came from, when it was obvious that the society of 2154 was a spacefaring one.
The presence of manned starships would presume a serious colonization of the Sol system, yet we are told that Earth (meaning human society) is in trouble if it doesn’t get its hands on a mineral called unobtanium, which costs ten million per kilogram. Well, that price is understandable if one needs to haul a precious mineral across 25 trillion miles of deep space! It also seems fairly ridiculous for a society that should be occupying much of an entire solar system, where there are plenty of planetoids and moons and certain planets whose resources can be exploited.
Motives for the Great Voyage
So this leads us to the ultimate question: By the time we are ready to explore the stars and colonize alien worlds, will we actually do so? Will it be necessary to spread out into the galaxy? I think so, but I also have to wonder if the ones who do such actual interstellar exploring and colonizing will be very different from us, certainly much more different that the humans in Avatar. Will this mean that such encounters as depicted in the film will not happen, because the beings that do leave Earth will not be much like us, if at all?
And the aliens we come across may not resemble much at all certain native peoples of our planet’s past and present. The point that is often missed in plans for interstellar exploration and colonization is this: Whether we go into the galaxy with peaceful intentions or for reasons of empire, the odds seem good that the intelligent species out there may have serious difficulties in relating to us in any meaningful way, and we may have similar issues.
Will it eventually lead to new understandings on certain levels, or will we ignore each other, or actually try to destroy one another either from fear or a lack of awareness of the intelligence of the other? It will be very interesting to see what really takes us to the stars.
How to Get to Alpha Centauri
By Charles Q. Choi
If the nearest star system, Alpha Centauri, does harbor rocky planets similar to Earth as new findings suggest, there exist a host of ways to get us there, in theory.
Sending a person to Alpha Centauri within a human lifetime wouldn't be easy. Alpha Centauri is 4.37 light-years away more than 25.6 trillion miles, or more than 276,000 times the distance from the Earth to the sun.
"Interstellar travel is extremely hard," said science fiction author and NASA physicist Geoffrey Landis. But the lure has never been stronger. Conventional rockets are nowhere near efficient enough.
At a maximum speed of about 17,600 mph (about 28,300 kph), it would take the space shuttle, for example, about 165,000 years to reach Alpha Centauri. In any case, "the problem with conventional rockets is that if you're carrying fuel, you need fuel just to carry all the fuel you bring with you, and it just gets exponentially worse," Landis said. But antimatter engines might work. These drives rely on the extraordinary amount of energy released when antimatter and matter annihilate each other. The problem, however, is creating enough and storing any antimatter for the trip.
"All of the current methods of manufacturing antimatter require enormous particle accelerators and produce antimatter in very small quantities," Landis said. "And to store antimatter, if you need a ton of magnets for one gram of antimatter, the entire idea of a lightweight way to store immense amounts of energy is no longer lightweight." Although one could in principle freeze anti-hydrogen and thus bypass the need for magnets, "if even the tiniest amount ever leaked out and touched the walls surrounding it, you'd produce a lot of heat, which in turn would heat up the frozen anti-hydrogen, and the whole thing catastrophically goes away," Landis said.
Suck it up
Instead of rockets that carry all their fuel with them, spaceships might scoop it up along the way. One design proposed by physicist Robert Bussard (who died last year) would employ giant electromagnetic fields to suck in hydrogen to fuel a nuclear rocket. Unfortunately, this "ramscoop" or Bussard ramjet, probably could not work. "The interstellar medium is not as dense as Bob Bussard thought it would be," Landis said. "And so far all attempts to design some kind of scoop had the unfortunate effect of producing more drag than you get back thrust, working kind of like parachutes."
Moreover, "we don't really have any notion of how to use the pure hydrogen we find in interstellar space as fusion fuel," Landis added. All of the proposals for fusion in the lab use deuterium-tritium (two isotopes of hydrogen) or deuterium with helium-3 (an isotope of helium) — "we don't have any suggestions for pure hydrogen in a fusion reaction," he said. "It was a clever idea, but the devil's in the details."
Light sails might be another way to go — giant, thin, lightweight reflective sails that rely on the slight push provided by light beams. "The point is to not carry the energy you need for propulsion with you, but to get it transmitted to you," explained Jordin Kare, a Seattle-based technical consultant on advanced space systems. Instead of relying just on the enormous amount of light given off by the sun, light sails to Alpha Centauri could also ride laser beams that earthlings would fire carefully at those ships to give an extra boost, especially when sails were too far away to catch much light from our sun.
You just keep accelerating, albeit gradually. The problem with interstellar travel with laser sails is that a lot of light needs to be used for a long time to get fast enough to get to Alpha Centauri within a human lifetime. This means very powerful and extraordinarily large lasers are needed in order to focus on sails that get farther and farther away, Kare explained. An idea similar to light sails that Landis helped come up with involved firing a particle beam at a spaceship that would ride that energy.
Another idea for space travel would involve riding explosions through space. Such "pulsed propulsion" would hurl bombs behind a ship, which is shielded with a giant plate. The explosions would push against the plate, propelling the ship. Project Orion suggested using nuclear bombs, while other proposals have since proposed smaller explosives. "Nuclear pulsed propulsion works best for really big systems. If you want to send a colony of 1,000 people to space, an Orion-type ship is definitely the way to do it," Kare said. "If you want to send a one-ton probe, I would say a laser system is the way to go."
A variant on both the laser sail and pulsed propulsion idea that Kare came up with was the "sail beam." Essentially, a laser would propel lots of miniature sails like bullets at a distant ship. The impact of these sails would propel the spacecraft. "The idea is to get a craft up to about a tenth of the speed of light that way," Kare said. "It could get you to Alpha Centauri in 60 to 70 years."
Destination Alpha Centauri
WHY GO TO ALPHA CENTAURI?: Alpha Centauri lies only 4.35 light-years from our Sun, but it is in reality a triple star system. The two brightest components of the trinary star system are referred to as Alpha Centauri "A" and Alpha Centauri "B".
These two stars form a binary union within the group as they orbit each other, an orbit which takes 80 full years to complete and has a mean separation of 23 astronomical units (1 astronomical unit = 1 AU = the distance that we measure as existing between the Sun and the Earth) between the two stars.
The third star of this trinary system is labeled Alpha Centauri C. "C" lies 13,000 AU from both A and B (a distance roughly equivalent to 400 times the distance between our Sun and the eighth planet in our system, Neptune).
The distance between "A" and "B" and their relationship with "C" is so far that it is not known whether Alpha Centauri "C" is really bound to the twin movements and orbits of "A" and "B", or if "C" will simply leave the union of its own accord in the next several million years.
Alpha Centauri "C" lies measurably closer to us than either "A" or "B", being located at a distance of only 4.22 light-years away. Alpha Centauri "C" is the nearest individual star to our Sun. Because of this proximity, and its proximity to both Alpha Centauri "A" and "B", Alpha Centauri "C" is also called Proxima (Centauri).
Alpha Centauri "A" is a yellow star with a spectral type of G2, matching almost exactly the characteristics, including temperature and color, as our own Sun. Alpha Centauri "B" is an orange star with a spectral type of K1, somewhat cooler than our own Sun and Alpha Centauri "A" in both color and temperature. Whereas Alpha Centauri "A" and "B" are stars with very similar characteristics to our own Sun, and therefore high percentages for the existence of life supporting planets, Proxima Centauri is a dim red dwarf with a spectral type of M5.
Proxima Centauri is much fainter, cooler, smaller and fainter in appearance than our Sun, so much so that astronomers did not discover the existence of Proxima Centauri until 1915. Alpha Centauri is a very interesting star system because it may offer ideal life conditions similar to that which occur in our own solar system. A star must pass five tests before scientists can consider it to be a possible place for life, as we know it, terrestrial life, to exist.
Most stars in our Milky Way galaxy fail these simple tests, however, in the case of Alpha Centauri, we see that Alpha Centauri "A" passes all five tests, Alpha Centauri "B" passes all but one, with Proxima Centauri failing to be capable of supporting any life as we know it. The first test of any known or newly discovered star is the main sequence test, which is administered to be sure of the star's maturity and stability. A test for the star's maturity and stability means that the star has to lie along the main sequence.
Main-sequence stars fuse hydrogen into helium at their cores, generating both heat and light as emitted energy. The second test, or spectral type test, is to determine if a star's spectral type is compatible with life as we know it. This test in turn determines how much energy the star emits in both light and heat forms, two very important criteria to judge when trying to determine if a star can support life or not.
These stars are within the realm for producing the correct amount of heat and light energy to maintain both a long solar life and the right amount of energy to support life over that lifetime. Applying this test to Alpha Centauri "A" finds that our neighbor star is in the exact same class as our Sun. Alpha Centauri "B" is a K1 star, hotter and brighter than most other K spectral class stars, therefore it may pass this test or it may not. The tiny red dwarf Proxima Centauri fails this test completely.
For the third test, a system must demonstrate stable energy emission conditions. A star's brightness may not vary in such a wide range that the star would alternately burn and freeze any life that does manage to develop around it. When viewed from the surface of a planet of one of the stars, the brightness of the other star increases as the stars approach and naturally decreases as the stars recede. Fortunately, the variation, as far as scientists can currently determine, is too small to matter. Given this result of the test, Alpha Centauri "A" and Alpha Centauri "B" both pass the third test.
First Ark to Alpha Centauri
By Abdul Ahad
[Link no longer available]
James Cameron has a passionate interest for space exploration and it would be a safe bet that he researched the science of traveling to Alpha Centauri. Whether any scientific detail about the journey to our nearest star system surfaces in the film, we will find out in December.
Here's a novel in the same vein from Authored Astronomer Abdul Ahad. In First Ark to Alpha Centauri, Abdul dives into the dark side of the journey itself and the affects such a long trek would have on the human travelers.
You can click on the link above to order his book along with his second novel, First Ark to Alpha Centauri 2: The Price of Immortality.
From Abdul's biography page: Born in the Sylhet district of Bangladesh on 15 December 1968, later moved across to the United Kingdom at the age of nine, which he considers to be his home country. Ahad obtained his secondary school education in the United Kingdom and graduated from the University of Luton in 1994 with a Higher National Diploma in Business & Finance. He has since held a number of executive and management posts in industry, developing a wide business career within multi-national bluechip companies across such functions as operations planning, supply chain process management and brands marketing.
Abdul Ahad is a keen astronomer ; his enthusiasm for the subject was first sparked off in the early 1980s at the age of 12, when he showed a notable leaning toward mathematical and positional astronomy. When he was just 15, at the dawn of the present era of home computers, Ahad compiled his own celestial mechanics algorithms for the precise computation of positions of planets, comets and minor planets from orbital elements.
Ahad's scientific interests later branched out into such fields as space technology, spaceflight simulations and models, space science missions and robotics. In January 2002, he founded the 'AA Institute of Space Science & Technology', a conceptual research institute dedicated to his own creative works and research projects.
Ahad put forward a hypothetical human interstellar spaceflight proposal ("Reaching Alpha Centauri using the resources of comets and planetoids") for bridging the gulf to our nearest star, by systematically relying on the safety of overlapping Oort clouds for possible mining/refuelling. He conceptualised the mechanics for excavation, capture and interior habitation of an asteroid - the "Celestial Titanic". . . . . click on the link above for his complete bio.
First Ark to Alpha Centauri Synopsis
Late in the 23rd century, in view of the deteriorating environment here on Earth with massive climatic shifts, deadly disease epidemics and looming economic and technological collapse, world governments unanimously vote to build a giant (6 mile x 9 mile) ark ship in orbit around our planet.
In one last desperate effort to safeguard our survival as a species, the ship was to carry a colony of people, plants and animals on an epic, one way mission to New Earth, a planet located in our neighboring solar system of Alpha Centauri. In a vigorous and competitive political battle and much bloodshed along the way, a colony crew of just 900 people manage to escape onboard the ark ship, placing their future destinies into their own hands on an immensely daring, 50,000 year long journey into the forever...
Two thousand years into the voyage, as the ship travels further into deep space away from the bright neighbourhood of our own Sun, a future generation onboard begins to experience a series of psychologically disturbing nightmares. Mysterious creatures from the cosmic darkness are seen to approach the lonely ark ship from all directions in space and attack its occupants during sleep, putting the mission into jeopardy.
"First Ark to Alpha Centauri" is an epic tale of love, loneliness, nightmarish horror and action adventure, envisioning what could possibly become the most realistic way that humanity is likely to one day travel safely and comfortably to another solar system beyond our own.
"There can be no goal in the human heart more noble and higher aspiring than to reach for the high frontiers of space"
. . . . .Abdul Ahad on Usenet, March 2004