Animavore wrote:Do you have an explanation at hand as to how a moon around a gas giant is able to sustain life like on Pandora? From what we know of our own solar system (and a couple of others) gas giants are way out of the goldilocks zone and the one moon which may have life, Europa, gets its heat internally due to the constant contraction and expansion of the moon due to Jupiter's immense gravitational field. From what I know its possible it may contain microscopic organisms or may some larger jelly fish things but as far as I know it would be quite impossible for it to house any life like on Earth. Anything on that?
Some articles:
http://www.space.com/entertainment/0912 ... ience.html
http://www.sciencedaily.com/releases/20 ... 183444.htm
In this article the science of Avatar is graded, it refers to the planet, star system and flora and fauna of Pandora (the following is just an extract):
http://www.aintitcool.com/node/43440
WORLD AND STAR SYSTEM
Pandora is a moon of Polyphemus, a fictional gas giant orbiting Alpha
Centauri A. I’ve always wanted to know what the view would be from
the moon of a gas giant. Can you imagine a quarter of the sky being
taken up by a massive cloud-covered planet visible night or day? We
get to see it in Avatar, and since Jupiter is the king of the gods,
maybe majestic is an appropriate word to describe it. I wonder if
Cameron’s choice to set this on the moon of a gas giant wasn’t a slap
in the face to Lucas, as if to say “this is RETURN OF THE JEDI done
right.” (I know it is ambiguous in the Star Wars universe whether or
not Endor orbits a gas giant.)
But what had me really geeking out is the choice of the star system.
Alpha Centauri A is perfect. First, as the closest star system to the
sun (4.37 light years), it may well be the first star we travel to.
Second, it is familiar in that you can see it with the naked eye if
you live in the southern hemisphere – it is the brightest star in
Centaurus. Actually, what appears to be a single star can be resolved
as a binary system if you use a telescope. It is Alpha Centauri A, a
bit more massive than the sun (1.1 solar masses), and Alpha Centauri
B, a bit less massive than the sun (0.9 solar masses). The choice of
G-type stars near the mass of the sun is great – they last for
billions of years – plenty of time for life to evolve. They are in an
elliptical orbit around a common center of mass, which means they come
together and drift apart over the course of one 80 year orbit. The
two stars get as close as 11 astronomical units (an AU is the average
Earth-Sun distance; 11 AU is about the distance to Saturn), and get as
far apart as 36 AU (about the distance to Pluto).
Would you see the companion star (Alpha Cen B) in the sky from
Pandora? That depends on where it is in its orbit. At the farthest
distance it would be a few hundred times the brightness of the full
Moon as seen from Earth. But your eyes are logarithmic detectors, so
it would actually only seem a few times brighter than we perceive the
Moon. At its closest approach, Alpha Cen B would be a few thousand
times as bright as we see our Moon. This is not all that bright – in
comparison, on Earth the Sun is about half a million times brighter
than the Moon. So on Pandora, if Alpha Cen B is up in the daytime
then you might not even notice it, depending on how far away it is in
the sky from Alpha Cen A. But if it is up at night (as it would be
for half the year), it would never get completely dark – the sky would
just be kind of dark blue.
Technically, there is a third star in the system, Proxima Centauri,
but it is a tiny red dwarf a huge distance, about 12,000 AU, away – it
is not even clear it is bound to the system. At any rate, it would
not be prominent in the sky as seen from Pandora. Incidentally, my
first job as a graduate student was to help calibrate the fine
guidance sensors on the Hubble Space Telescope to help my advisor look
for planets around Proxima Centauri. Sadly, we didn’t find any.
It is an interesting question as to whether planets around either
Alpha Cen A or B could exist in stable orbits that would last for
billions of years. You might think they couldn’t because the gravity
of the other star would perturb any forming planet.
However, simulations show that at least at Earth-like distances,
stable planets can form in that system.
Grade for astronomy: for the choice of star system, setting in on a
moon, and around a gas giant, Cameron gets an A+.