'The Force Awakens': Expert says Star Wars worlds Tatooine, Hoth could exist
Beneath the fading light of Tatooine's two suns, a desolate desert landscape stands between a young Luke Skywalker and his destiny as he gazes longingly into the binary sunset.
Tatooine is the first planet audiences ever encountered in a galaxy far, far away when Star Wars first debuted in 1977.
Since then, the films' creator, George Lucas, has taken audiences to the jungle moon of Yavin 4, the icy, snow-covered world of Hoth, the dense swamp planet of Dagobah, the tranquil Cloud City on Bespin and the lush, Ewok-inhabited forest moon of Endor.
In addition, the prequel trilogy utilized CGI technology and took audiences to the Earth-like planet Naboo, and others that were far more alien, like the ocean planet, Kamino, and the fiery, volcanic planet, Mustafar.
It is on the Lars' family moisture farm that audiences first meet the saga's wayward hero from Tatooine who would eventually follow Jedi Master Obi-Wan Kenobi to rescue a princess, join a rebellion, battle against an evil empire and learn the ways of the galaxy's ancient knights.
Luke Skywalker, and his uncle, Owen Lars, are moisture farmers by trade and harvest water from Tatooine's atmosphere with devices called vaporators.
The entire planet is covered by a barren desert and located in a binary star system, something that has just recently been discovered by NASA's Kepler mission.
Even NASA made the comparison to Star Wars' Tatooine during the discovery of a similar binary planet in a 2011 press release.
"Kepler has found a fair number out there," Pennsylvania State University NASA Sagan Postdoctoral Fellow Paul Robertson said, referring to binary planets that exist in star systems like Tatooine's.
Not only has the Kepler mission unveiled the existence of planets in binary star systems but has also revealed planets that would be located in what is considered a "habitable zone" from their stars.
While many of the exoplanets that have been discovered are gas giants, astronomers have recently discovered exoplanets the size of the Earth and smaller. There is nothing in known physics preventing a Tatooine planet from actually existing, Robertson said.
Some stellar binaries feature a larger star with a smaller star orbiting it. Others feature stars which are nearly equal in mass and create a common center of orbit as seen in Star Wars.
"That is how Tatooine is portrayed," Robertson said. "If you are a Star Wars fan, these discoveries are very exciting."
Filming for 1977's Tatooine scenes took place in Tunisia, North Africa.
According to the 2004 documentary film, "Empire of Dreams: The Story of the Star Wars Trilogy," temperatures often topped 100 degrees Fahrenheit by mid-morning during the shoot, and harsh weather conditions caused numerous problems for the cast and crew before Lucas moved filming to a sound stage in London.
Following the destruction of the Empire's Death Star battle station in the first film, the rebel forces retreat into hiding on the remote, frozen world of Hoth.
In 1980's "The Empire Strikes Back," audiences get their first glimpse of the planet as Han Solo and Luke Skywalker traverse the vast, frozen wasteland on the backs of Tauntauns, an indigenous species.
Snowball planets, or planets that are completely frozen, like Hoth, do exist, but understanding the nature of their surface and composition of their atmosphere is still difficult even with today's technology, Robertson said.
"This could be a temporary or permanent state," he said. "In the case of Earth, there is good geologic evidence that it has gone through at least one snowball phase."
For more permanent frozen states, planets that orbit far from their stars do not bask in enough solar energy and remain in a perpetual state of deep-freeze.
With NASA's New Horizons mission, scientists now have been able to glimpse the surface of the Dwarf Planet Pluto, revealing a diverse surface and blue atmosphere. Robertson said this discovery will help further the understanding of how these types of surface features form.
Falling snow would also be impossible on a snowball planet, Robertson said, citing the need for a water cycle for precipitation.
"It would be a desert like Antarctica," he said, adding that there is still some accuracy in "The Empire Strikes Back" during the Battle of Hoth as snow does not fall in many of the scenes.
While some scenes in the film feature movie magic utilizing painted backgrounds and scale models, many of the Hoth scenes were shot at Hardangerjøkulen glacier in Norway, according to the documentary.
According to producer Gary Kurtz's interview, filming was plagued by many weather-related problems, with one of the worst winters in 50 years hitting Scandinavia at the time.
The region was hammered with 18 feet of snow and temperatures that dipped to minus 20 F, Kurtz recalled.
In addition to facing white-out conditions, director Irvin Kershner recalled a wall of snow that prevented the film crew from leaving their hotel early on in filming.
In order to film the scenes where Luke Skywalker flees the Wampa, actor Mark Hamill had to venture into the elements while the crew filmed from inside the doorway of their hotel, Kershner said.
In the 1983 film, "Return of the Jedi," the climactic battle to deactivate the shield which will allow the rebel fleet to destroy the Empire's second Death Star is fought on the forest moon of Endor.
The lush, Ewok-inhabited Endor is one of the most memorable locations in the Star Wars saga and is unique in that it is a moon that orbits a gas giant of the same name.
"This is an example of real-life analogues," Robertson said. "We have found gas giants in the habitable zone."
At this point, no moons have been observed around these exoplanets as they are extremely hard to detect, but it is plausible they exist as gas giants in our solar system have moons.
Because of the fierce gravity generated by a gas giant, these moons would be subject to extreme tidal forces and conditions unlike anything seen on Earth, he added.
"You would be talking about massive tidal waves and incredible volcanic activity," Robertson said.
Even in our solar system, many moons orbit around Jupiter and the other gas giants.
One of Jupiter's moons, Europa, is thought to have more liquid water beneath its surface than Earth's oceans combined, Robertson said.
In addition, Saturn's moon, Titan, has a very dense atmosphere and may be somewhat akin to the Star Wars planet, Dagobah.
"It does not have an Earth-like chemistry, but it would be like a frozen swamp," Robertson said, adding that it has lakes of liquid natural gas and scientists speculate on the moon's unique organic chemistry.
In order to achieve a moon like Endor in the habitable zone, it would need to have enough mass to retain an atmosphere. In addition, the interior would be molten due to the intense gravitational forces.
For many of Endor's scenes, filming was conducted at Redwood National Park in California.
Despite its varied and Earth-like appearance in the 1999 film, "The Phantom Menace," Naboo is one of the stranger planets in the Star Wars universe due to its core.
In the film, Qui-Gon Jinn and a young Obi-Wan Kenobi venture through the planet's underwater core with Jar Jar Binks to reach the city of Theed.
"If it weren't completely physically impossible, you would not want to pass through the planet's core," Robertson said. "The high pressures would cause the water to solidify into high-pressure ice."
The intense pressures at those depths would not only force water into a solid, but also the planet could not be dynamically stable with a hollow core and would collapse in on itself, he added.
In one of the most memorable battles of the prequel trilogy, Obi-Wan Kenobi faces off in the rain against the bounty hunter Jango Fett on an oceanic landing platform outside of Kamino's cloning facilities.
Kamino is a water world covered in a vast ocean, but it is a very plausible that this type of habitable stormy, ocean planet could exist in our galaxy, Robertson said.
"[It was once thought] that ocean planets were more hypothetical," he said. "What we've learned from Kepler is that super-Earths— planets between the size of Earth and Neptune —are extremely common. We don't know if some are ocean planets, but that is one possibility for a super Earth."
Technology is not at the point where scientists can determine if these worlds could have fresh water, salt water or if they could sustain life.
"You could conceivably have a breathable atmosphere and fresh water," he said, adding that identifying more specific details about these exoplanets is difficult and scientists are still learning.
The tragic fall of Anakin Skywalker and his transformation into Darth Vader is reflected in the fiery, nightmare world of Mustafar featured in the final scenes of 2005's "Revenge of the Sith."
In an epic battle between brothers, Obi-Wan Kenobi and Anakin duel against the backdrop of fierce volcanic eruptions and over the glowing lava flows of the planet.
The molten planet is akin to the early Earth as it slowly cooled, as well as other worlds found close to their stars.
"It would have to be very close to the star for it to be permanently molten," Robertson said, citing that the intense gravitational forces and radiation would generate extreme tidal forces and heat.
"It would also likely be tidally locked," he said, stating that only one side of the planet would receive starlight as the planet orbits the star while the other would have a much cooler night side.
"You could not live on that planet," he said, citing the volcanic gases, poisonous atmosphere, intense heat and molten surface that would likely be found on a planet like Mustafar.
Like all of the planets featured in the Star Wars films, the weather of each world affects the films' overall atmosphere, creates conflict for the characters and generates an emotional response in viewers.
As the new film, "Star Wars Episode VII: The Force Awakens," debuts in theaters on Dec. 18, audiences will likely once again be transported to new, fantastic worlds to experience the same thrills and timeless adventures that they've experienced since 1977.
