What's the weather like in a galaxy far, far away? Find out
Friday, May 4, 2018, 7:01 - A long time ago, in a galaxy far, far away, there seemed to be an awful lot of weird places, each with but one climate dominating the entire planet. So, how could these mono-climate planets come to be?
Here on Earth, we have numerous climates, all on one planet. Spread about on different continents, there are icy wastelands, temperate plains, tropical rainforests and scorching deserts, just to name a few. Their location is based on latitude, and thus the amount of sunlight they receive throughout the year, and the general weather patterns in the atmosphere.
Look to the Star Wars galaxy, however, and the planets and habitable moons we've been shown all have only one climate.
While unusual, this is certainly not impossible.
This special episode of For Science! takes a brief look at the monoclimate worlds from the original trilogy, to show they could form and what the weather would be like there.
Tatooine is a desert world baked by twin suns. Like Mars, it may have had a much wetter environment in the past, and the Dune Sea is possible evidence of it having a large ocean in the past. Perhaps some cataclysmic event caused it to lose that water, or maybe the oceans were simply boiled off as the binary stars Tatoo I and Tatoo II heated up as they aged. Either way, only a small amount of moisture remains in the atmosphere.
Jedi Master Yoda escapes to Dagobah in the wake of the fall of the Jedi Order. Courtesy: StarWars.com
Dagobah, the swamp planet where Luke Skywalker was trained by Jedi Master Yoda, is apparently covered in swamps and bogs, very likely due to the thick layer of clouds that blankets the planet. Similar to what we see on Venus, these clouds would trap light and heat, producing a fairly uniform range of temperatures across the entire surface.
The ice planet Hoth could develop fairly easily, simply by having an Earth-like world form (or migrate) farther out from its star. It's also possible that Hoth was simply going through a climatic change, similar to the Snowball Earth stage our planet may have gone through, around 650 million years ago. It's thought that, at the time, either the eruption of a supervolcano pumped enough dust or sunlight-reflecting sulfur compounds into the atmosphere, or the concentration of greenhouse gases in the atmosphere fell to levels far below the roughly 300 ppm average, triggering a global cooling event that froze much, if not all, of the water on the surface. A more interesting question about Hoth is in regards to its three moons, and how these moons could exist so close to the planet's surface.
Luke Skywalker flees the ice planet Hoth in his X-Wing starfighter. Courtesy Lucasfilm/Disney
For the forest moons of Yavin and Endor, the infrared radiation given off by gas giants - in some cases, totalling more than twice the energy they receive from their parent star - would be an abundant heat source for any moons orbiting closely around them. Jupiter and Saturn are too far from our Sun - outside of the 'habitable zone' - to sustain ice-free moons, but move Jupiter closer to the Sun, say to around the orbit of Mars, and its Galilean moons - Io, Europa, Ganymede and Callisto - could develop far more habitable environments.
Another location visited in the original trilogy, but not discussed in the video, is the gas giant Bespin, the home of Cloud City. While gas giants are likely all monoclimate worlds, Bespin appears to be a somewhat unusual example. Gas giants are mostly hydrogen and helium, and planets like Jupiter and Saturn have abundant water vapour, methane, ammonia and even hydrogen sulfide in their cloud layers. These are very inhospitable worlds, and they certainly don't have a breathable atmosphere. Bespin, on the other hand, appears to have enough oxygen in its atmosphere, at the level Cloud City floats at, to sustain life as we know it. This implies that there is abundant photosynthetic life at that level of the planet's atmosphere, to replenish that oxygen. There may be gas giants out in the universe where this happens, but we haven't found one yet.
In Star Wars: The Force Awakens, we are treated to even more monoclimate worlds:
Jakku, a desert world like Tatooine, but it only has one star at the centre of the system. Sources say that the planet was once a lush forest world, but some catastrophe change it to its current state. It's unclear what kind of catastrophe could cause an Earth-like planet to be turned into a desert world - even lacking frozen polar ice caps - however images from the film reveal an immense impact scar on the surface. An immense battle took place above the world, evidenced by the Star Destroyers littering its deserts, but this impact scar would easily stretch across a continent the size of North America. The impact of a massive asteroid could have put enough dust and ash into the atmosphere to block out the Sun, killing off these forests, while flooding the atmosphere with potent greenhouse gases, thus locking in this hotter, much drier environment once the atmosphere cleared.
The planet Jakku, and its giant impact scar. Courtesy Disney.
Takodana is a lush world, where Rey says "I didn't know there was this much green in the whole galaxy." Apparently dominated by lakes, rivers, mountains and forests, this planet is strangely uniform, lacking climate zones and polar ice caps.
D'kar, the location of the Resistance headquarters, is a jungle world with rings of rocky debris surrounding it. An interesting implication of this: the debris rings may be due to a large moon orbiting the planet being drawn closer than the planet's Roche limit - the point where the mutual gravitational pull between the planet and the moon overcomes the moon's tensile strength, and tears it apart. Still, no indication of climate bands or polar ice caps.
Hosnian Prime, the home of the New Republic Senate, appeared to have continents covered in immense cities, before it was destroyed by Starkiller Base.
Even Starkiller Base, which was built out of a small planet or large moon, displays a mountainous, forest terrain over the entire surface. While it is covered in ice and snow when we see it in the film, that could simply be due to its habit of eating any nearby star to power its dreaded superweapon.
A galaxy of monoclimates
Other mono-climate planets, from the original trilogy and the prequels:
• Coruscant's urban sprawl
• Naboo's temperate forests
• Geonosis' vast rocky deserts
• Kamino's global ocean
How BIG is the Sanctuary Moon?
Some sources, namely the Wookieepedia, claim that the Forest Moon of Endor is 4,900 km in diameter. This was also used in a draft white paper penned by Purdue University planetary scientist Dave Minton, presented by Tech Insider on Dec 23. However, examining footage from Star Wars: Return of the Jedi, the size of this moon needs to be re-evaluated.
The size of the Sanctuary Moon, deduced from visuals taken prior to the destruction of Death Star II. Credits: LucasFilm/Wookieepedia/S. Sutherland
The size of the Forest Moon would imply that the gas giant, Endor, has considerable mass. It could even be a brown dwarf - a failed star at least 10 times as massive as Jupiter - which would put out considerable heat to warm the surface of the moon.
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