Hey, What’s Up With The Planets In Star Wars?

Volcanologist Dr. Andrews and astrophysicist Dr. Carpineti have a ponder on the planetary peculiarities of Star Wars.

Since today is Force Friday, it would seem pertinent – and wonderfully geeky of us – to discuss some real science that goes on in the fictional universe of the galaxy far, far away.

Planetary ideas and descriptions have been very hit and miss throughout the saga – if you’re aware of a little planetary science, that is. The concept of Tatooine orbiting two suns was considered by most scientists to be an improbable for an exoplanet, but we now know that the conditions for that to happen are not as complex as we once thought. The life forms that exist on that planet, however, don’t make much sense for a desert planet: those furry Banthas would surely overheat in such harsh, hot environments. They also look like herbivores to us, but there doesn’t seem to be much vegetation on the sandy seas, so what would they eat if they weren’t fed by the humanoid inhabitants of the desert planet?

Something that has been even less accurate – if you’re nit-picking, of course – are the climates shown on the various planets. For example, we have Dagobah, a swamp planet, and even Tatooine itself as a desert planet. In reality, planets, especially full of life and oxygen, must have climates, weather and variation.


There are, however, exceptions to this in the Star Wars cinematic universe. Something akin to Mustafar, the magmatic world we encounter in the final battle in Revenge of the Sith can in fact be found Io, one of the four Galilean satellites of Jupiter. This is one of the few objects in the universe that has active volcanoes (that we know of, of course), although Venus does have a strange form of magmatic volcanism called “pancake volcanism”: under huge pressures, lava oozes out of great fissures in the ground and is squashed by the atmosphere as it does so, producing gigantic, untasty pancakes of lava. The magma lakes on Io are even stranger: they are hotter than the volcanoes on Earth, with plumes of dust that are shot into the sky at over 2000 Km/h, and reaching heights up to forty or fifty times that of Mount Everest on our slightly calmer Earth. Unlike the surface of Mustafar – which seems pretty toasty to us – the surface of Io is actually freezing for the most part, as there is barely any atmosphere to trap the heat in. That does make us wonder how a planet such as Mustafar, with constant, enormous volcanic eruptions, is not suffering from a choking atmosphere akin to the Venusian one: mostly carbon dioxide and sulphuric compounds. Either way, it does make for a brilliant setting for climactic lightsaber battles.

Another peculiarity is Hoth, a base for the rebel alliance shown in the opening act of The Empire Strikes Back. Hoth is a frozen planet with life forms that have evolved to survive in the harsh climate: this is reasonable. Jupiter’s moon Europa could prove to be such an object, although it is not clear if Hoth conceals a subterranean ocean in the way Europa almost certainly does. It seems Hoth is more like a perpetual Siberia: an icy region dominated by compacted snow, not huge plates of water ice.

Europa’s internal heat comes from the intense tidal forces from Jupiter; the same forces that conspire to make Io a world of lava and magma. In very much the same way that our own moon’s gravitational pull primarily controls the oceans’ tides, Jupiter and its interaction with its larger moons generates such intense gravitational fields than the solid rock itself within Io is ripped apart into a liquid state; similarly, the ice and water within Europa is moved around with such energy that an internal flow of heat is generated. Hoth, however, does not appear to have an internal ocean, but rather is bathed in ice and snow across its entire surface.

Hoth Star Wars

Earth itself has been through periodic and severe changes in its climate. Volcanoes first enriched the atmosphere with water vapour and other gaseous components that eventually produced an atmosphere amiable to extremely primitive life. Also, ice ages have been a geologically common occurrence for our planet. Perhaps Hoth is experiencing its own ice age in the same way Earth does: it has essentially “wobbled” on its axis of rotation, moving it further away from its star, leading to a cooler phase.

If we are looking at Hoth in a similar scenario akin to the ages before complex life evolved on our planet, some scientists posit that Earth went through a chilling phase known as the Snowball Earth about 650 million years ago.

Some initial cooling mechanism – for example, the eruption of a supervolcano, which would release massive amounts of radiation-reflecting particles into the atmosphere – would have had to initially occur. The global temperature would fall, and some of the liquid water would freeze into snow and ice. This increase in Hoth’s coverage of highly reflective snow and ice across its surface would then reflect more incoming radiation from its parent star, cooling the planet further, leading to the production of more snow and ice. This runaway effect is known as a positive feedback system, wherein the output of a process feeds back into the input, increasing its strength (or “magnitude”) each and every time.

Star Wars

Venus experienced a global warming positive feedback system to become the hellish environment it is today; Hoth underwent a global cooling version of events.

Although recent evidence unearthed by earth scientists suggests that Snowball Earth did not in fact occur, the process invoked – one that could generate such an icy world through positive feedback in this way – is perfectly plausible. So perhaps that’s why Hoth is uniformly icy and snowy as seen in one of cinema’s classic films.

Don’t get us wrong though: when the film comes out, we won’t be thinking about any of this at all. We just want to see Kylo Ren and Finn face off in the forest.

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