Ever wonder what seasons are like on other planets? Do you ever get tired of having to switch out your snow pants for swim trunks? Well, if you’re tired of dealing with Earth's predictable seasons, many planets in our universe present other options. For example, astronomers are pondering a recently discovered planet called Kepler 413b, that they think might have Game of Thrones-ike seasons. Yes, much like Westeros, it has seasons of wildly varying length - moving from summer to winter seemingly without warning, which from a wardrobe perspective sounds like a huge hassle. But how do scientists know what seasons are like there? The answer comes down to a trait that varies from planet to planet all across the universe.

(Intro)

Planets get their seasons, if they have them, from their axial tilt – that jaunty little angle at which the poles tilt relative to the orbital plane. Earth, for example, sits at 23.5 degrees as it orbits the sun. This tilt, or obliquity, means that for part of our 365-day orbit, sunlight strikes the northern hemisphere more directly, creating summer, while it’s winter in the southern hemisphere. And as we move through our orbit, the whole thing is of course reversed, and the sun then reaches the northern hemisphere at a more oblique angle creating winter. The result of the whole cycle is four roughly equal seasons each lasting about 90 days.

But imagine the alternatives to this scenario, like if a planet had no tilt at all or a huge tilt or a tilt that changed over time. As it happens, you can find examples of these extremes within our own solar system. Mercury, Venus, and Jupiter, for example, have zero or very little tilt and thus no seasons. Mars, Saturn and Neptune meanwhile have tilts like ours plus or minus a few degrees, creating even seasons from year to year. And don’t get me started on Uranus. It’s tilted a full 98 degrees, basically lying on its side and rolling around the sun. This means that one pole is pointed directly at the sun and gradually reverses over the course of a Uranian year. So summer in the northern hemisphere lasts 42 Earth years followed by 42 years of winter. 42 years of summer, now that’s a vacation, or it would be if weren’t, like, the coldest planet in the solar system.

But now, let’s leave our solar system and consider Kepler 413b. Its axial tilt actually wobbles, or precesses, like a spinning top, varying by as much as 30 degrees over 11 of its years. This means seasons there change fast, furiously, and unreliably from year to year. You’d hardly know whether to reach into your closet for a balaclava or a bikini. Our planet also undergoes this kind of precession but much more gradually. Our tilt changes 23.5 degrees over 26,000 years. That’s one degree every 72 years. There are probably lots of other planets like 413b out there with their own weird axial tilt oddities just waiting to be discovered. But so far, astronomers haven’t found many other examples with such extreme variations of seasons. Just goes to show - anything we can imagine in fiction may be out there in the universe. For now, if you want to experience Game of Thrones-like seasons, you’ll have to wait until we can travel 2,300 light years to Kepler 413b.

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