Worldbuilder’s Guide to Stars, Planets, Moons, & Comets – Use the Cosmos to Create Awesome Worlds!

Multiple moons, perpetual daylight, extreme weather, strange fauna, and a blue Sun in the sky above. The physical settings of your world are the foundation for your story – and science doesn’t just explain awesome worldbuilding choices, it inspires them!  

In this article, we’ll share our tips for worldbuilding on a cosmic scale – scratching the surface of stars, planets, moons, and comets – and how you can create an epic world for your next novel or TTRPG campaign.

And, if you like what you see, check out The Creator’s Compendium, which explores these topics and many more in incredible depth – the quintessential storyteller’s guide to the cosmos!

How would an Earthlike planet differ from ours if it had two moons, was half the size, or was located in a star system with two stars? The Creator’s Compendium answers that and much more – check it out on Kickstarter here!


The Sun is yellow and the sky is blue, right? Well, what if I told you the Sun is blue in a sky of red when seen from the surface of Mars? 

It’s true. Simply moving your planet a few million miles away from its nearest host star can, quite literally, change the lighting setting of your world – and increase the planet’s orbit around its star so a year would last much longer. Just take Neptune, where you’d only get to celebrate your birthday once every 165 Earth years!

You could also create a world that’s tidally locked to a star – like the Moon is to Earth – which would put one side of the planet in perpetual daylight and banish the other side to never-ending darkness! That’s a pretty cool starting point for your next setting.

And what if your world had multiple stars in its system? In Isaac Asimov’s novel Nightfall, we follow the people on a planet with six stars and perpetual sunshine as they face a total eclipse, with no experience and a pretty overwhelming fear of darkness – an intriguing recipe for disaster.


A planet’s size, rotation, density, and distance to the nearest star also influence all-important stuff like gravity, weather, daylight cycles, and geothermal activity! 

Just consider what would happen if your world didn’t have a proper magnetosphere to deflect pesky radiation from its host star’s stellar flares. Life might be forced to live underground, organisms might develop metal shells to protect themselves – or suffer from all sorts of strange mutations!

Gravity, one of the most obvious influences we have on a world, is also directly tied to the planet’s mass – and even minor changes in gravity could cause life to evolve differently. On a small planet with half of Earth’s gravity, like on Mars, plants and trees could reach several times the height, while animals could grow massive frames as they devoted less of their anatomy to muscles. Conversely, lifeforms on a massive planet with twice Earth’s gravity would be much smaller, stockier, and lower to the ground.

Written by a Ph.D. in astrophysics, The Creator’s Compendium tackles complex concepts with humor and visual aids as it explains how (much of) the Universe works and provides tools to easily create a unique world from scratch!


How would an Earth-like be different from ours if it didn’t have a moon? Or if it had two moons instead of one? The effects of moons are much more numerous and interesting than even stories of werewolves would have us think! 

Tides are famously the result of our Moon – and, if the Moon were twice its size, we’d have much more extreme tides that could reshape our coastlines, cause severe flooding, and disrupt ecosystems that rely on tidal zones. 

Astronomy buffs might know about Earth’s axis, and the fact that it doesn’t stay perfectly straight; it wobbles over time and whirls about. But luckily, the Moon, a stalwart ally, helps keep Earth’s axis stable. If it didn’t, drastic and erratic seasons would likely decimate ecologies that depend on a stable climate! 

Comets & Asteroids

And what about comets, their blurry tails arcing across the sky and inspiring panic in villages and metropolises alike? Or a devastating asteroid impact like the one that likely led to the end of the dinosaur dynasty on Earth and completely changed the evolution of life on our planet? 

The arrival of comets in a world’s past might have brought the water it needed for life to thrive; and tiny microbes, frozen in the icy crust through an interstellar journey over countless thousands of years, only to become the seeds of life on a barren world – perhaps the one you’re creating!

Smaller meteorites that arrived in the past (or even recently) may have carried new materials that could lead to complete disruption of societies in your world – like how a comet filled with rare metals or elements might have the nations of Earth scrambling to harvest its treasures.

The options are endless – we’re just providing the toolbox to choose among them!

Check out The Creator’s Compendium on Kickstarter and grab a copy of the ultimate guide to worldbuilding!


When a best-selling sci-fi and fantasy author like Brandon Sanderson highlights defining the physical settings as one of the most important first steps when creating your world, it’s because they are the roots from which life, culture, and everything else in your world has evolved – the arena in which your story plays out. 

Multiple stars, perpetual sunshine, and extreme tides aren’t just awesome visual effects for your world – they are the settings from which cultures, cities, and conflicts within your world have arisen.

In this article, we’ve simply scratched the surface of the worldbuilding tools in The Creator’s Compendium to show you how you can use stars, planets, moons, asteroids, and comets to make an intriguing and unique world.

The Creator’s Compendium takes things much further across its 200+ pages. Stellar flares, supernovae, neutron stars, microbiology, black holes… The Universe is vast and despite our brains’ limited capacity, what we already do know is astounding – and right there for you to use in your worldbuilding! 

So, if you’re ready to build an amazing world, check out The Creator’s Compendium on Kickstarter now! 

Need visual aids? The Creator’s Compendium is filled with sketches and drawings!

The Creator’s Compendium covers all the basic astronomy – from the tiniest comet to behemoth stars – before diving deeper into more mind-boggling cosmic concepts such as time travel, terraforming, and wicked ways to destroy your world! Yes, there’s a whole section dedicated to destroying your world – and that’s only half of it!  

The 200+ page guidebook also provides numerous sample worlds and settings that illustrate how wormholes, cataclysms, and violent weather can be used to create compelling stories set in unique worlds – and easy-to-use checklists with adjustable features for star systems, planets, and much, much more!  

Building an authentic world may seem a bit daunting, but, luckily, you get to choose what’s important to your story – whether that’s two moons, extreme weather, or weird gravity, The Creator’s Compendium has you covered! 

Click here to check out The Creator’s Compendium and get the ultimate guide to worldbuilding on a cosmic scale! 

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