Scientists have discovered lone planets wandering the galaxy without a star.  They even think these planets may be more common than planets found in solar systems.  Learn how to incorporate rogue planets into your game after the break!

A Little Background

Rogue planets can form in one of 2 ways:

First, they can form as part of a solar system and then get kicked out by the gravitational effects of other objects in their system.  These planets can be any size.

They can also form without a solar system.  In this case, they form the same way stars do: from gas and dust collapsing into an object due to gravity.

Regardless of how they formed, all planets outside of a solar system are considered “Rogue Planets.”

Rogue planets can be orbited by moons, comets or other objects they’ve picked up throughout their travels.

How to Use Them

Rogue Planets are very versatile.  You could use this in a near future setting like Shadowrun where humans are still earthbound.  You could also use it in a setting as futuristic as Star Trek, where the enterprise encounters Rogue Planet life or has to help with a rescue effort.  You can also use them in a hyper-realistic, hard sci-fi type of setting.

Disrupting a Solar System

Just to clarify, this is not something you should worry about happening.  Space is insanely vast and even with all the rogue planets out there in the galaxy, it’s very unlikely that one of them will come hurtling through our solar system. Even if it did pass through, its gravity is so small that it probably wouldn’t even cause any damage.

Unless, of course, you want it to.

What happens then depends on a few different things: the arrangement of the planets in the solar system, the speed and size of the rogue planet and where in the solar system the rogue planet crosses.

If you want your planet to cause any destruction, it needs to be large: 10-100 times the size of earth. Make it Jupiter sized (over 300 times the size of earth) for maximum destruction.  You want it to be relatively slow moving, (spend several months passing through) so that it has plenty of time to disturb the orbits of the other planets.  Finally, you need it to come VERY close to the other planets to have any effect.  If all the planets are clumped up on one side of the sun, and the rogue planet passes on the other, it would have basically no effect.  It could pass through the Oort cloud and basically have no effect.  It could even knock Saturn and Neptune completely out of orbit and have pretty much no effect on Earth.

If you want to mess up Earth with this planet, it has to ruin the orbit of Jupiter and/or spend a lot of time in the inner solar system right next to Earth. The possibility that this object could hit Earth is very small, but that would be far more likely if it were, say, piloted by hostile aliens.

Which leads us to point 2.

A Source of Alien Life

If a rogue planet is not endangering the solar system, (or even if it is) it could be an opportunity to introduce alien life into your setting.

The aliens could be in the form of a bacteria that reigns down on earth causing a plague.  They could be hostile and riding through space on the rogue planet looking for a new home.  They could be friendly ambassadors, or refugees clinging to the last remnants of their solar system.  Maybe they want to set up on Earth or Mars.

The aliens might have control over their planets trajectory, or they might not.  Either way, they’re likely either to be just passing through or planning an invasion. Both might be good additions to your setting.

A Human Space Colony

If your setting lacks FTL travel, one of the ways humans could explore the galaxy is by riding on rogue planets (or their moons) to visit new destinations.  This would likely be a one way trip, with the colonists arriving with certain basic resources and then living of off the resources of the planet as they travel through space.

The rogue planet functions like a generation ship.  The humans might leave some kind of marker in each solar system they cross, or maybe a splinter colony.  Communication with the world back home would be very limited, but there’d be great potential for adventure.

Deep Space Mining

If we could snag a few of these rogue planets, we could bring them into the solar system and mine them for resources.  Maybe there’s a station at Jupiter or Neptune where the mining takes place.  Who knows what kind of resources could be found from mining a whole planet.  Compounds and minerals might not be the only thing you find on a rogue planet.  Maybe there are ruins of an ancient civilization, or the egg of a giant space beast!

In Closing

Rogue planets are a cool feature of the universe that can be used in many different types of future games.  Whether as a temporary danger, or a permanent part of the setting, rogue planets have a lot of potential for adventures.

Check out this article and the comments for more information about rogue planets: http://blogs.discovermagazine.com/badastronomy/2011/05/19/are-we-in-danger-from-a-rogue-planet/#.UTaVDxzvuxt

Have you ever used a rogue planet?  Have I left anything out?  Any great ideas?  Let us know in the comments!

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About Ophelia

Ophelia has been gaming since 2003 and writing for even longer. She has played a variety of systems but started with D&D 3.0. Her first experience as a tabletop gamer was in high school when, lacking money for dice, she and the other players had to roll by picking numbered strips of paper out of a cup. She works as a photo retoucher and hopes to one day publish a novel.