creating planets and system

[kevsurp]

ok not sure where to post this but any advice or rules for creating planet's stats like size, gravity and day and years and such?

[Ancient Chuckles]

Try this: https://donjon.bin.sh/scifi/tsg/ It's Donjon's random system generator for Traveler. Traveler has been out forever, and it has a huge online fanbase. It's a good source to pilfer from for Starfinder campaigns, especially if you want to play space games without dying during character creation.

[Ancient Chuckles]

For space maps, use Inkarnate.com , Hexographer, or any of the myriad of hex mapping tools available. It's useful for doing a full scale system map and encounter battle maps. Welsh piper has a ton of Hex templates in easy print format so you can lay stuff out with some sense of scale. NASA has a ton of high res space images for free download.

[kevsurp]

traveller stuff doesn't have how to figure how long a day or year is.

just wondering how they came up with theirs

[Omnius]

Honestly, determining different day/year lengths isn't hugely important most of the time.

But if you want to do it, just invent an arbitrary number.

[John Napier 698]

kevsurp wrote:

traveller stuff doesn't have how to figure how long a day or year is.

just wondering how they came up with theirs

I respectfully disagree. Classic Traveller did (Book 6: Scouts). Here is a wiki page that details the mathematics orbital periods. Enjoy.

[John Napier 698]

For Day Length, consult GURPS (4th Edition): Space. But if you want something quick and easy, roll 4d6 hours and add one to the result for every Billion Years of the Planet's age.

[Mynex]

If you want to calculate the orbital rotation (how long it takes the planet to orbit it's sun), you're looking at some serious trig... If you want the planetary rotation, that you'll have to make up.

There is no 'simple real world formula' out there... I've been putting together things to come up with density, diameter, year, gravity, star spectral type, etc into excel... and I've learned more about astrophysics and remember more trigonometry than I probably ever wanted to know (well, before now, it IS fascinating as hell!).

There are some RPG supplements on DriveThruRPG/RPGNow that gives you some 'roll these dice to get this'.. from galazies down to moons... but they're overly complicated for RPG casual use (note, I said casual, if you like all the stats/numbers, they're definitely up for that!).

So.. yea, the donjon one works well enough for casual use/info, but you'll still have to make some things up.

[John Napier 698]

All that trig can be simplified to take the square root of the cube of the planet's distance to the sun. This is what Newton came up with.

[Omnius]

That's what roleplaying games need! More square roots! :P

[Lane_S]

If you look at the examples in the book you may notice that they do not follow realistic stats. Make the planet what you want.

This is one I created.
http://paizo.com/threads/rzs2ulx1?New-Worlds#1