NationStates Jolt Archive

Looking forwards to an oncoming possible RP, I'm wondering if anyone could help me out with a gravity problem. I'm wanting a ferrinian planet (primarily metallic planetary body, a la this: http://www.onewest.net/~dollan/ARCPCLferrinian01.html) with a density around 10-15 grams/cc (2-3x Earth) but a gravity at 1 Earth gees +/- a maximum .1. What sort of equatorial radius would I need to reduce a planet to for this...

g = (GM[1]M[2])/R^2 --> a[due to gravity] = (GM[planet])/R^2

Have fun.

BTW, the a[dtg] corresponding to 1G is 9.8 m/s^2.

You would need a planet with half to a third of the volume of earth, if the density is 2 to 3 times that of earth to give the same gravitational pull.

4/3 pi * r^3 is the formula for calculating the volume from the radius, so calculate the volume of the earth, then divide by two or three (depending on the density you choose) and calculate back to find the radius.

ANd obviously, the star system that gave birth to it would be inimicable to life, so perhaps it could be a captured planet pulled away by another star system that collided/passed through the first. Which probably means it has an exotic orbit.

And obviously, the star system that gave birth to it would be inimicable to lifeOur specific kind of life at least...

Our specific kind of life at least...

True. And I can't claim to be an expert or anything. It just seems that being blasted by a large and energetic sun and having an atmosphere that consists only of helium and hydrogen would make it rather difficult for life to start.

True. And I can't claim to be an expert or anything. It just seems that being blasted by a large and energetic sun and having an atmosphere that consists only of helium and hydrogen would make it rather difficult for life to start.

Combined with high temperatures and stellar radiation, especially at such a close distance, it's highly unlikely. However, it's possible that life might have developed inside of the planet where the heavy metals might shield it from the radiation and the rock would keep it from burning up; without carbon, however, it would be very strange.

For a density of 12.50 g/cc and a surface gravitational field of 9.807 m / s^2, use a radius of 2807 km.