Can Inclined Binary Planets Be Stable??

Okay this video really had me on the ropes!! The amount of time my poor laptop spent whirring away on these simulations (only for me to realize I messed them up multiple times, gah!) A deceptively simple question--after all, Uranus and its moons exist, so why not a binary planet with a much smaller mass ratio?? Wellll...let me introduce you to my friend the Kozai-Lidov effect!

Fun fact, I learned about this effect in grad school, and for a long time I only heard people talk about it. And for like a year I thought when they said "Kozai" they meant "cos i", as in the cosine of the inclination. Totally logical, since the effect is related to the orbital inclination!! And yet so wrong. 🤣🤣

As promised, here is a Python file that will set up and run a binary planet simulation in REBOUND. The additional effects that I discussed in the video (oblateness and tides) are not included here, although the radius is given to help with collision detection. You can add those effects using the companion package REBOUNDx, though! I've linked to both the REBOUND and REBOUNDx pages in case you're interested.

File: https://galaxy.nora-bailey.com/wp-con... (you will need to change the file ending to .py after downloading, or copy and paste into your favorite editor)
REBOUND: https://rebound.readthedocs.io/en/lat...
REBOUNDx: https://reboundx.readthedocs.io/en/la...

Oh here's another fun tidbit, I tried to do collision detection manually at first and wasn't checking often enough and y'all I ended up running one simulation for THIRTEEN DAYS of calendar time only to realize that the planets actually would have collided within the first hour of it. 🙃

Find me: http://galaxy.nora-bailey.com/linktree/

#astronomy #planets #orbitaldynamics