Allow me to introduce Alex Mustill’s latest paper, where he focuses on “The formation of transiting circumplanetary 🔭🪐 debris discs from the disruption of satellite systems during planet-planet scattering” which features one of the coolest diagrams I’ve seen. /1 https://arxiv.org/abs/2404.12239#astronomy#astrodon
This started as a discussion about the curious case of small transiting disks - the first was discovered by Saul Rappaport’s team in 2019, which was found in Kepler data. /2
There’s only one transit seen per star in the Kepler data - when combined with the speed that the disk moves across in front of their parent stars, if they were on circular orbits, we should have seen a second eclipse in the Kepler data. /4
But since no other eclipse was seen, it means that the disks were on eccentric orbits, and we’d caught them during periastron, where they’re closest to the star in their orbit, and are moving faster than the equivalent circular orbit. /5
Elliptical orbits, with small, tilted disks? They’re tricky to make and keep stable for long periods of time. Where did the disks come from, and how are their parent substellar companions in elliptical orbits? Two mysteries in one. /6
Talking with Alex, he had an idea: let’s assume there were two gas giant exoplanets with a retinue of moons around each planet (a bit like Jupiter and Saturn) initially on circular orbits, but then they gravitationally interact with each other… /7
What would happen to the planets? What would happen to the moons? Alex ran detailed simulations to find out…and the answer is - many possible outcomes, including moon-moon collision, moon-moon exchange, moon scattering, planet scattering - you name it, it can happen! /8
Alex made diagrams that encode the history of both planets and ALL the moons. These “Mustill plots” are beautiful since almost every line contains information about the simulation - Edward Tufte would be proud. /9
The interesting takeaway is that when two Jupiter/moon systems interact with each other, in 9 out of every 10 cases, there’s a small disk made, with tilts consistent with what is seen with the three disks found so far! Go look at Alex's paper and make sure to check out the plots at the end. /fin
Add comment