One of my favourite parts of AAS meetings is attending plenaries way out of my subfield. Pleased to be able to still do that virtually #AAS237 -in "Comets, Unseen Planets, and the Outer Fringes of the Solar System", by Scott Tremaine.

I never thought about how comet brightness depends on distance^4 - 2 powers from the Sun to the comet, and 2 powers back to us on Earth.

Short period comets (P<20 yrs) are mostly found in/near the plane of the Solar system, while long period comets come from a roughly spherical blob around the Sun. Cool.

I enjoyed the G=M=1 explanation of Orbital Energy = 1 for the Earth (in theorist units!).

Cool - Tremaine explaining that the existence of the Oort cloud (as a set of comets bound to the Sun by gravity) rules out some alternative models of gravity! I love things like that.