Oort Cloud
Clues to comets origin
- Composition: “dirty snowball” Z 81
- refractory (silicate rock) dust
- ice matrix
- Come from “ice zone” beyond Jupiter’s orbit
- size ~ 10 km diameter
- i.e. like our “planetesimals”
- Orbits youngest (long-period) comets
- nearly parabolic
- orbit of an object falling toward Sun from infinity
- aphelion 1,000’s of AU from Sun
- not in ecliptic
- Oort cloud TA 106
- spherical cloud ~50,000 AU in radius
- perturbed by passing stars
- Comets were planetesimals removed from disk by gravitational interaction with Jupiter 4.6 billion y. ago