Let's look at the 1/a distribution again:
- We only see objects with q ≤ 2 AU.
- The comets in the peak are coming through the planetary system for the first time.
- Because if the comet has been through before, the planets would remove it from peak.
- So, is the Oort cloud really a shell with a ~ 20,000 AU?
- No, because of the Jupiter barrier.