79
Where do comets come from?
Long period comets:  The Oort Cloud
•Most (original) orbits have aphelions of  >1000 AU
•
•Need ~6 trillion comets out there to produce number seen in here
•Total mass of 38 MEarth
•
•Passing stars deflect comets in from the cloud
The New Solar System,  Beatty et al.
¼ to 1 parsec