The dust which produces the light echo is not quite at the same distance as
the supernova and the inner ring but they aren't far from it. One can draw
it as.
ring of
dust
/ --
/ --
ring of / --
dust / --1000 ly dust ring.
/ ------ / --
/ / --------> 400 ly ring --
/ / ----------- --
inner/ / ----------- --
ring------------- ----------- -->
| / / --------->heated ring light path----> ----->
| / / -------------->
star-------------------->direct------------------------------------------->e
arth
| ------------->
| -------->----------------------------
inner- -----------
ring
^
|
400 ly same reflection paths over here
old ring of dust
^
|
1000 ly
old ring of dust
The reflection points along the old rings of dust lie along a parabolic path.
>I had thought the explanation would be quite simple, but I don't think
>it has been resolved yet.
Does this make it clear?
glenn
Adam, Apes and Anthropology
Foundation, Fall and Flood
& lots of creation/evolution information
http://www.isource.net/~grmorton/dmd.htm