Re: supernova rings

Bill Payne (
Wed, 29 Apr 1998 23:19:07 -0600

Paul Arveson wrote:

> These captions (also see the pictures) indicate that the rings
> were formed from gas shed by the star thousands of years before
> it exploded in a supernova. The rings are now several
> thousands of light years in radius. Light from the supernova explosion
> lit up the dust in the rings, although the rings are now
> fading because the central source is fading. The pictures show
> this.

Thanks for the info Paul. Now, please help me understand this. SN1987A
exploded some time in the past. Immediately, light from the explosion
radiated out in all directions. Some of the light travelled in a
straight line to the earth and arrived here in 1987. Some of the light
travelled perpendicular to the SN1987A-earth path, hit the rings, and
then bounced off the rings and travelled to the earth, arriving in
February, 1988. If the echo was one light year behind the initial light
that travelled in a direct straight line from the supernova to the
earth, then it would seem to me (and I think Glenn as well) that the
ring radius is one light year. If the ring radius were thousands of
light years, then the echo should be thousands of light years after the
1987 explosion.

What am I missing?