> Let me try again. The light ring is a reflection off of gas that lies
> between the earth and the supernova.
>
>
> dust
> light travels / \then reflects back to earth
> to dust / \
> / \
> / \
> star----light travels to earth directly-------->earth
>
> The distance from the star to the earth is 169,000 light years. The
> diameter of the ring is 400 light years, giving a 200 lightyear radius.
>
> Pythagorean theorem tells us that the travel path of the light from the
> star to the dust then to the earth is
>
> d
> /|\
> a / | \ b
> / 200 \
> / | \
> s--169000--e
>
> to find the travel distance for side a we have
>
> a=sqrt[(169000/2)^2 +(200)^2] =84500.2366
> b=sqrt[(169000/2)^2 +(200)^2] =84500.2366
>
> The total travel path from the star to the dust to the earth is:
> 169,000.47 lightyers compared with the 169,000 lightyears direct
distance.
> With the ring as I drew it, the reflected light from the ring should get
> here about 6 months after the light from the initial explosion.
>
> The inner ring is at the star, not at the dust.
>
> Does this help?
Perhaps. I had assumed that the rings were actually spheres, and we are
only able to see what is the thickest part of the sphere from our
vantage point, which would be the part of the sphere of dust that is
perpendicular to our line of sight at the center of the star. Are you
saying that the
outer ring actually is a ring and not a sphere, and that the ring is
perfectly centered around SN 1987A from our particular vantage point?
Bill Payne