Secondly, once you know the diameter of the inner ring, you can calculate
the distance to the supernova (pure trigonometry). And once you know that
distance you can use it and the angular diameter of the light echo to
calculate the size of the light echos. Simple trig.
> The light from the inner ring is not actually quite the same as
>> a light echo. it is radiation from a heated body of gas. The gas in the
>> inner ring was heated by x-rays from the supernova. Now, it glows on its
>> own, which is why it is so much brighter than the light echo.
>OK, so you're saying the inner ring has a radius of 1 light year because
>its "radiation echo" is 1 year behind the explosion and first sighting
>of the direct straight-line path of light from the explosion? Is that
Since I didn't have time early this morning to search my files, here is
documentation that the inner ring was dark prior to the explosion and it
explains what I meant early this morning.
"The ring, made of material ejected from the supernova's
progenitor star in its red supergiant phase, already girdled the
star five thousand years before it exploded. But it was cold and
dark. Only when the radiation from the supernova blast reached
the ring and heated it to 2 X 10^4 K did it become observable to
ultraviolet and visible-light telescopes."
~Bertram Schwarzschild, "Ring Around 1987 Supernova Provides a
New Yardstick,", Physics Today, February 1991, p. 20.
The outer rings were found after the entire astronomical community turned
their telescopes on this single star.
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