Page 625 - 89 history of astronomy_opt

The nebular illumination as seen in pho-
tographs, taken from August to November,
seemed to spread out slowly in a gradu-
ally increasing circle at the rate of 90” in
forty-eight days. Kapteyn put this down to
the velocity of light, the original outburst
sending its illumination to the nebulous gas
and illuminating a spherical shell whose ra-
dius increased at the velocity of light. This
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