What invisible message did Supernova 1987A provide to modern astronomers that early observers could not see?

Answer

The first direct detection of neutrinos from a core-collapse supernova

When Supernova 1987A exploded, its light carried the first direct detection of neutrinos from a core-collapse supernova, which gave scientists direct evidence of the physical collapse happening inside the star's core.

What invisible message did Supernova 1987A provide to modern astronomers that early observers could not see?
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