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“All I saw was a blue flash,” Dillon said.

Aristotle noticed that if he struck the surface of the sea with a rod, the water sometimes produced a bright blue flash.

A sudden blue flash illuminated the seating area for a second as the fly zapper on the ceiling took out a bug.

But when astronomers spotted a supernova in the nearby Pinwheel galaxy within hours of its ignition in 2011, they saw no blue flash.

Other telescopes able to obtain spectra from thousands of objects simultaneously will enable astronomers to study the explosions for the features—the blue flash, the hydrogen absorption lines—that could betray the involvement of a giant star.