Supernova echoes take us back in time

摘要

It's a case of cosmic deja vu. Four hundred years ago, Danish astronomer Tycho Brahe launched his career with an account of a dazzling stellar explosion as bright as the planet Venus. It later turned out to be a supernova in the Milky Way. Now a team of astronomers has watched the same explosion, long after the dying star fizzled out, by measuring "light echoes" -light from the original explosion that has reflected off interstellar dust and headed in our direction. They also saw faint reflected flashes from Cassiopeia A, the most recent supernova known to have occurred in our galaxy.