‘Light echo’ illuminates Tycho’s supernova

More than 400 years after Danish astronomer Tycho Brahe challenged established wisdom about the heavens by analyzing a strange new light in the sky, scientists say they’ve nailed down just what he saw.

They knew the light came from a supernova, a huge star explosion. But what kind?

A new study confirms that it was the common kind that involves the thermonuclear explosion of a white dwarf star with a nearby companion.

The research was published Thursday in the journal Nature by scientists from Germany, Japan and the Netherlands.

The story of what’s commonly called Tycho’s supernova began on Nov. 11, 1572, when Brahe saw what he thought was a brilliant new star in the constellation Cassiopeia. The light eventually became as bright as Venus. After 16 months, it disappeared.

Brahe established that the light didn’t move in relation to the stars. That meant it lay far beyond the moon -- a shock to the view at the time that the distant heavens were perfect and unchanging.

Brahe was inspired to launch a career of observations that helped lay the foundations of early modern astronomy, said Michael Shank, a history of science professor at the University of Wisconsin-Madison.

The supernova’s light swept past Earth long ago. But some of it struck dust clouds in deep space. That “light echo” was still observable, and the new study was based on analyzing wavelengths of light from that.