When the great Danish astronomer Tycho Brahe gazed into the heavens on November 11, 1572, he witnessed one of the defining events in the history of his science.

In the constellation of Cassiopeia, he clearly made out what appeared to be an entirely new star, brighter even than Venus, that had not been there before. Though he did not know it, he was among the first people to see a supernova — a violent explosion in which certain stars end their lives.

More than four centuries after Tycho, an unorthodox nobleman who wore a golden nose after losing his own in a duel, made his observations, they have now been confirmed and deepened by his modern successors, who have used “light echoes” from the blast to relive it and then to study it in unprecedented detail.

Using powerful telescopes in Hawaii and Spain, the scientists have identified the precise type of supernova that Tycho saw 436 years ago, making it the oldest to be confirmed and classified in the Milky Way. Supernova SN 1572, or Tycho’s supernova, as it is known, is one of only six supernovas of any kind known to have happened in our galaxy during the past millennium. It is now shedding new yet ancient light on a phenomenon without which life would not exist: all the heavy elements that are critical to life are forged in these stellar furnaces and then scattered through the Universe when they explode.

Tomonori Usuda, of the Subaru Telescope in Hawaii, said: “Using light echoes in supernova remnants is time-travelling in a way, in that it allows us to go back hundreds of years to observe the first light from a supernova event. We got to relive a significant historical moment and see it as the famed astronomer Tycho Brahe did hundreds of years ago. More importantly, we get to see how a supernova in our own galaxy behaves from its origin.”

Although supernovas flare and die over a short period — Tycho’s had disappeared by March 1573 — their legacy lives on for hundreds of years in the shape of “light echoes”. These occur because some light from the original explosion bounces off dust in the surrounding interstellar clouds, and ultimately reaches Earth much later than the bulk emitted by the main event.

The remarkable observations, led by Oliver Krause, of the Max Planck Institute for Astronomy in Germany, are published in the journal Nature and also involved the Calar Alto observatory in Spain. They used light echoes from SN 1572 to study its spectrum, and thus confirm it as a type Ia supernova.

This type of supernova occurs from small but dense stars nearing the end of their lives, called white dwarfs, in binary systems in which two stars orbit one another. The white dwarf gradually accumulates gas from its companion star, which compresses it until a runaway nuclear reaction triggers the supernova explosion.

Type Ia supernovas are the main source of heavy elements — all the elements apart from hydrogen, helium and a little lithium are formed in stars and spread by supernovas. Elements such as carbon and oxygen, which are critical to life, would thus not exist on Earth without these explosions.

Tycho’s original observations of SN 1572 were particularly important as he immediately concluded that the new star that he saw could not be closer than the Moon. This challenged the Aristotelian view of the cosmos, widely accepted since ancient times, which held that the sky beyond the Moon never changed.

He described his discovery in a book entitled De Stella Nova (Latin for “on the new star”), which was later used to coin the term “supernova”.

Times Recommends

• An officer and a gentle woman
• Dame Helen Mirren is worthy of the Epidaurus
• Foods that can help to prevent swine flu