Here are the remnants of last supernova that is known to explode in our galaxy Milky Way. The light of explosion had reached the Earth some 400 years back and had amazingly lit up the night sky in October 1604.
The then mathematician and astronomer Johannes Kepler had then studied the event. But that was the time when telescope was not invented. In his memory, the event has been termed as Kepler’s Supernova Remnant.
Now we have not just telescopes but we also have giant orbiting space telescopes which keep on exploring and scanning the stellar events.
Here is the explanation of NASA about the event :
The supernova produced a bright new star in early 17th century skies within the constellation Ophiuchus. It was studied by astronomer Johannes Kepler and his contemporaries, without the benefit of a telescope, as they searched for an explanation of the heavenly apparition. Armed with a modern understanding of stellar evolution, early 21st century astronomers continue to explore the expanding debris cloud, but can now use orbiting space telescopes to survey Kepler’s SNR across the spectrum.
Recent X-ray data and images of Kepler’s Supernova Remnant taken by the orbiting Chandra X-ray Observatory has shown relative elemental abundances typical of a Type Ia supernova, and further indicated that the progenitor was a white dwarf star that exploded when it accreted too much material from a companion Red Giant star and went over Chandrasekhar’s limit. About 13,000 light years away, Kepler’s supernova represents the most recent stellar explosion seen to occur within our Milky Way galaxy.