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Kepler's Supernova Remnant in X-Rays

What caused this mess? Some type of star exploded to create the unusually
shaped nebula known as Kepler's supernova remnant, but which type? Light
from the stellar explosion that created this energized cosmic cloud was first
seen on planet Earth in October 1604, a mere four hundred years ago. 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, with
out 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 supernova remnant (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 more typical of a Type Ia supernova,
indicating that the progenitor was a white dwarf star that exploded when it accreted
too much material 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.