The center of our galaxy is a crowded kitchen where several dishes are simmering at once, and their steam blends into a single cloud. X-rays from the exploded star's remnant, from the stellar wind around the supermassive black hole, and from hot gas between stars all overlap. Separating them is like trying to tell from the taste of a soup how much carrot and how much onion went into it.
Astronomers took hundreds of hours of observations from the Chandra X-ray Observatory and applied a method that decomposes a mixed signal into independent components. This allowed them to isolate the glow of the supernova remnant Sgr A East — the cloud left behind after a star exploded. It turned out that iron in this cloud is concentrated at the center, like the filling in a pastry, while sulfur, argon, and calcium are scattered around the edges. This is a typical picture for remnants that have already mixed with surrounding material.
By separating the remnant from the "steam" of the stellar wind, scientists were able to measure its properties precisely for the first time. They found that the shock wave from the explosion has run into a dense cloud of gas and is now actively interacting with it. This is like a wave from a stone thrown into a pond crashing into a log sticking out of the water — spray flies in all directions, and you can see exactly where the water and the obstacle met.
Such signal separation is like tuning a radio receiver that pulls one clean station out of the static. Thanks to this, astronomers can now study the Galactic center without interference and better understand how stellar explosions affect the vicinity of the black hole.
The supernova remnant Sgr A East is so bright in X-rays that its emission rivals the glow of millions of suns, but from Earth it is invisible without special telescopes: it is all hidden behind clouds of dust.