18 Years Later: A Supernova Lights Up the Radio
A supernova explosion is the death of a massive star, leaving behind a gas cloud. If there's plenty of hydrogen around, the shock wave spreads like an echo from a distant gunshot.
The Galactic Center Ridge: A Break in the Gamma-Ray Spectrum
At the center of the Milky Way, where the supermassive black hole Sagittarius A* churns gas clouds like a millstone, astronomers have caught an irregular pulse. Gamma-ray emission, the most energetic light in the universe, arrives not as a smooth wave but with a break, as if the Galaxy's heart beats with arrhythmia.