Supernova remnant. X-ray image showing the remains of supernova G1.9+0.3. This supernova is the most recent, in Earth's time frame, known to have occurred in the Milky Way. It is thought to lie around 28,000 light years from Earth near the center of the Milky Way. The source of G1.9+0.3 was most likely a white dwarf star that underwent a thermonuclear detonation and was destroyed after merging with another white dwarf, or pulling material from an orbiting companion star. This is a particular class of supernova explosions (known as Type Ia) that are used as distance indicators in cosmology because they are so consistent in brightness and incredibly luminous. Imaged by NASA's Chandra X-ray Observatory.