X-ray: NASA/CXC/RIKEN/D.Takei et al; Optical: NASA/STScI; Radio: NRAO/VLA

Modern astronomers nail down the source of a 1437 stellar explosion

In a piece of scientific detective work spanning centuries, researchers have finally discovered the source of a classical nova witnessed by Korean royal astronomers on 11 March 1437. The nova, a giant thermonuclear explosion, lingered as a bright spot between two stars in the constellation Wei—a part of Scorpius—for 14 days before vanishing. Using x-ray, ultraviolet, and photographic images from as far back as 1923, the team traced its source to what is now a dim star in Scorpius, they report today in Nature. The images showed the expanding shell of hydrogen ejected by the explosion. Unlike a supernova, in which stars blow themselves apart with terrifying finality, classical novae are smaller events in which gas from one star in a closely spaced binary system is captured by the other star, accumulating until it erupts in a giant thermonuclear explosion (like the one above). Classical novae are believed to occur on multithousand-year cycles, hard to track with astronomy records that rarely reach back more than 100 years. But the new data give modern astronomers another gift, revealing that the star system produced at least three smaller eruptions—known as dwarf novae—in the years since it was first photographed. That means both types of explosions are likely part of the same 100,000-year process. Study author and astronomer Michael Shara, of the American Museum of Natural History in New York City, calls them “butterflies and caterpillars. [These are] different stages in a cycle that goes ‘round and ‘round and ‘round.”