Two astrophotos of the Fireworks Galaxy. The left view, in color, was taken on May 26, 2006; the right, showing the new supernova, was taken June 25, 2017.
The Fireworks Galaxy has that nickname for a good reason: more supernovas have popped off there than in any other known island universe. Counting the latest, the supernova discovered by Patrick Wiggins at 8:28 p.m. on May 13, a total of 10 of these largest known explosions have occurred in the galaxy since 1917.
The Fireworks Galaxy, technically called NGC 6946, is a beautiful looping structure with odd arms, only 22 million light-years away. An ordinary galaxy like ours, which is at least twice its size, is reckoned to experience supernovas about once a century.
Wiggins, a long-time leader of the Salt Lake Astronomical Society and a resident of Tooele County, has discovered three supernovas. The latest is by far the most interesting, as it’s taking place close enough for the blast to be visible with a good amateur telescope. It has generated scores of photographs since that Saturday evening, according to the webpage at rochesterastronomy.org dedicated to this supernova, maintained by the Rochester Academy of Science.
NGC 6946 is counted among the deep-space objects in the constellation Cepheus the king, and is located on the border between Cepheus and Cygnus. A moderate-sized galaxy in the northern sky, it’s visible all year but especially well in October. It is a face-on barred spiral galaxy, with a bridge of stars across the center and that confusing set of spiral arms.
Robert Bernham Jr., author of the magnificent — though somewhat outdated — set of astronomy books, Burnham’s Celestial Handbook: An Observer’s Guide to the Universe Beyond the Solar System, comments on the strange arms. “Multiple branching of the arms makes it difficult to trace the course of any one arm from its point of origin in the central mass to its gradual disappearance on the galaxy’s outer rim. There are, however, at least four well-defined arm segments, and several further branches or ‘sub arms,'” he wrote in the 1978 three-volume edition published by Dover…