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Composite X-ray, IR and optical image of SNR 1181
Credit: X-ray: (Chandra) NASA/CXC/U. Manitoba/C. Treyturik, (XMM-Newton) ESA/C. Treyturik; Optical: (Pan-STARRS) NOIRLab/MDM/Dartmouth/R. Fesen; Infrared: (WISE) NASA/JPL/Caltech/; Image Processing: Univ. of Manitoba/Gilles Ferrand and Jayanne English


The Hunt for the Hidden Supernova

It's hard to hide a stellar explosion for centuries, but that's apparently what happened. In the 12th century CE, between August 4 and August 6, 1181, a star in what we now call the constellation of Cassiopeia exploded. This "guest star" was one of only a handful of dramatic celestial brightenings to be recorded by humans before the invention of the telescope, and is recorded in separate texts by contemporary Chinese and Japanese skywatchers. The explosion was visible for about half a year, then faded away to obscurity. Since that time, astronomers have struggled to find the glowing remnant of the material ejected in the explosion. An extended radio object called 3c58 was thought to be the remnant of the 1181 explosion at one point, since it contained a neutron star pulsar. But the pulsar was spinning too fast to have been produced in 1181, leading many to continue the search. In 2013, an astronomer noticed a circular infrared source in Cassiopeia in observations obtained by NASA's Wide-Field Infrared Survey Explorer (or WISE for short). Follow-up X-ray observations with XMM-Newton showed that this extended source was also an extended X-ray source, indicating that the source was associated with a powerful, high-energy event, while high spatial resolution observations by the Chandra X-ray Observatory revealed the presence of a point-source of X-rays near the center of the nebula. This central source was found to be the hottest known object in the sky, with a temperature of almost 200,000 degrees C, with a stellar wind blowing into space at 16,000 km/s (equivalent to 35 million miles per hour), one of the fastest stellar winds ever seen. Although the nebula is faint in optical light, it does show radial structure in the visible produced by knots of heated material. Astronomers believe that this nebula is the real remnant of the 1181 event. This explosion is believed to be a peculiar supernova triggered by the collision of two white dwarf stars,which somehow left behind a weird, massive, hot white dwarf at the center of the remnant.
Published: May 6, 2024


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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 13-May-2024 14:40:59 EDT