Credit: X-ray: NASA/CXC/Penn State Univ./S. Dichiara; IR: NASA/ESA/STScI; Illustration: ERC BHianca 2026 / Fortuna and Dichiara, CC BY-NC-SA 4.0; Image Processing: NASA/CXC/SAO/P. Edmonds
Crash into You
Thermonuclear fusion reactions at the cores of massive stars produce most of the elements necessary for life to exist in the Universe. These fusion reactions gradually build up increasingly complex atomic nuclei (like helium, carbon, and oxygen) by merging simpler atomic nuclei together. But this process has a finite limit, and can only produce elements up to iron - when iron forms in the core of a star, the star explodes as a supernova, usually leaving behind the collapsed core of the star as an ultradene object called a neutron star. The density of a neutron star is about the same as that of an atomic nucleus, so in some sense neutron stars are similar to giant atomic nuclei, having the size of a large city. Since stars are often found in binary pairs, sometimes the thermonuclear evolution of stars in such binary systems will produce a pair of neutron stars, gravitationally bound and in orbit around each other. As nature would have it, all such systems are doomed to merge due to the increasing emission of gravitational radiation, shaking the very foundation of the Universe more and more violently. The mergers of these "giant atomic nuclei" are the believed to be the foundaries in which gold and other precious metals are forged. Merging neutron stars do not go quietly; such mergers produce some of the most powerful explosions known, producing short, tell-tale bursts of high-energy gamma radiation, as well as earth-shaking gravitational waves. On September 6, 2023, the Fermi Gamma-ray Space Telescope, in its scan of the skies, discovered a rapid burst of gamma rays from a previous nondescript corner of the Universe. The burst was so short, less than a second, indicating that the explosion was produced by the merger of two neutron stars. Quick followup observations in X-rays with the Chandra X-ray Observatory to pinpoint the source of the burst, and the Hubble Space Telescope to probe the environment of the merger, showed something peculiar. The gamma-ray burst seems to reside in a low density stream of material which was pulled from a galaxy in a remote galaxy cluster. The image above shows, in the upper left, a composite of a Chandra X-ray image (in blue) and Hubble image of the region of the burst, along with artist's illustration of the merging system (lower left), which produces a disk of material along with a particle beam jet produed by the merger, with an overview of the stream of material where the merger resides. Scientists postulate that the neutron stars that mergered were perhaps associated with a burst of massive star formation produced by the long-ago collision of two galaxies in the cluster.
Published: March 23, 2026
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Page Author: Dr. Michael F. Corcoran
Last modified Monday, 23-Mar-2026 11:54:11 EDT