Uncovered with JWST: A neutron star in the remnant of Supernova 1987A

Astronomers using the James Webb Space Telescope (JWST) have found conclusive evidence of a neutron star in the remnant of Supernova 1987A, the only supernova visible to the naked eye in the last 400 years and the most studied supernova in history. Although Supernova 1987A has been observed for more than three decades, scientists have not seen the compact object expected to have been produced during the explosion. Some indirect evidence had suggested that the supernova produced a neutron star, but a black hole wasn’t ruled out, so the nature of the compact object has remained a topic of debate. Core-collapse supernovae occur when stars more than 8 times the mass of the Sun explode at the end of their lives. They are the main source of some chemical elements, including oxygen, silicon, and magnesium. The expired core of these exploding stars can leave behind a much smaller neutron star, composed of the densest material in the Universe, or can produce a black hole. Supernova 1987A, located in a neighboring dwarf galaxy, was the nearest and brightest supernova seen for four centuries. Neutrinos were produced in the explosion and detected on Earth a few hours before light from the supernova arrived, indicating that a neutron star probably formed, though might have later collapsed into a black hole. However, neither a neutron star nor a black hole have been directly detected, because the expanding debris from the explosion hides the compact object in dense gas and dust. Now, researchers led by Claes Fransson have observed the supernova remnant at infrared wavelengths with JWST, using spectroscopy to examine the gas composition and motions. They found emission lines from highly ionized argon and sulfur gas located close to where the star exploded. The gas composition and ionization can only be explained if there is a bright source of ultraviolet and X-ray radiation from a neutron star, either directly or indirectly; a black hole would not produce the observed lines. The JWST observations provide compelling evidence for a neutron star in the remnant of Supernova 1987A.