Supernovas are the spectacular end result of the collapse of stars with a mass greater than 8-10 times that of the sun. This process creates chemical elements such as carbon, oxygen, silicon and iron that make life possible. However, supernovas are also responsible for the creation of neutron stars and black holes, the most exotic objects in the universe.
Supernova 1987A (or SN 1987A for short) exploded on 23 February 1987 in the Large Magellanic Cloud in the southern skies at a distance of 160,000 light years. Visible to the naked eye, it was the closest supernova to be seen in more than 400 years. Modern observatories gave astronomers an unprecedented close-up view of the supernova blast. Despite being one of the most studied objects in the sky, SN 1987A still holds its mysteries. One of the most intriguing questions is, “What was left over from the exploded star?” The detection of neutrinos, incredibly tiny subatomic particles produced in the supernova, indicated that a neutron star must have formed. What remained unknown, however, was whether the neutron star survived or collapsed to form a black hole. Even after three-and-a-half decades of intense monitoring by highly advanced world-class observatories, convincing proof of the presence of a neutron star in the centre of SN 1987A remained elusive. Until now.
In a new publication in the journal Science, an international team of astronomers announce new discoveries made using the powerful James Webb Space Telescope (JWST). Observations using the JWST’s Mid-Infrared Instrument (MIRI) and Near-Infrared Spectrometer (NIRSpec) have revealed light emitted by ionised argon and sulphur in the centre of the supernova remnant (see Figs. 1 and 2). Thanks to the spatial resolution of the JWST and the ability to precisely determine the speed of the emission source, we know that the source is located close to the centre of the 1987 explosion. This is exactly what is expected from a compact central stellar remnant, given that most of the exploding star was blown out at up to 10,000 km/second and is now already far away from the centre. Ionisation of argon and sulphur indicates the emission of energetic photons, such as UV or X-rays, from a compact source at the centre. We thus see the unique signature of a newly created neutron star, as was predicted in 1992. According to the researchers, the radiation comes either from the million-degree heat of the neutron star itself or from energetic particles in the strong magnetic field of a very rapidly rotating neutron star, known as a pulsar wind nebula.
“Although there’s too much material swarming around the neutron star for us to see it directly, we can detect it indirectly using the JWST’s spectrometers,” says Professor Joris Blommaert of the Astronomy and Astrophysics Research Group of Vrije Universiteit Brussel, co-author of the publication. “We can form a picture, and for every pixel in that picture, we get a spectrum of electromagnetic radiation. That enables us to create a precise map of the radiation and localise its source,” adds Prof. Blommaert. Blommaert worked from the early 2000s onwards on the development of MIRI, which was crucial to detecting the spectra. “Thanks to our contribution to MIRI, we obtained observation time to study SN 1987A on the JWST, which ultimately enabled us to gather strong evidence for the existence of the central neutron star.”
The study is the work of 34 authors from 12 European countries and the United States.
Reference: C. Fransson et al., Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A. Science 383, 898-903(2024). DOI:10.1126/science.adj5796
Source and more info: https://press.vub.ac.be/james-webb-space-telescope-research-team-with-t…