It shone in the Large Magellanic Cloud in 1987 and fascinated astronomers around the world. But only now has it been possible to clarify with the help of the Webb telescope what emerged from the famous supernova 1987A: Instead of a black hole, a neutron star was formed after the stellar explosion. This is evident from the signature of ionized gas in the area of the relic, which can be explained by radiation from a neutron star, the scientists say.
Massive stars don't just burn up - they end their existence with a huge bang: when they have used up their supply of fuel, they collapse under their own weight and explode - a core collapse supernova occurs. The surrounding space is flooded with dazzling light: a supernova can briefly shine as intensely as an entire galaxy. Astronomers have now recorded many of these cosmic detonations. But the supernova that shone in 1987 occupies a special position. It occurred in one of our neighboring galaxies - the Large Magellanic Cloud - and could even be seen in the sky with the naked eye. This put many astronomers in their sights, recorded its path and also examined what happened after the explosion. The supernova 1987A is considered the most intensively researched stellar explosion to date.
What was left of the star?
Shortly after the supernova, astronomers wondered which of the two possible relics could have emerged from the star's death. It is assumed that after stars with more than eight to ten times the mass of the sun explode, an extremely compact remnant is formed: either a black hole or a neutron star. The detection of neutrinos that reached Earth as part of the supernova 1987A suggested the formation of a neutron star. But it seemed possible that this was only a short-term condition: the neutron star could then have quickly collapsed into a black hole. However, it has not yet been possible to clearly clarify which object is present because the relic is obscured by dust that formed after the explosion.
In order to solve the mystery, the international team of astronomers led by Claes Fransson from Stockholm University has set its sights on the area of supernova 1987A using the James Webb Space Telescope (JWST). Its instruments have recorded in detail the radiation in the infrared wavelength range emanating from the cosmic complex. Spectroscopic analyzes of these emissions made it possible to draw conclusions about the presence of potentially informative substances in the cloud, the scientists explain.
Neutron star radiation ionizes gas
As they report, they identified the spectroscopic signatures of the elements argon and sulfur in the central area of the cloud - in the ionized state. The team then modeled different scenarios for the formation of these two substances. They made it clear that the ionized atoms could only have been created by irradiating the supernova material with ultraviolet and X-rays. “To produce these ions, there must be a source of high-energy radiation at the center of the remnant of supernova 1987A,” says Fransson.
Such radiation does not escape from a black hole, so the only possible cause is a neutron star or the rapidly rotating form of these objects - a pulsar. “This radiation can be emitted from the surface of the neutron star, which is around a million degrees hot, as well as from a pulsar wind nebula,” explains co-author Mike Barlow from University College London. It is not yet possible to say exactly what type of neutron star it is. But at least the fundamental question now appears to be clarified: “The mystery of whether a neutron star or a black hole is hidden in the dust has existed for more than 30 years and we are pleased to have now solved it,” said Barlow.
The team wants to continue to keep an eye on the exciting system: This year, more intensive observations with the Webb telescope and ground-based telescopes are planned. The research team hopes that these studies can provide more clarity about what exactly is and is going on at the heart of the remnant of Supernova 1987A. According to the scientists, these observations could ultimately lead to a fundamentally better understanding of the development processes in the context of core collapse supernovae.
Source: NASA, University College London, specialist article: Science, doi: 10.1126/science.adj5796