NASA’s James Webb Space Telescope has found the best evidence yet for ejections from a neutron star at the site of a recently observed supernova. The supernova, known as SN 1987A, was a core-collapse supernova, meaning the compacted remnant at its core became either a neutron star or a black hole. Evidence of such a compact object has long been sought, and while there has been indirect evidence of the existence of a neutron star before, this is the first time that the effects of a high-energy emission from a potentially young neutron star have been detected. Is.

A supernova – the explosive final death of some massive stars – explodes in hours, and the brightness of the explosion peaks in a few months. The remnants of the exploding star will continue to evolve rapidly over the next decades, giving astronomers a rare opportunity to study an important astronomical process in real time.

Supernova 1987A

Supernova SN 1987A occurred in the Large Magellanic Cloud, 160,000 light-years from Earth. It was first observed on Earth in February 1987 and its brightness peaked in May of that year. It was the first supernova that could be seen with the naked eye since Kepler’s observation of a supernova in 1604.

About two hours before the first visible-light observation of SN 1987A, three observatories around the world detected a neutrino burst lasting just a few seconds. Two different types of observations were linked to the same supernova event, and provided important evidence to inform the theory of how supernova core-collapse occurs. This theory included the expectation that this type of supernova would form a neutron star or black hole. Astronomers have since looked for evidence of one or another of these compact objects at the core of the expanding remnant material.

Indirect evidence for the presence of a neutron star at the core of a remnant has been found in the past few years, and observations of very old supernova remnants – such as the Crab Nebula – confirm that many supernova remnants contain neutron stars. However, no direct evidence of a neutron star resulting from SN 1987A (or any other such recent supernova explosion) had been observed until now.

Klais Fransson of Stockholm University, and lead author of the study, explained: “From theoretical models of SN 1987A, the 10-second burst of neutrinos observed just before the supernova suggests that the explosion produced a neutron star or black star. The hole was formed. But we haven’t observed the forcing signature of such a newborn object from a supernova explosion. With this observatory, we now have direct evidence of emission from a newborn compact object, most likely a neutron star. are.”

Webb’s observations of SN 1987A

Webb began the science observations in July 2022, and the Webb observations behind this work were taken on July 16, making SN 1987A one of the first objects observed by Webb. The team used the Medium Resolution Spectrograph (MRS) mode of Webb’s MIRI (Mid-Infrared Instrument), which members of the same team helped develop. The MRS is a type of device called an integral field unit (IFU).

IFUs are capable of imaging an object and taking its spectrum at the same time. An IFU creates a spectrum at each pixel, allowing observers to see spectroscopic differences throughout the object. Analysis of the Doppler shift of each spectrum also allows evaluation of the velocity at each position.

Spectral analysis of the results showed a strong signal due to ionized argon from the core of the ejected material around the origin of SN 1987A. Later observations using Webb’s NIRSpec (near-infrared spectrograph) IFU at shorter wavelengths found even more heavily ionized chemical elements, notably pentavalently ionized argon (that is, an argon atom that has five of its 18 electrons). are lost). Such ions require highly energetic photons to form, and those photons have to come from somewhere.

“To create the ions we observed in the ejecta, it was clear that there must have been a source of high-energy radiation at the core of the SN 1987A remnant,” Francisson said. “In this paper we discuss different possibilities, finding that only a few scenarios are likely, and all of them involve a newly born neutron star.”

More observations are planned this year with web and ground-based telescopes. The research team hopes that ongoing studies will provide more clarity about what is happening at the heart of the SN 1987A remnant. It is hoped that these observations will stimulate the development of more detailed models, ultimately enabling astronomers to better understand not only SN 1987A, but all primary collapsing supernovae.

The findings were published in the journal science.