What lies at the heart of supernova SN 1987A has been a mystery for four decades. Now, Dr Patrick Kavanagh and a team of astronomers have found an answer.
Almost exactly 37 years ago on this day, an explosion occurred in the Large Magellanic Cloud – a satellite galaxy of the Milky Way – that gave birth to the first recorded supernova in four centuries bright enough to be visible to the naked eye.
Since then, this supernova known as SN 1987A has captured the imagination of astronomers around the world and has been the subject of countless studies to unravel mysteries by observing in unprecedented detail what happens during one of the most violent events in the known universe.
One question that has endured is: What did the explosion leave behind?
It has boggled scientists using some of the most advanced observatories – including the Hubble Space Telescope – to study what lies at the heart of the supernova, a phenomenon that usually leaves behind one of two exotic objects: neutron stars or black holes.
The question had remained unanswered, until now. “It was so exciting looking at the James Webb Space Telescope (JWST) observations of SN 1987A for the first time,” said Dr Patrick Kavanagh of Maynooth University.
Kavanagh is the co-author of a study published in Science today (22 February) that has for the first time provided conclusive evidence for the presence of an elusive neutron star at the heart of SN 1987A.
Using the James Webb Space Telescope, the international team discovered narrow emission lines from ionised argon and sulphur atoms located at the centre of a nebula around the supernova.
Kavanagh said that while checking data from the mid-infrared instrument and near-infrared spectrograph aboard the James Webb, the very bright emission from argon at the centre of SN 1987A “jumped out”.
“We knew immediately that this was something special that could finally answer the question on the nature of the compact object,” he explained.
Essentially, the study shows that the emission line strengths observed by the James Webb must be triggered by radiation from the hot neutron star or from a pulsar wind nebula around the neutron star.
This, according to lead author Claes Fransson, would not have been possible without the James Webb, the most powerful space telescope we’ve ever built.
“Thanks to the superb spatial resolution and excellent instruments on JWST, we have for the first time been able to probe the centre of the supernova and what was created there,” said Fransson, who teaches in the Department of Astronomy at Stockholm University.
“We now know that there is a compact source of ionising radiation, most likely by a neutron star. We have been looking for this from the time of the explosion but had to wait for JWST to be able to verify the predictions.”
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