NASA’s Chandra X-ray Observatory and its NuSTAR (Nuclear Spectroscopic Telescope Array) has indirectly detected what it thinks is the remnant stellar core of Supernova 1987A, the first naked-eye supernova discovered in more than 400 years. Located in the nearby Large Magellanic Cloud, a dwarf galaxy located some 170,000 light years away, Supernova 1987A (or SN 1987A) was first spotted from a lonely Chilean observatory mountaintop on Feb. 23, 1987.
In a paper published in The Astrophysical Journal, an international team of astronomers note that after three decades of searching, they have used x-ray emissions to detect the supernova’s neutron star core. The team also used data from the ground-based Atacama Large Millimeter Array (ALMA) in Chile to support their claims.
“For 34 years, astronomers have been sifting through the stellar debris of SN 1987A to find the neutron star we expect to be there,” Emanuele Greco, of the University of Palermo in Italy, the study leader said in a statement. “There have been lots of hints that have turned out to be dead ends, but we think our latest results could be different.”
These objects have been dubbed neutron stars, because they are made nearly exclusively of densely packed neutrons, says NASA. Rapidly rotating and highly magnetized neutron stars, called pulsars, produce a lighthouse-like beam of radiation that astronomers detect as pulses when its rotation sweeps the beam across the sky, the space agency notes. However, there is a subset of pulsars, says NASA. that produce winds from their surfaces – sometimes at nearly the speed of light – that create intricate structures of charged particles and magnetic fields known as “pulsar wind nebulae.”
NASA says the most likely explanations for this energetic X-ray emission is that it’s being produced by just such a pulsar wind nebula.
As for the type of supernova explosion that created such a neutron star?
The most likely scenario involves a core collapse supernovae. The progenitors of core collapse supernova are massive stars which undergo the core collapse of their iron cores. That is, when the star’s nuclear material simply can no longer support the weight of the star’s gravity.
In fact, SN 1987A offered astronomers the first direct confirmation that heavy elements are produced in supernovae.
SN 1987A is known to be a Type II core collapse supernovae subsequently left behind a compact remnant, either a neutron star or a black hole, as I noted here in a previous post. But in SN 1987A’s case, there is still some debate about whether the explosion might have been caused by the merger of two stars.
Astronomers have long known that 1987A’s light curve behaved oddly from the get-go. For one reason, it never got as bright as typical core collapse supernova, which is why it’s officially classified as a Type II ‘Peculiar’ supernova. That means it simply doesn’t fit any of the known supernova core collapse Type II subcategories.
As for the supernova’s progenitor star?
It’s known that at least one of its progenitors was Sanduleak -69 202, a blue supergiant star of some 20 solar masses. Whether the explosion at the heart of the supernova was caused by the collapse of a single massive blue star or caused by the merger of two stars remains open for debate.
But NASA thinks that if there is indeed a pulsar at the center of this 34-year-old supernova remnant, it would be the youngest one ever found. As a result, it will be therefore ideally suited to watch its development.
The hope is that the stellar debris surrounding the putative pulsar will disperse over the next few years. If so, NASA says that in about a decade, the pulsar’s emission will emerge unobstructed, revealing the existence of this recently-formed, spinning neutron star.