On February 23, 1987, astronomers recorded one of the brightest supernovae in more than four hundred years, SN 1987A. The stellar explosion of 100 million suns was observed several months after its discovery.
Located in the Large Magellanic Cloud, one of the Milky Way's companion galaxies, SN 1987A was the closest supernova to Earth in several centuries. It quickly became the most studied supernova of all time. Over the past thirty years, detailed observations of the supernova remnant with both space and ground-based telescopes have allowed astronomers to study the death of a massive star in unprecedented detail, from star stage to supernova and from supernova to supernova remnant. The result was a veritable revolution in our understanding of these cosmic cataclysms
In fact, we saw live the emergence of the "echo." The radiation from the flare and the decay energy of the short-lived radioactive isotopes (Nickel 56 and Cobalt 56) illuminated the cocoon of matter, released into the surrounding space by the dead luminary during its short life. Outwardly, this was expressed in the emergence of bright rings surrounding the flare site.
As the isotopes decayed, the rings gradually began to fade. But then they glowed again. The fact is that 14 years after the flare, a shock wave moving at a speed of 7,000 km/s finally reached the inner boundary of the gas-dust cocoon. This led to heating and active emission of matter in the X-ray range.
Beginning in 2013, the rings began to fade again. The fact is that the shock wave, having thoroughly slowed down, passed the main cocoon. In addition, the main part of the isotopes decayed. According to calculations, the rings should stop being observed sometime in the next decade. However, the scientists hope that in the future, the shockwave may catch some earlier ejections of the star, which will allow to complete the picture of its life.
SN 1987A has provided astronomers with a lot of unique data about supernovae, but it has also generated one mystery. So far, they have never been able to find its remnant. Based on the estimated mass of the star, a neutron star should have formed as a result of its collapse. This is also indicated by the recorded neutrinos. But despite all the efforts, the pulsar could not be detected.
The remnant of SN 1987A
According to one theory, as in the anecdote, although the neutron star is not visible, but in fact it exists, it is just hidden by dust clouds that do not let anything through. According to another version, for some reason it has an extremely weak magnetic field. According to the third, the pulsar captured part of the matter ejected during the flare, gained mass exceeding the Oppenheimer-Wolkov limit, and turned into a black hole. The problem is that no traces of the activity of this hypothetical black hole have yet been found. There are more unusual versions, such as the fact that the outburst formed something much more exotic, like a quark star.
We can only hope that in the future, astronomers will clarify the mystery of the missing remnant of SN 1987A. As for the matter ejected from it, it will scatter throughout the galaxy and eventually become part of new luminaries and planetary systems, and maybe even some kind of living creatures. After all, as one classicist said, we are all made of stardust.
