Twenty thousand years ago, the star that would become supernova 1987A put on a ring. Not one — three. The two outer ones, like lampshades, tilted relative to the equatorial ring, and the star's light, struggling through them, barely reached an observer who happened to be in the plane of the equatorial ring. For several hundred years, the star dimmed to five percent of its former brightness. Today, such an event would be called a 'failed supernova'—a star that faded but didn't explode. But it had simply hidden behind its own ring.
The rings are gas ejected by the star long before the explosion. The equatorial ring is expanding at 10.3 kilometers per second — thirty times slower than the ISS orbits. Over twenty thousand years, it has inflated to a radius a hundred times the distance from the Sun to the Earth. As the star's light passes through such a ring, it scatters off the ring's particles, like a flashlight beam in thick fog. For an observer exactly in the ring's plane, the star nearly vanishes. For an observer above or below, it shines as if nothing happened.
Such a coincidence makes one wonder: aren't some 'failed supernovae' simply stars that temporarily hid behind their own rings? If so, the statistics of massive star collapses could be skewed. Astronomers search for black holes born without a bang, and perhaps they find stars playing hide-and-seek.
But the work has a second part. The rings of supernova 1987A are not aligned with the bipolar ejecta structure — the 'Keyhole'. It's as if the star first spun around one axis, then exploded along another. The author proposes a scenario: the star's companion, as it was disrupted, transferred angular momentum to the core. The spin was moderate — insufficient for a thin accretion disk, but enough for late accretion to come from inclined directions. Thus, the jet axis became tilted.
This scenario remains speculative, but it provides a concrete mechanism to explain the axis misalignment. If correct, the jittering-jets mechanism, explosions by jets that change direction, gets another confirmation. And supernova 1987A itself becomes not just a supernova remnant, but a time machine: it shows what the star looked like twenty thousand years before it truly faded.
The equatorial ring of Supernova 1987A is expanding at 10.3 km/s—30 times slower than the International Space Station's orbital speed. Over 20,000 years, it has inflated to a radius of about 1.5×$10^{18}$ cm, roughly 100 times the distance from the Sun to Earth.