Supernovae are among the most spectacular stellar events we can witness. From the Earth, we see a star undergo sudden brightening, and rush to image the death throes. It has blown off much of its mass in a steady stellar wind, and is surrounded by shells of gas. The resounding flash of light that announces the supernova lights up these shells.
What we don't see are the events happening inside the star. Over millennia of evolution, the supergiant star has created within itself an iron core. That core collapses catastrophically, and tremendous amounts of energy are released outward through the rest of the star. The core itself rebounds and also rips through the rest of the star -- tearing it apart in a matter of hours. The shock wave reaches the surface of the star, and announces itself as a flash of bright, bright light. That is the point where our observational powers come into play.
In 1987, a blue supergiant star exploded in the Large Magellanic Cloud. The star itself lay nearly 170,000 light years away from us, and so the light from that inferno had been traveling that long to reach our eyes. In the millennia before the explosion, the supergiant had been releasing its mass in the form of a strong stellar wind. That mass had formed a large bubble around the star.
When the star exploded, it lit up the bubble, and what we saw from Earth was a ring of light. Over time, the light traveled outward from the star, illuminating more and more of the surrounding gas shells. What we saw with the Hubble Space Telescope in 1994 was an astounding sight: what looked like a triple ring surrounding the remnant of the dying star. The peculiar set of events that interacted to form this ghostly sight is one that we are still trying to understand. What -- aside from the dying central star -- is lighting up the shells? Are the gas shells shaped more like an hourglass? Or, are there two stars in the center of this explosion, each sending a jet of radiation out to light up parts of the shell?
As the Hubble and other telescopes continue to focus our attention on this supernova remnant, we'll know more details about its intricate scenario of death. This supernova will join the pantheon of others that have expanded our knowledge of star death -- and the effects that it has on the rest of the universe.