Almost everybody has heard the word “supernova”, and most people (even gradeschool kids) know that it refers to a massive exploding star. You may also have heard that a single supernova can outshine the multi-billions of not-exploding stars in its host galaxy, and that supernovas (supernovae to traditionalists) seed the space around them with elements that can only be created inside of massive stars. These elements would not otherwise be released, but once blown free, they help to form succeeding generations of stars which condense from interstellar gas and dust. These elements also help to form the planets around those new stars… and, of course, whatever evolves on said planets.

So, yes — you and much of what is around you are composed, in part, of supernova detritus!

I’ve been lucky enough to see a handful of supernovas with my telescope during 40-odd years as an astronomy hobbyist. Invariably, they appeared as mere pinpoints of light within a small smudge of a galaxy, all of them being tens of millions of light years away.

Now, given the vast numbers of stars per galaxy and the equally enormous number of galaxies within the grasp of our largest telescopes, there are detectable supernovas blowing up practically all the time. In any large galaxy like our own, they occur — on average — once or twice every hundred years. In short, although it’s not uncommon for astronomers to see a supernova “as it happens”, to see one nearby is very rare. In fact, the last time anyone saw a supernova going off in our own Milky Way galaxy was in 1604. We’re overdue for another. I frequently find myself looking at the stars, hopeful that this might be the night a supernova appears, bright enough to be seen with just my bare eyes.

One of my fellow Canadians knows what it’s like to go outside and look up at a brand-new supernova. On this date (Feb. 24) in 1987, Ian Shelton discovered a supernova in one of the Milky Way’s satellite galaxies, the so-called Large Magellanic Cloud. Shelton was, at the time, working at the University of Toronto’s Las Campanas observatory in the high Andes mountains of Chile. He’d been photographing parts of the LMC through a small and aging telescope, and during the photo-processing he came across a bright star image where he knew one shouldn’t exist. Unconvinced that such a bright object was real, he went outside and looked up to see a previously-invisible star sparkling right where his picture showed it. Conferring with others at the observatory, Shelton realized it had to be a supernova, and he reported it as quickly as he could to the International Astronomical Union’s notification distribution centre in Cambridge, Massachusetts. As a result, SN 1987A became the most thoroughly-observed supernova in history. Its expanding three-ringed remnant continues to intrigue astronomers today, and will doubtless be studied for years — perhaps centuries — to come.

��3t/ð