Happy 35th, Supernova 1987a!

This week marks the 35th anniversary of Supernova 1987a, the first supernova seen with the naked eye since the one recorded by Johannes Kepler back in 1604.  The supernova actually occurred not in our Galaxy but the Large Magellanic Cloud, a smaller galaxy that orbits the Milky Way.  Though it happened in the south and could not be seen from Canada, it was actually first spotted by a Canadian, Ian Shelton, who at the time was working at the University of Toronto’s Southern Observatory at Las Campanas, Chile.  He had just observed the Large Magellanic Cloud for some other project and spotted the surprise bright object in his image.  He went outside to see for himself and confirmed it with his own eyes.  Fortunately, Ian was able to get word out to the global astronomy community as fast as possible – in those days there was no world wide web, so an astronomical telegram was issued.   As you can imagine, this supernova was a Big Deal, and the world’s telescopes (at least the ones in the south that could see it) were quickly trained on the object to follow its rapid evolution.  Even back in Canada, the excitement was palpable.  The event occurred during my first year at the University of Toronto, and the professor who taught my introductory astronomy class, Ernie Seaquist, threw the day’s lecture out the window to improvise a memorable lecture about the supernova and its significance instead. 

Since the last naked eye one was almost 400 years prior, you could say it is quite rare to see one in the sky.  Given that the Galaxy has about 400 billion stars or more, and the stars that end their existences in fiery supernovae are rarer, high-mass stars, the expected average rate of them occurring is about one every 50 years or so.  So, statistically we are still overdue one occurring somewhere in our Galaxy.  That said, the supernova could occur anywhere in the disk of our Galaxy, which is about 100,000 light years wide, so there’s always the possibility of one occurring so far away or being obscured by intervening Galactic dust that we might not be able to see it with our own eyes.  (Fortunately, no supernova precursors appear to be close enough to the Sun for their future explosions to affect us.)  Nevertheless, some astronomers are eagerly anticipating that next big one when it happens, and you can read an excellent article recently published in Nature about these preparations here.  Thanks to Jim Hesser for bringing that article to my attention!  (PS. Ian Shelton comes around DAO now and then, most recently to help us out with our photodensitometer (photographic plate scanning) equipment on the first floor.  He’s a nice guy, so hopefully we can have him back again soon!). For fun, here’s a link to a short but cool timelapse video of the evolution of the shockwave from Supernova 1987A as seen by Hubble over two decades.

Extra info sent to me by Joel Roediger: “Relatedly, a Twitter account has been set up specifically to replay the history of this event. It has been a fun follow!”