When was the last supernova in our galaxy?
This questions sounds straightforward but it’s actually a little bit convoluted to answer. But just a little, so sit back and let’s talk about a science communication mistake, light travel time, and what happens when an entire star explodes. Sometimes two.
So. I recently wrote about a stellar explosion 900 years ago called Supernova 1181, and how astronomers have finally identified the expanding debris from that catastrophic event.
When I wrote about this on Twitter to promote the blog article, I said there have been no supernovae seen in our galaxy since the invention of the telescope:
But that’s wrong!
He’s right; the supernova G1.9+0.3 is far more recent, and in fact I mention this supernova in passing in an article I wrote in 2020. That means I’ve known about this supernova for some time but I simply forgot about it when writing that tweet. Oops.
So what’s the deal here?
Very roughly speaking, we expect that there’s one supernova explosion in our galaxy every century. That’s an average, and could easily be more or fewer. The last one definitively visible by eye (that is, without a telescope of any kind) was ...