Sometime between early 1995 and 1996, a supernova went off in a very nearby galaxy. The weird thing is, nobody noticed.
That's… bizarre. How do you miss an entire exploding star?
Yet everyone did. It went completely unrecorded, not discovered until years later. The reasons no one saw it at the time may simply be that it was a faint explosion as such things go, and it happened in a part of the sky where there's so much stuff going on that it was hard to spot.
A Hubble image of the Circinus Galaxy taken in 1999, after SN1996cr exploded but before it was discovered, with an arrow representing the approximate location of the supernova. The red glow is from hydrogen, likely in the star-forming region where the massive star that exploded was born. Credit: NASA/ESA/Hubble/Judy Schmidt
The story starts in a galaxy technically named ESO 97-G13, but everyone just calls it the Circinus Galaxy, due to the constellation we see it in. It's one of the closest galaxies to us, just 12 million light years away. That's only about 5 times as far as the Andromeda Galaxy, one of the brightest in the sky, so you'd expect it to ...