Supernova 2011dh in the Whirlpool Galaxy. Image Credit: Peter Edwards
Supernovae, the explosive end of the life of some stars, are among the most powerful and most spectacular events in the universe. They are also very rare. Our Milky Way galaxy, with tens of billions of stars, sees one of them explode every 100 years or so. The last known supernova in our galaxy was seen in 1604 and was studied by the famous astronomer Johannes Kepler. Since that time, we think that at least two stars may have exploded in the Milky Way, with the explosions veiled by some of the Milky Way's many thick, opaque clouds of dust and gas. But none have been seen.
Thankfully, there are lots of galaxies in the universe. So, when astronomers want to study supernovae, they look at a lot of galaxies. Such surveys for supernovae are turning up new explosions in distant galaxies all the time. Still, many of these galaxies are fairly far away, and it is rare to find a supernova in our neck of the woods.
Enter the Whirlpool Galaxy, also called Messier 51. The Whirlpool is nearby, as far as galaxies go – "only" 26 million light-years ...