Astronomy Cast Ep. 176: Mysteries of the Milky Way, Part 1

There are many mysteries in our galaxy that have puzzled astronomers for many years.
Blue stragglers are stars in globular clusters that are not old and neither off of the main sequence nor are red dwarfs. These stars are high mass blue stars on the main sequence that are well above the main-sequence turn off. These stars shouldn't last more than a few millions years, but they are part of clusters that are billions of years old. One theory is that these stars formed later, but this idea does not fit our models of the universe. The other idea is that two stars collided and formed one big, bright, blue star. The two star could also be members of a binary that merged or have had mass-transfers.
Supernovae are supposed to occur every century, however our Milky Way Galaxy has not produced a supernovae since 1680. Dust clouds could have possibly blocked our sight of some of these supernovae.
Another question is whether the Magellanic Clouds are satellite galaxies or not. Due to the presence and uncertainty of dark matter, calculations are not certain about whether the galaxies are related to our own or not. Depending on calculations, the two galaxies could either be unattached and zipping past us, or could be gravitationally bound together around the Milky Way.
Proxima Centauri is believed to be part of the Alpha Centauri system, but it could also be just very close to Alpha Centauri A+B. Alpha Centauri's stars have the same composition, but Proxima Centauri has a different composition. Also, Proxima Centauri is at the farthest point in its projected orbit, so it is uncertain whether Proxima Centauri is connected to Alpha Centauri or not.
Eta Carina is a massive object in the constellation Carina. Eta Carina had a "false nova event" in 1843. Other stars that have gone through this turned into supernovas. Therefore, we could see a supernova from Eta Carina very soon.