In today's class we started Bobby's work on black holes. I taught him the difference between the stellar remnant left behind after a Sun-like star evolves through its life cycle which is a white dwarf, and the resulting remnant when a star tens of times bigger than the Sun has exhausted its fuel which is a black hole (or a neutron star depending on the initial mass of the star). We discussed the differences between a planetary nebula (for the Sun-like star) and a supernova remnant (for the more massive star). We also covered the two (main) types of black hole – stellar and supermassive. Bobby asked some very interesting questions!