Rutgers University Physics/Astronomy Colloquium - Irons Lecture

Several decades ago, astronomers discovered that certain sources once believed to be peculiar stars within our own galaxy (the Milky Way) in fact have vastly greater distances and luminosities. These "quasars" indeed turn out to be the most luminous objects in the Universe. But what causes them to produce such enormous quantities of radiation? Since their discovery, accumulating evidence has suggested that quasars are powered by matter spiraling in towards massive black holes-- objects whose gravitational pull is so powerful that not even light can escape. I will discuss recent, ultra-high-resolution observations with large ground-based telescopes that prove beyond any reasonable doubt that *the center of our own Milky Way* hosts precisely such a massive black hole. These observations also indicate that our galaxy's central black hole may be rotating rapidly. I will close by discussing our present knowledge about the formation and evolution of these massive black holes in the early Universe.