On this episode of Our Island Universe: The dark mystery that lurks at the center of our Galaxy.
Host: Shanil Virani, Director of the John C. Wells Planetarium Harrisonburg, VA.
Follow on Twitter as shanilv
Transcript:
Lurking at the center of our Milky Way galaxy is an object we cannot see, it weighs about 4 million times the mass of our Sun, and occupies a volume of space about the size of our Solar System. Oh, and it devours everything in its immediate vicinity. Do you know what this monster in the dark is?! Its a supermassive black hole!
Black holes have long been a mathematical curiosity predicted by Einstein's equations of general relativity. And as weird as they, surely they don't exist in nature we once thought. In fact, how would you even go about finding something you cannot even see?! Astronomers using the Keck telescopes atop Mauna Kea, Hawaii have been staring at the center of our galaxy every few months or so for the last 20 years. What they've found are a number of stars orbiting an object that we don't see in the optical. But just as we can figure out the mass of our Sun from knowing what the average Sun-Earth distance is and that it takes a year to make one complete orbit, we can use the same Keplerian physics to measure that the center of our Galaxy is home to a black hole that weighs ~4 million times the mass of our Sun. This is the object those stars are orbiting! The existence of the supermassive black hole at our galactic center is betrayed by its gravitational effect on nearby stars!
How did it get there?! How did it grow so big?! What role does it play in how our galaxy changes with time? Great questions, but we don't really know! But the next time your child is afraid of monsters lurking in the dark, tell them about the one at the center of our Galaxy!