NPR Story 11:11 am Fri October 5, 2012  How Astronomers Measured
the Edge of a Black Hole  Originally published on Fri October 5,
2012 12:41 pm    This is SCIENCE FRIDAY. I'm Ira Flatow. A team
of astronomers using a network of radio dishes to peer to the
edge of a massive black hole at the heart of a galaxy that is 15
million light years away, for the first time, they have measured
the invisible boundary around the black hole - it's called an
event horizon - where nothing, not even light, can escape its
strong gravitational pull. So what secrets did the astronomers
uncover at the black hole's edge? Shep Doeleman is the lead
author of the study, which was published last week in the
journal Science. He's assistant director at the MIT Haystack
Observatory in Westford, Massachusetts. Welcome to the program.
SHEP DOELEMAN: Hi, Ira. Really good to be here.  FLATOW: Thank
you. What is - exactly is an event horizon?  DOELEMAN: Well,
let's back up a second and ask what a black hole is because it's
a great question.