From Lab to Life: Finding a Huge Black Hole

Prof. Andrea Ghez won a recent Nobel Prize for physics, for discovering (proving the existence of) a super-massive black hole – right in our neighborhood, at the center of the Milky Way galaxy, near the constellation of Sagittarius. Only 26,000 light years away.

Black holes are super-dense objects in the universe, so dense that their pull of gravity keeps everything (including light) from escaping it.  Hmmm… so if even light can’t escape – how do astronomers like Ghez find them? Answer:  By inference.  She analyzed the orbits of stars near the black hole, and inferred from their orbits that they were subject to the pull of gravity of a super-massive object (e.g. black hole) relatively nearby.

Ghez, a faculty member at UCLA, developed a method for inferring the existence of the black hole – but she was initially turned down for grants and told it would not work, could not work, waste of time.  She persisted.  As a very young child, she was given a telescope by her mother – and thus began her stellar career in astrophysics. I learn from this:  Crucially important to stimulate even very young children, and encourage their early passions.

Black hole theory was initially developed by Stephen Hawking. Ghez observes that we still do not understand black holes fully – because the physics of the stuff inside them is subject to laws we do not yet fathom.  And truth be told, we do not yet fully understand gravity either – the key to black holes.

It turns out that there are probably black holes at the center of most galaxies. Why at the center?  Because, just as a stone sinks to the bottom of a lake,  the heaviest objects in the galaxy tend to drift toward its center, where the gravitational pull is strongest.  (E.g., the center of gravity of the galaxy).

How massive is the Sagittarius A  black hole?   Say, 4 million times the mass of our entire solar system!    All of this, concentrated in a relatively tiny volume.

Dr. Ghez had a stroke of luck.  Just as she was beginning to implement astronomical measures to prove the black hole’s existence, a new and powerful telescope came online.  It did the trick.