Albert Einstein’s theory of relativity predicted that the gravity of an extremely dense body could bend a ray of light so severely that it could not escape.  In 1939, J Robert Oppenheimer and another physicist calculated that such drastic compression could happen to the biggest stars after they ran out of hydrogen and other gases.  Telescope observations backed up the theory in the 1960’s and 1970’s.  Quasars, extremely bright illuminations, were later discovered.  Astronomers thought that these could only come about by the pulling together of millions of suns in a small volume.  They later called this a supermassive black hole.  Scientists later discovered stars in our Milky Way that seemed to be keeping tight orbits around small black holes that they called stellar-mass black holes.

Advances in technology have enabled scientists to get clearer images of black holes.  The Hubble Space Telescope was able to measure how fast the innermost parts of other galaxies rotate – up to 1.1 million miles per hour.  One of its greatest achievements was the discovery that there were supermassive black holes at the core of most galaxies.  However, even from Hubble, the core of the Milky Way was still a mystery.

Two teams of astronomers, one in Germany and one from the U.S., independently deduced that only a black hole could explain the behavior of stars at Milky Way’s core.  By meticulously collecting infrared photographs taken months and years apart, the two teams tracked the innermost stars.  They agreed that something was trapping the stars in a deep whirlpool.  A black hole made the most sense.

Because dust obscures visible light from the center of the galaxy, Ghez and her colleagues used adaptive optics technology to compensate for the atmosphere’s blur.  They used the powerful W.M. Keck telescope atop Hawaii’s Mauna Kea.  They were able to chart startling speeds for stars close to the galaxy’s center and were convinced that a massive black hole is responsible.

Scientists hope that soon they will be able to have the first image of the Milky Ways black hole.  New millimeter wave telescopes won’t be able to technically see the hole itself, but rather they’ll be able to photograph the shadow the black hole casts on a curtain of gas behind it.  They are hoping that this will show a black hole shadow with a distinctive shape.  It would be an image that scientists can’t wait to see.