Editor’s Note: Don Lincoln is a senior scientist at the Fermi National Accelerator Laboratory. He is the author of “The Large Hadron Collider: The Extraordinary Story of the Higgs Boson and Other Stuff That Will Blow Your Mind.” He also produces a series of science education videos. Follow him on Facebook. The opinions expressed in this commentary are solely his. View more opinion articles on CNN.
Of all of the crazy sounding things in the pantheon of modern physics, it’s hard to beat a black hole. Generally speaking, black holes are the burned-out hulks of long dead stars, with a strong enough gravitational field that not even light can escape them.
The gravity near a black hole is so strong that it warps the very fabric of space and time. Black holes sound more like science fiction than fact, but there has been considerable indirect evidence that they exist. They are accepted by the scientific community in spite of an embarrassing admission: nobody has ever directly seen one. Well, until now.
Scientists have announced the first direct observation of a black hole at the center of a galaxy named M87. M87 is a supergiant elliptical galaxy in the constellation Virgo. It is one of the largest galaxies in the nearby universe. (Where “nearby” is the staggering distance of 53 million light years. Astronomers really do think big.)
Now a little bit of care is necessary to understand exactly what was done. Black holes are, well, black. By definition, they do not emit any light. So, the black hole was not observed directly. However, black holes are also surrounded by ordinary matter that is caught in the hole’s gravitational grip.
This matter, which is typically just gas of the same type that makes up our sun, orbits the black hole at very high speeds. All of that fast-moving gas gets heated up to the point where it glows and emits all sorts of forms of electromagnetic radiation, from heat to light to radio waves. Intervening gas blocks the visible heat and light, so astronomers look for the radio waves.
You’d think that astronomers would announce that they detected this halo of radio waves surrounding the hole, and that is part of the story. However, it’s more complicated than that. Because of the very strong gravity near the black hole, some of the light and radio waves are captured by it and don’t escape. The result is that a black hole looks like a ring of light, with a shadow in the middle. Essentially, from a distance, the picture astronomers released of the M87 black hole looks like a coffee ring left on a piece of paper, albeit a colored one.
Since the astronomers used radio waves to see the black hole, the colors aren’t what you would see with your eye. But they do have meaning. What we are seeing is the gas surrounding the black hole. One side is bright and one is dim because the black hole is spinning. The yellow shows the side of the black hole spinnin