But black holes sometimes take inexplicable breaks. The one at the center of our galaxy , for example, seems to be dieting right now. Barely nibbling at its surroundings, it emits only radio signals. Seeing the invisible Measuring X-rays, radio waves and other emissions is one way researchers know black holes exist. They also see the effects of their tremendous gravity, which pulls all nearby matter and energy, including light, into an inescapable abyss.
Scientists are as baffled as a sushi chef at a vegan party.
As recently as a few centuries ago, according to a new study of X-ray energy, our Milky Way's black hole went on a feeding frenzy fueled by an exploding giant star. This supernova, as it is called, sent a shock wave of heavy metals plowing into the gravity sink. Once the material was gobbled up, researchers suspect, the black hole reverted to starvation. Another recent study found that 90 percent of black holes are inactive at any given time, but evidence indicates that something reactivates them, because they continue to grow.