Contrary to what its name suggests, the black hole at the center of our Milky Way galaxy is not an empty void. It’s a piece of space that weighs as much as several million suns. Here, gravity reigns, and it is relentless; the black hole tugs inexorably at anything that gets too close—a cloud of cosmic dust, an entire star the size of our sun—and swallows it. Nothing, not even light, can escape a black hole’s maw, which means astronomers on Earth, watching the meal from afar, can’t see it.
Astronomers know that the black hole is there because they can observe what’s happening around it. With telescopes, they have captured the chaotic conditions around a seemingly empty spot in space. Stars whip around at extraordinary speeds. Gas and dust accumulate into a rotating disk that glows brightly as it moves. Streams of powerful radiation and energetic particles erupt from this disk and surge into space.
This pinwheel of cosmic matter at the heart of the galaxy can be difficult for us layfolk to fathom. But we don’t have to rely on our imagination.
Astronomers on Wednesday reported new telescope observations of the environment around the Milky Way’s supermassive black hole, named Sagittarius A* (pronounced “a-star”), and they transformed the data into a lively animation:
The video is positively ghostly. Clumps of gas swirl around the black hole, traveling at about 30 percent of the speed of light.
Astronomers collected the data for the visualization using an instrument on the European Southern Observatory’s Very Large Telescope, located in the deserts of northern Chile. The instrument, appropriately named GRAVITY, detected flares of infrared radiation coming from the disk surrounding Sagittarius A*. The researchers believe the bursts originated very close to the black hole, in an incredibly tumultuous region known as the innermost stable orbit. Here, cosmic material is slung around violently, but it remains far away enough that it can circle the black hole safely without getting sucked into the darkness.
If the thought of orbiting a monstrous, star-gobbling black hole spooks you, don’t worry. Earth, located about two-thirds out from the center of the Milky Way, is at a very safe distance. The planet is in no danger of being consumed and wiped off the face of the universe.
But like everything else in the galaxy, it has long been subject to the black hole’s whims. When black holes belch radiation into space, the outflow can heat surrounding gas so much that it prevents the gas from cooling. If cosmic dust can’t cool, it can’t condense to form individual, brand-new stars, including ones like our sun. Scientists suspect that the fates of galaxies—whether they produce new stars or stop altogether—rest with the supermassive black holes at their centers.
But if the thought of the Milky Way’s black hole eating all by its lonesome makes you sad, or if you’re rather offended that black holes are routinely described as monsters, don’t worry about that either. Sagittarius A* has plenty of friends. Some astronomers predict that as many as 10,000 smaller black holes reside near the center of the galaxy.