New Study Suggests Supermassive Black Holes Cannibalize Their Own Galaxies
Astronomers believe that nearly every galaxy, including our own Milky Way, have a black hole at their center. Ours happens to be one of many supermassive black holes that are theorized to exist. While their gravity is so intense that not even light can escape them, the effects of a black hole can be observed by the way it interacts with gas and stars that are nearby. The picture below is a prediction of what the event horizon of Sagittarius A* (pronounced Sagittarius A-star), the black hole at the center of the Milky Way Galaxy, will look like when it’s imaged by the Event Horizon Telescope.
Black holes are essentially invisible, but astronomers are developing technology to image the immediate surroundings of these enigmas like never before. Within a few years, experts say, scientists may have the first-ever picture of the environment around a black hole, and could even spot the theorized “shadow” of a black hole itself.
We’ve known that the life cycle of most galaxies involves a supermassive black hole eating away at the stars and gas around them over the course of billions of years. Many stars will even form, go through their own life cycles, then die during this timeframe – all independent of the supermassive black hole itself.
Scientists have also observed large galaxies, that appear to be healthy, stop producing new stars. This was accepted as common, though the underlying cause was not known. Now, a new study published by scientists at the University of California Santa Cruz in Nature suggests that this may be due to supermassive black holes leeching energy from the galaxy to feed its insatiable hunger.
The black holes could be taking so much energy from the galaxy itself then sending the fuel outside of the galaxy itself. Sort of like exhaust on your car, but on an enormous cosmic scale. When the supermassive black holes become too supermassive, they suck up much of the cold gas that would otherwise be creating new stars, and the galaxy dies.
Gizmodo explains further:
Using data collected by the Hobby-Eberly Telescope Massive Galaxy Survey, Martín-Navarro’s team analyzed the spectra of light coming from distant galaxies. This allowed them to separate and measure the varying wavelengths of light coming from these distant objects. The scientists used this data to create a historical snapshot of a galaxy’s star formation history. They then compared this history with black holes of different masses, which resulted in some striking differences—differences that correlated with black hole mass, but not the shape, size, or other properties of black holes.
What this ultimately means is that star formation will likely occur for a longer period of time with galaxies whose central black hole isn’t as massive (meaning less hungry). The Milky Way Galaxy is currently transitioning from a period of star formation to a slower, more passive period of star birthing, and in a few billion years, the Milky Way will die and Sagittarius A* will become one with the void. Comforting, right?