How Black Holes Could Determine the Future of Life on Earth
Think of the universe as a flat sheet stretched out and held at four corners. Now put a bowling ball in the middle.
When night falls on the West Coast, Misty Bentz sits at a desk in her Atlanta office, logs into a program on her laptop and tells an 11-foot-wide telescope in New Mexico where to point in the sky.
She’s more than 1,300 miles away from Apache Point Observatory, but no matter. From her living room sofa or on campus at Georgia State, where Bentz is an assistant professor of astronomy, she can observe black holes in faraway galaxies.
“As soon as I’m done observing, I can close my laptop and go sleep in my own bed and not have to fly all the way to New Mexico and sit on top of the mountain to control the telescope,” she says. Georgia State is a part owner of the observatory, splitting time with researchers from 15 other universities.
Bentz tells the telescope to take photos and can even control the length of the exposure and other details of the instrument setup. A chat window lets her talk to someone near the observatory in the Sacramento Mountains and details how the equipment is positioned.
She uses the telescope to take measurements she needs to determine the masses of black holes in surrounding galaxies, a project funded by the National Science Foundation that could help explain fundamental mysteries of the universe, such as how galaxies evolve.
Think of the universe as a flat sheet stretched out and held at four corners. Now put a bowling ball in the middle. The sheet will sag underneath and be distorted, just as our universe is distorted by mass. At some point, if the ball is heavy enough, it’s going to rip through the fabric.
That’s basically what a black hole is, Bentz says.
“Black hole is a terrible name,” she says. “People think of a hole as something that’s empty. But a black hole is something that’s as full as can possibly be. You’ve squished as much stuff into that space as you can.”
Bentz looks at nearby galaxies with active black holes and measures the gravitational force of glowing gas around the black hole, among other things. Because active black holes are “eating” or ingesting gas and other materials, a huge amount of light, or radiation, is emitted around them. As more gas falls onto the black hole and gets closer and closer, the gas becomes super heated, glowing brightly.
The force of gravity in black holes is so strong even light can’t escape, so they’re invisible to us. It’s that superheated gas that allows scientists to find them. (The gas wouldn’t be glowing that brightly if there wasn’t a black hole it was falling onto.) Astronomers also locate black holes by using satellites and telescopes to study stars that are close to them.
But why are scientists so interested in black holes in the first place?
Because they could answer questions about human existence and the conditions that allowed life to form on Earth—and maybe even in other galaxies, Bentz says.
How can black holes help explain why we’re here?
“We don’t really understand why there’s life on Earth,” Bentz says. “We don’t understand it chemically, biologically or physically.”
What we do know is the supermassive black hole in our galaxy, the Milky Way galaxy, is important to why we’re here.
Galaxies can be shaped as footballs or pancakes, and some have rectangles or spiral arms like pinwheels.The Milky Way, for instance, is shaped like a pinwheel. Scientists are trying to understand how the conditions of galaxies with certain shapes might be better at supporting life than others.
The way galaxies form and evolve over time could also tell us something about how stars and planets form within those galaxies. Stars are critical to life on planets—a planet too far from a star is too cold to support life, but get too close and the heat can’t be withstood—and star formation seems to be regulated by black holes.
“In order to understand why galaxies and the universe look the way they do, we have to understand something about black holes,” Bentz says. “They seem to have a lot to say about how a galaxy is going to turn out later on.”
Scientists initially tried to build galaxies through computer simulations. They programmed in the laws of gravity and radiation, added a bunch of particles and an extra-dense region and observed how the system changed over time.
“What they found in these computer simulations is that just based on the physical laws that we know about, the galaxies were not turning out to look like the galaxies that we actually see,” Bentz says. “They were forming lots and lots of stars and too many of them. We didn’t know how to make galaxies in a simulation. We’re missing something.”
Piecing the puzzle together
Scientists have since discovered that their simulations need to account for something called feedback, which is the process of energy coming out from near a black hole and disrupting what’s happening in the galaxy. If black holes are “eating,” there’s feedback coming out. This energy can blow gas out of the galaxy, at which point it could either fall back into the galaxy or stay blown out completely. Stars form out of gas, so if there’s none available, no more stars can form in the galaxy.
When researchers added some amount of feedback from the black holes to their computer simulations, they found they could make galaxies that look like the ones we actually see. This indicates that black holes have an impact on the appearance and characteristics of galaxies.
The information scientists gather about black holes helps us understand our own place in the universe, Bentz says.
“If you want to understand where you come from, that’s more than just, ‘Where did my ancestors come from?’” she says. “It’s, ‘How am I able to be here today?’ To understand that, you have to understand what happened in the universe around us. We don’t know these answers yet, but we hope that by looking at various pieces of the puzzle and putting those pieces together, we’ll get a good picture of how all that has happened.”
ART DIRECTION: BASIL ISKANDRIAN
ANIMATION: WILLIAM DAVIS
PHOTOGRAPHY: STEVEN THACKSTON