Near the center of the Milky Way galaxy is a massive object that astronomers call Sagittarius A*. Perhaps this “supermassive” black hole grew with our galaxy, not alone. Scientists suspect that such giants lurk at the heart of almost all major galaxies in space.

Some can really get big, says Joseph Simon, a postdoctoral fellow in the Department of Astrophysics and Planetary Sciences at the University of Colorado at Boulder.

“The black hole at the center of our galaxy has a mass millions of times that of the Sun, but we also see others that we think are billions of times that of the Sun,” he said.

The astrophysicist devoted his career to studying the behavior of these elusive objects. In a recent study, he used computer simulations or “models” to estimate the masses of the largest supermassive black holes in the universe; this is a mathematical concept known as the black hole mass function. In other words, Simon was trying to determine what would be found if you put each of these black holes one by one on a large scale.

Their calculations show that billions of years ago, black holes may have been, on average, much larger than scientists once thought. These findings could help researchers unravel an even bigger mystery by explaining the forces that shaped objects like Sagittarius A*, which evolved from tiny black holes into the giants they are today.

“We’re starting to see from different sources that there were pretty big things going on in the universe from the very beginning,” Simon said.

He published his findings on May 30. Astrophysical Journal Letters.

galactic symphony

For Simon, these “pretty big things” are his bread and butter. The astrophysicist is part of a second research initiative called the North American Nanohertz Gravitational Waves Observatory (NANOGrav). Thanks to this project, Simon and hundreds of other scientists from the United States and Canada have spent 15 years investigating a phenomenon known as the “gravitational wave background.” This concept refers to the continuous flow of gravitational waves or giant waves in space and time that fluctuate on an almost constant basis throughout the universe.

This cosmic motion also owes its origin to supermassive black holes. Simon explained that if two galaxies collide in space, black holes at the center could also collide and even merge. They spin around each other and then crash into each other like two cymbals in an orchestra – only that cymbal slam creates gravitational waves that literally dissolve the very fabric of the universe.

But to understand the background of gravitational waves, scientists first need to know how big the supermassive black holes in the universe really are. Bigger plates created a larger explosion and created much larger gravitational waves, Simon said.

There is only one problem.

“We have really good measurements of the masses of supermassive black holes for our own galaxy and nearby galaxies,” he said. “We don’t have the same measurements for distant galaxies. We can only guess.”

In his new work, Simon decided to predict in a completely new way.

First, it gathered information on hundreds of thousands of galaxies, some of which are billions of years old. (Light can travel very fast, so people are looking back in time when observing more distant galaxies.) Simon used this information to calculate the approximate black hole masses of the largest galaxies in the universe. He then used computer models to simulate the background gravitational waves that these galaxies could create and are currently washing the Earth.

Simon’s results reveal a full smorgasbord of supermassive black hole masses in the universe dating back about 4 billion years. He also noticed something strange: Billions of years ago, it seemed that there were many more massive galaxies in the universe than some previous studies had predicted. It doesn’t make sense.

“You were expected to see these really large systems only in the near universe,” Simon said. “Black holes take time to grow.”

However, his research adds to growing evidence that it may not last as long as astrophysicists once thought. For example, the NANOGrav team saw similar signs of giant black holes lurking in the universe billions of years ago. Simon now hopes to explore the entire spectrum of black holes stretching back even further, uncovering clues to how the Milky Way Galaxy and ultimately our Solar System formed.

“Understanding the mass of black holes is critical to some of these fundamental questions, such as the background of gravitational waves and how galaxies grow and how our universe evolves,” Simon said. Said. Source