Supermassive black holes were even bigger in the past

June 21 () –

Computer models have been used to predict the masses of the largest supermassive black holes in the universe, a mathematical concept known as the black hole mass function.

Joseph Simon, a postdoctoral researcher in the Department of Astrophysical and Planetary Sciences at the University of Colorado Boulder, sought to determine what you might find if you could put each of these black holes one by one on a gigantic scale.

Their calculations suggest that billions of years ago, black holes may have been much larger on average than scientists once suspected.

The findings could help researchers unravel an even bigger mystery, shedding light on the forces that shaped objects like the Sagittarius A star — the supermassive black hole at the center of our Milky Way galaxy — as they grew from tiny. black holes to the giants they are today.

“We are starting to see from a variety of different sources that there have been some pretty massive things in the universe since very early,” he said. it’s a statement Simon, who published his findings in The Astrophysical Journal Letters.

The astrophysicist is part of a second research effort called the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). Through the project, Simon and hundreds of other scientists in the US and Canada have spent 15 years searching for a phenomenon known as “gravitational wave background.” The concept refers to the constant flow of gravitational waves, or giant waves in space and time, that undulate through the universe almost constantly.

This cosmic turmoil also owes its origin to supermassive black holes. Simon explained that if two galaxies collide with each other in space, their central black holes can also collide and even merge. They go round and round each other before colliding like two cymbals in an orchestra, only this clash of cymbals generates gravitational waves, literally deforming the fabric of the universe.

However, to understand the background of gravitational waves, scientists first need to know how massive the supermassive black holes in the universe really are. The older ones, Simon said, they produce a bigger bang and produce much bigger gravitational waves.

“We have very good measurements of the masses of supermassive black holes in our own galaxy and in nearby galaxies,” he said. “We don’t have those same kinds of measurements for more distant galaxies. We just have to guess.”

In his new investigation, Simon decided to guess in a whole new way. First, gathered information on millions of thousands of galaxies, some billions of years old. (Light can only travel so fast, so when humans look at galaxies that are farther away, they’re looking back in time.) Simon used that information to calculate the approximate masses of the black holes in the largest galaxies in the universe. He then used computer models to simulate the background of gravitational waves that these galaxies could create and that currently washes over Earth.

Simon’s results reveal the smorgasbord of supermassive black hole masses in the universe dating back about 4 billion years. He also noticed something strange: There seemed to be much larger galaxies scattered throughout the universe billions of years ago than some previous studies predicted. That didn’t make much sense.

“There was an expectation that you would only see these really massive systems in the near universe,” Simon said. “It takes time for black holes to grow.”

Their research, however, adds to a growing body of evidence that suggests they may not need as long as astrophysicists believed. The NANOGrav team, for example, has seen similar hints of giant black holes lurking in the universe billions of years ago.

For now, Simon hopes to explore the full range of black holes that extend even further back in time, revealing clues to how the Milky Way came to be, and eventually our own solar system.

“Understanding the masses of black holes is critical to some of these fundamental questions, such as the gravitational wave background, but also how galaxies grow and how our universe has evolved,” Simon said.