This article was originally published on Conversation. The magazine contributed the article to Space.com. Expert Voices: Opinion Articles and Insights. Fan Zhou He is a graduate student at Pennsylvania State University. W. Neil Brandt He is a professor of astronomy and astrophysics at Pennsylvania State University.
Black holes are fascinating astronomical objects with such strong gravity that nothing, not even light, can escape them. The most gigantic black holes, known as supermassive black holes, can weigh millions to billions of times the mass of the Sun.
These giants They usually live in the centers of galaxies.Our galaxy, the Milky Way, also has a supermassive black hole at its heart.
So how do these supermassive black holes become so massive? To answer this question, Our Team Who is it?RPhysicists We looked back in time through the 13.8 billion-year history of the universe to trace how supermassive black holes grew from the earliest days to today.
We have built a model for Total growth history Of the supermassive black holes that have spanned the past 12 billion years.
How do supermassive black holes grow?
Supermassive black holes grow primarily in two ways. They can consume gas from their host galaxies in A process called accumulation.They can also merge with each other When two galaxies collide.
When supermassive black holes consume gas, they Almost always emits strong x-rays.a type of high-energy light that is invisible to the naked eye. You may have heard of X-rays at the dentist, where they are sometimes used to examine your teeth. X-rays used by astronomers Their energies are usually lower than medical X-rays.
So how can any light, even invisible X-rays, escape from black holes? Strictly speaking, the light doesn’t come from black holes themselves, but from gas just outside them. As the gas is drawn toward the black hole, it heats up and glows to produce light, such as X-rays. The more gas a supermassive black hole consumes, the more X-rays it produces.
With more than 20 years of data from three of the most powerful X-ray facilities ever launched into space – Chandra, XMM-Newton and Aerosita Astronomers are able to capture X-rays from a large number of supermassive black holes accreting in the universe.
This data allows our research team to estimate how fast supermassive black holes grow by consuming gas. On average, a supermassive black hole can consume enough gas to reach roughly the mass of the Sun every year, with the exact value depending on various factors.
For example, The data shows The growth rate of a black hole, which averages over millions of years, is closely related to the mass of all the stars in its host galaxy.
How often do supermassive black holes merge?
In addition to feeding on gas, supermassive black holes can also grow by merging with each other to form a single, more massive black hole when galaxies collide.
Cosmic simulation using supercomputer The frequency of these events can be predicted. This simulation aims to model how the universe grows and evolves over time. The countless galaxies flying through space are like the bricks that build the universe.
these Simulation shows that Galaxies and the supermassive black holes they host can undergo multiple mergers over the course of cosmic history.
Our team tracked these two growth channels — gas consumption and mergers — using X-rays and supercomputer simulations, and then combined them to build this comprehensive growth history, which maps the growth of black holes across the universe over billions of years.
Our growth history revealed Supermassive black holes grew much faster billions of years ago, when the universe was younger.
In the early days of the universe, there was more gas for supermassive black holes to consume, and supermassive black holes continued to appear. As the universe aged, the gas gradually ran out, and the growth of supermassive black holes slowed. About 8 billion years ago, the number of supermassive black holes stabilized. It has not increased significantly since then.
When there isn’t enough gas to grow supermassive black holes by accretion, the only way they can grow is by merging. We haven’t seen many cases of that in our history of growth. On average, the most massive black holes can accumulate mass from merging at a rate of about the mass of the Sun every few decades.
Looking forward
This research has helped us understand how more than 90% of the mass in black holes has accumulated over the past 12 billion years.
However, we still need to investigate how they grow in very early universe To explain the few percent of mass left in black holes. The astronomical community is beginning to make progress in exploring these early supermassive black holes, and we hope to find more answers soon.
This article was republished from Conversation Under a Creative Commons license. Read Original Article.
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