Black holes are Gravity is too strong The largest black holes are called “supermassive” black holes, and are millions or even billions of times the mass of the sun.
These giants They usually live in the center of the galaxy.Our galaxy, the Milky Way, Supermassive black holes exist In your heart too.
So how do these supermassive black holes become so massive? To answer this question, Our TeamAstrophysicist We looked back 13.8 billion years into the history of the universe and traced how supermassive black holes have grown from the early universe to the present.
we, Overall Growth History A record of supermassive black holes over the past 12 billion years.
How do supermassive black holes grow?
Supermassive black holes grow in two main ways: by consuming gas from their host galaxy A process called accumulationand they also merge with each other When two galaxies collide.
An illustration of the accumulation of supermassive black holes. The central black hole is black, while the surrounding gas heats up and glows, producing light. (Photo by Nahks Tr’Ehnl, Pennsylvania State University)
When a supermassive black hole consumes gas, Emits strong X-rays almost all the timeis a type of high-energy light that is invisible to the naked eye. You may have heard that dentists sometimes use X-rays to examine teeth. X-rays used by astronomers They generally have lower energy than medical x-rays.
So how can light, including invisible X-rays, escape a black hole? Strictly speaking, the light doesn’t come from the black hole itself, but from the gas just outside it. As the gas is attracted to the black hole, it heats up and glows, producing X-ray-like light. The more gas a supermassive black hole consumes, the more X-rays it produces.
Thanks to more than 20 years of data from three of the most powerful X-ray facilities ever launched into space, Chandra, XMM-Newtonand Eroshita– Astronomers can capture X-rays from many supermassive black holes in the universe.
This data allows the team to estimate how quickly supermassive black holes consume gas and grow. On average, a supermassive black hole grows at a rate of about Mass of the Sun The exact amount each year varies depending on a variety of factors.
for example, The data shows The growth rate of a black hole, averaged over millions of years, is strongly related to the mass of all the stars in its host galaxy.
How often do supermassive black holes merge?
Supermassive black holes grow not only by absorbing gas, but also by merging with each other when galaxies collide to form a single, more massive black hole.
Cosmological simulation using a supercomputer We can predict how often these events will occur. These simulations aim to model how the universe will grow and evolve over time. The countless galaxies flying around in space are like the bricks that build the universe.
these According to the simulation Galaxies and the supermassive black holes they contain can merge multiple times throughout the history of the universe.
Our team used X-rays and supercomputer simulations to trace two growth pathways – gas consumption and merging – and combine them to build a holistic growth history that maps the growth of black holes throughout the Universe over billions of years.
The story of our growth is revealed Billions of years ago, when the universe was young, supermassive black holes grew much faster.
In the early universe, there was a lot of gas for supermassive black holes to consume, and supermassive black holes appeared one after another. As the universe aged, the gas gradually depleted and the growth of supermassive black holes slowed down. About 8 billion years ago, the number of supermassive black holes stabilized. Since then, it has not increased significantly.
Diagram showing the merger of two supermassive black holes. Scott Noble (Courtesy of NASA GSFC)
If there is not enough gas for a supermassive black hole to grow by accretion, the only way it can get bigger is by merging. In the history of growth, this has not happened often. On average, the most massive black holes can accumulate mass by merging at a rate that would allow them to reach the mass of the Sun every few decades.
I’m looking forward to
The study helped understand how more than 90% of the black hole’s mass has accumulated over the past 12 billion years.
But how they developed remains to be investigated. The very early universe To explain the remaining few percent of mass of the black hole. The astronomy community is beginning to make progress in searching for these early supermassive black holes, and we hope to find more answers soon.
Fan Zou is a graduate student in astronomy and astrophysics at Pennsylvania State University. W. Niel Brandt is a professor of astronomy and astrophysics at Pennsylvania State University. This article is reprinted from conversation Under Creative Commons License. read Original Article.
