How Black Holes Shape the Universe: Forces Interact with Galaxies' Big Bulges
Black holes possess immense forces working within and around them. These structures in particular are some of the most important shapers and movers of the universe. Now, scientists have taken a closer look at black holes and galaxies' central bulges, revealing how black holes shape the universe.
The universe is made up of thousands of millions of galaxies which each contain anywhere from hundreds of thousands to hundreds of billions of stars. A large amount of these galaxies are actually elliptical in shape, red and mostly made up of old stars. Another large category of these galaxies are spiral-shaped with arms that wind out in a blue thin disk from a central red bulge.
Almost all galaxies have supermassive black holes at their centers. The mass of the bulge of a galaxy is actually closely tied to this black hole; the more massive the black hole, the more energy is released into the surrounding galaxy in the form of powerful jets and X-ray emission. This can actually blow away material and stop new stars from forming.
In this case, the researchers examined data from the Sloan Digital Sky Survey to learn more about galaxies in general. They grouped together half a million galaxies of all different colors, shapes and masses. They then measured the shape of each one to see how the proportion of red stars in a galaxy varies with its other properties.
So what did they find? It turns out that the mass in the central bulge is key to knowing the color of the whole galaxy. This means that the black holes in the center of the galaxies are also key to determining the color.
"A relatively simple result, that large galaxy bulges mean red galaxies, has profound consequences," said Asa Bluck, one of the researchers, in a news release. "Big bulges mean big black holes and these can put an end to star formation."
The findings are published in the journal Monthly Notices of the Royal Astronomical Society.