The total energy output from the supermassive black holes in AGN and quasars is comparable to the total energy holding the constituent stars of their galaxies together. Monsters Lurking in the Centers of Galaxies
KIPAC scientists study the gamma-ray emission from blazars to understand jets and their relation to the black holes and the accretion disks, as well as the contributions blazars have made to the evolution of the Universe as a whole. Blazars are strongly variable in all observable bands of the electromagnetic spectrum, and simultaneous observations with instruments sensitive to different wavelengths of radiation are critical for studying them. When jets point toward Earth, the AGN is called a blazar. At the same time, powerful winds carry energy out into the galaxy.
In radio galaxies and radio-loud AGN, jets that can tap into the energy of a spinning black hole emanate vast distances out of the host galaxy, carrying vast amounts of kinetic energy into the surrounding gas. The X-rays that are emitted from a corona of energetic particles close to the black hole shine down on the accretion disk of gas spiralling in, allowing KIPAC astronomers to map out the extreme environment just outside the event horizon. These observations are then coupled with theoretical models and computer simulations to map out and understand the extreme environments around various types of black holes. KIPAC scientists use observations of black holes and their jets taken by X-ray telescopes (Chandra, Swift, XMM-Newton and NuSTAR), the Fermi gamma-ray telescope, and a wide range of optical and radio telescopes. Jets travel close to the speed of light some can even span great distances, reaching far out of their host galaxies. On top of impressive light shows, some black holes are able to launch streams of material into jets. When gas falls into a supermassive black hole at the center of a galaxy, it lights up active galactic nuclei (AGN) or quasars, the most powerful continuous sources of light we can see from the farthest reaches of the Universe. We can observe stellar mass black holes in our galaxy when they feed on material from a companion star in an X-ray binary. Fortunately, when matter falls into a black hole, it becomes superheated and produces an intense source of light before it crosses the horizon. Black holes are difficult to observe directly, since no light can escape from within the event horizon. This includes Sagittarius A*, which is found at the heart of our own Milky Way galaxy. In addition, supermassive black holes, a million to a billion times more massive than the Sun, sit in the centers of galaxies. Scientists at KIPAC are working to understand many aspects of black holes: how they formed, how they grew, the exact processes by which energy is released as material falls into them, and the process by which some black holes are able to launch jets.īlack holes with masses comparable to that of the Sun (or, stellar mass black holes) are scattered through the Milky Way and neighboring galaxies, and are formed when the most massive stars come to the ends of their lives. At that point it is said to have formed a black hole, and the point of no return - the distance around it from which nothing can escape - is called the event horizon.
The matter is pulled together and eventually becomes so compact and dense that its gravitational force becomes so strong that nothing can escape it, not even light. When enough matter, whether from the remnants left at the end of the life of a massive star, or gas at the center of a galaxy, is compressed into a small enough volume, the force of gravity (the mutual attraction, pulling everything together) becomes so strong that no other force can match it. Black holes are the most extreme manifestation of the force of gravity.
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