Zap! A Black Hole Scores a Direct Hit With its Jet

Most galaxies are thought to play host to black holes. At the center of Centaurus A, a galaxy 12 million light years away, a jet is being fired out into space. Images that have been captured by NASA’s Chandra X-ray observatory show that the high energy particles have struck a nearby object creating a shockwave. The target is thought to be a giant star, maybe even a binary system, where the collision and turbulence has increased density in the region.

A black hole is an object and a region of space! At the centre is the singularity, a single point object where density is infinite and all the laws of physics seem to fail us. Surrounding the singularity is a region of space where the velocity needed to escape the singularity’s gravitational pull is in excess of the speed of light. The boundary between the region of space dominated by the singularity and dare I say ‘normal space’ is known as the event horizon. Collectively we call this phenomenon a black hole. 

Black holes at the centre of galaxies are usually supermassive, often millions to billions of times more massive than the Sun. They exert an immense pull of gravity which has an impact on the motion of stars and gas within their host galaxy. Matter getting drawn toward a black hole by its immense gravitational pull forms into an accretion disk surrounding the black hole. Here the gravitational force is high and so it heats the incoming material. The material falling in to the black hole gets heated to extreme temperatures generating strong electromagnetic fields. The fields can accelerate the particles outward forming into the familiar jet structure. 

Our own Milky Way galaxy has a black hole at the centre as does the galaxy Centaurus A. At a distance of 12 million light years, it’s relatively in our back yard! A team of astronomers have turned NASA’s Chandra X-Ray observatory on Centaurus A and found the jet of its black hole striking an unidentified object. The team of astronomers discovered that parts of the jet are moving at speeds close to the speed of light. They also detected the region where it seemed to be striking something, appearing as a bright source of X-rays in the image, known as C4. 

At a distance of 12 million light years, it’s too far away for the object to be seen but the team theorise that it’s either a massive star or one with a companion star. It’s thought that the X-rays are caused by a collision between the particles in the jet and the stellar wind from the star. The impact from the collision can be the generation of turbulence which leads to an increase in the density of gas in the jet, driving the X-ray emissions that have been detected. 

In the deepest image from Chandra, at the C4 source there appeared a strange V-shaped structure. The shape is not fully understood but analysis revealed the arms of the ‘V’ are at least 700 light years long! The results were published in the Astrophysical Journal by lead author David Bogensberger from the University of Michigan and a team of US astronomers. 

Source : Black Hole Jet Stumbles Into Something in the Dark

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