Enormous Jets emitted from a supermassive Black Hole

The Pictor A galaxy has a supermassive black hole at its center, and material falling onto the black hole is driving an enormous beam, or jet, of particles at nearly the speed of light into intergalactic space. This composite image contains X-ray data obtained by Chandra at various times over 15 years (blue) and radio data from the Australia Telescope Compact Array (red). By studying the details of the structure seen in both X-rays and radio waves, scientists seek to gain a deeper understanding of these huge collimated blasts. — The image shows the location of the supermassive black hole, the jet and the counterjet. Also labeled is a “radio lobe” where the jet is pushing into surrounding gas and a “hotspot” caused by shock waves – akin to sonic booms from a supersonic aircraft – near the tip of the jet. Credit: X-ray: NASA/CXC/Univ of Hertfordshire/M.Hardcastle et al., Radio: CSIRO/ATNF/ATCA

Pictor A is a galaxy located about 500 million light years from Earth. A supermassive black hole located at its center, causes material to fall towards the event horizon, releasing a huge amount of gravitational energy. This energy produces a jet of particles travelling at nearly the speed of light into intergalactic space.

Astronomers used data from NASA’s Chandra X-ray Observatory, along with radio data from the Australia Telescope Compact Array, over a period of more than 15 years, to study the galaxy. Combing observation in X-rays and radio waves, scientists try to understand the physics of these huge blasts.

The jet in Pictor A shows a continuous X-ray emission over a distance of 300,000 light years (the entire Milky Way is about 100,000 light years in diameter). Additionally to the prominent jet, another jet pointing in the opposite direction has been found. Astronomers, led by M. J. Hardcastle, recently reported, that this X-ray emission likely comes from synchrotron radiation, i.e. from electrons spiraling around magnetic field lines that are continuously re-accelerated as they move out along the jet. The exact mechanism of this phenomenon, though, is not fully understood. Another possible mechanism to produce the jets, is electrons that fly away from the black hole and collide with CMB photons, i.e. the Cosmic Microwave Background radiation that has been left over from the hot early phase of the Universe after the Big Bang. These collisions can boost the photon’s energy up into the X-ray band. Which mechanism is favorable depends on local conditions. The latter mechanism doesn’t seem plausible though, in the case of Pictor A. The brightness of the X-ray emitted from the jet and counterjet does not match what is expected in the process involving the CMB. Neverthess, high-resolution radio observations of jets are required to draw strong conclusions.

Source: Chandra

Publication: Hardcastle et al. 2016