SS 433, a microquasar located within our Milky Way, has long been a subject of fascination for scientists. This binary star system consists of a black hole and a companion star orbiting each other, with the black hole drawing material from the star’s surface and creating a hot accretion disk. What sets SS 433 apart is the presence of oppositely directed beams of plasma, known as jets, that spiral away from the disk’s surface at a remarkable speed of over a quarter of the speed of light.
In a groundbreaking discovery, the H.E.S.S. observatory in Namibia has detected very high energy gamma rays from the jets of SS 433. This detection has allowed scientists to gain valuable insights into the mechanisms behind gamma-ray emissions and particle acceleration within these relativistic jets. The findings challenge existing theories and provide a closer look at the processes driving cosmic phenomena.
The detection of gamma rays from SS 433’s jets is significant because it marks the first time such emissions have been observed in a microquasar. This discovery opens up new possibilities for studying particle acceleration within astrophysical jets. While the relevant region of the jets in SS 433 is much smaller than those of active galaxies, its proximity to Earth makes it easier to study with current gamma-ray telescopes.
The H.E.S.S. observatory conducted an observation campaign of the SS 433 system, resulting in around 200 hours of data and a clear detection of gamma-ray emission from the jets. The superior angular resolution of the H.E.S.S. telescopes allowed researchers to pinpoint the origin of the gamma-ray emission within the jets for the first time. Surprisingly, the position of the gamma-ray emission shifted when viewed at different energies.
The highest energy gamma-ray photons were detected at the point where the jets abruptly reappear, while lower energy gamma rays were observed further along each jet. This energy-dependent morphology in the gamma-ray emission of an astrophysical jet is a groundbreaking observation. It suggests that efficient particle acceleration is taking place at the sites where the jets reappear, indicating the presence of a strong shock.
Particles within the jets are accelerated to extreme energies, and when these fast particles collide with light particles, they produce high-energy gamma photons through a process called the inverse Compton effect. The simulation of the observed energy dependence of the gamma-ray emission allowed scientists to estimate the velocity of the outer jets, which differs from the velocity at which the jets are launched.
The discovery of particle acceleration in SS 433 is significant as it provides crucial insights into the dynamics of this unique system. The H.E.S.S. result not only pinpoints the site of acceleration but also sheds light on the nature of the accelerated particles and allows scientists to study the motion of the large-scale jets launched by the black hole.
While there is still much to learn about the origin of shocks at the sites where the jets reappear, this discovery opens up new avenues for research. Understanding particle acceleration in relativistic jets is not only important for studying SS 433 but also for unraveling the mysteries surrounding larger jets in active galaxies and quasars.
The study of SS 433’s gamma-ray emission and particle acceleration is a testament to the advancements in observational techniques and our growing understanding of cosmic phenomena. As scientists continue to unravel the secrets of this unique system, we move closer to a comprehensive understanding of the mechanisms driving relativistic jets and their role in shaping our universe.
