Description:

Much of the history of radio astronomy concerns sources like Cygnus A, first observed in the late 1930s. Originally thought to be stars, they were eventually shown to comprise double sources straddling distant galaxies. It was then discovered that these are powered by anti-parallel, relativistic jets emanating from the nuclei of these galaxies which are exceptionally bright when pointed in our direction. Today we know that they are formed near massive black holes, no larger than our solar system. The theoretical interpretation has evolved in parallel and is now focused on identifying the rotational energy of the black hole as the power source and attributing the collimation of the jets to helical magnetic field twisted by a disk of infalling and outflowing gas. The talk will conclude with a discussion of the implications of the observations of M 87 (Virgo A) by the Event Horizon Telescope Collaboration and future prospects for learning more about these fascinating astronomical sources.

Roger Blandford, KIPAC, Stanford University

Host: Zadeh

Keywords: Physics, Astronomy, Radio Astronomy