An Introduction to Radio Astronomy

Abstract

The data give for the coordinates of the region from which the disturbance comes, a right ascension of 18 hours and declination of −10 • .-Karl G. Jansky 1933 Jansky's discovery of radio emission from the Milky Way is now seen as the birth of the new science of radio astronomy. Most astronomers remained unaware of this momentous event for at least the next decade, and its full significance only became apparent with the major discoveries in the 1950s and 1960s of the 21 cm hydrogen line, the evolution of distant radio sources, quasars, pulsars, and the cosmic microwave background. Radio astronomy had revealed a previously unseen Universe and is now one of the prime observational tools available to astronomers. There are several fields of application in which it is especially, sometimes uniquely, useful, as follows. The cosmic microwave background (CMB) The early Universe is observable as a black body whose ∼ 2.7 K temperature has maximum emissivity at millimetre wavelengths. High energy processes in galaxies and quasars These emit intense radio waves from charged particles, usually electrons, moving at relativistic velocities. Cosmic magnetic fields These are revealed in radio sources and in interstellar space by the polarization of radio waves. Astrochemistry Molecular constituents of clouds in the Milky Way and in distant galaxies are observable by radio spectroscopy. Star and planet formation Condensations of atoms and molecules are mapped by millimetre-wave synthesis arrays. Kinetics of galaxies Radio spectroscopy, especially of the 21 cm hydrogen line, reveals the dynamic structure of galaxies. Neutron stars The timing and structure of pulses from pulsars opens a wide field of research, from condensed matter in neutron star interiors to the gravitational interactions of binary star systems. General relativity Pulsars, the most accurate clocks in the Universe, are used to measure the geometry of space-time. 3

Black hole superradiance and polarization-dependent bending of light

“…What is relevant for astrophysical observations is light intensity rather than field amplitude. For this reason it is useful to introduce the four Stokes parameters [62]…”

A Subgrid Turbulent Mean Field Dynamo Model for Cosmological Galaxy Formation Simulations

“…Faraday rotation corresponds to the rotation of the plane of polarisation of electromagnetic radiation propagating through a magnetised plasma (Burke et al 2019). The Rotation Measure (RM) is defined as the ratio between the gradient of the polarisation angle 𝜒 and the wavelength 𝜆 2 :…”

One-Bit DoA Estimation via Sparse Linear Arrays

“…In consequence, deployment of high-resolution ADCs in many modern applications, e.g. cognitive radio [26], cognitive radars [27], automotive radars [28], radio astronomy [29] and massive multiple-input multiple-output (MIMO) systems [30], is not economically viable owing to their very high bandwidth. In order to reduce energy consumption and production cost in such applications, researchers and system designers have recently proposed using low-resolution ADCs.…”