4. Windows in the sky

Radio Waves ◽

Transverse Waves ◽

The atmosphere influences much of what can be seen through a telescope. Most of the atmosphere lies within 16 km from the Earth’s surface. Further out, the air becomes thinner until it merges with outer space. In the ionosphere—a layer 75–1000 km high—neutral atoms are ionized by solar radiation and high-energy cosmic ray particles arriving from distant parts of the Universe. ‘Windows in the sky’ explains electromagnetic radiation and the electromagnetic spectrum from gamma rays through to visible light and radio waves. Electromagnetic waves are transverse waves that can be polarized. The atmosphere acts as a filter and blocks cosmic electromagnetic radiation. Atmospheric turbulence distorts starlight resulting in ‘twinkling’ stars.

6. Electromagnetic waves

Waves: A Very Short Introduction ◽

10.1093/actrade/9780198803782.003.0006 ◽

2018 ◽

pp. 70-99

Author(s):

Mike Goldsmith

Keyword(s):

Electromagnetic Radiation ◽

Infrared Radiation ◽

Electromagnetic Waves ◽

Scientific Investigation ◽

The Other ◽

X Rays ◽

Radio Waves ◽

History Of ◽

Insight Into

‘Electromagnetic waves’ considers the history of the scientific investigation into the electromagnetic spectrum, including Einstein’s insight into the quantized nature of electromagnetic radiation. It explains that the only difference between light, radio waves, and all the other forms of electromagnetic radiation is the length of the fictitious-but-convenient waves or, equivalently, the energy of the photons involved. These different energies lead to different mechanisms for the formation and absorption of the different kinds of radiation, and it is this which gives rise to their different behaviours. Radio waves, microwaves, infrared radiation, light, ultraviolet light, X-rays, and gamma rays are all discussed.

1. Waves in essence

Waves: A Very Short Introduction ◽

10.1093/actrade/9780198803782.003.0001 ◽

2018 ◽

pp. 1-29

Author(s):

Mike Goldsmith

Keyword(s):

Phase Velocity ◽

Electromagnetic Radiation ◽

Particle Velocity ◽

Electromagnetic Waves ◽

Seismic Waves ◽

Fundamental Difference ◽

Radio Waves ◽

Transverse Waves ◽

The Difference ◽

Wave Phenomena

Most waves can be defined by just a few parameters: period, frequency, wavelength, amplitude, particle velocity, phase velocity, and group velocity. ‘Waves in essence’ explains these parameters in turn and then goes on to discuss the spreading and fading of waves and the complexities of waves that arise through their interactions with objects and other waves resulting in diffraction and interference. It also describes the difference between longitudinal and transverse waves and the important wave phenomena of refraction and reflection. It then outlines the fundamental difference between pressure waves like sound, ocean, and seismic waves, and electromagnetic waves, which include light and radio waves. All electromagnetic radiation is made of particles called photons.

Hunting Gravitational Waves with Multi-Messenger Counterparts: Australia’s Role

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2015.49 ◽

2015 ◽

Vol 32 ◽

Cited By ~ 9

Author(s):

E. J. Howell ◽

A. Rowlinson ◽

D. M. Coward ◽

P. D. Lasky ◽

D. L. Kaplan ◽

...

Keyword(s):

Gravitational Wave ◽

Gamma Ray ◽

Cosmic Ray ◽

High Energy ◽

Design Sensitivity ◽

New Era ◽

Worldwide Network ◽

AbstractThe first observations by a worldwide network of advanced interferometric gravitational wave detectors offer a unique opportunity for the astronomical community. At design sensitivity, these facilities will be able to detect coalescing binary neutron stars to distances approaching 400 Mpc, and neutron star–black hole systems to 1 Gpc. Both of these sources are associated with gamma-ray bursts which are known to emit across the entire electromagnetic spectrum. Gravitational wave detections provide the opportunity for ‘multi-messenger’ observations, combining gravitational wave with electromagnetic, cosmic ray, or neutrino observations. This review provides an overview of how Australian astronomical facilities and collaborations with the gravitational wave community can contribute to this new era of discovery, via contemporaneous follow-up observations from the radio to the optical and high energy. We discuss some of the frontier discoveries that will be made possible when this new window to the Universe is opened.

High Redshift Radio Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900081894 ◽

1996 ◽

Vol 175 ◽

pp. 571-576

Author(s):

K. Meisenheimer ◽

H. Hippelein ◽

M. Neeser

Keyword(s):

Radio Emission ◽

Electromagnetic Waves ◽

High Redshift ◽

Radio Galaxies ◽

Early History ◽

Radio Telescopes ◽

Radio Waves ◽

History Of ◽

The Universe ◽

Travel Distances

One hundred years after G. Marconi recorded radio waves over a distance of more than 1000 m, the most sensitive radio telescopes are able to detect the radio emission from light travel distances at least 1.4 × 1023 times greater. The electromagnetic waves from these distant objects are red shifted by Δλ/λ = z > 4. It is not the mere distance of high redshift objects which is fascinating, but rather the fact that one looks back into the early history of the universe by observing them: Objects at a redshift of 4 shined at a time when the universe had reached only about 1/5 of its present age.

On the flux of high-energy cosmogenic neutrinos and the influence of the extragalactic magnetic field

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz083 ◽

2019 ◽

Vol 488 (1) ◽

pp. L119-L122 ◽

Cited By ~ 1

Author(s):

David Wittkowski ◽

Karl-Heinz Kampert

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Large Scale ◽

Neutrino Flux ◽

Cosmic Ray ◽

High Energy ◽

Observation Time ◽

Cosmological Time ◽

Cosmic Background ◽

ABSTRACT Cosmogenic neutrinos originate from interactions of cosmic rays propagating through the universe with cosmic background photons. Since both high-energy cosmic rays and cosmic background photons exist, the existence of high-energy cosmogenic neutrinos is certain. However, their flux has not been measured so far. Therefore, we calculated the flux of high-energy cosmogenic neutrinos arriving at the Earth on the basis of elaborate 4D simulations that take into account three spatial degrees of freedom and the cosmological time-evolution of the universe. Our predictions for this neutrino flux are consistent with the recent upper limits obtained from large-scale cosmic-ray experiments. We also show that the extragalactic magnetic field has a strong influence on the neutrino flux. The results of this work are important for the design of future neutrino observatories, since they allow to assess the detector volume and observation time that are necessary to detect high-energy cosmogenic neutrinos in the near future. An observation of such neutrinos would push multimessenger astronomy to hitherto unachieved energy scales.

On the origin of the TeV gamma-ray emission from Cygnus X-3

EPJ Web of Conferences ◽

10.1051/epjconf/201920814008 ◽

2019 ◽

Vol 208 ◽

pp. 14008

Author(s):

V.G. Sinitsyna ◽

V.Y. Sinitsyna

Keyword(s):

Energy Range ◽

Particle Production ◽

Cosmic Ray ◽

High Energy ◽

Wide Energy Range ◽

Essential Information ◽

Wide Range ◽

Γ Ray ◽

Very High

Cygnus X-3 binary system is a famous object studied over the wide range of electromagnetic spectrum. Early detections of ultra-high energy gamma-rays from Cygnus X-3 by Kiel, Havera Park and then by Akeno triggered the construction of several large air shower detectors. Also, Cygnus X-3 has been proposed to be one of the most powerful sources of charged cosmic ray particles in the Galaxy. The results of twenty-year observations of the Cyg X-3 binary at energies 800 GeV - 85 TeV are presented with images, spectra during periods of flaring activity and at low flux periods. The correlation of TeV flux increases with flaring activity at the lower energy range of X-ray and radio emission from the relativistic jets of Cygnus X-3 is found as well as 4.8-hour orbital modulation of TeV γ-ray intensity. Detected modulation of TeV γ-ray emission with orbit and important characteristics of Cyg X-3 such as the high luminosity of the companion star and the close orbit leads to an efficient generation of γ-ray emission through inverse Compton scattering in this object. The different type variability of very high-energy γ-emission and correlation of radiation activity in the wide energy range can provide essential information on the mechanism of particle production up to very high energies.

The investigation of the Universe by radio astronomy

Notes and Records the Royal Society journal of the history of science ◽

10.1098/rsnr.1961.0012 ◽

1961 ◽

Vol 16 (1) ◽

pp. 65-68

Keyword(s):

Wavelength Range ◽

Radio Astronomy ◽

Outer Space ◽

Sunspot Cycle ◽

Short Wave ◽

Radio Waves ◽

Residual Noise ◽

The Earth ◽

Long Wave ◽

Although nearly all the major advances in radio astronomy have taken place during the last fifteen years the basic discoveries were made 30 years ago. At that time Jansky realized that the residual noise in his receiving equipment had a daily sidereal variation and must be the result of radio waves reaching the earth from outer space, and Appleton in the U. K. with Breit and Tuve in America through their studies of the ionosphere laid the foundation of the radio echo techniques of radio astronomy. The radio emission from outer space can be received on earth in the wavelength range from a few millimetres to 10 or 20 metres. The short wave end is limited by absorption in the atmosphere and the long wave end by the ionosphere, and this upper limit tends to vary in sympathy with ionospheric conditions throughout the sunspot cycle. These hindrances will soon be overcome when suitable equipment can be carried in earth satellites; then it should be possible to determine the true wavelength range of these extraterrestrial emissions.

Interpreting correlated observations of cosmic rays and gamma-rays from Centaurus A with a proton blazar inspired model

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3343 ◽

2020 ◽

Vol 500 (1) ◽

pp. 1087-1094

Author(s):

Prabir Banik ◽

Arunava Bhadra ◽

Abhijit Bhattacharyya

Keyword(s):

Cosmic Rays ◽

Gamma Rays ◽

Gamma Ray ◽

Cosmic Ray ◽

High Energy ◽

Energy Scale ◽

Ultrahigh Energy ◽

Large Area ◽

Centaurus A

ABSTRACT The nearest active radio galaxy Centaurus (Cen) A is a gamma-ray emitter in GeV–TeV energy scale. The high energy stereoscopic system (HESS) and non-simultaneous Fermi–Large Area Telescope observation indicate an unusual spectral hardening above few GeV energies in the gamma-ray spectrum of Cen A. Very recently the HESS observatory resolved the kilo parsec (kpc)-scale jets in Centaurus A at TeV energies. On the other hand, the Pierre Auger Observatory (PAO) detects a few ultrahigh energy cosmic ray (UHECR) events from Cen-A. The proton blazar inspired model, which considers acceleration of both electrons and hadronic cosmic rays in active galactic nuclei (AGN) jet, can explain the observed coincident high-energy neutrinos and gamma-rays from Ice-cube detected AGN jets. Here, we have employed the proton blazar inspired model to explain the observed GeV–TeV gamma-ray spectrum features including the spectrum hardening at GeV energies along with the PAO observation on cosmic rays from Cen-A. Our findings suggest that the model can explain consistently the observed electromagnetic spectrum in combination with the appropriate number of UHECRs from Cen A.

What Are Gamma-Ray Bursts?

10.23943/princeton/9780691145570.001.0001 ◽

2011 ◽

Author(s):

Joshua S. Bloom

Keyword(s):

Gamma Ray ◽

Decisive Role ◽

High Energy ◽

Big Bang ◽

Gamma Ray Bursts ◽

Star Forming ◽

New Findings ◽

Ultimate Fate ◽

Gamma-ray bursts are the brightest—and, until recently, among the least understood—cosmic events in the universe. Discovered by chance during the Cold War, these evanescent high-energy explosions confounded astronomers for decades. But a rapid series of startling breakthroughs beginning in 1997 revealed that the majority of gamma-ray bursts are caused by the explosions of young and massive stars in the vast star-forming cauldrons of distant galaxies. New findings also point to very different origins for some events, serving to complicate but enrich our understanding of the exotic and violent universe. This book is an introduction to this fast-growing subject, written by an astrophysicist who is at the forefront of today's research into these incredible cosmic phenomena. The book gives readers a concise and accessible overview of gamma-ray bursts and the theoretical framework that physicists have developed to make sense of complex observations across the electromagnetic spectrum. The book traces the history of remarkable discoveries that led to our current understanding of gamma-ray bursts, and reveals the decisive role these phenomena could play in the grand pursuits of twenty-first century astrophysics, from studying gravity waves and unveiling the growth of stars and galaxies after the big bang to surmising the ultimate fate of the universe itself. This book is an essential primer to this exciting frontier of scientific inquiry, and a must-read for anyone seeking to keep pace with cutting-edge developments in physics today.

ULTRA HIGH ENERGY COSMIC RAYS: ORIGIN AND PROPAGATION

Modern Physics Letters A ◽

10.1142/s0217732310033530 ◽

2010 ◽

Vol 25 (18) ◽

pp. 1467-1481 ◽

Cited By ~ 4

Author(s):

TODOR STANEV

Keyword(s):

Cosmic Rays ◽

Gamma Rays ◽

Cosmic Ray ◽

High Energy ◽

Ultra High Energy ◽

Ultrahigh Energy ◽

High Energy Cosmic Rays ◽

Astrophysical Objects ◽

Ultrahigh Energy Cosmic Rays ◽

We introduce the highest energy cosmic rays and briefly review the powerful astrophysical objects where they could be accelerated. We then introduce the interactions of different cosmic ray particles with the photon fields of the Universe and the formation of the cosmic ray spectra observed at Earth. The last topic is the production of secondary gamma rays and neutrinos in the interactions of the ultrahigh energy cosmic rays.