Portal:Radiation astronomy

Radiation astronomy
This image is a composite of several types of radiation astronomy: radio, infrared, visual, ultraviolet, soft and hard X-ray. Credit: NASA.

Radiation astronomy is astronomy applied to the various extraterrestrial sources of radiation, especially at night. It is also conducted above the Earth's atmosphere and at locations away from the Earth, by satellites and space probes, as a part of explorational (or exploratory) radiation astronomy.

Seeing the Sun and feeling the warmth of its rays is probably a student's first encounter with an astronomical radiation source. This will happen from a very early age, but a first understanding of the concepts of radiation may occur at a secondary educational level.

Radiation is all around us on top of the Earth's crust, regolith, and soil, where we live. The study of radiation, including radiation astronomy, usually intensifies at the university undergraduate level.

And, generally, radiation becomes hazardous, when a student embarks on graduate study.

Cautionary speculation may be introduced unexpectedly to stimulate the imagination and open a small crack in a few doors that may appear closed at present. As such, this learning resource incorporates some state-of-the-art results from the scholarly literature.

The laboratories of radiation astronomy are limited to the radiation observatories themselves and the computers and other instruments (sometimes off site) used to analyze the results.

Selected radiation astronomy
The Hubble Space Telescope image shows four high-velocity, runaway stars plowing through their local interstellar medium. Credit: NASA - Hubble's Advanced Camera for Surveys.

The image on the right shows four high-velocity, runaway stars plowing through their local interstellar medium.

"Resembling comets streaking across the sky, these four speedy stars are plowing through regions of dense interstellar gas and creating brilliant arrowhead structures and trailing tails of glowing gas."

"These bright arrowheads, or bow shocks, can be seen in these four images taken with NASA's Hubble Space Telescope. The bow shocks form when the stars' powerful stellar winds, streams of matter flowing from the stars, slam into surrounding dense gas. The phenomenon is similar to that seen when a speeding boat pushes through water on a lake." Read more...

Selected lecture

Electromagnetic forces

The electric vectors of PKS0521-36 show clear structure and alignment. Credit: Keel.

"The emission of electromagnetic radiation from a superluminal (faster-than-light in vacuo) charged particle [is such] that no physical principle forbids emission by extended, massless superluminal sources. A polarization current density (dP/dt; see Maxwell's fourth equation) can provide such a source; the individual charged particles creating the polarization do not move faster than c, the speed of light, and yet it is relatively trivial to make the envelope of the polarization current density to do so."[1]

The "emitted radiation has many unusual characteristics, including: (i) the intensity of some components decays as the inverse of the distance from the source, rather than as 1/(distance)2 (i.e. these components are non-spherically-decaying); (ii) the emission is tightly beamed, the exact direction of the beam depending on the source speed; and (iii) the emission contains very high frequencies not present in the synthesis of the source. Note that the non-spherically decaying components of the radiation do not violate energy conservation. They result from the reception, during a short time period, of radiation emitted over a considerably longer period of (retarded) source time; their strong electromagnetic fields are compensated by weak fields elsewhere [1]."[1]

The "emission occupies a very small polar angular width of order 0.8 degrees in the far field. Based on these findings, we suggest that a superluminal source could act as a highly directional transmitter of MHz or THz signals over very long distances."[1]

"The magnetic field is well-ordered in many jets, as shown by polarization measurements. Synchrotron radiation can be very highly polarized (50%) if the field is globally ordered, and some sources [approach] this level. The electric vectors show clear structure and alignment; an especially common pattern is for the field lines to be along the jet in the inner portions and transition to an azimuthal configuration farther out. This is seen in [PKS0521-36 at 2 cm]."[2]

References

  1. 1.0 1.1 1.2 J. Singleton, A. Ardavan, H. Ardavan, J. Fopma and D. Halliday (2005). Non-spherically-decaying radiation from an oscillating superluminal polarization current: possible low-power, deep-space communication applications in the MHz and THz bands, 16th International Symposium on Space Terahertz Technology (PDF). p. 117. Retrieved 2014-03-18.CS1 maint: multiple names: authors list (link)
  2. Bill Keel (October 2003). Jets, Superluminal Motion, and Gamma-Ray Bursts. Tucson, Arizona USA: University of Arizona. Retrieved 2014-03-19.
Selected theory

Mathematical radiation astronomy

This animation depicts the collision between our Milky Way galaxy and the Andromeda galaxy. Credit: Visualization Credit: NASA; ESA; and F. Summers, STScI; Simulation Credit: NASA; ESA; G. Besla, Columbia University; and R. van der Marel, STScI.

Most of the mathematics needed to understand the information acquired through astronomical radiation observation comes from physics. But, there are special needs for situations that intertwine mathematics with phenomena that may not yet have sufficient physics to explain the observations. Both uses constitute radiation mathematics, or astronomical radiation mathematics, or a portion of mathematical radiation astronomy.

Astronomical radiation mathematics is the laboratory mathematics such as simulations that are generated to try to understand the observations of radiation astronomy.

The mathematics needed to understand radiation astronomy starts with arithmetic and often needs various topics in calculus and differential equations to produce likely models.

Selected topic

Emissions

The Hubble Space Telescope [Advanced Camera for Surveys] ACS image has H-alpha emission of the Red Rectangle shown in blue. Credit: ESA/Hubble and NASA.

"[T]he extended red emission (ERE) [is] observed in many dusty astronomical environments, in particular, the diffuse interstellar medium of the Galaxy. ... silicon nanoparticles provide the best match to the spectrum and the efficiency requirement of the ERE."[1]

References

  1. Adolf N. Witt, Karl D. Gordon and Douglas G. Furton (July 1, 1998). "Silicon Nanoparticles: Source of Extended Red Emission?". The Astrophysical Journal Letters 501 (1): L111-5. doi:10.1086/311453. http://iopscience.iop.org/1538-4357/501/1/L111. Retrieved 2013-07-30. 
Selected X-ray astronomy article

Compare the Chandra X-ray Observatory X-ray image with the Hubble Space Telescope visual image. Sirius A is spectral type A1V, whereas Sirius B is a white dwarf of type DA2.

The image of Sirius A and Sirius B taken by Hubble Space Telescope. The diffraction spikes and concentric rings are instrumental effects.
The image of Sirius A and Sirius B taken by the Chandra X-ray Observatory.

With the initial detection of an extrasolar X-ray source, the first question usually asked is "What is the source?" An extensive search, such as from a list of stars by constellation, is often made in other wavelengths such as visible or radio for possible coincident objects. But, there are inherent difficulties in making X-ray/optical, X-ray/radio, and X-ray/X-ray identifications based solely on positional coincidents, especially with handicaps in making identifications, such as the large uncertainties in positional determinants made from balloons and rockets, poor source separation in the crowded region toward the galactic center, source variability, and the multiplicity of source nomenclature.

Extrasolar X-ray source astrometry is a branch of astrometry that focuses on discriminating X-ray sources and determining their positions accurately.

Objects
Selected image
DEM L316 in Dorado.jpg

This is an X-ray image (red and green)/optical (purple) for DEM L316 of two hot gas shells produced by supernova explosions in the constellation Dorado. Image is 5.7 arcmin across. RA 05h 47m 15.00s Dec -69º 42' 25.00" in Dorado. Observation date: 27 July 2002. Color code: X-ray (Red 0.8-1.5 keV, Green 1.5-8 keV, Blue 0.3-8 keV); Optical (Purple). Instrument: ACIS. Aka: WCD97 Shell A, WCD97 Shell B. Credit: X-ray: NASA/CXC/U. Illinois/R. Williams & Y.-H. Chu; Optical: NOAO/CTIO/U. Illinois/R. Williams & MCELS coll.{{Fair use}}

Selected lesson

First ultraviolet source in Sagittarius

These two photographs were made by combining data from NASA's Galaxy Evolution Explorer spacecraft and the Cerro Tololo Inter-American Observatory in Chile. Credit: NASA/JPL-Caltech/JHU.

The first ultraviolet source in Sagittarius is unknown.

The field of ultraviolet astronomy is the result of observations and theories about ultraviolet sources detected in the sky above.

The first astronomical ultraviolet source discovered may have been the Sun.

But, ultraviolet waves from the Sun are intermingled with other radiation so that the Sun may appear as other than a primary source for ultraviolet waves.

The early use of sounding rockets and balloons to carry ultraviolet detectors high enough may have detected ultraviolet waves from the Sun as early as the 1940s.

This is a lesson in map reading, coordinate matching, and searching. It is also a project in the history of ultraviolet astronomy looking for the first astronomical ultraviolet source discovered in the constellation of Sagittarius.

Nearly all the background you need to participate and learn by doing you've probably already been introduced to at a secondary level and perhaps even a primary education level.

Some of the material and information is at the college or university level, and as you progress in finding ultraviolet sources, you'll run into concepts and experimental tests that are an actual search.

Selected quiz

Blue astronomy quiz

This is a detailed, photo-like view of Earth based largely on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. Credit: Robert Simmon and Marit Jentoft-Nilsen, NASA.

Blue astronomy is a lecture from the radiation astronomy department for the course on the principles of radiation astronomy.

You are free to take this quiz based on blue astronomy at any time.

To improve your scores, read and study the lecture, the links contained within, listed under See also, External links, and in the {{principles of radiation astronomy}} template. This should give you adequate background to get 100 %.

As a "learning by doing" resource, this quiz helps you to assess your knowledge and understanding of the information, and it is a quiz you may take over and over as a learning resource to improve your knowledge, understanding, test-taking skills, and your score.

Suggestion: Have the lecture available in a separate window.

To master the information and use only your memory while taking the quiz, try rewriting the information from more familiar points of view, or be creative with association.

Enjoy learning by doing!

Selected laboratory

Electron beam heating laboratory

This is an X-ray image of the coronal clouds near the Sun. Credit: NASA Goddard Space Flight Center.

This laboratory is an activity for you to create a method of heating the solar corona or that of a star of your choice. While it is part of the astronomy course principles of radiation astronomy, it is also independent.

Some suggested entities to consider are electromagnetic radiation, electrons, positrons, neutrinos, gravity, time, Euclidean space, Non-Euclidean space, magnetic reconnection, or spacetime.

More importantly, there are your entities.

Please define your entities or use available definitions.

Usually, research follows someone else's ideas of how to do something. But, in this laboratory you can create these too.

Okay, this is an astronomy coronal heating laboratory.

Yes, this laboratory is structured.

I will provide an example of electron beam heating calculations. The rest is up to you.

Please put any questions you may have, and your laboratory results, you'd like evaluated, on the laboratory's discussion page.

Enjoy learning by doing!

Selected problems

Angular momentum and energy

This diagram describes the relationship between force (F), torque (τ), momentum (p), and angular momentum (L) vectors in a rotating system. 'r' is the radius. Credit: Yawe.

Angular momentum and energy are concepts developed to try to understand everyday reality.

An angular momentum L of a particle about an origin is given by

where r is the radius vector of the particle relative to the origin, p is the linear momentum of the particle, and × denotes the cross product (r · p sin θ). Theta is the angle between r and p.

Please put any questions you may have, and your results, you'd like evaluated, on the problem set's discussion page.

Enjoy learning by doing!

Selected X-ray astronomy pictures
M31 Core in X-rays.jpg

Using the orbiting Chandra X-ray telescope, astronomers have imaged the center of our near-twin island universe, finding evidence for a bizarre object. Like the Milky Way, Andromeda's galactic center appears to harbor an X-ray source characteristic of a black hole of a million or more solar masses. Seen above, the false-color X-ray picture shows a number of X-ray sources, likely X-ray binary stars, within Andromeda's central region as yellowish dots. The blue source located right at the galaxy's center is coincident with the position of the suspected massive black hole. While the X-rays are produced as material falls into the black hole and heats up, estimates from the X-ray data show Andromeda's central source to be very cold - only about million degrees, compared to the tens of millions of degrees indicated for Andromeda's X-ray binaries.

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