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.

"This is one of the early spectra obtained with the SPIRE fourier transform spectrometer on Herschel. Shown here is a portion of the SPIRE spectrum of VY Canis Majoris (VY CMa), a red supergiant star near the end of its life, which is ejecting huge quantities of gas and dust into interstellar space. The inset is a SPIRE camera map of VY CMa, in which it appears as a bright compact source near the edge of a large extended cloud."

"The VY CMa spectrum is amazingly rich, with prominent features from carbon monoxide (CO) and water (H2O). More than 200 other spectral features have been identified so far in the full spectrum, and several unidentified features are being investigated. Many of the features are due to water, showing that the star is surrounded by large quantities of hot steam. Observations like these will help to establish a detailed picture of the mass loss from stars and the complex chemistry occurring in their extended envelopes. As in all of the SPIRE spectra, the underlying emission increases towards shorter wavelengths, and is due to the emission from dust grains. The shape of the dust spectrum provides information on the properties of the dust."

"VY Canis Majoris (VY CMa) is a red supergiant star located about 4900 light years from Earth in the constellation Canis Major. It is the largest known star, with a size of 2600 solar radii, and also one of the most luminous, with a luminosity in excess of 100 000 times that of the Sun. The mass of VY CMa lies in the range 30-40 solar masses, and it has a mass-loss rate of 2 x 10-4 solar masses per year." 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. 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

## Theoretical astronomy

This image is a theory for the interior of the Sun. Credit: Pbroks13.

Theoretical astronomy at its simplest is the definition of terms to be applied to astronomical entities, sources, and objects.

Def. an "expanse of space that seems to be [overhead] like a dome"[1] is called a sky.

Computer simulations are usually used to represent astronomical phenomena.

Part of the fun of theory is extending the known to what may be known to see if knowing is really occurring, or is it something else.

The laboratories of astronomy are limited to the observatories themselves. The phenomena observed are located in the heavens, far beyond the reach, let alone control, of the astronomical observer.[2] “So how can one be sure that what one sees out there is subject to the same rules and disciplines of science that govern the local laboratory experiments of physics and chemistry?”[2] “The most incomprehensible thing about the universe is that it is comprehensible.” - Albert Einstein.[2]

## References

1. Philip B. Gove, ed. (1963). Webster's Seventh New Collegiate Dictionary. Springfield, Massachusetts: G. & C. Merriam Company. p. 1221. Retrieved 2011-08-26.
2. Narlikar JV (1990). Pasachoff JM, Percy JR (ed.). Curriculum for the Training of Astronomers ‘’In: The Teaching of astronomy. Cambridge, England: Cambridge University Press.
Selected topic

## Backgrounds

This graph shows the power density spectrum of the extragalactic or cosmic gamma-ray background (CGB). Credit: pkisscs@konkoly.hu.

In the figure at right, CUVOB stands for the cosmic ultraviolet and optical background.

The diffuse extragalactic background light (EBL) is all the accumulated radiation in the Universe due to star formation processes, plus a contribution from active galactic nuclei (AGNs). This radiation covers the wavelength range between ~ 0.1-1000 microns (these are the ultraviolet, optical, and infrared regions of the electromagnetic spectrum). The EBL is part of the diffuse extragalactic background radiation (DEBRA), which by definition covers the overall electromagnetic spectrum. After the cosmic microwave background, the EBL produces the second-most energetic diffuse background, thus being essential for understanding the full energy balance of the universe.

Selected X-ray astronomy article
This composite image contains the first picture of the Earth in X-rays, taken in March 1996, with the orbiting Polar satellite. The area of brightest X-ray emission is red. Such X-rays are not dangerous because they are absorbed by lower parts of the Earth's atmosphere. Credit: Polar, PIXIE, NASA. (The caption and image are from the Astronomy Picture of the Day for December 30, 1996.)

X-ray generation is producing X-radiation by a variety of phenomena. For example, when high-energy X-rays, gamma-rays, electrons, or protons bombard materials, the excited atoms within emit characteristic "secondary" (or fluorescent) X-rays. Alternately, whenever charged particles pass within certain distances of each other without being in fixed orbits, the accelerations (or decelerations) can give off X-rays.

Objects
Selected image

The Crab Nebula is a remnant of an exploded star. This is the Crab Nebula in various energy bands, including a hard X-ray image from the HEFT data taken during its 2005 observation run. Each image is 6′ wide. Credit: NASA.

Selected lesson

## First neutron source in Volans

This is a visual image of NGC 2788A near the edge of the constellation Volans. Credit: Aladin at SIMBAD.

The first neutron source in Volans is unknown.

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

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

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

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

This is a lesson in map reading, coordinate matching, and researching. It is also a research project in the history of neutron astronomy looking for the first astronomical neutron source discovered in the constellation of Volans.

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 neutron sources, you'll run into concepts and experimental tests that are actual research.

Selected quiz

## Cyan astronomy quiz

The visual image shows the natural cyan color of planetary nebula NGC 7048. Credit: Aladin from CDS.

Cyan astronomy is a lecture as part of the radiation astronomy department course on the principles of radiation astronomy.

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

To improve your score, 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!

 ...Archive Try the quiz...
Selected laboratory

## Cosmogony laboratory

This is an image of Chaos magnum from a book. Credit: Sailko.

This laboratory is an activity for you to create a universe. While it is part of the astronomy course principles of radiation astronomy, it is also independent.

Some suggested primordial entities to consider are electromagnetic radiation, neutrinos, mass, time, Euclidean space, Non-Euclidean space, dark matter, dark energy, purple phantoms, and spacetime.

More importantly, there are your primordial entities.

And, yes, you can create a universe from a peanut butter and jelly sandwich if you wish to.

You may choose to define your primordial entities or not.

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

This is an astronomy cosmogony laboratory, but you may create what an astronomy, a cosmogony, or a laboratory is.

Yes, this laboratory is structured. And, you are providing it. Or, not, an unstructured universe is okay too.

I will provide an example of a cosmogony. The rest is up to you.

Questions, if any, are best placed on the discussion page. Please put your laboratory results, you'd like evaluated, on the laboratory's discussion page.

 ...Archive Experiment...
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

${\displaystyle \mathbf {L} =\mathbf {r} \times \mathbf {p} }$

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!

 ...Archive Try the problems...
Selected X-ray astronomy pictures

Chandra X-ray Observatory image of the hot X-ray emitting gas that pervades the galaxy cluster MS 0735.6+7421 in the constellation Camelopardalis. Two vast cavities - each 600,000 lyrs in diameter appear on opposite sides of a large galaxy at the center of the cluster. These cavities are filled with a two-sided, elongated, magnetized bubble of extremely high-energy electrons that emit radio waves. Image is 4.2 arcmin per side. RA 07h 41m 50.20s Dec +74° 14' 51.00". Observation date: November 30, 2003. Credit: NASA/CXC/Ohio U./B.McNamara.

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