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 resource

## Beta particles

The simulation attempts to answer how thunderstorms launch particle beams into space. Credit: NASA/Goddard Space Flight Center.

A number of subatomic reactions can be detected in astronomy that yield beta particles. The detection of beta particles or the reactions that include them in an astronomical situation is beta-particles astronomy.

Beta particles are high-energy, high-speed electrons or positrons.

Beta particles may be the key to fusion. "If the exterior of the capsule is maintained at a uniform temperature of about 19.5 K, the natural beta decay energy of the tritium will accomplish this through a process known as "beta layering." The very low energy beta particles from tritium decay deposit their energy very close to the location of the original tritium atoms."[1]

"Beta-particles leaving the upper surface of the lunar sample could trigger the upper beta detector, while the lower beta-detector was triggered by beta particles from the lower surface of the sample."[2]

Notation: let the symbol β designate an unbound electron in motion.

Notation: let β+ designate an unbound positron in motion.

Notation: let TGF stand for a Terrestrial Gamma-ray Flash.

### References

1. K. R. Schultz (September 1998). "Cost Effective Steps to Fusion power: IFE target fabrication, injection and tracking". Journal of Fusion Energy 17 (3): 237-46. doi:10.1023/A:1021814514091. Retrieved 2012-06-08.
2. L. A. Rancitelli, R. W. Perkins, W. D. Felix, and N. A. Wogman (1971). "Erosion and mixing of the lunar surface from cosmogenic and primordial radio-nuclide measurements in Apollo 12 lunar samples". Proceedings of the Lunar Science Conference 2: 1757-72. Retrieved 2012-06-08.
Selected lecture

The image shows a chain of craters on Ganymede. Credit: Galileo Project, Brown University, JPL, NASA.

Def. a hemispherical pit a basinlike opening or mouth about which a cone is often built up any large roughly circular depression or hole is called a crater.

The image at right shows a chain of 13 craters (Enki Catena) on Ganymede measuring 161.3 km in length. "The Enki craters formed across the sharp boundary between areas of bright terrain and dark terrain, delimited by a thin trough running diagonally across the center of this image. The ejecta deposit surrounding the craters appears very bright on the bright terrain. Even though all the craters formed nearly simultaneously, it is difficult to discern any ejecta deposit on the dark terrain.

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. pp. 1221.
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.

Objects
Selected image

This is a ROSAT false-color image in X-rays between 500 eV and 1.1 keV of the constellation Chamaeleon, Chamaeleon I dark cloud. The contours are 100 µm emission from dust measured by the IRAS satellite. Credit: D. Burrows, J. Mendenhall, and E. Feigelson. Penn State University using the US/German ROSAT satellite.

Selected lesson

## First green source in Tucana

The first green source in Tucana is unknown.

The field of green astronomy is the result of observations and theories about green, or green-ray sources detected in the sky above.

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

But, green rays from the Sun are intermingled with other colors so that the Sun may appear yellow-white rather than green.

The early use of sounding rockets and balloons to carry green, optical, or visual detectors high enough may have detected green-rays 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 green astronomy looking for the first astronomical green source discovered in the constellation of Tucana.

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 green sources, you'll run into concepts and experimental tests that are an actual search.

Selected quiz

This is an animation of a radiation scintillation counter. Credit: KieranMaher.

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

You are free to take this quiz based on radiation astronomy detectors 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.

This quiz may need up to an hour to take and is equivalent to an hourly.

Enjoy learning by doing!

Selected laboratory

## Electric orbits

Main source: Electric orbits
Electrons in a beam are moving in a circle in a magnetic field (cyclotron motion). Lighting is caused by excitation of atoms of gas in a bulb. Credit: Marcin Białek.

This laboratory is an activity for you to calculate an electric or magnetic orbit of an astronomical object. While it is part of the astronomy course principles of radiation astronomy, it is also independent.

Some suggested entities to consider are electric fields, magnetic fields, mass, charge, Euclidean space, Non-Euclidean space, or spacetime.

Okay, this is an astronomy orbits laboratory, specifically to try out electric/magnetic orbits and where possible compare them to those calculated using gravity.

Yes, this laboratory is structured.

I will provide an example of an electric/magnetic orbit. 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

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

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!

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