# 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.

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This image of Venus is taken through a violet filter by the Galileo spacecraft on February 14, 1990. Credit: NASA/JPL-Caltech.

Violet astronomy is the astronomy of emissions (and absorptions), reflections or fluorescences, and transmissions over the wavelength band 380–450 nm.

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Selected lecture

## Radiation astronomy objects

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.

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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]

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## References

1. Philip B. Gove, ed. (1963). Webster's Seventh New Collegiate Dictionary. Springfield, Massachusetts: G. & C. Merriam Company. p. 1221. `|access-date=` requires `|url=` (help)
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.
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## 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]

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### 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. Retrieved 2013-07-30.
Objects
Selected image

The Swift Gamma-Ray Burst Mission, Swift XRT, contains a grazing incidence Wolter I telescope to focus X-rays onto a state-of-the-art CCD. The complete mirror module for the XRT consists of the X-ray mirrors, thermal baffle, a mirror collar, and an electron deflector. To prevent on-orbit degradation of the mirror module's performance, it is maintained at 20 ± 5 °C, with gradients of <1 °C by an actively controlled thermal baffle (purple, in the schematic) similar to the one used for JET-X. A composite telescope tube holds the focal plane camera (red), containing a single CCD-22 detector. Credit: Swift PI: Neil Gehrels, Responsible NASA Official: Phil Newman, Web Curator: J.D. Myers, PAO Contact: Francis Reddy.

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## 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.

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Selected quiz

## Electromagnetic radiation astronomy quiz

A new image from all three of NASA's Great Observatories--Chandra, Hubble, and Spitzer--has been created of the star-forming region 30 Doradus, also known as the Tarantula Nebula. Credit: NASA.

Electromagnetic astronomy is a lecture from the astronomy department.

This is a quiz based on the lecture that you are free to take at any time or knowledge level.

Once you’ve read and studied the lecture itself, the links contained within the article and lecture, listed under See also and External links, you should have adequate background to take the quiz and score highly. The templates `{{astronomy resources}}` and `{{principles of radiation astronomy}}` may also be helpful.

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.

Enjoy learning by doing!

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Selected laboratory

## Astronomical analysis laboratory

Circinus X-1 is imaged with the Chandra X-ray Observatory. Credit: X-ray: NASA/CXC/Univ. of Wisconsin-Madison/S.Heintz et al.

This laboratory is an activity for you to analyze an astronomical situation. While it is part of the astronomy course principles of radiation astronomy, it is also independent.

Astronomical analysis is the detailed examination of the elements or structure of some astronomical thing (an entity, source, or object), typically as a basis for discussion or interpretation.

Once an astronomical situation has been selected, it must be separated into its constituent elements, for example, the identification and measurement of the chemical constituents of a substance or specimen.

You may choose an astronomical situation to dissect.

I will provide one example of this process. 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!

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Selected problems

## Cosmic circuits

The arcing, graceful structure is actually a bow shock about half a light-year across, created from the wind from the star L.L. Orionis colliding with the Orion Nebula flow. Credit: NASA.
This diagram suggests a simple electrical circuit. Credit: GorillaWarfare.

Voyager 1 has found only electrons streaming into the heliosphere from elsewhere in the galaxy. This problem set poses several problems to calculate the possibility that a simple electrical circuit is involved.

The diagram at right suggests a simple electrical circuit.

Def. an enclosed path of an electric current is called a circuit.

In the diagram at right are three components:

1. a voltage (V), or current (i), source,
2. an enclosed path, and
3. a resistance, or resistor, (R).

According to Ohm's law:

${\displaystyle V=iR.}$

With respect to an enclosed path, consider a path from outside the heliosphere, inward toward the Sun, and out again. Let the incoming electrons have 500 MeV of energy and a flux of 8.5 x 104 e- cm-2 s-1.

Def. a time rate of flow of electric charge is called a current.

Def. that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 metre apart in vacuum, would produce between these conductors a force equal to 2 x 10–7 newton per metre of length is called an ampere.

Def. an amount of electrostatic potential between two points in space is called a voltage.

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