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.

Representation of upper-atmospheric lightning and electrical-discharge phenomena are displayed. Credit: Abestrobi.

Lightning is more than ground-to-cloud electron transfer.

"Cloud flashes sometimes have visible channels that extend out into the air around the storm (cloud-to-air or CA), but do not strike the ground. The terms sheet lightning or intra-cloud lightning (IC) refers to lightning embedded within a cloud that lights up as a sheet of luminosity during the flash. A related term, heat lightning, is lightning or lightning-induced illumination that is too far away for thunder to be heard. Lightning can also travel from cloud-to-cloud (CC). Spider lightning refers to long, horizontally traveling flashes often seen on the underside of stratiform clouds."

"Large thunderstorms are capable of producing other kinds of electrical phenomena called transient luminous events (TLEs) that occur high in the atmosphere. They are rarely observed visually and not well understood. The most common TLEs include red sprites, blue jets, and elves." 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

## Cosmogony

This is an image of the painting about Urknall. Credit: Hans Breinlinger.

Cosmogony is any scientific theory concerning the coming into existence, or origin, of the cosmos or universe, or about how what sentient beings perceive as "reality" came to be.

Usually, the philosophy of cause and effect needs a beginning, a first cause. Modal logic may only require a probability rather than a sequence of events. The concept of uncountable suggests an unknown somewhere between a finite number of likely rationales and an infinite number of possibilities.

From a sense of time as moving forward from yesterday to today and onward to tomorrow, there is again a suggestion of a prehistoric time before the first hominins.

The use of any system of thought or emotion to perceive reality suggests that some existences may precede others.

When more detail becomes available an existence may be transformed into something, an entity, a source, an object, a rocky object, or out of existence.

As a topic in astronomy, cosmogony deals with the origin of each astronomical entity.

Observation, for example, using radiation astronomy may provide some details.

Theoretical astronomy may provide some understanding, or at least some perspective.

In astronomy, cosmogony refers to the study of the origin of particular astrophysical objects or systems, and is most commonly used in reference to the origin of the solar system.[1][2]

### References

1. Ian Ridpath (2012). A Dictionary of Astronomy. Oxford University Press.
2. M. M. Woolfson (1979). "Cosmogony Today". Quarterly Journal of the Royal Astronomical Society 20 (2): 97-114.
Selected topic

## Bands

This is Saturn imaged with the Stockholm Infrared Camera (SIRCA) in the H2O band. Credit: M. Gålfalk, G. Olofsson and H.-G. Florén, Nordic Optical Telescope.

At the right is Saturn imaged by the Stockholm Infrared Camera (SIRCA) in the H2O infrared band to show the presence of water vapor. The image is cut off near the top due to the presence of Saturn's rings.

The Sun's emission in the lowest UV bands, the UVA, UVB, and UVC bands, are of interest, as these are the UV bands commonly encountered from artificial sources on Earth. The shorter bands of UVC, as well as even more energetic radiation as produced by the Sun, generate the ozone in the ozone layer when single oxygen atoms produced by UV photolysis of dioxygen react with more dioxygen. The ozone layer is especially important in blocking UVB and part of UVC, since the shortest wavelengths of UVC (and those even shorter) are blocked by ordinary air.

Selected X-ray astronomy article
Remnant of SN 1572 is seen in X-ray light by the Chandra X-ray Observatory.

"In 1572, the Danish astronomer Tycho Brahe observed and studied the explosion of a star [in Cassiopeia, at about 13,000 light years, RA 00h 25m 17s | Dec +64° 08' 37] that became known as Tycho's supernova. More than four centuries later, Chandra's image of the supernova remnant shows an expanding bubble of multimillion degree debris (green and red) inside a more rapidly moving shell of extremely high energy electrons (filamentary blue) [Red 0.95-1.26 keV, Green 1.63-2.26 keV, Blue 4.1-6.1 keV]."[1]

"The supersonic expansion (about six million miles per hour) of the stellar debris has created two X-ray emitting shock waves - one moving outward into the interstellar gas, and another moving back into the debris. These shock waves produce sudden, large changes in pressure and temperature, like an extreme version of sonic booms produced by the supersonic motion of airplanes."[1]

The "stellar debris has kept pace with the outer shock and is only about half a light year behind."[1]

A "large fraction of the energy of the outward-moving shock wave is going into the acceleration of atomic nuclei to speeds approaching the speed of light. The Chandra observations provide the strongest evidence yet that nuclei are indeed accelerated and that the energy contained in the high-speed nuclei in Tycho's remnant is about 100 times that observed in high-speed electrons."[1]

"Since their discovery in the early years of the 20th century, many sources of cosmic rays have been proposed, including flares on the sun and similar events on other stars, pulsars, black hole accretion disks, and the prime suspect - supernova shock waves. Chandra's observations of Tycho's supernova remnant strengthen the case for this explanation."[1]

Objects
Selected image

This is a composite image (X-ray - red, optical - blue & white) of the spiral galaxy M74 with an ultraluminous X-ray source (ULX) indicated inside the box. Image is 9 arcmin per side at RA 01h 36m 41.70s Dec +15° 46' 59.0" in Pisces. Observation dates: June 19, 2001; October 19, 2001. Aka: NGC 628, ULX: CXOU J013651.1+154547. Credit: X-ray; J. Liu (U.Mich.) et al., CXC, NASA - Optical; Todd Boroson/NOAO/AURA/NSF.`{{Fair use}}`

Selected lesson

## First microwave source in Cepheus

This image shows the Cepheus molecular cloud complex as seen through the glow of carbon monoxide (CO) with Planck (blue). Credit: ESA/Planck Collaboration.

The first microwave source in Cepheus is unknown.

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

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

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

The early use of sounding rockets and balloons to carry microwave detectors high enough may have detected microwaves 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 microwave astronomy looking for the first astronomical microwave source discovered in the constellation of Cepheus.

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

If stellar flares have origins similar to solar flares, then flare stars produce microwaves.

Selected 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 radiation 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 `{{radiation 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!

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.

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

## Furlongs per fortnight

It's about the chains. Credit: Stilfehler.`{{free media}}`

Furlongs per fortnight is a problem set with a contained quiz that focuses on the fundamentals of observational and deductive astronomy. In the activity Energy phantoms you learned about the value of distance, or displacement, and motion, speed, velocity, and acceleration. Here, you can practice and test yourself on converting from units that may or have occurred in the literature to units popular today.

Notation: let the symbol ${\displaystyle R_{\oplus }}$ indicate the Earth's radius.

Notation: let the symbol ${\displaystyle R_{J}}$ indicate the radius of Jupiter.

Notation: let the symbol ${\displaystyle R_{\odot }}$ indicate the solar radius.

Both physics and astronomy use units and dimensions to describe observations.

Units of Physics and Astronomy
Dimension Astronomy Symbol Physics Symbol Conversion
time 1 day d 1 second s 1 d = 86,400 s[2]
time 1 "Julian year"[3] J 1 second s 1 J = 31,557,600 s
distance 1 astronomical unit AU 1 meter m 1 AU = 149,597,870.691 km[2]
angular distance 1 parsec pc 1 meter m 1 pc ~ 30.857 x 1012 km[2]

### References

1. J. Warren & J. Hughes; et al. (29 April 2003). Tycho's Supernova Remnant: Tycho's Remnant Provides Shocking Evidence for Cosmic Rays. 60 Garden Street, Cambridge, MA 02138 USA: Harvard-Smithsonian Center for Astrophysics. Retrieved 2016-12-02. Explicit use of et al. in: `|author=` (help)
2. P. K. Seidelmann (1976). Measuring the Universe The IAU and astronomical units. International Astronomical Union. Retrieved 2011-11-27.
3. International Astronomical Union "SI units" accessed February 18, 2010. (See Table 5 and section 5.15.) Reprinted from George A. Wilkins & IAU Commission 5, "The IAU Style Manual (1989)" (PDF file) in IAU Transactions Vol. XXB
Selected X-ray astronomy pictures

Image of the M74 galaxy in Infrared at 3.6 (blue), 8.0 (green) and 24 (red) µm. The image has been made by myself (Médéric Boquien) from the data retrieved on the SINGS project public archives of the Spitzer Space Telescope (courtesy NASA/JPL-Caltech). Compare this with v:File:Messier 74 ULX.jpg a composite image (X-ray - red, optical - blue & white) of the spiral galaxy M74 with an ultraluminous X-ray source (ULX) indicated inside the box. Image is 9 arcmin per side at RA 01h 36m 41.70s Dec +15º 46' 59.0" in Pisces. Observation dates: June 19, 2001; October 19, 2001. Aka: NGC 628, ULX: CXOU J013651.1+154547. Credit: X-ray: NASA/CXC/U. of Michigan/J. Liu et al.; Optical: NOAO/AURA/NSF/T.Boroson.

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