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 lecture

In source astronomy, the question is "Where did it come from?"

Source astronomy has its origins in the actions of intelligent life on Earth when they noticed things or entities falling from above and became aware of the sky. Sometimes what they noticed is an acorn or walnut being dropped on them or thrown at them by a squirrel in a tree. Other events coupled with keen intellect allowed these life forms to deduce that some entities falling from the sky are coming down from locations higher than the tops of local trees.

Def. a source or apparent source detected or “created at or near the time of the [ event or] events”[1] is called a primary source.

Direct observation and tracking of the origination and trajectories of falling entities such as volcanic bombs presented early intelligent life with vital albeit sometimes dangerous opportunities to compose the science that led to source astronomy.

### References

1. primary source. San Francisco, California: Wikimedia Foundation, Inc. February 16, 2012. Retrieved 2012-07-14.
Selected theory

## Stellar fissions

Star fission is the splitting of a star at a critical angular momentum, or period in its history, with the consequence of zero-age contact in the resultant binary star. This splitting may have its highest probability of occurring during early star formation.

Def. any small luminous dot appearing in the cloudless portion of the night sky, especially with a fixed location relative to other such dots or a luminous celestial body, made up of plasma (particularly hydrogen and helium) and having a spherical shape is called a star.

When any effort to acquire a system of laws or knowledge focusing on a stellar astr, aster, or astro, that is, any natural star in the sky especially at night, succeeds even in its smallest measurement, stellar astronomy is the name of the effort and the result.

Selected topic

## Absorptions

"[P]referential absorption of sunlight by ozone over long horizon paths gives the zenith sky its blueness when the sun is near the horizon".[1]

"For quenched galaxies, the Hα absorption trough is deep and can be traced through the nucleus and along the major axis. It extends to a radius at or beyond 2 Rd [where Rd is the galaxy disk scale length] in all but three cases. This makes it possible to determine a velocity width from the optical spectrum as is done for emission line flux, with appropriate corrections between stellar and gas velocities (see discussion in Paper I, also Neistein, Maoz, Rix, & Tonry, 1999). In the few cases where a velocity width can also be measured from the H I data, it is found to be in good agreement with that taken from the Hα absorption line flux."[2]

### References

1.
2. Nicole P. Vogt and Martha P. Haynes, Riccardo Giovanelli, and Terry Herter (June 2004). "M/L, Hα Rotation Curves, and HI Gas Measurements for 329 Nearby Cluster and Field Spirals. III. Evolution in Fundamental Galaxy Parameters". The Astronomical Journal 127 (6): 3325-37. doi:10.1086/420703. Retrieved 2013-12-20.
Selected X-ray astronomy article

The Perseus Cluster (Abell 426) is a cluster of galaxies in the constellation Perseus. It is one of the most massive objects in the universe, containing thousands of galaxies immersed in a vast cloud of multimillion degree gas.

The detection of X-ray emission from Perseus XR-1 occurred during an Aerobee rocket flight on March 1, 1970. The source may have been associated with NGC 1275 (Per A, 3C 84), and was reported in 1971. More detailed observations from Uhuru confirmed the earlier detection and associated the source with the Perseus cluster.

The image on the right is 284 arcsec across. Right ascension (RA) 03h 19m 47.60s Declination (Dec) +41° 30' 37.00" in Perseus. Observation dates: 13 pointings between August 8, 2002 and October 20, 2004. Color code: Energy (Red 0.3-1.2 keV, Green 1.2-2 keV, Blue 2-7 keV). Instrument: ACIS.

Objects
Selected image

A launch of the Black Brant 8 Microcalorimeter at the turn of the century as a part of the joint undertaking by the University of Wisconsin-Madison and NASA's Goddard Space Flight Center known as the X-ray Quantum Calorimeter (XQC) project. Credit: Dan McCammon at Wisconsin and by Andrew Szymkowiak and Scott Porter at Goddard.

Selected lesson

## First infrared source in Crux

The first infrared source in Crux is unknown.

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

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

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

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

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

Selected quiz

Radiation chemistry, or astronomical radiation chemistry, is a lecture for the course principles of radiation astronomy about the abundance and reactions of chemical elements and molecules in the universe.

You are free to take this quiz at any time and as many times as you wish to improve your score.

Enjoy learning by doing!

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

## Electron beam heating laboratory

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!

 ...Archive Experiment...
Selected problems

## Energy phantoms

Students start from specific situations of motion, determine how to calculate energy and convert units, then evaluate types of energy.

Def. a quantity that denotes the ability to do work and is measured in a unit dimensioned in mass × distance²/time² (ML²/T²) or the equivalent is called energy.

Def. a physical quantity that denotes ability to push, pull, twist or accelerate a body which is measured in a unit dimensioned in mass × distance/time² (ML/T²): SI: newton (N); CGS: dyne (dyn) is called force.

In astronomy we estimate distances and times when and where possible to obtain forces and energy.

The key values to determine in both force and energy are (L/T²) and (L²/T²). Force (F) x distance (L) = energy (E), L/T² x L = L²/T². Force and energy are related to distance and time using proportionality constants.

 Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them:[1] ${\displaystyle F=G{\frac {m_{1}m_{2}}{r^{2}}}\ }$,where: F is the force between the masses, G is the gravitational constant, m1 is the first mass, m2 is the second mass, and r is the distance between the centers of the masses. The diagram shows two masses attracting one another. Credit: Dna-Dennis.

In the International System of Units (SI) units, F is measured in newtons (N), m1 and m2 in kilograms (kg), r in meters (m), and the constant G is approximately equal to 6.674×1011
N m2 kg−2
.[2]

Observationally, we may not know the origin of the force.

Coulomb's law states that the electrostatic force ${\displaystyle F}$ experienced by a charge, ${\displaystyle q}$ at position ${\displaystyle r_{q}}$, in the vicinity of another charge, ${\displaystyle Q}$ at position ${\displaystyle r_{Q}}$, in vacuum is equal to:

${\displaystyle F={qQ \over 4\pi \varepsilon _{0}}{1 \over {r^{2}}},}$

where ${\displaystyle \varepsilon _{0}}$ is the electric constant and ${\displaystyle r}$ is the distance between the two charges.

Coulomb's constant is

${\displaystyle k_{e}=1/(4\pi \varepsilon _{0}\varepsilon ),}$

where the constant ${\displaystyle \varepsilon _{0}}$ is called the permittivity of free space in SI units of C2 m−2 N−1.

For reality, ${\displaystyle \varepsilon }$ is the relative (dimensionless) permittivity of the substance in which the charges may exist.

The energy ${\displaystyle E}$ for this system is

${\displaystyle E=F\cdot D,}$

where ${\displaystyle D}$ is the displacement.

 ...Archive Try the problems...

### References

1. - Proposition 75, Theorem 35: p.956 - I.Bernard Cohen and Anne Whitman, translators: Isaac Newton, The Principia: Mathematical Principles of Natural Philosophy. Preceded by A Guide to Newton's Principia, by I. Bernard Cohen. University of California Press 1999 ISBN 0-520-08816-6 ISBN 0-520-08817-4
Selected X-ray astronomy pictures

Classified as a Peculiar star, Eta Carinae exhibits a superstar at its center as seen in this image from Chandra. The new X-ray observation shows three distinct structures: an outer, horseshoe-shaped ring about 2 light years in diameter, a hot inner core about 3 light-months in diameter, and a hot central source less than 1 light-month in diameter which may contain the superstar that drives the whole show. The outer ring provides evidence of another large explosion that occurred over 1,000 years ago. Credit: Chandra Science Center and NASA.

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