Portal:Radiation astronomy

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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.

Selected radiation astronomy
Northern Lights are usually green, but in this image there is the very rare blue light. Credit: Varjisakka.

Green astronomy is the study and use of emission and absorption lines or bands in the wavelength range 495-570 nm. The use of filters with respect to this wavelength range are common when studying the Sun. Green astronomy also studies green sources and objects.

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

Selected theory

Stellar surface fusion

RHESSI observes high-energy phenomena from a solar flare. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio.

Stellar surface fusion occurs above a star's photosphere to a limited extent as found in studies of near coronal cloud activity.

Surface fusion is produced by reactions during or preceding a stellar flare and at much lower levels elsewhere above the photosphere of a star.

"Nuclear interactions of ions accelerated at the surface of flaring stars can produce fresh isotopes in stellar atmospheres."[1]

"This energy [1032 to 1033 ergs] appears in the form of electromagnetic radiation over the entire spectrum from γ-rays to radio burst, in fast electrons and nuclei up to relativistic energies, in the creation of a hot coronal cloud, and in large-scale mass motions including the ejections of material from the Sun."[2]

"The new reaction 208Pb(59Co,n)266Mt was studied using the Berkeley Gas-filled Separator [BGS] at the Lawrence Berkeley National Laboratory [LBNL] 88-Inch Cyclotron."[3]

266Mt has been produced using the 209Bi(58Fe,n)266Mt reaction.[3]

"Reactions with various medium-mass projectiles on nearly spherical, shell-stabilized 208Pb or 209Bi targets have been used in the investigations of transactinide (TAN) elements and their decay properties for many years. These so-called “cold fusion” reactions produce weakly excited (10-15 MeV) [1] compound nuclei (CNs) at bombarding energies at or near the Coulomb barrier that de-excite by the emission of one to two neutrons."[3]

"The laboratory-frame, center-of-target energy used was 291.5 MeV, corresponding to a CN excitation energy of 14.9 MeV."[3]

"At the start of the experiment the BGS magnet settings were chosen to guide products with a magnetic rigidity of 2.143 T·m to the center of the [focal plane detector] FPD. After the first event of 266Mt was detected in strip 45 (near one edge of the FPD), the magnetic field strength was decreased to 2.098 T·m in an effort to shift the distribution of products toward the center of the detector."[3]

"258Db [has been produced] via the 209Bi(50Ti,n) and 208Pb(51V,n) reactions [15], and 262Bh via the 209Bi(54Cr,n) and 208Pb(55Mn,n) reactions [13, 16]."[3]

"Hofmann et al. at Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, and Morita et al., at the Institute of Physical and Chemical Research (RIKEN) in Saitama, Japan, have studied the 209Bi(64Ni,n)272Rg reaction [7, 17, 18]. The complementary 208Pb(65Cu,n)272Rg reaction was studied by Folden et al. at the Lawrence Berkeley National Laboratory (LBNL) [19]."[3]

"Based on the observation of the long-lived isotopes of roentgenium, 261Rg and 265Rg (Z = 111, t1/2 ≥ 108 y) in natural Au, an experiment was performed to enrich Rg in 99.999% Au. 16 mg of Au were heated in vacuum for two weeks at a temperature of 1127°C (63°C above the melting point of Au). The content of 197Au and 261Rg in the residue was studied with high resolution inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). The residue of Au was 3 × 10−6 of its original quantity. The recovery of Rg was a few percent. The abundance of Rg compared to Au in the enriched solution was about 2 × 10−6, which is a three to four orders of magnitude enrichment."[4]

References

  1. Vincent Tatischeff, J.-P. Thibaud, I. Ribas (January 2008). "Nucleosynthesis in stellar flares". eprint arXiv:0801.1777. http://arxiv.org/pdf/0801.1777. Retrieved 2012-11-09. 
  2. R. P. Lin and H. S. Hudson (September-October 1976). "Non-thermal processes in large solar flares". Solar Physics 50 (10): 153-78. doi:10.1007/BF00206199. http://adsabs.harvard.edu/full/1976SoPh...50..153L. Retrieved 2013-07-07. 
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 S. L. Nelson, K. E. Gregorich, I. Dragojević, J. Dvořák, P. A. Ellison, M. A. Garcia, J. M. Gates, L. Stavsetra, M. N. Ali, and H. Nitsche (February 25, 2009). "Comparison of complementary reactions in the production of Mt". Physical Review C 79 (2): e027605. doi:10.1103/PhysRevC.79.027605. http://prc.aps.org/abstract/PRC/v79/i2/e027605. Retrieved 2014-04-07. 
  4. A. Marinov, A. Pape, D. Kolb, L. Halicz, I. Segal, N. Tepliakov and R. Brandt (2011). "Enrichment of the Superheavy Element Roentgenium (Rg) in Natural Au". International Journal of Modern Physics E 20 (11): 2391-2401. doi:10.1142/S0218301311020393. http://www.phys.huji.ac.il/~marinov/publications/Rg_261_arXiv_77.pdf. Retrieved 2014-04-08. 
Selected topic

Absorptions

A spectrum is taken of blue sky clearly showing solar Fraunhofer lines and atmospheric water absorption band. Credit: Remember the dot.

"[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. Craig F. Bohren. Atmospheric Optics. http://homepages.wmich.edu/%7Ekorista/atmospheric_optics.pdf. 
  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. http://iopscience.iop.org/1538-3881/127/6/3325. Retrieved 2013-12-20. 
Selected X-ray astronomy article
This X-ray image of Cygnus X-1 was taken by a balloon-borne telescope, the High Energy Replicated Optics (HERO) project. NASA image.

Cygnus X-1 (abbreviated Cyg X-1) is a well known galactic X-ray source in the constellation Cygnus. Cygnus X-1 was the first X-ray source widely accepted to be a black hole candidate and it remains among the most studied astronomical objects in its class. It is now estimated to have a mass about 8.7 times the mass of the Sun and has been shown to be too compact to be any known kind of normal star or other likely object besides a black hole.

Objects
Selected image
Bullet cluster.jpg

X-ray photo is by the Chandra X-ray Observatory of the Bullet Cluster (two colliding galaxy clusters). Exposure time was 140 hours. The scale is shown in megaparsecs. Redshift (z) = 0.3, meaning its light has wavelengths stretched by a factor of 1.3. Credit: Mac_Davis.

Selected lesson

First X-ray source in Apus

The graph shows the spatial distribution of ROSAT all-sky survey X-ray sources in the Chamaeleon cloud complex. Credit: J.M. Alcalá, J. Krautter, J.H.M.M. Schmitt, E. Covino, R. Wichmann and R. Mundt.

The first X-ray source in Apus discovered by our X-ray observatory satellites or rockets is unknown.

Above is a sky plot of the X-ray sources detected by the ROSAT all-sky survey in the Chamaeleon star-forming cloud complex. X-ray sources (Xs in the diagram) along the 14:00 h longitude are in the constellation Apus.

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

Nearly all the background you need to participate and learn by doing you've probably already been introduced to at a secondary educational level.

Some of the material and information you'll be introduced to is at the college or university level, and as you progress in finding X-ray sources, you'll run into concepts and experimental tests that are actual research.

To succeed in finding an X-ray source in Apus is the first step. Next, you'll need to determine the time stamp of its discovery and compare it with any that have already been found. Over the history of X-ray astronomy a number of sources have been found, many as point sources in the night sky. These points are located on the celestial sphere using coordinate systems. Familiarity with these coordinate systems is not a prerequisite. Here the challenge is geometrical, astrophysical, and historical.

Selected quiz

Color astronomy quiz

Gases above Io's surface produced a ghostly glow that could be seen at visible wavelengths (red, green, and violet). Credit: NASA/JPL/University of Arizona.

Color astronomy is a lecture as part of the radiation astronomy department course development of principles of radiation astronomy.

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

To improve your scores, read and study the lecture, the links contained within, and listed under See also, External links and the {{radiation astronomy resources}} and {{principles of radiation astronomy}} templates. 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.

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

Suggestion: Have the lecture available in a separate window.

Enjoy learning by doing!

Selected laboratory

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

Energy phantoms

This is an optical image in the visual range of Theta Ursae Majoris. It is listed in SIMBAD as an F7V spectral type star with a parallax of 74.19 mas. Credit: Aladin at SIMBAD.

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]
,

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 experienced by a charge, at position , in the vicinity of another charge, at position , in vacuum is equal to:

where is the electric constant and is the distance between the two charges.

Coulomb's constant is

where the constant is called the permittivity of free space in SI units of C2 m−2 N−1.

For reality, is the relative (dimensionless) permittivity of the substance in which the charges may exist.

The energy for this system is

where is the displacement.

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
  2. CODATA2006. http://www.physics.nist.gov/cgi-bin/cuu/Value?bg. 
Selected X-ray astronomy pictures
Arp270 xray 420.jpg

Chandra image of two galaxies (Arp 270) in the early stage of a merger in the constellation Leo Minor. In the image, red represents low, green intermediate, and blue high-energy (temperature) X-rays. Image is 4 arcmin on a side. RA 10h 49m 52.5s Dec Template:Dec. Observation date: April 28, 2001. Instrument: ACIS. Credit: NASA/U. Birmingham/A.Read.

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