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| The '''flux unit''' or '''jansky''' (symbol '''Jy''') is a non-[[SI]] unit of '''spectral [[flux density]]''',<ref>http://science.jrank.org/pages/57879/jansky.html {{dead link|date=April 2013}}</ref> or '''[[spectral irradiance]]''', equivalent to 10<sup>−26</sup> [[watt]]s per [[square metre]] per [[hertz]]. The ''flux density'' or ''monochromatic flux'', <math>S</math>, of a source is the integral of the spectral radiance, <math>B</math>, over the source [[solid angle]]:
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| <math>S = \iint_{\mathrm{source}} B(\theta,\phi)\mathrm{d}\Omega</math>
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| The unit is named after pioneering US radio astronomer [[Karl Guthe Jansky]], and is defined as:
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| <math>1 \ \mathrm{ Jy} = 10^{-26} \frac{ \mathrm{W} }{ \mathrm{m^2} \cdot \mathrm{Hz} }</math> ([[SI]]) <math> = 10^{-23} \frac{\mathrm{erg}}{ \mathrm{s} \cdot \mathrm{cm^2} \cdot \mathrm{Hz} }</math> ([[centimetre gram second system of units|cgs]])<ref>{{cite book
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| | author=Burke, Bernard F.; Graham-Smith, Francis
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| | title=An Introduction to Radio Astronomy
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| | page=9 | edition=3rd | year=2009
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| | publisher=Cambridge University Press
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| | isbn=0-521-87808-X }}<!-- Citation is for the first equivalence in this expression. --></ref>
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| Since the jansky is obtained by integrating over the whole source solid angle, it is most simply used to describe point sources; for example, the [[Third Cambridge Catalogue of Radio Sources]] (3C) reports results in Jy. For extended sources, the surface brightness is often described with units of Jy per solid angle; for example, Far Infra-Red (FIR) maps from the [[IRAS]] satellite are in MJy/sr. While extended sources at all wavelengths can be reported with these units, for radio frequency maps, extended sources have traditionally been described in terms of a [[brightness temperature]]; for example the [http://adsabs.harvard.edu/abs/1985BICDS..28...49H Haslam et al.] 408 MHz all-sky continuum survey is reported in terms of a brightness temperature in K.
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| ==Unit Conversions==
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| ===AB Magnitude===
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| The flux density in Jy can be converted to a magnitude basis, for suitable assumptions about the spectrum. For instance, converting an [[AB magnitude]] to a flux-density in microjanskys is straightforward:<ref name="fuk95">{{cite journal | author=M. Fukugita
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| | title=Galaxy Colors in Various Photometric Band Systems | journal=PASP | year=1995 | volume=107 | pages=945–958 | doi=10.1086/133643 | last2=Shimasaku | first2=K. | last3=Ichikawa | first3=T.
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| |bibcode = 1995PASP..107..945F }}</ref>
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| <math>S_v \ [\mathrm{\mu Jy}] = 10^{6} \cdot 10^{23} \cdot 10^{-(\mathrm{AB}+48.6)/2.5} = 10^{(23.9-\mathrm{AB})/2.5}</math> | |
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| ===dBW/m<sup>2</sup>/Hz===
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| The linear flux density in Jy can be converted to a [[decibel]] basis, suitable for use in fields of telecommunication and radio engineering. 1 Jansky is equivalent to -260 [[Decibel watt|dBW]]/m<sup>2</sup>/Hz.<ref>http://www.iucaf.org/sschool/mike/Units_and_Calculations.ppt</ref>
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| <math>P_{dBW/m^2/Hz} = 10 \log_{10}(P_{Jy}) - 260 | |
| </math>
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| ==Usage==
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| The flux to which the jansky refers can be in any form of energy. It was created for and is still most frequently used in reference to electromagnetic energy, especially in the context of radio astronomy. The brightest [[astronomical radio source]]s have flux densities of the order of one to one hundred janskys. For example, the [[Third Cambridge Catalogue of Radio Sources|3C]] lists some 300 to 400 radio sources in the Northern Hemisphere brighter than 9 Jy at 159 MHz. This range makes the jansky a suitable unit for [[radio astronomy]].
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| [[Gravitational waves]] also carry energy, so their flux density can also be expressed in terms of janskys. Though gravitational waves have never been directly observed, typical signals on Earth are expected to be 10<sup>20</sup>Jy or more.<ref>{{cite web
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| | author = B. S. Sathyaprakash
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| | last2 = Schutz
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| | publisher = Living Reviews in Relativity
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| | title = Physics, Astrophysics and Cosmology with Gravitational Waves
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| | url=http://www.livingreviews.org/lrr-2009-2
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| | date=2009-03-04
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| | accessdate = 2011-02-01 }}</ref> However, because of the poor coupling of gravitational waves to matter, such signals are difficult to detect.
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| It is important to understand the meaning of the ''per hertz'' component of the jansky unit. When measuring broadband continuum emissions, where the energy is roughly evenly distributed across the detector [[Bandwidth (signal processing)|bandwidth]], the detected signal will increase in proportion to the bandwidth of the detector (as opposed to signals with bandwidth narrower than the detector bandpass). To calculate the flux density in janskys, the total power detected (in watts) is divided by the receiver collecting area (in square meters), and then divided by the detector bandwidth (in hertz). The flux density of astronomical sources is many orders of magnitude below 1 W/(m<sup>2</sup>·Hz), so the result is multiplied by 10<sup>26</sup> to get a more appropriate unit for natural astrophysical phenomena.<ref>{{cite web
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| | last = Ask Dr. SETI
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| | publisher = Seti League
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| | title = Research: Understanding the Jansky
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| | url=http://www.setileague.org/askdr/jansky.htm
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| | date=2004-12-04
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| | accessdate = 2007-06-13 }}</ref>
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| The milliJansky, mJy, was sometimes referred to as a milli flux unit (m.f.u.) in the astronomical literature.<ref name=Ross75>{{cite journal
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| | author=Ross, H.N.
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| | title= Variable radio source structure on a scale of several minutes of arc
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| | bibcode=1975ApJ...200..790R|doi = 10.1086/153851 }}</ref>
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| ==Orders of magnitude==
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| {| class="wikitable"
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| ! Jansky (Jy)
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| ! Source
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| |-
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| | 110,000,000
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| | [[Radio-frequency interference]] from a [[GSM]] phone transmitting 0.5W@1800 MHz at a distance of 1 km ([[RSSI]] of -70 [[dBm]])<ref>http://www.iucaf.org/SSS2010/presentations/day2/Clegg(Units).ppt</ref>
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| |-
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| | 20,000,000
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| | [[Sunspots|Disturbed Sun]] at 20 MHz ([[Karl Guthe Jansky]] initial discovery published in 1933)
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| |-
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| | 4,000,000
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| | Sun at 10 GHz
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| |-
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| | 1,000,000
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| | [[Milky Way]] at 20 MHz
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| |-
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| | 2,000
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| | [[Milky Way]] at 10 GHz
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| |-
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| | 1,000
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| | [[Sunspots|Quiet Sun]] at 20 MHz
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| |}
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| Note: unless noted, all values are as seen from earth surface.<ref>{{cite book
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| | author=John Daniel Kraus
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| | title=Radio Astronomy
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| | isbn=1882484002 }}, table: radio spectrum of astronomical sources: http://astro.u-strasbg.fr/~koppen/10GHz/basics.html</ref>
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| ==References==
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| {{reflist}}
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| [[Category:Radio astronomy]]
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| [[Category:Units of measurement]]
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| [[Category:Non-SI metric units]]
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| [[Category:Units of measurement in astronomy]]
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Professionals a strategy and also battle activation where your entire family must manage your be the owner of tribe and also protect it. You have to build constructions which will provide protection for your soldiers along with the very instruction. First really focus on your protection as well as the after its recently been quite taken treatment. You will need to move forward with the criminal offense plan. As well as your Military facilities, you likewise require to keep in go the way your indigneous group is certainly going. For instance, collecting indicates as well as fostering your own tribe may be the key to good results.
Interweaving social styles form every strong net in and we are all caught up. When The Tygers of Pan Tang performed 'It's lonely at this top. Everybody's your to do you in', these people borrowed plenty from clash of clans hack tool no survey. A society without clash of clans compromise tool no survey is really like a society which has no knowledge, in which often it is quite helpful.
Be sure to pay attention to a game's evaluation when purchasing an existing. This evaluation will allow you to comprehend what age level clash of clans hack tool is most suitable for and will make it known when the sport would be violent. It can help you figure out whether you'll want to buy the sport.
Investigate evaluations and see each of our trailers before buying another video game. Ensure it is one thing you are considering before you get the house. These video games aren't low-cost, and also you likely to get nearly as substantially cash whenever you inside a employed video game which you have solitary utilized several times.
Be certain to may not let online games take over your the world. Game titles can be quite additive, time also have to make assured you moderate the free time that you investing trying to play such games. In case you invest an excessive involving time playing video game, your actual life have the ability to begin to falter.
To access it into excel, copy-paste this continued equation into corpuscle B1. If you again gain an majority of second in abnormal in corpuscle A1, the bulk to treasures will arise appearing in B1.
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