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[[:en:Wilkinson Microwave Anisotropy Probe]]
=[[en:Bulbous corpuscle]]=
=[[Corpuscolo di Ruffini]]=
Il '''Wilkinson Microwave Anisotropy Probe''' ('''WMAP'''), conosciuto anche come [[sonda spaziale]] per l<nowiki>'</nowiki>[[anisotropia]] delle [[microonde]] ({{en}}: '''Microwave Anisotropy Probe''' ('''MAP''')), e '''Explorer 80''', è un satellite che misura ciò che rimane delle radiazioni dovute al [[Big Bang]], ovvero la [[radiazione cosmica di fondo]]. Diretto dal professore della Johns Hopkins University [[Charles L. Bennett]], si tratta di un progetto che prevede la collaborazione tra il [[Goddard Space Flight Center]] della [[NASA]] e l<nowiki>'</nowiki>[[Università di Princeton]].<ref name="2003PressRelease" /> Il satellite WMAP è stato lanciato il [[30 giugno]] [[2001]], alle ore 19:46 (GDT) dallo stato della [[Florida]]. Il WMAP è l'erede dei satelliti [[COBE]] e [[MIDEX (satellite)|MIDEX]] previsti dal [[programma Explorer]]. Tale satellite è stato così chiamato in onore di [[David Todd Wilkinson]] (1935-2002).<ref name="2003PressRelease" />
{{anatomia
Le rilevazioni del WMAP sono più precise di quelle dei suoi predecessori; secondo il [[modello Lambda-CDM]], l<nowiki>'</nowiki>[[età dell'universo]] è stata calcolata in 13.73 ± 0.12 miliardi di anni, con una [[costante di Hubble]] di 70.1 ± 1.3 km·s<sup>-1</sup>·Mpc<sup>-1</sup>, una composizione del 4,6% di [[Barione|materia barionica]] ordinaria; 23 % di [[materia oscura]] di natura sconosciuta, la quale non assorbe o emette luce; 72% di [[energia oscura]] la quale accelera l'espansione; infine meno del 1% di [[neutrino|neutrini]]. Tutti questi dati sono coerenti con l'ipotesi che l'universo abbia una [[Forma_dell'universo#Universo_piatto|geometria piatta]], e anche con il rapporto tra densità d'energia e [[Equazioni di Friedmann|densità critica]] di Ω = 1.02 ± 0.02. Questi dati supportano il modello Lambda-CDM e gli scenari [[Cosmologia (astronomia)|cosmologici]] dell<nowiki>'</nowiki>[[Inflazione (cosmologia)|inflazione]], dando anche prova della [[radiazione cosmica di fondo di neutrini]].<ref name="2008Hinshaw">Hinshaw et al. (2008)</ref>
|Nome=Corpuscolo di Ruffini
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|Didascalia=Terminazioni nervose del corpuscolo di Ruffini
|Sviluppo embriologico=
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Il '''corpuscolo di Ruffini''' è una classe di [[meccanorecettore|meccanorecettori]] ad adattamento lento. Si pensa che siano presenti solo nelle zone naturalmente glabre del [[derma]] (dorso della [[mano]], pianta del [[Piede (anatomia)|piede]], [[labbro|labbra]], [[piccole labbra]] e [[glande]]), e nell'[[ipoderma]] umano. Il nome deriva dal medico italiano [[Angelo Ruffini]].
Ma questi dati contengono anche caratteristiche inspiegate: una anomalia nella massima misura ngolare del [[Momento di quadrupolo elettrico|momento quadrupolico]], ed una grande [[macchia fredda nella radiazione cosmica di fondo]]. Secondo la rivista scientifica ''Science'', il WMAP è stato il ''Breakthrough of the Year for 2003'' (scoperta dell<nowiki>'</nowiki>anno 2003).<ref name="2003Seife">Seife (2003)</ref> I risultati di questa missione sono stati al primo e al secondo posto della lista "Super Hot Papers in Science Since 2003".<ref name="incites">{{cite web | url=http://www.in-cites.com/hotpapers/shp/1-50.html | title="Super Hot" Papers in Science | publisher=in-cites | month=ottobre | year=2005 | accessdate=15-02-2009}}</ref> Alla fine del 2008 il satellite WMAP era ancora in funzione, mentre è prevista la sua dismissione per il mese di settembre 2009.
==Function==
This spindle-shaped receptor is sensitive to skin stretch, and contributes to the kinesthetic sense of and control of finger position and movement.<ref>{{Cita libro|cognome=Mountcastle |nome=Vernon C. |anno=2005 |titolo=The Sensory Hand: Neural Mechanisms of Somatic Sensation |editore=Harvard University Press |p=34}}</ref> It is believed to be useful for monitoring slippage of objects along the surface of the skin, allowing modulation of grip on an object.
Ruffinian endings are located in the deep layers of the skin, and register mechanical deformation within joints, more specifically angle change, with a specificity of up to 2 degrees, as well as continuous pressure states.They also act as a thermoreceptors that respond for a long time, so in case of deep burn there will be no pain as these receptors will be burned off.<ref>{{Cita libro|cognome=Hamilton |nome=Nancy |anno=2008 |titolo=Kinesiology: Scientific Basis of Human Motion |editore=McGraw-Hill |pp=76–7}}</ref>
==Footnotes and references==
<references />
==External links==
* {{Cita pubblicazione|autore= Paré M, Behets C, Cornu O |titolo= Paucity of presumptive ruffini corpuscles in the index finger pad of humans. |rivista= J Comp Neurol |volume= 456 |numero= 3 |pp= 260–6 |anno= 2003 | pmid = 12528190 | doi = 10.1002/cne.10519}}
<nowiki>
[[Category:Sensory receptors]]
[[cs:Ruffiniho tělísko]]
==Obiettivi==
[[de:Ruffini-Körperchen]]
[[Image:CMB Timeline75.jpg|thumb|La linea del tempo dell'universo, dall'inflazione al WMAP]]
[[es:Corpúsculos de Ruffini]]
[[fr:Corpuscule de Ruffini]]
Lo scopo primario del progetto WMAP è la misurazione delle differenze di temperatura nella [[radiazione cosmica di fondo]]. Le [[Anisotropia|anisotropie]] della radiazione vengono quindi utilizzate per calcolare la [[geometria dell'universo]], il suo contenuto e l<nowiki>'</nowiki>evoluzione, e per testare i modelli del [[Big Bang]] e dell<nowiki>'</nowiki>[[inflazione (cosmologia)|inflazione cosmologica]].<ref name="2003Bennett" /> Per questo, questo satellite sta creando una mappa completa della radiazione di fondo, con una risoluzione di 13 [[Primo (geometria)|arcominuti]] tramite una osservazione multi frequenza. Tale mappa, per assicurare una accuratezza angolare pari alla sua risoluzione, richiede alcuni [[Errore sistematico|errori sistematici]], pixel di [[Rumore_di_fondo|rumore]] non correlati tra loro ed una calibrazione accurata.<ref name="2003Bennett">Bennett et al. (2003a)</ref> La mappa è formata da 3,145,728 [[pixel]] e usa lo schema [[HEALPix]] per trasformare in pixel la sfera.<ref name="2003Bennettb" /> Il telescopio misura inoltre la polarizzazione E-mode della radiazione di fondo<ref name="2003Bennett" />, e la polarizzazione in primo piano. <ref name="2008Hinshaw" /> La sua vita è di 27 mesi: 3 mesi per ricercare la posizione [[Punti_di_Lagrange#L2|L2]], ed i restanti 24 mesi di osservazione.<ref name="2003Bennett" />
[[gl:Corpúsculo de Ruffini]]
[[he:גופיף רפיני]]
==Sviluppo==
[[pl:Ciałka Ruffiniego]]
[[Image:BigBangNoise.jpg|thumb|Paragone tra le sensibilità del WMAP e del COBE. I dati sono simulati]]
[[pt:Corpúsculo de Ruffini]]</nowiki>
La missione MAP venne proposta alla [[NASA]] nel [[1995]], selezionata per uno studio approfondito nel [[1996]] e approvata per lo sviluppo definitivo nel [[1997]].<ref name="news_facts">{{cite web | url=http://map.gsfc.nasa.gov/news/facts.html | title=news sul WMAP: fatti | publisher=NASA | date=[[22 April]] [[2008]] | accessdate=2008-04-27}}</ref><ref name="news_events">{{cite web | url=http://map.gsfc.nasa.gov/news/events.html | title=WMAP News: Events | publisher=NASA | date=[[17 aprile]] [[2008]] | accessdate=19 febbraio 2009}}</ref>
Il WMAP è stato preceduto da altri due satelliti per l'analisi della radiazione di fondo:
* la sonda sovietica [[RELIKT-1]], la quale ha riportato i limiti superiori dell'analisi delle anisotropie della radiazione di fondo;
* la sonda statunitense [[COBE]], la quale ha riportato fluttuazioni su larga scala della radiazione di fondo.
Vi sono stati anche altri 3 esperimenti, basati però sull'utilizzo di palloni sonda, che hanno analizzato piccole porzioni di cielo ma in modo più dettagliato:
* il pallone [[Esperimento BOOMERanG|BOOMERanG]];
* il [[Cosmic Background Imager]];
* il [[Very Small Array]].
Il WMAP, rispetto al suo predecessore COBE, ha una sensibilità 45 volte superiore, ed una risoluzione angolare più precisa di 33 volte.<ref name="2008Limon">Limon et al. (2008)</ref>
==La sonda==
[[Image:WMAP spacecraft diagram.jpg|thumb|Illustrazione della sonda WMAP]]
Gli specchi primari del WAMP sono una coppia di [[Telescopio gregoriano|gregoriani]], di dimensioni 1,4 metri e 1,6 metri, rivolti in direzioni opposte tra loro, i quali focalizzano il segnale ottico su degli specchi secondari grandi 0,9 m x 1,0 m. Questi specchi sono stati modellati per ottenere delle prestazioni ottimali: una corazza in [[fibra di carbonio]] che protegge un nocciolo in [[Korex]], ricoperto ulteriormente da uno strato sottile di [[alluminio]] e [[ossido di silicio]]. Gli specchi secondari riflettono il segnale a dei sensori ondulati, posti sul [[piano focale]] tra i due specchi primari.<ref name="2003Bennett" />
[[Image:WMAP receivers.png|thumb|Illustrazione dei ricevitori del WMAP]]
I ricevitori sono costituiti da dei [[radiometro|radiometri]] differenziali sensitivi alla [[Polarizzazione della radiazione elettromagnetica|polarizzazione elettromagnetica]]. Il segnale viene amplificato quindi da un [[amplificatore a basso rumore]] di tipo [[HEMT]]. Sono presenti 20 alimentatori, 10 per ogni direzione, dai quali i radiometri raccolgono i segnali; la misura finale corrisponde nella differenza tra i segnali provenienti da direzioni opposte. La separazione azimuth direzionale è di 180 gradi; l'angolo totale è di 141 gradi.<ref name="2003Bennett" />
Per evitare di captare anche segnali di disturbo provenienti dalla [[Via Lattea]], il WMAP lavora su 5 frequenze radio discrete, da 23 GHz a 94 GHz.<ref name="2003Bennett" />
{| border="2" cellpadding="4" cellspacing="0" style="margin: 1em 1em 1em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse; font-size: 90%;"
|- bgcolor="#B0C4DE" align="center"
|+ Proprietà del WMAP a differenti frequenze<ref name="2003Bennett" />
! Proprietà !! Banda K !! Banda Ka !! Banda Q !! Banda V !! Banda W
|-
| [[Lunghezza d'onda]] centrale (mm) || 13 || 9.1 || 7.3 || 4.9 || 3.2
|-
| [[Frequenza]] centrale ([[GHz]]) || 23 || 33 || 41 || 61 || 94
|-
| [[Larghezza di banda]] (GHz) || 5.5 || 7.0 || 8.3 || 14.0 || 20.5
|-
| Misura del raggio ([[arcominuto|arcominuti]]) || 52.8 || 39.6 || 30.6 || 21 || 13.2
|-
| Numero di [[Radiometro|radiometri]] || 2 || 2 || 4 || 4 || 8
|-
| Temperatura del sistema ([[Kelvin|K]]) || 29 || 39 || 59 || 92 || 145
|-
| Sensibilità (mK s<math>^{1/2}</math>) || 0.8 || 0.8 || 1.0 || 1.2 || 1.6
|}
Passive thermal radiators cool the WMAP to ca. 90 degrees K; they are connected to the low-noise amplifiers. The telescope consumes 419 [[watt|W]] of power. The available telescope heaters are emergency-survival heaters, and there is a transmitter heater, used to warm them when off. The WMAP spacecraft's temperature is monitored with [[platinum resistance thermometer]]s.<ref name="2003Bennett" />
The WMAP's calibration is effected with the CMB dipole and measurements of [[Jupiter]]; the beam patterns are measured against Jupiter. The telescope's data are relayed daily via a 2GHz [[transponder]] providing a 667[[kbit/s]] downlink to a 70m [[Deep Space Network]] telescope. The spacecraft has two transponders, one a redundant back-up; they are minimally active — ca. 40 minutes daily — to minimize [[radio frequency interference]]. The telescope's position is maintained, in its three axes, with three [[reaction wheel]]s, [[gyroscope]]s, two [[star tracker]]s and sun sensors, and is steered with eight [[hydrazine]] thrusters.<ref name="2003Bennett" />
La base del WMAP è costituita da un [[pannello solare]] di 5 metri di diametro, il quale tiene la sonda costantemente all'ombra durante il rilevamento della radiazione di fondo.<ref name="">Questo avviene mantenendo la sonda ad un'angolatura costante di 22 gradi rispetto al Sole</ref> Al di sopra del pannello si trova l'apparato di raffreddamento della sonda. Tra questo apparato di raffreddamento e gli specchi, è posizionato un cilindro per l'isolamento termico, dellla lunghezza di 33 cm.<ref name="2003Bennett" />
Il raffreddamento del WMAP è affidato a dei radiatori passivi, i quali raggiungono una temperatura di 90 K circa (-183,15 °C); questi radiatori sono connessi agli amplificatori a basso rumore. Il consumo totale del telescopio arriva a 419 [[watt|W]]. La temperatura della sonda è controllata da una [[termoresistenza]] di platino.<ref name="2003Bennett" />
La calibrazione di WMAP viene effettuata eseguendo una misurazione di [[Giove (astronomia)|Giove]] rispetto al dipolo della radiazione cosmica di fondo.
== Launch, trajectory, and orbit ==
[[File:Orbita WMAP.png|thumb|The WMAP's trajectory and orbit.]]
The WMAP satellite arrived at the Kennedy Space Center on 20 April 2001, was tested for two months, mounted atop a Delta II 7425 rocket, and fired to outer space on 30 June 2001.<ref name="2008Limon" /><ref name="news_facts" /> It began operating on its internal power five minutes before its launching, and so continued operating until the solar panel array deployed. The WMAP was activated and monitored while it cooled. On 2 July, it began working, first with in-flight testing (from launching 'til 17 August), then began constant, formal work.<ref name="2008Limon" /> Afterwards, it effected three Earth-Moon phase loops, measuring its [[sidelobe]]s, then flew by the Moon on 30 July, enroute to the the L2 Sun-Earth [[Lagrangian point]], arriving there on 1 October 2001, becoming, thereby, the first CMB observation mission permanently posted there.<ref name="news_facts" />
[[Image:WMAP orbit.jpg|thumb|WMAP's orbit and sky scan strategy]]
The satellite's orbit at Lagrange 2, (1.5 million kilometers from Earth) minimizes the amount of contaminating solar, terrestrial, and lunar emissions registered, and to thermally stabilize it. To view the entire sky, without looking to the sun, the WMAP orbits around L2 in a [[Lissajous orbit]] ca. 1.0 degree to 10 degrees,<ref name="2003Bennett" /> with a 6-month period.<ref name="news_facts" /> The telescope rotates once every 2 minutes, 9 seconds" (0.464 rpm) and processes at the rate of 1 revolution per hour.<ref name="2003Bennett" /> WMAP measures the entire sky every six months, and completed its first, full-sky observation in April 2002.<ref name="news_events" />
== Foreground radiation subtraction ==
The WMAP observes in five frequencies, permitting the measurement and subtraction of foreground contamination (from the Milky Way and extra-galactic sources) of the CMB. The main emission mechanisms are [[synchrotron radiation]] and [[free-free emission]] (dominating the lower frequencies), and [[astrophysical dust]] emissions (dominating the higher frequencies). The spectral properties of these emissions contribute different amounts to the five frequencies, thus permitting their identification and subtraction.<ref name="2003Bennett" />
Foreground contamination is removed in several ways. First, subtract extant emission maps from the WMAP's measurements; second, use the components' known, spectral values to identify them; third, simultaneously fit the position and spectra data of the foreground emission, using extra data sets. Foreground contamination also is reduced by using only the the full-sky map portions with the least foreground contamination, whilst masking the remaining map portions.<ref name="2003Bennett" />
{| border="2" cellpadding="4" cellspacing="0" style="margin: 1em 1em 1em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse; font-size: 90%;"
|+ The five-year models of foreground emission, at different frequencies. Red = Synchrotron; Green = free-free; Blue = thermal dust.
|-
| [[Image:WMAP 2008 23GHz foregrounds.png|150px|23 GHz]] || [[Image:WMAP 2008 33GHz foregrounds.png|150px|33 GHz]] || [[Image:WMAP 2008 41GHz foregrounds.png|150px|41 GHz]] || [[Image:WMAP 2008 61GHz foregrounds.png|150px|61 GHz]] || [[Image:WMAP 2008 94GHz foregrounds.png|150px|94 GHz]]
|-
| 23 GHz || 33 GHz || 41 GHz || 61 GHz || 94 GHz
|}
== Measurements and discoveries ==
=== One-year data release ===
[[Image:Baby Universe.jpg|thumb|The first-year map of the CMB.]]
On 11 February 2003, based upon one year's worth of WMAP data, NASA published the latest calculated age, composition, and image of the universe to date, that "contains such stunning detail, that it may be one of the most important scientific results of recent years"; the data surpass previous CMB measurements.<ref name="2003PressRelease">{{cite web | url=http://www.gsfc.nasa.gov/topstory/2003/0206mapresults.html | title=New image of infant universe reveals era of first stars, age of cosmos, and more | publisher=NASA / WMAP team | date=[[11 February]] [[2003]] | accessdate=2008-04-27}}</ref>
Based upon the [[Lambda-CDM model]], the WMAP team produced cosmological parameters from the WMAP's first-year results. Three sets are given below; the first and second sets are WMAP data; the difference is the addition of spectral indices, predictions of some inflationary models. The third data set combines the WMAP constraints with those from other CMB experiments ([[ACBAR]] and [[CBI]]), and constraints from the [[2dF Galaxy Redshift Survey]] and [[Lyman alpha forest]] measurements. Note that there are degenerations among the parameters, the most significant is between <math>n_s</math> and <math>\tau</math>; the errors given are at 68% confidence.<ref name="2003spergel" />
<center>
{| border="2" cellpadding="4" cellspacing="0" style="margin: 1em 1em 1em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse; text-align:center;"
|- bgcolor="#B0C4DE" align="center"
|+ Best-fit [[Lambda-CDM model|cosmological parameters]] from WMAP one-year results<ref name="2003spergel">Spergel et al. (2003)</ref>
! Parameter !! Symbol !! Best fit (WMAP only) !! Best fit (WMAP, extra parameter) !! Best fit (all data)
|-
| [[Hubble's constant]] ( {{frac|km|[[parsec|Mpc]]·s}} ) || <math>H_0</math> || 0.72 ± 0.05 || 0.70 ± 0.05 || <math>0.71^{+0.04}_{-0.03}</math>
|-
| [[Baryon]]ic content || <math>\Omega_b h^2</math> || 0.024 ± 0.001 || 0.023 ± 0.002 || 0.0224 ± 0.0009
|-
| Matter content || <math>\Omega_m h^2</math> || 0.14 ± 0.02 || 0.14 ± 0.02 || <math>0.135^{+0.008}_{-0.009}</math>
|-
| [[Optical depth]] to [[reionization]] || <math>\tau</math> || <math>0.166^{+0.076}_{-0.071}</math> || 0.20 ± 0.07 || 0.17 ± 0.06
|-
| Amplitude || <math>A</math> || 0.9 ± 0.1 || 0.92 ± 0.12 || <math>0.83^{+0.09}_{-0.08}</math>
|-
| Scalar spectral index || <math>n_s</math> || 0.99 ± 0.04 || <math>0.93^{+0.07}_{-0.07}</math> || 0.93 ± 0.03
|-
| Running of spectral index || <math>dn_s / dk</math> ||—||-0.047 ± 0.04 || <math>-0.031^{+0.016}_{-0.017}</math>
|-
| Fluctuation amplitude at 8h<sup>−1</sup> Mpc|| <math>\sigma_8</math> || 0.9 ± 0.1 ||—|| 0.84 ± 0.04
|-
| [[Age of the universe]] ([[Annum|Ga]]) || <math>t_0</math> || 13.4 ± 0.3|| — || 13.7 ± 0.2
|-
| Total density of the universe || <math>\Omega_{tot}</math> || — || — || 1.02 ± 0.02
|}
</center>
Using the best-fit data and theoretical models, the WMAP team determined the times of important universal events, including the redshift of [[reionization]], 17 ± 4; the redshift of [[decoupling]], 1089 ± 1 (and the universe's age at decoupling, <math>379^{+8}_{-7}</math> kyr); and the redshift of matter/radiation equality, <math>3233^{+194}_{-210}</math>. They determined the thickness of the [[surface of last scattering]] to be 195 ± 2 in redshift, or <math>118^{+3}_{-2}</math> kyr. They determined the current density of baryons, <math>(2.5 \pm 0.1) \times 10^{-7} cm^{-1}</math>, and the ratio of baryons to photons, <math>(6.1^{+0.3}_{-0.2}) \times 10^{-10}</math>. The WMAP's detection of an early reionization excluded [[warm dark matter]].<ref name="2003spergel" />
The team also examined Milky Way emissions at the WMAP frequencies, producing a 208-[[point source]] catalogue. Also, they observed the [[Sunyaev-Zel'dovich effect]] at <math>2.5 \sigma</math> the strongest source is the [[Coma cluster]].<ref name="2003Bennettb">Bennett et al. (2003b)</ref>
=== Three-year data release ===
[[Image:Microwave Sky polarization.png|thumb|A map of the polarization from the 3rd year results]]
The three-year WMAP data were released on 17 March 2006. The data included temperature and [[polarization]] measurements of the CMB, which provided further confirmation of the standard flat [[Lambda-CDM model]] and new evidence in support of inflation.
The 3-year WMAP data alone shows that the universe must have dark matter. Results were computed both only using WMAP data, and also with a mix of parameter constraints from other instruments, including other CMB experiments ([[ACBAR]], [[CBI]] and [[BOOMERANG]]), [[SDSS]], the [[2dF Galaxy Redshift Survey]], the [[Supernova Legacy Survey]] and constraints on the Hubble constant from the [[Hubble Space Telescope]].<ref name="2007Spergel" />
<center>
{| border="2" cellpadding="4" cellspacing="0" style="margin: 1em 1em 1em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse; text-align:center;"
|- bgcolor="#B0C4DE" align="center"
|+ Best-fit [[Lambda-CDM model|cosmological parameters]] from WMAP three-year results<ref name="2007Spergel">Spergel et al. (2007)</ref>
! Parameter !! Symbol !! Best fit (WMAP only)
|-
| [[Hubble's constant]] ( {{frac|km|Mpc·s}} ) || <math>H_0</math> || <math>0.732^{+0.031}_{-0.032}</math>
|-
| [[Baryon]]ic content || <math>\Omega_b h^2</math> || 0.0229 ± 0.00073
|-
| Matter content || <math>\Omega_m h^2</math> || <math>0.1277^{+0.0080}_{-0.0079}</math>
|-
| [[Optical depth]] to [[reionization]] <sup>{{ref|a|[a]}}</sup> || <math>\tau</math> || 0.089 ± 0.030
|-
| Scalar spectral index ||<math>n_s</math> || 0.958 ± 0.016
|-
| Fluctuation amplitude at 8h<sup>−1</sup> Mpc ||<math>\sigma_8</math> || <math>0.761^{+0.049}_{-0.048}</math>
|-
| [[Age of the universe]] ([[Annum|Ga]]) || <math>t_0</math> || <math>13.73^{+0.16}_{-0.15}</math>
|-
| Tensor-to-scalar ratio <sup>{{ref|b|[b]}}</sup> || <math>r</math> || <0.65
|}
</center>
[a] {{note|a}} Optical depth to reionization improved due to polarization measurements.<ref name="2007Hinshaw">Hinshaw et al. (2007)</ref><br>
[b] {{note|b}} < 0.30 when combined with [[SDSS]] data. No indication of non-gaussianity.<ref name="2007Spergel" />
=== Five-year data release ===
[[Image:WMAP 2008.png|thumb|5 year WMAP image of background cosmic radiation (2008)]]
The five-year WMAP data were released on 28 February 2008. The data included new evidence for the [[cosmic neutrino background]], evidence that it took over half a billion years for the first stars to reionize the universe, and new constraints on [[cosmic inflation]].<ref name="2008PressRelease">{{cite web | url=http://map.gsfc.nasa.gov/news/ | title=WMAP Press Release — WMAP reveals neutrinos, end of dark ages, first second of universe | publisher=NASA / WMAP team | date=[[7 March]] [[2008]] | accessdate=2008-04-27}}</ref>
The improvement in the results came from both having an extra 2 years of measurements (the data set runs between midnight on 10 August 2001 to midnight of 9 August 2006), as well as using improved data processing techniques and a better characterization of the instrument, most notably of the beam shapes. They also make use of the 33GHz observations for estimating cosmological parameters; previously only the 41 and 61GHz channels had been used. Finally, improved masks were used to remove foregrounds.<ref name="2008Hinshaw" />
[[Image:WMAP 2008 TT and TE spectra.png|thumb|The five-year total-intensity and polarization spectra from WMAP]]
Improvements to the spectra were in the 3rd acoustic peak, and the polarization spectra.<ref name="2008Hinshaw" />
The measurements put constraints on the content of the universe at the time that the CMB was emitted; at the time 10% of the universe was made up of neutrinos, 12% of atoms, 15% of photons and 63% dark matter. The contribution of dark energy at the time was negligible.<ref name="2008PressRelease" />
The WMAP five-year data was combined with measurements from [[Type Ia supernova]] (SNe) and [[Baryon acoustic oscillations]] (BAO).<ref name="2008Hinshaw" />
[[File:Contenuto universo calcolato dal WMAP 2008.png|thumb|Matter content in the current universe]]
<center>
{| border="2" cellpadding="4" cellspacing="0" style="margin: 1em 1em 1em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse; font-size: 90%;"
|- bgcolor="#B0C4DE" align="center"
|+ Best-fit [[Lambda-CDM model|cosmological parameters]] from WMAP five-year results<ref name="2008Hinshaw" />
! Parameter !! Symbol !! Best fit (WMAP only) !! Best fit (WMAP + SNe + BAO)
|-
| [[Hubble's constant]] ( {{frac|km|Mpc·s}} ) || <math>H_0</math> || <math>0.719^{+0.026}_{-0.027}</math> || 0.701 ± 0.013
|-
| [[Baryon]]ic content || <math>\Omega_b h^2</math> || 0.02273 ± 0.00062 || 0.02265 ± 0.00059
|-
| Cold dark matter content || <math>\Omega_c h^2</math> || 0.1099 ± 0.0062 || 0.1143 ± 0.0034
|-
| [[Dark energy]] content || <math>\Omega_\Lambda</math> || 0.742 ± 0.030 || 0.721 ± 0.015
|-
| [[Optical depth]] to [[reionization]] || <math>\tau</math> || 0.087 ± 0.017 || 0.084 ± 0.016
|-
| Scalar spectral index || <math>n_s</math> || <math>0.963^{+0.014}_{-0.015}</math>|| <math>0.960^{+0.014}_{-0.013}</math>
|-
| Running of spectral index || <math>dn_s / dk</math> || −0.037 ± 0.028 || <math>-0.032^{+0.021}_{-0.020}</math>
|-
| Fluctuation amplitude at 8h<sup>−1</sup> Mpc || <math>\sigma_8</math> || 0.796 ± 0.036 || 0.817 ± 0.026
|-
| [[Age of the universe]] (Ga) || <math>t_0</math> || 13.69 ± 0.13 || 13.73 ± 0.12
|-
| Total density of the universe || <math>\Omega_{tot}</math> || <math>1.099^{+0.100}_{-0.085}</math> || 1.0052 ± 0.0064
|-
| Tensor-to-scalar ration || <math>r</math> || <0.20 || —
|}
</center>
The data puts a limits on the value of the tensor-to-scalar ratio, r < 0.20 (95% certainty), which determines the level at which gravitational waves affect the polarization of the CMB, and also puts limits on the amount of primordial [[non-gaussianity]]. Improved constraints were put on the redshift of reionization, which is 10.8 ± 1.4, the redshift of [[decoupling]], <math>1091.00^{+0.72}_{-0.73}</math> (as well as age of universe at decoupling, <math>375,938^{+3148}_{-3115}</math> years) and the redshift of matter/radiation equality, <math>3280^{+88}_{-89}</math>.<ref name="2008Hinshaw" />
The [[extragalactic]] source catalogue was expanded to include 390 sources, and variability was detected in the emission from [[Mars]] and [[Saturn]].<ref name="2008Hinshaw" />
{| border="2" cellpadding="4" cellspacing="0" style="margin: 1em 1em 1em 0; background: #f9f9f9; border: 1px #aaa solid; border-collapse: collapse; font-size: 90%;"
|- bgcolor="#B0C4DE" align="center"
|+ The five-year maps at different frequencies from WMAP with foregrounds (the red band)
|-
| [[Image:WMAP 2008 23GHz.png|150px|23 GHz]] || [[Image:WMAP 2008 33GHz.png|150px|33 GHz]] || [[Image:WMAP 2008 41GHz.png|150px|41 GHz]] || [[Image:WMAP 2008 61GHz.png|150px|61 GHz]] || [[Image:WMAP 2008 94GHz.png|150px|94 GHz]]
|-
| 23 GHz || 33 GHz || 41 GHz || 61 GHz || 94 GHz
|}
== Future measurements ==
[[Image:Planck satellite.jpg|thumb|upright|Artist's impression of the [[Planck satellite]]]]
The original timeline for WMAP gave it two years of observations; these were completed by September 2003. Mission extensions were granted in both 2002 and 2004, giving the spacecraft a total of 8 observing years (the originally proposed duration), which end in September 2009.<ref name="news_facts" />
WMAP's results will be built upon by several other instruments that are currently under construction. These will either be focusing on higher sensitivity total intensity measurements or measuring the polarization more accurately in the search of [[B-mode polarization]] indicative of primordial [[gravitational wave]]s.
The next space-based instrument will be the [[Planck satellite]], which is currently being built and will launch in early 2009. This instrument aims to measure the CMB more accurately than WMAP at all angular scales, both in total intensity and polarization. Various ground- and balloon-based instruments are being constructed to look for B-mode polarization, including [[Clover (telescope)|Clover]] and [[The E and B Experiment|EBEX]].
== References ==
{{Reflist|2}}
=== Technical pages ===
{{refbegin}}
* {{cite journal | title=The Microwave Anisotropy Probe (MAP) Mission | first=C. | last=Bennett | coauthors=et al. | journal=[[Astrophysical Journal]] | volume=583 | pages=1–23 | year=2003a | url=http://adsabs.harvard.edu/abs/2003ApJ...583....1B | doi=10.1086/345346}}
* {{cite journal | title=First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Emission | last=Bennett | first=C. | coauthors=et al. | journal=Astrophysical Journal Supplement | volume=148 | pages=97–117 | year=2003b | doi=10.1086/377252}}
* {{cite journal | doi= 10.1086/513698 | title=Three-Year Wilkinson Microwave Anisotropy Probe (WMAP1) Observations: Temperature Analysis | first=G. | last=Hinshaw | coauthors=et al. | journal=Astrophysical Journal Supplement | volume=170 | pages=288–334 | year=2007}}
* {{cite journal | title=Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results | first=G. | last=Hinshaw | coauthors=et al. | journal=[[Astrophysical Journal]] Supplement (submitted) | year=2008 | url=http://lambda.gsfc.nasa.gov/product/map/dr3/pub_papers/fiveyear/basic_results/wmap5basic.pdf |format=PDF| id={{arxiv|0803.0732}}}}
* {{cite web | title=Wilkinson Microwave Anisotropy Probe (WMAP): Five–Year Explanatory Supplement |
first=M. | last=Limon | coauthors=et al. | date=[[20 March]] [[2008]] | url=http://lambda.gsfc.nasa.gov/product/map/dr3/pub_papers/fiveyear/supplement/WMAP_supplement.pdf | format=[[PDF]]}}
* {{cite journal | authorlink=Charles Seife | last=Seife | first= Charles | title=Breakthrough of the Year: Illuminating the Dark Universe | url=http://www.sciencemag.org/cgi/content/full/302/5653/2038 | journal=Science | year=2003 | volume=302 | pages=2038–2039 | doi=10.1126/science.302.5653.2038 | pmid=14684787}}
* {{cite journal | title=First-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters | last=Spergel | first=D. N. | coauthors=et al. | journal=Astrophysical Journal Supplement | volume=148 | pages=175–194 | year=2003 | url=http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:astro-ph/0302209 | doi=10.1086/377226}}
* {{cite journal | title=Three-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Implications for Cosmology | last=Sergel | first=D. N. | coauthors=et al. | journal=Astrophysical Journal Supplement | volume=170 | pages=377–408 | year=2007 | url=http://adsabs.harvard.edu/cgi-bin/bib_query?arXiv:astro-ph/0603449 | doi=10.1086/513700}}
* [http://arxiv.org/abs/0803.0547v2 E. Komatsu ''et al.'': ''WMAP Cosmological Interpretation'' 2008]
{{refend}}
== External links ==
{{commonscat|WMAP}}
* [http://www.bioedonline.org/news/news.cfm?art=977 Sizing up the universe]
* [http://www.space.com/scienceastronomy/map_mission_basics_030211.html About WMAP and the Cosmic Microwave Background] - Article at Space.com
* [http://www.newscientist.com/article.ns?id=dn4879 Big Bang glow hints at funnel-shaped Universe], [[NewScientist]], [[2004-04-15]]
* [http://www.nasa.gov/home/hqnews/2006/mar/HQ_06097_first_trillionth_WMAP.html NASA [[March 16]], [[2006]] WMAP inflation related press release]
* {{cite journal | last = Seife | first = Charles |authorlink=Charles Seife | title=With Its Ingredients MAPped, Universe's Recipe Beckons | journal=Science | year=2003 | volume=300 | issue=5620 |
pages=730–731 | url=http://adsabs.harvard.edu/abs/1998RPPh...61...77K | doi=10.1126/science.300.5620.730 | pmid=12730575 }}
{{CMB_experiments}}
{{Explorer program}}
{{Space telescopes}}
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