 Wilkinson Microwave Anisotropy Probe (WMAP) satellite | |
| Names | Explorer 80 MAP Microwave Anisotropy Probe MIDEX-2 WMAP |
|---|---|
| Mission type | Cosmic microwave backgroundAstronomy |
| Operator | NASA |
| COSPAR ID | 2001-027A |
| SATCATno. | 26859 |
| Website | http://map.gsfc.nasa.gov/ |
| Mission duration | 27 months (planned) 9 years (achieved)[1] |
| Spacecraft properties | |
| Spacecraft | Explorer LXXX |
| Spacecraft type | Wilkinson Microwave Anisotropy Probe |
| Bus | WMAP |
| Manufacturer | NRAO |
| Launch mass | 840 kg (1,850 lb)[2] |
| Dry mass | 763 kg (1,682 lb) |
| Dimensions | 3.6 × 5.1 m (12 × 17 ft) |
| Power | 419watts |
| Start of mission | |
| Launch date | 30 June 2001, 19:46:46UTC[3] |
| Rocket | Delta II 7425-10 (Delta 246) |
| Launch site | Cape Canaveral,SLC-17B |
| Contractor | Boeing Launch Services |
| Entered service | 1 October 2001 |
| End of mission | |
| Disposal | Graveyard orbit |
| Deactivated | 20 October 2010[4] |
| Last contact | 19 August 2010 |
| Orbital parameters | |
| Reference system | Sun-Earth L2 orbit |
| Regime | Lissajous orbit |
| Main telescope | |
| Type | Gregorian |
| Diameter | 1.4 × 1.6 m (4 ft 7 in × 5 ft 3 in) |
| Wavelengths | 23 GHz to 94 GHz |
| Instruments | |
| Pseudo-Correlation Radiometer | |
 Wilkinson Microwave Anisotropy Probe mission patch Explorer program | |
TheWilkinson Microwave Anisotropy Probe (WMAP), originally known as theMicrowave Anisotropy Probe (MAP andExplorer 80), was aNASA spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in thecosmic microwave background (CMB) – the radiant heat remaining from theBig Bang.[5][6] Headed by ProfessorCharles L. Bennett ofJohns Hopkins University, the mission was developed in a joint partnership between the NASAGoddard Space Flight Center andPrinceton University.[7] The WMAP spacecraft was launched on 30 June 2001 fromFlorida. The WMAP mission succeeded theCOBE space mission and was the second medium-class (MIDEX) spacecraft in the NASAExplorer program. In 2003, MAP was renamed WMAP in honor of cosmologistDavid Todd Wilkinson (1935–2002),[7] who had been a member of the mission's science team. After nine years of operations, WMAP was switched off in 2010, following the launch of the more advancedPlanck spacecraft byEuropean Space Agency (ESA) in 2009.
WMAP's measurements played a key role in establishing the current Standard Model of Cosmology: theLambda-CDM model. The WMAP data are very well fit by a universe that is dominated bydark energy in the form of acosmological constant. Other cosmological data are also consistent, and together tightly constrain the Model. In the Lambda-CDM model of the universe, theage of the universe is13.772±0.059 billion years. The WMAP mission's determination of the age of the universe is to better than 1% precision.[8] The current expansion rate of the universe is (seeHubble constant)69.32±0.80 km·s−1·Mpc−1. The content of the universe currently consists of4.628%±0.093% ordinarybaryonic matter;24.02%+0.88%
−0.87%cold dark matter (CDM) that neither emits nor absorbs light; and71.35%+0.95%
−0.96% ofdark energy in the form of a cosmological constant thataccelerates theexpansion of the universe.[9] Less than 1% of the current content of the universe is in neutrinos, but WMAP's measurements have found, for the first time in 2008, that the data prefer the existence of acosmic neutrino background[10] with an effective number of neutrino species of3.26±0.35. The contents point to a Euclideanflat geometry, with curvature () of−0.0027+0.0039
−0.0038. The WMAP measurements also support thecosmic inflation paradigm in several ways, including the flatness measurement.
The mission has won various awards: according toScience magazine, the WMAP was theBreakthrough of the Year for 2003.[11] This mission's results papers were first and second in the "Super Hot Papers in Science Since 2003" list.[12] Of the all-time most referenced papers in physics and astronomy in theINSPIRE-HEP database, only three have been published since 2000, and all three are WMAP publications. Bennett,Lyman A. Page Jr., and David N. Spergel, the latter both of Princeton University, shared the 2010Shaw Prize in astronomy for their work on WMAP.[13] Bennett and the WMAP science team were awarded the 2012Gruber Prize in cosmology. The 2018Breakthrough Prize in Fundamental Physics was awarded to Bennett, Gary Hinshaw, Norman Jarosik, Page, Spergel, and the WMAP science team.
In October 2010, the WMAP spacecraft wasderelict in aheliocentricgraveyard orbit after completing nine years of operations.[14] All WMAP data are released to the public and have been subject to careful scrutiny. The final official data release was thenine-year release in 2012.[15][16]
Some aspects of the data are statistically unusual for the Standard Model of Cosmology. For example, the largest angular-scale measurement, thequadrupole moment, is somewhat smaller than the Model would predict, but this discrepancy is not highly significant.[17] A largecold spot and other features of the data are more statistically significant, and research continues into these.
The WMAP objective was to measure the temperature differences in theCosmic Microwave Background (CMB) radiation. The anisotropies then were used to measure the universe's geometry, content, andevolution; and to test theBig Bang model, and thecosmic inflation theory.[18] For that, the mission created a full-sky map of the CMB, with a 13arcminutes resolution via multi-frequency observation. The map required the fewestsystematic errors, no correlated pixel noise, and accurate calibration, to ensure angular-scale accuracy greater than its resolution.[18] The map contains 3,145,728 pixels, and uses theHEALPix scheme to pixelize the sphere.[19] The telescope also measured the CMB's E-mode polarization,[18] and foreground polarization.[10] Its service life was 27 months; 3 to reach theL2 position, and 2 years of observation.[18]
The MAP mission was proposed to NASA in 1995, selected for definition study in 1996, and approved for development in 1997.[20][21]
The WMAP was preceded by two missions to observe the CMB; (i) the SovietRELIKT-1 that reported the upper-limit measurements of CMB anisotropies, and (ii) the U.S.COBE satellite that first reported large-scale CMB fluctuations. The WMAP was 45 times more sensitive, with 33 times the angular resolution of its COBE satellite predecessor.[22] The successor European Planck mission (operational 2009–2013) had a higher resolution and higher sensitivity than WMAP and observed in 9 frequency bands rather than WMAP's 5, allowing improved astrophysical foreground models.
The telescope's primary reflecting mirrors are a pair ofGregorian 1.4 × 1.6 m (4 ft 7 in × 5 ft 3 in) dishes (facing opposite directions), that focus the signal onto a pair of 0.9 × 1.0 m (2 ft 11 in × 3 ft 3 in) secondary reflecting mirrors. They are shaped for optimal performance: acarbon fibre shell upon a Korex core, thinly-coated with aluminium andsilicon oxide. The secondary reflectors transmit the signals to the corrugated feedhorns that sit on afocal plane array box beneath the primary reflectors.[18]
The receivers arepolarization-sensitive differentialradiometers measuring the difference between two telescope beams. The signal is amplified withHigh-electron-mobility transistor (HEMT)low-noise amplifiers, built by theNational Radio Astronomy Observatory (NRAO). There are 20 feeds, 10 in each direction, from which a radiometer collects a signal; the measure is the difference in the sky signal from opposite directions. The directional separationazimuth is 180°; the total angle is 141°. To improve subtraction of foreground signals from ourMilky Way galaxy, the WMAP used five discrete radio frequency bands, from 23 GHz to 94 GHz.[18]
| Property | K-band | Ka-band | Q-band | V-band | W-band |
|---|---|---|---|---|---|
| Centralwavelength (mm) | 13 | 9.1 | 7.3 | 4.9 | 3.2 |
| Centralfrequency (GHz) | 23 | 33 | 41 | 61 | 94 |
| Bandwidth (GHz) | 5.5 | 7.0 | 8.3 | 14.0 | 20.5 |
| Beam size (arcminutes) | 52.8 | 39.6 | 30.6 | 21 | 13.2 |
| Number of radiometers | 2 | 2 | 4 | 4 | 8 |
| System temperature (K) | 29 | 39 | 59 | 92 | 145 |
| Sensitivity (mK s) | 0.8 | 0.8 | 1.0 | 1.2 | 1.6 |
The WMAP's base is a 5.0 m (16.4 ft)-diametersolar panel array that keeps the instruments in shadow during CMB observations, (by keeping the craft constantly angled at 22°, relative to theSun). Upon the array sit a bottom deck (supporting the warm components) and a top deck. The telescope's cold components: the focal-plane array and the mirrors, are separated from the warm components with a cylindrical, 33 cm (13 in)-long thermal isolation shell atop the deck.[18]
Passive thermal radiators cool the WMAP to approximately 90 K (−183.2 °C; −297.7 °F); they are connected to thelow-noise amplifiers. The telescope consumes 419 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 withplatinum resistance thermometers.[18]
The WMAP's calibration is effected with the CMB dipole and measurements ofJupiter; the beam patterns are measured against Jupiter. The telescope's data are relayed daily via a 2-GHztransponder providing a 667kbit/s downlink to a 70 m (230 ft)Deep Space Network station. The spacecraft has two transponders, one a redundant backup; they are minimally active – about 40 minutes daily – to minimizeradio frequency interference. The telescope's position is maintained, in its three axes, with threereaction wheels,gyroscopes, twostar trackers andSun sensors, and is steered with eighthydrazine thrusters.[18]
The WMAP spacecraft arrived at theKennedy Space Center on 20 April 2001. After being tested for two months, it was launched viaDelta II 7425 launch vehicle from theCape Canaveral Space Force Station on 30 June 2001.[20][22] It began operating on its internal power five minutes before its launching, and continued so operating until the solar panel array deployed. The WMAP was activated and monitored while it cooled. On 2 July 2001, it began working, first with in-flight testing (from launching until 17 August 2001), then began constant, formal work.[22] Afterwards, it effected three Earth-Moon phase loops, measuring itssidelobes, then flew by the Moon on 30 July 2001, en route to the Sun-EarthL2Lagrange point, arriving there on 1 October 2001, becoming the first CMB observation mission posted there.[20]
Locating the spacecraft atLagrange 2, (1,500,000 km (930,000 mi) from Earth) thermally stabilizes it and minimizes the contaminating solar, terrestrial, and lunar emissions registered. To view the entire sky, without looking to the Sun, the WMAP traces a path aroundL2 in aLissajous orbit ca. 1.0° to 10°,[18] with a 6-month period.[20] The telescope rotates once every 2 minutes 9 seconds (0.464rpm) andprecesses at the rate of 1 revolution per hour.[18] WMAP measured the entire sky every six months, and completed its first, full-sky observation in April 2002.[21]
The WMAP instrument consists of pseudo-correlation differential radiometers fed by two back-to-back 1.5 m (4 ft 11 in) primary Gregorian reflectors. This instrument uses five frequency bands from 22 GHz to 90 GHz to facilitate rejection of foreground signals from our own Galaxy. The WMAP instrument has a 3.5° x 3.5°field of view (FoV).[23]
The WMAP observed 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 aresynchrotron radiation andfree-free emission (dominating the lower frequencies), andastrophysical 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.[18]
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 was reduced by using only the full-sky map portions with the least foreground contamination, while masking the remaining map portions.[18]
 |  |  |  |  |
| 23 GHz | 33 GHz | 41 GHz | 61 GHz | 94 GHz |
On 11 February 2003, NASA published the first-year's worth of WMAP data. The latest calculated age and composition of the early universe were presented. In addition, an image of the early universe, that "contains such stunning detail, that it may be one of the most important scientific results of recent years" was presented. The newly released data surpass previous CMB measurements.[7]
Based upon theLambda-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 andCBI), and constraints from the2dF Galaxy Redshift Survey andLyman alpha forest measurements. There are degenerations among the parameters, the most significant is between and; the errors given are at 68% confidence.[24]
| Parameter | Symbol | Best fit (WMAP only) | Best fit (WMAP, extra parameter) | Best fit (all data) |
|---|---|---|---|---|
| Age of the universe (Ga) | 13.4±0.3 | – | 13.7±0.2 | |
| Hubble's constant (km⁄Mpc·s ) | 72±5 | 70±5 | 71+4 −3 | |
| Baryonic content | 0.024±0.001 | 0.023±0.002 | 0.0224±0.0009 | |
| Matter content | 0.14±0.02 | 0.14±0.02 | 0.135+0.008 −0.009 | |
| Optical depth toreionization | 0.166+0.076 −0.071 | 0.20±0.07 | 0.17±0.06 | |
| Amplitude | A | 0.9±0.1 | 0.92±0.12 | 0.83+0.09 −0.08 |
| Scalar spectral index | 0.99±0.04 | 0.93±0.07 | 0.93±0.03 | |
| Running of spectral index | — | −0.047±0.04 | −0.031+0.016 −0.017 | |
| Fluctuation amplitude at 8h−1 Mpc | 0.9±0.1 | — | 0.84±0.04 | |
| Totaldensity of the universe | – | – | 1.02±0.02 |
Using the best-fit data and theoretical models, the WMAP team determined the times of important universal events, including the redshift ofreionization,17±4; the redshift ofdecoupling,1089±1 (and the universe's age at decoupling,379+8
−7 kyr); and the redshift of matter/radiation equality,3233+194
−210. They determined the thickness of thesurface of last scattering to be195±2 in redshift, or118+3
−2 kyr. They determined the current density ofbaryons,(2.5±0.1)×10−7 cm−1, and the ratio of baryons to photons,6.1+0.3
−0.2×10−10. The WMAP's detection of an early reionization excludedwarm dark matter.[24]
The team also examined Milky Way emissions at the WMAP frequencies, producing a 208-point source catalogue.
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 ofinflation.
The 3-year WMAP data alone shows that the universe must havedark matter. Results were computed both only using WMAP data, and also with a mix of parameter constraints from other instruments, including other CMB experiments (Arcminute Cosmology Bolometer Array Receiver (ACBAR),Cosmic Background Imager (CBI) andBOOMERANG),Sloan Digital Sky Survey (SDSS), the2dF Galaxy Redshift Survey, theSupernova Legacy Survey and constraints on theHubble constant from theHubble Space Telescope.[25]
| Parameter | Symbol | Best fit (WMAP only) |
|---|---|---|
| Age of the universe (Ga) | 13.73+0.16 −0.15 | |
| Hubble's constant (km⁄Mpc·s ) | 73.2+3.1 −3.2 | |
| Baryonic content | 0.0229±0.00073 | |
| Matter content | 0.1277+0.0080 −0.0079 | |
| Optical depth toreionization[a] | 0.089±0.030 | |
| Scalar spectral index | 0.958±0.016 | |
| Fluctuation amplitude at 8h−1 Mpc | 0.761+0.049 −0.048 | |
| Tensor-to-scalar ratio[b] | r | <0.65 |
[a]^ Optical depth to reionization improved due to polarization measurements.[26]
[b]^ <0.30 when combined withSDSS data. No indication of non-gaussianity.[25]
The five-year WMAP data were released on 28 February 2008. The data included new evidence for thecosmic neutrino background, evidence that it took over half billion years for the first stars to reionize the universe, and new constraints oncosmic inflation.[27]
The improvement in the results came from both having an extra two 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 33-GHz observations for estimating cosmological parameters; previously only the 41-GHz and 61-GHz channels had been used.
Improved masks were used to remove foregrounds.[10] Improvements to the spectra were in the 3rd acoustic peak, and the polarization spectra.[10]
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 ofdark energy at the time was negligible.[27] It also constrained the content of the present-day universe; 4.6% atoms, 23% dark matter and 72% dark energy.[10]
The WMAP five-year data was combined with measurements fromType Ia supernova (SNe) andBaryon acoustic oscillations (BAO).[10]
The elliptical shape of the WMAP skymap is the result of aMollweide projection.[28]
| Parameter | Symbol | Best fit (WMAP only) | Best fit (WMAP + SNe + BAO) |
|---|---|---|---|
| Age of the universe (Ga) | 13.69±0.13 | 13.72±0.12 | |
| Hubble's constant (km⁄Mpc·s ) | 71.9+2.6 −2.7 | 70.5±1.3 | |
| Baryonic content | 0.02273±0.00062 | 0.02267+0.00058 −0.00059 | |
| Cold dark matter content | 0.1099±0.0062 | 0.1131±0.0034 | |
| Dark energy content | 0.742±0.030 | 0.726±0.015 | |
| Optical depth toreionization | 0.087±0.017 | 0.084±0.016 | |
| Scalar spectral index | 0.963+0.014 −0.015 | 0.960±0.013 | |
| Running of spectral index | −0.037±0.028 | −0.028±0.020 | |
| Fluctuation amplitude at 8h−1 Mpc | 0.796±0.036 | 0.812±0.026 | |
| Total density of the universe | 1.099+0.100 −0.085 | 1.0050+0.0060 −0.0061 | |
| Tensor-to-scalar ratio | r | <0.43 | <0.22 |
The data puts limits on the value of the tensor-to-scalar ratio, r <0.22 (95% certainty), which determines the level at which gravitational waves affect the polarization of the CMB, and also puts limits on the amount of primordialnon-gaussianity. Improved constraints were put on the redshift of reionization, which is10.9±1.4, the redshift ofdecoupling,1090.88±0.72 (as well as age of universe at decoupling,376.971+3.162
−3.167 kyr) and the redshift of matter/radiation equality,3253+89
−87.[10]
Theextragalactic source catalogue was expanded to include 390 sources, and variability was detected in the emission fromMars andSaturn.[10]
 |  |  |  |  |
| 23 GHz | 33 GHz | 41 GHz | 61 GHz | 94 GHz |
The seven-year WMAP data were released on 26 January 2010. As part of this release, claims for inconsistencies with the standard model were investigated.[29] Most were shown not to be statistically significant, and likely due toa posteriori selection (where one sees a weird deviation, but fails to consider properly how hard one has been looking; a deviation with 1:1000 likelihood will typically be found if one tries one thousand times). For the deviations that do remain, there are no alternative cosmological ideas (for instance, there seem to be correlations with the ecliptic pole). It seems most likely these are due to other effects, with the report mentioning uncertainties in the precise beam shape and other possible small remaining instrumental and analysis issues.
The other confirmation of major significance is of the total amount of matter/energy in the universe in the form of dark energy – 72.8% (within 1.6%) as non 'particle' background, and dark matter – 22.7% (within 1.4%) of non baryonic (sub-atomic) 'particle' energy. This leaves matter, orbaryonic particles (atoms) at only 4.56% (within 0.16%).
| Parameter | Symbol | Best fit (WMAP only) | Best fit (WMAP +BAO[31] + H0[32]) |
|---|---|---|---|
| Age of the universe (Ga) | 13.75±0.13 | 13.75±0.11 | |
| Hubble's constant (km⁄Mpc·s ) | 71.0±2.5 | 70.4+1.3 −1.4 | |
| Baryon density | 0.0449±0.0028 | 0.0456±0.0016 | |
| Physicalbaryon density | 0.02258+0.00057 −0.00056 | 0.02260±0.00053 | |
| Dark matter density | 0.222±0.026 | 0.227±0.014 | |
| Physicaldark matter density | 0.1109±0.0056 | 0.1123±0.0035 | |
| Dark energy density | 0.734±0.029 | 0.728+0.015 −0.016 | |
| Fluctuation amplitude at 8h−1 Mpc | 0.801±0.030 | 0.809±0.024 | |
| Scalar spectral index | 0.963±0.014 | 0.963±0.012 | |
| Reionizationoptical depth | 0.088±0.015 | 0.087±0.014 | |
| *Total density of the universe | 1.080+0.093 −0.071 | 1.0023+0.0056 −0.0054 | |
| *Tensor-to-scalar ratio, k0 = 0.002 Mpc−1 | r | < 0.36 (95% CL) | < 0.24 (95% CL) |
| *Running of spectral index, k0 = 0.002 Mpc−1 | −0.034±0.026 | −0.022±0.020 | |
| Note: * = Parameters for extended models (parameters place limits on deviations from theLambda-CDM model)[30] |
 |  |  |  |  |
| 23-GHz | 33-GHz | 41-GHz | 61-GHz | 94-GHz |
On 29 December 2012, the nine-year WMAP data and related images were released.13.772±0.059 billion-year-old temperature fluctuations and a temperature range of ± 200 microkelvins are shown in the image. In addition, the study found that 95% of the early universe is composed ofdark matter anddark energy, the curvature of space is less than 0.4% of "flat" and the universe emerged from thecosmic Dark Ages "about 400 million years" after theBig Bang.[15][16][33]
| Parameter | Symbol | Best fit (WMAP only) | Best fit (WMAP + eCMB +BAO + H0) |
|---|---|---|---|
| Age of the universe (Ga) | 13.74±0.11 | 13.772±0.059 | |
| Hubble's constant (km⁄Mpc·s ) | 70.0±2.2 | 69.32±0.80 | |
| Baryon density | 0.0463±0.0024 | 0.04628±0.00093 | |
| Physicalbaryon density | 0.02264±0.00050 | 0.02223±0.00033 | |
| Cold dark matter density | 0.233±0.023 | 0.2402+0.0088 −0.0087 | |
| Physicalcold dark matter density | 0.1138±0.0045 | 0.1153±0.0019 | |
| Dark energy density | 0.721±0.025 | 0.7135+0.0095 −0.0096 | |
| Density fluctuations at 8h−1 Mpc | 0.821±0.023 | 0.820+0.013 −0.014 | |
| Scalar spectral index | 0.972±0.013 | 0.9608±0.0080 | |
| Reionizationoptical depth | 0.089±0.014 | 0.081±0.012 | |
| Curvature | 1 | −0.037+0.044 −0.042 | −0.0027+0.0039 −0.0038 |
| Tensor-to-scalar ratio (k0 = 0.002 Mpc−1) | r | < 0.38 (95% CL) | < 0.13 (95% CL) |
| Running scalar spectral index | −0.019±0.025 | −0.023±0.011 |
The main result of the mission is contained in the various oval maps of the CMB temperature differences. These oval images present the temperature distribution derived by the WMAP team from the observations by the telescope during the mission. Measured is the temperature obtained from aPlanck's law interpretation of the microwave background. The oval map covers the whole sky. The results are a snapshot of the universe around 375,000 years after theBig Bang, which happened about 13.8 billion years ago. The microwave background is very homogeneous in temperature (the relative variations from the mean, which presently is still 2.7 kelvins, are only of the order of5×10−5). The temperature variations corresponding to the local directions are presented through different colors (the "red" directions are hotter, the "blue" directions cooler than the average).[citation needed]
The original timeline for WMAP gave it two years of observations; these were completed by September 2003. Mission extensions were granted in 2002, 2004, 2006, and 2008 giving the spacecraft a total of 9 observing years, which ended August 2010[20] and in October 2010 the spacecraft was moved to aheliocentric "graveyard" orbit.[14]
ThePlanck spacecraft also measured the CMB from 2009 to 2013 and aims to refine the measurements made by WMAP, both in total intensity and polarization. Various ground- and balloon-based instruments have also made CMB contributions, and others are being constructed to do so. Many are aimed at searching for the B-mode polarization expected from the simplest models of inflation, includingThe E and B Experiment (EBEX),Spider,BICEP and Keck Array (BICEP2),Keck,QUIET,Cosmology Large Angular Scale Surveyor (CLASS),South Pole Telescope (SPTpol) and others.
On 21 March 2013, the European-led research team behind the Planck spacecraft released the mission's all-sky map of the cosmic microwave background.[34][35] The map suggests theuniverse is slightly older than previously thought. According to the map, subtle fluctuations in temperature were imprinted on the deep sky when the cosmos was about 370,000 years old. The imprint reflects ripples that arose as early, in the existence of the universe, as the first nonillionth (10−30) of a second. Apparently, these ripples gave rise to the present vastcosmic web ofgalaxy clusters anddark matter. Based on the 2013 data, the universe contains 4.9%ordinary matter, 26.8%dark matter and 68.3%dark energy. On 5 February 2015, new data was released by the Planck mission, according to which the age of the universe is13.799 ± 0.021billion years and the Hubble constant is67.74 ± 0.46 (km/s)/Mpc.[36]
This article incorporates text from this source, which is in thepublic domain.The WMAP (Wilkinson Microwave Anisotropy Probe) mission is designed to determine the geometry, content, and evolution of the universe via a 13arcminutesFWHM resolution full sky map of the temperature anisotropy of the cosmic microwave background radiation.
This article incorporates text from this source, which is in thepublic domain.Only with very sensitive instruments, such as COBE and WMAP, can cosmologists detect fluctuations in the cosmic microwave background temperature. By studying these fluctuations, cosmologists can learn about the origin of galaxies and large-scale structures of galaxies, and they can measure the basic parameters of the Big Bang theory.
This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain. This article incorporates text from this source, which is in thepublic domain.
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