![]() A model of Planck | |||||||
Names | COBRAS/SAMBA | ||||||
---|---|---|---|---|---|---|---|
Mission type | Space telescope | ||||||
Operator | ESA | ||||||
COSPAR ID | 2009-026B | ||||||
SATCAT no. | 34938 | ||||||
Website | www | ||||||
Mission duration | Planned: >15 months Final: 4 years, 5 months, 8 days | ||||||
Spacecraft properties | |||||||
Manufacturer | Thales Alenia Space | ||||||
Launch mass | 1,950 kg (4,300 lb) [1] | ||||||
Payload mass | 205 kg (452 lb) | ||||||
Dimensions | Body: 4.20 m × 4.22 m (13.8 ft × 13.8 ft) | ||||||
Start of mission | |||||||
Launch date | 14 May 2009, 13:12:02 UTC | ||||||
Rocket | Ariane 5 ECA | ||||||
Launch site | Guiana Space Centre, French Guiana | ||||||
Contractor | Arianespace | ||||||
Entered service | 3 July 2009 | ||||||
End of mission | |||||||
Disposal | Decommissioned | ||||||
Deactivated | 23 October 2013, 12:10:27 UTC | ||||||
Orbital parameters | |||||||
Reference system | Sun-Earth L2 orbit (1,500,000 km / 930,000 mi) | ||||||
Regime | Lissajous | ||||||
Main telescope | |||||||
Type | Gregorian | ||||||
Diameter | 1.9 m × 1.5 m (6.2 ft × 4.9 ft) | ||||||
Wavelengths | 300 μm – 11.1 mm (frequencies between 27 GHz and 1 THz) | ||||||
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![]() ESA astrophysics insignia for Planck |
Planck was a space observatory operated by the European Space Agency (ESA) from 2009 to 2013. It was an ambitious project that aimed to map the anisotropies of the cosmic microwave background (CMB) at microwave and infrared frequencies, with high sensitivity and angular resolution. The mission was highly successful and substantially improved upon observations made by the NASA Wilkinson Microwave Anisotropy Probe (WMAP).
The Planck observatory was a major source of information relevant to several cosmological and astrophysical issues. One of its key objectives was to test theories of the early Universe and the origin of cosmic structure. The mission provided significant insights into the composition and evolution of the Universe, shedding light on the fundamental physics that governs the cosmos.
Planck was initially called COBRAS/SAMBA, which stands for the Cosmic Background Radiation Anisotropy Satellite/Satellite for Measurement of Background Anisotropies. The project started in 1996, and it was later renamed in honor of the German physicist Max Planck (1858–1947), who is widely regarded as the originator of quantum theory by deriving the formula for black-body radiation.
Built at the Cannes Mandelieu Space Center by Thales Alenia Space, Planck was created as a medium-sized mission for ESA's Horizon 2000 long-term scientific program. The observatory was launched in May 2009 and reached the Earth/Sun L2 point by July 2009. By February 2010, it had successfully started a second all-sky survey.
On 21 March 2013, the Planck team released its first all-sky map of the cosmic microwave background. The map was of exceptional quality and allowed researchers to measure temperature variations in the CMB with unprecedented accuracy. In February 2015, an expanded release was published, which included polarization data. The final papers by the Planck team were released in July 2018, marking the end of the mission.
At the end of its mission, Planck was put into a heliocentric graveyard orbit and passivated to prevent it from endangering any future missions. The final deactivation command was sent to Planck in October 2013.
The mission was a remarkable success and provided the most precise measurements of several key cosmological parameters. Planck's observations helped determine the age of the universe, the average density of ordinary matter and dark matter in the Universe, and other important characteristics of the cosmos.
The mission had a wide variety of scientific aims, including: [2]
Planck had a higher resolution and sensitivity than WMAP, allowing it to probe the power spectrum of the CMB to much smaller scales (×3). It also observed in nine frequency bands rather than WMAP's five, with the goal of improving the astrophysical foreground models.
It is expected that most Planck measurements have been limited by how well foregrounds can be subtracted, rather than by the detector performance or length of the mission, a particularly important factor for the polarization measurements.[ needs update ] The dominant foreground radiation depends on frequency, but could include synchrotron radiation from the Milky Way at low frequencies, and dust at high frequencies.[ needs update ]
The spacecraft carries two instruments: the Low Frequency Instrument (LFI) and the High Frequency Instrument (HFI). [2] Both instruments can detect both the total intensity and polarization of photons, and together cover a frequency range of nearly 830 GHz (from 30 to 857 GHz). The cosmic microwave background spectrum peaks at a frequency of 160.2 GHz.
Planck's passive and active cooling systems allow its instruments to maintain a temperature of −273.05 °C (−459.49 °F), or 0.1 °C above absolute zero. [3] From August 2009, Planck was the coldest known object in space, until its active coolant supply was exhausted in January 2012. [4]
NASA played a role in the development of this mission and contributes to the analysis of scientific data. Its Jet Propulsion Laboratory built components of the science instruments, including bolometers for the high-frequency instrument, a 20-kelvin cryocooler for both the low- and high-frequency instruments, and amplifier technology for the low-frequency instrument. [5]
Frequency (GHz) | Bandwidth (Δν/ν) | Resolution (arcmin) | Sensitivity (total intensity) ΔT/T, 14-month observation (10−6) | Sensitivity (polarization) ΔT/T, 14-month observation (10−6) |
---|---|---|---|---|
30 | 0.2 | 33 | 2.0 | 2.8 |
44 | 0.2 | 24 | 2.7 | 3.9 |
70 | 0.2 | 14 | 4.7 | 6.7 |
The LFI has three frequency bands, covering the range of 30–70 GHz, covering the microwave to infrared regions of the electromagnetic spectrum. The detectors use high-electron-mobility transistors. [2]
Frequency (GHz) | Bandwidth (Δν/ν) | Resolution (arcmin) | Sensitivity (total intensity) ΔT/T, 14-month observation (10−6) | Sensitivity (polarization) ΔT/T, 14-month observation (10−6) |
---|---|---|---|---|
100 | 0.33 | 10 | 2.5 | 4.0 |
143 | 0.33 | 7.1 | 2.2 | 4.2 |
217 | 0.33 | 5.5 | 4.8 | 9.8 |
353 | 0.33 | 5.0 | 14.7 | 29.8 |
545 | 0.33 | 5.0 | 147 | N/A |
857 | 0.33 | 5.0 | 6700 | N/A |
The HFI was sensitive between 100 and 857 GHz, using 52 bolometric detectors, manufactured by JPL/Caltech, [6] optically coupled to the telescope through cold optics, manufactured by Cardiff University's School of Physics and Astronomy, [7] consisting of a triple horn configuration and optical filters, a similar concept to that used in the Archeops balloon-borne experiment. These detection assemblies are divided into 6 frequency bands (centred at 100, 143, 217, 353, 545 and 857 GHz), each with a bandwidth of 33%. Of these six bands, only the lower four have the capability to measure the polarisation of incoming radiation; the two higher bands do not. [2]
On 13 January 2012, it was reported that the on-board supply of helium-3 used in Planck's dilution refrigerator had been exhausted, and that the HFI would become unusable within a few days. [8] By this date, Planck had completed five full scans of the CMB, exceeding its target of two. The LFI (cooled by helium-4) was expected to remain operational for another six to nine months. [8]
A common service module (SVM) was designed and built by Thales Alenia Space in its Turin plant, for both the Herschel Space Observatory and Planck missions, combined into one single program. [2]
The overall cost is estimated to be €700 million for the Planck [9] and €1,100 million for the Herschel mission. [10] Both figures include their mission's spacecraft and payload, (shared) launch and mission expenses, and science operations.
Structurally, the Herschel and Planck SVMs are very similar. Both SVMs are octagonal in shape and each panel is dedicated to accommodate a designated set of warm units, while taking into account the dissipation requirements of the different warm units, of the instruments, as well as the spacecraft. On both spacecraft, a common design was used for the avionics, attitude control and measurement (ACMS), command and data management (CDMS), power, and tracking, telemetry and command (TT&C) subsystems. All units on the SVM are redundant.
On each spacecraft, the power subsystem consists of a solar array, employing triple-junction solar cells, a battery and the power control unit (PCU). The PCU is designed to interface with the 30 sections of each solar array, to provide a regulated 28 volt bus, to distribute this power via protected outputs, and to handle the battery charging and discharging.
For Planck, the circular solar array is fixed on the bottom of the satellite, always facing the Sun as the satellite rotates on its vertical axis.
This function is performed by the attitude control computer (ACC), which is the platform for the attitude control and measurement subsystem (ACMS). It was designed to fulfil the pointing and slewing requirements of the Herschel and Planck payloads.
The Planck satellite rotates at one revolution per minute, with an aim of an absolute pointing error less than 37 arc-minutes. As Planck is also a survey platform, there is the additional requirement for pointing reproducibility error less than 2.5 arc-minutes over 20 days.
The main line-of-sight sensor in both Herschel and Planck is the star tracker.
The satellite was successfully launched, along with the Herschel Space Observatory , at 13:12:02 UTC on 14 May 2009 aboard an Ariane 5 ECA heavy launch vehicle from the Guiana Space Centre. The launch placed the craft into a very elliptical orbit (perigee: 270 km [170 mi], apogee: more than 1,120,000 km [700,000 mi]), bringing it near the L2 Lagrangian point of the Earth-Sun system, 1,500,000 kilometres (930,000 mi) from the Earth.
The manoeuvre to inject Planck into its final orbit around L2 was successfully completed on 3 July 2009, when it entered a Lissajous orbit with a 400,000 km (250,000 mi) radius around the L2 Lagrangian point. [11] The temperature of the High Frequency Instrument reached just a tenth of a degree above absolute zero (0.1 K) on 3 July 2009, placing both the Low Frequency and High Frequency Instruments within their cryogenic operational parameters, making Planck fully operational. [12]
In January 2012 the HFI exhausted its supply of liquid helium, causing the detector temperature to rise and rendering the HFI unusable. The LFI continued to be used until science operations ended on 3 October 2013. The spacecraft performed a manoeuvre on 9 October to move it away from Earth and its L2 point, placing it into a heliocentric orbit, while payload deactivation occurred on 19 October. Planck was commanded on 21 October to exhaust its remaining fuel supply; passivation activities were conducted later, including battery disconnection and the disabling of protection mechanisms. [13] The final deactivation command, which switched off the spacecraft's transmitter, was sent to Planck on 23 October 2013 at 12:10:27 UTC. [14]
Planck started its First All-Sky Survey on 13 August 2009. [16] In September 2009, the European Space Agency announced the preliminary results from the Planck First Light Survey, which was performed to demonstrate the stability of the instruments and the ability to calibrate them over long periods. The results indicated that the data quality is excellent. [17]
On 15 January 2010 the mission was extended by 12 months, with observation continuing until at least the end of 2011. After the successful conclusion of the First Survey, the spacecraft started its Second All Sky Survey on 14 February 2010. The last observations for the Second All Sky Survey were made on 28 May 2010. [11]
Some planned pointing list data from 2009 has been released publicly, along with a video visualization of the surveyed sky. [16]
On 17 March 2010, the first Planck photos were published, showing dust concentration within 500 light years from the Sun. [18] [19]
On 5 July 2010, the Planck mission delivered its first all-sky image. [20]
The first public scientific result of Planck is the Early-Release Compact-Source Catalogue, released during the January 2011 Planck conference in Paris. [21] [22]
On 5 May 2014 a map of the galaxy's magnetic field created using Planck was published. [23]
The Planck team and principal investigators Nazzareno Mandolesi and Jean-Loup Puget shared the 2018 Gruber Prize in Cosmology. [24] Puget was also awarded the 2018 Shaw Prize in Astronomy. [25]
On 21 March 2013, the European-led research team behind the Planck cosmology probe released the mission's all-sky map of the cosmic microwave background. [26] [27] This map suggests the Universe is slightly older than thought: according to the map, subtle fluctuations in temperature were imprinted on the deep sky when the Universe 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. It is theorised that these ripples gave rise to the present vast cosmic web of galactic clusters and dark matter. According to the team, the Universe is 13.798±0.037 billion-years-old, and contains 4.82%±0.05% ordinary matter, 26.8%±0.4% dark matter and 69%±1% dark energy. [28] [29] [30] The Hubble constant was also measured to be 67.80±0.77 (km/s)/Mpc. [26] [28] [31] [32] [33]
Parameter | Symbol | Planck Best fit | Planck 68% limits | Planck+lensing Best fit | Planck+lensing 68% limits | Planck+WP Best fit | Planck+WP 68% limits | Planck+WP +HighL Best fit | Planck+WP +HighL 68% limits | Planck+lensing +WP+highL Best fit | Planck+lensing +WP+highL 68% limits | Planck+WP +highL+BAO Best fit | Planck+WP +highL+BAO 68% limits |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Baryon density | 0.022068 | 0.02207±0.00033 | 0.022242 | 0.02217±0.00033 | 0.022032 | 0.02205±0.00028 | 0.022069 | 0.02207±0.00027 | 0.022199 | 0.02218±0.00026 | 0.022161 | 0.02214±0.00024 | |
Cold dark matter density | 0.12029 | 0.1196±0.0031 | 0.11805 | 0.1186±0.0031 | 0.12038 | 0.1199±0.0027 | 0.12025 | 0.1198±0.0026 | 0.11847 | 0.1186±0.0022 | 0.11889 | 0.1187±0.0017 | |
100x approximation to rs / DA (CosmoMC) | 1.04122 | 1.04132±0.00068 | 1.04150 | 1.04141±0.00067 | 1.04119 | 1.04131±0.00063 | 1.04130 | 1.04132±0.00063 | 1.04146 | 1.04144±0.00061 | 1.04148 | 1.04147±0.00056 | |
Thomson scattering optical depth due to reionization | 0.0925 | 0.097±0.038 | 0.0949 | 0.089±0.032 | 0.0925 | 0.089+0.012 −0.014 | 0.0927 | 0.091+0.013 −0.014 | 0.0943 | 0.090+0.013 −0.014 | 0.0952 | 0.092±0.013 | |
Power spectrum of curvature perturbations | 3.098 | 3.103±0.072 | 3.098 | 3.085±0.057 | 3.0980 | 3.089+0.024 −0.027 | 3.0959 | 3.090±0.025 | 3.0947 | 3.087±0.024 | 3.0973 | 3.091±0.025 | |
Scalar spectral index | 0.9624 | 0.9616±0.0094 | 0.9675 | 0.9635±0.0094 | 0.9619 | 0.9603±0.0073 | 0.9582 | 0.9585±0.0070 | 0.9624 | 0.9614±0.0063 | 0.9611 | 0.9608±0.0054 | |
Hubble's constant (km Mpc−1 s−1) | 67.11 | 67.4±1.4 | 68.14 | 67.9±1.5 | 67.04 | 67.3±1.2 | 67.15 | 67.3±1.2 | 67.94 | 67.9±1.0 | 67.77 | 67.80±0.77 | |
Dark energy density | 0.6825 | 0.686±0.020 | 0.6964 | 0.693±0.019 | 0.6817 | 0.685+0.018 −0.016 | 0.6830 | 0.685+0.017 −0.016 | 0.6939 | 0.693±0.013 | 0.6914 | 0.692±0.010 | |
Density fluctuations at 8h−1 Mpc | 0.8344 | 0.834±0.027 | 0.8285 | 0.823±0.018 | 0.8347 | 0.829±0.012 | 0.8322 | 0.828±0.012 | 0.8271 | 0.8233±0.0097 | 0.8288 | 0.826±0.012 | |
Redshift of reionization | 11.35 | 11.4+4.0 −2.8 | 11.45 | 10.8+3.1 −2.5 | 11.37 | 11.1±1.1 | 11.38 | 11.1±1.1 | 11.42 | 11.1±1.1 | 11.52 | 11.3±1.1 | |
Age of the Universe (Gy) | 13.819 | 13.813±0.058 | 13.784 | 13.796±0.058 | 13.8242 | 13.817±0.048 | 13.8170 | 13.813±0.047 | 13.7914 | 13.794±0.044 | 13.7965 | 13.798±0.037 | |
100× angular scale of sound horizon at last-scattering | 1.04139 | 1.04148±0.00066 | 1.04164 | 1.04156±0.00066 | 1.04136 | 1.04147±0.00062 | 1.04146 | 1.04148±0.00062 | 1.04161 | 1.04159±0.00060 | 1.04163 | 1.04162±0.00056 | |
Comoving size of the sound horizon at z = zdrag | 147.34 | 147.53±0.64 | 147.74 | 147.70±0.63 | 147.36 | 147.49±0.59 | 147.35 | 147.47±0.59 | 147.68 | 147.67±0.50 | 147.611 | 147.68±0.45 |
Results from an analysis of Planck's full mission were made public on 1 December 2014 at a conference in Ferrara, Italy. [34] A full set of papers detailing the mission results were released in February 2015. [35] Some of the results include:
Project scientists worked too with BICEP2 scientists to release joint research in 2015 answering whether a signal detected by BICEP2 was evidence of primordial gravitational waves, or was simple background noise from dust in the Milky Way galaxy. [34] Their results suggest the latter. [36]
Parameter | Symbol | TT+lowP 68% limits | TT+lowP +lensing 68% limits | TT+lowP +lensing+ext 68% limits | TT,TE,EE+lowP 68% limits | TT,TE,EE+lowP +lensing 68% limits | TT,TE,EE+lowP +lensing+ext 68% limits |
---|---|---|---|---|---|---|---|
Baryon density | 0.02222±0.00023 | 0.02226±0.00023 | 0.02227±0.00020 | 0.02225±0.00016 | 0.02226±0.00016 | 0.02230±0.00014 | |
Cold dark matter density | 0.1197±0.0022 | 0.1186±0.0020 | 0.1184±0.0012 | 0.1198±0.0015 | 0.1193±0.0014 | 0.1188±0.0010 | |
100x approximation to rs / DA (CosmoMC) | 1.04085±0.00047 | 1.04103±0.00046 | 1.04106±0.00041 | 1.04077±0.00032 | 1.04087±0.00032 | 1.04093±0.00030 | |
Thomson scattering optical depth due to reionization | 0.078±0.019 | 0.066±0.016 | 0.067±0.013 | 0.079±0.017 | 0.063±0.014 | 0.066±0.012 | |
Power spectrum of curvature perturbations | 3.089±0.036 | 3.062±0.029 | 3.064±0.024 | 3.094±0.034 | 3.059±0.025 | 3.064±0.023 | |
Scalar spectral index | 0.9655±0.0062 | 0.9677±0.0060 | 0.9681±0.0044 | 0.9645±0.0049 | 0.9653±0.0048 | 0.9667±0.0040 | |
Hubble's constant (km Mpc−1 s−1) | 67.31±0.96 | 67.81±0.92 | 67.90±0.55 | 67.27±0.66 | 67.51±0.64 | 67.74±0.46 | |
Dark energy density | 0.685±0.013 | 0.692±0.012 | 0.6935±0.0072 | 0.6844±0.0091 | 0.6879±0.0087 | 0.6911±0.0062 | |
Matter density | 0.315±0.013 | 0.308±0.012 | 0.3065±0.0072 | 0.3156±0.0091 | 0.3121±0.0087 | 0.3089±0.0062 | |
Density fluctuations at 8h−1 Mpc | 0.829±0.014 | 0.8149±0.0093 | 0.8154±0.0090 | 0.831±0.013 | 0.8150±0.0087 | 0.8159±0.0086 | |
Redshift of reionization | 9.9+1.8 −1.6 | 8.8+1.7 −1.4 | 8.9+1.3 −1.2 | 10.0+1.7 −1.5 | 8.5+1.4 −1.2 | 8.8+1.2 −1.1 | |
Age of the Universe (Gy) | 13.813±0.038 | 13.799±0.038 | 13.796±0.029 | 13.813±0.026 | 13.807±0.026 | 13.799±0.021 | |
Redshift at decoupling | 1090.09±0.42 | 1089.94±0.42 | 1089.90±0.30 | 1090.06±0.30 | 1090.00±0.29 | 1089.90±0.23 | |
Comoving size of the sound horizon at z = z* | 144.61±0.49 | 144.89±0.44 | 144.93±0.30 | 144.57±0.32 | 144.71±0.31 | 144.81±0.24 | |
100× angular scale of sound horizon at last-scattering | 1.04105±0.00046 | 1.04122±0.00045 | 1.04126±0.00041 | 1.04096±0.00032 | 1.04106±0.00031 | 1.04112±0.00029 | |
Redshift with baryon-drag optical depth = 1 | 1059.57±0.46 | 1059.57±0.47 | 1059.60±0.44 | 1059.65±0.31 | 1059.62±0.31 | 1059.68±0.29 | |
Comoving size of the sound horizon at z = zdrag | 147.33±0.49 | 147.60±0.43 | 147.63±0.32 | 147.27±0.31 | 147.41±0.30 | 147.50±0.24 | |
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![]() | This section needs expansion. You can help by adding to it. (January 2019) |
Parameter | Symbol | TT+lowE 68% limits | TE+lowE 68% limits | EE+lowE 68% limits | TT,TE,EE+lowE 68% limits | TT,TE,EE+lowE +lensing 68% limits | TT,TE,EE+lowE +lensing+BAO 68% limits |
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Baryon density | 0.02212±0.00022 | 0.02249±0.00025 | 0.0240±0.0012 | 0.02236±0.00015 | 0.02237±0.00015 | 0.02242±0.00014 | |
Cold dark matter density | 0.1206±0.0021 | 0.1177±0.0020 | 0.1158±0.0046 | 0.1202±0.0014 | 0.1200±0.0012 | 0.11933±0.00091 | |
100x approximation to rs / DA (CosmoMC) | 1.04077±0.00047 | 1.04139±0.00049 | 1.03999±0.00089 | 1.04090±0.00031 | 1.04092±0.00031 | 1.04101±0.00029 | |
Thomson scattering optical depth due to reionization | 0.0522±0.0080 | 0.0496±0.0085 | 0.0527±0.0090 | 0.0544+0.0070 −0.0081 | 0.0544±0.0073 | 0.0561±0.0071 | |
Power spectrum of curvature perturbations | 3.040±0.016 | 3.018+0.020 −0.018 | 3.052±0.022 | 3.045±0.016 | 3.044±0.014 | 3.047±0.014 | |
Scalar spectral index | 0.9626±0.0057 | 0.967±0.011 | 0.980±0.015 | 0.9649±0.0044 | 0.9649±0.0042 | 0.9665±0.0038 | |
Hubble's constant (km s−1 Mpc−1) | 66.88±0.92 | 68.44±0.91 | 69.9±2.7 | 67.27±0.60 | 67.36±0.54 | 67.66±0.42 | |
Dark energy density | 0.679±0.013 | 0.699±0.012 | 0.711+0.033 −0.026 | 0.6834±0.0084 | 0.6847±0.0073 | 0.6889±0.0056 | |
Matter density | 0.321±0.013 | 0.301±0.012 | 0.289+0.026 −0.033 | 0.3166±0.0084 | 0.3153±0.0073 | 0.3111±0.0056 | |
Density fluctuations at 8h−1 Mpc | S8 = (/0.3)0.5 | 0.840±0.024 | 0.794±0.024 | 0.781+0.052 −0.060 | 0.834±0.016 | 0.832±0.013 | 0.825±0.011 |
Redshift of reionization | 7.50±0.82 | 7.11+0.91 −0.75 | 7.10+0.87 −0.73 | 7.68±0.79 | 7.67±0.73 | 7.82±0.71 | |
Age of the Universe (Gy) | 13.830±0.037 | 13.761±0.038 | 13.64+0.16 −0.14 | 13.800±0.024 | 13.797±0.023 | 13.787±0.020 | |
Redshift at decoupling | 1090.30±0.41 | 1089.57±0.42 | 1087.8+1.6 −1.7 | 1089.95±0.27 | 1089.92±0.25 | 1089.80±0.21 | |
Comoving size of the sound horizon at z = z*(Mpc) | 144.46±0.48 | 144.95±0.48 | 144.29±0.64 | 144.39±0.30 | 144.43±0.26 | 144.57±0.22 | |
100× angular scale of sound horizon at last-scattering | 1.04097±0.00046 | 1.04156±0.00049 | 1.04001±0.00086 | 1.04109±0.00030 | 1.04110±0.00031 | 1.04119±0.00029 | |
Redshift with baryon-drag optical depth = 1 | 1059.39±0.46 | 1060.03±0.54 | 1063.2±2.4 | 1059.93±0.30 | 1059.94±0.30 | 1060.01±0.29 | |
Comoving size of the sound horizon at z = zdrag | 147.21±0.48 | 147.59±0.49 | 146.46±0.70 | 147.05±0.30 | 147.09±0.26 | 147.21±0.23 | |
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The cosmic microwave background is microwave radiation that fills all space in the observable universe. It is a remnant that provides an important source of data on the primordial universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dark. However, a sufficiently sensitive radio telescope detects a faint background glow that is almost uniform and is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s.
The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe, was a NASA spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic microwave background (CMB) – the radiant heat remaining from the Big Bang. Headed by Professor Charles L. Bennett of Johns Hopkins University, the mission was developed in a joint partnership between the NASA Goddard Space Flight Center and Princeton University. The WMAP spacecraft was launched on 30 June 2001 from Florida. The WMAP mission succeeded the COBE space mission and was the second medium-class (MIDEX) spacecraft in the NASA Explorer program. In 2003, MAP was renamed WMAP in honor of cosmologist David Todd Wilkinson (1935–2002), 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 advanced Planck spacecraft by European Space Agency (ESA) in 2009.
The Cosmic Background Explorer, also referred to as Explorer 66, was a NASA satellite dedicated to cosmology, which operated from 1989 to 1993. Its goals were to investigate the cosmic microwave background radiation of the universe and provide measurements that would help shape our understanding of the cosmos.
Observational cosmology is the study of the structure, the evolution and the origin of the universe through observation, using instruments such as telescopes and cosmic ray detectors.
In physical cosmology, the age of the universe is the time elapsed since the Big Bang. Astronomers have derived two different measurements of the age of the universe: a measurement based on direct observations of an early state of the universe, which indicate an age of 13.787±0.020 billion years as interpreted with the Lambda-CDM concordance model as of 2021; and a measurement based on the observations of the local, modern universe, which suggest a younger age. The uncertainty of the first kind of measurement has been narrowed down to 20 million years, based on a number of studies that all show similar figures for the age. These studies include researches of the microwave background radiation by the Planck spacecraft, the Wilkinson Microwave Anisotropy Probe and other space probes. Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang, and measurements of the expansion rate of the universe can be used to calculate its approximate age by extrapolating backwards in time. The range of the estimate is also within the range of the estimate for the oldest observed star in the universe.
The Cosmic Background Imager was a 13-element interferometer perched at an elevation of 5,080 metres at Llano de Chajnantor Observatory in the Chilean Andes. It started operations in 1999 to study the cosmic microwave background radiation and ran until 2008.
In physical cosmology, the inflationary epoch was the period in the evolution of the early universe when, according to inflation theory, the universe underwent an extremely rapid exponential expansion. This rapid expansion increased the linear dimensions of the early universe by a factor of at least 1026 (and possibly a much larger factor), and so increased its volume by a factor of at least 1078. Expansion by a factor of 1026 is equivalent to expanding an object 1 nanometer (10−9 m, about half the width of a molecule of DNA) in length to one approximately 10.6 light years (about 62 trillion miles).
The Herschel Space Observatory was a space observatory built and operated by the European Space Agency (ESA). It was active from 2009 to 2013, and was the largest infrared telescope ever launched until the launch of the James Webb Space Telescope in 2021. Herschel carries a 3.5-metre (11.5 ft) mirror and instruments sensitive to the far infrared and submillimetre wavebands (55–672 μm). Herschel was the fourth and final cornerstone mission in the Horizon 2000 programme, following SOHO/Cluster II, XMM-Newton and Rosetta.
The Degree Angular Scale Interferometer (DASI) was a telescope installed at the U.S. National Science Foundation's Amundsen–Scott South Pole Station in Antarctica. It was a 13-element interferometer operating between 26 and 36 GHz in ten bands. The instrument is similar in design to the Cosmic Background Imager (CBI) and the Very Small Array (VSA). In 2001 The DASI team announced the most detailed measurements of the temperature, or power spectrum of the cosmic microwave background (CMB). These results contained the first detection of the 2nd and 3rd acoustic peaks in the CMB, which were important evidence for inflation theory. This announcement was done in conjunction with the BOOMERanG and MAXIMA experiment. In 2002 the team reported the first detection of polarization anisotropies in the CMB.
Spider is a balloon-borne experiment designed to search for primordial gravitational waves imprinted on the cosmic microwave background (CMB). Measuring the strength of this signal puts limits on inflationary theory.
The Sky Polarization Observatory (SPOrt) was an Italian instrument planned for launch to the International Space Station in for a planned 2-year mission beginning in 2007. There it would observe 80% of the sky for the Cosmic microwave background radiation in the frequency range from 20 to 100 GHz. Apart from detecting large scale CMB polarization it will also provide maps of Galactic synchrotron emission at lowest frequencies.
Archeops was a balloon-borne instrument dedicated to measuring the Cosmic microwave background (CMB) temperature anisotropies. The study of this radiation is essential to obtain precise information on the evolution of the Universe: density, Hubble constant, age of the Universe, etc. To achieve this goal, measurements were done with devices cooled down at 100mK temperature placed at the focus of a warm telescope. To avoid atmospheric disturbance the whole apparatus is placed on a gondola below a helium balloon that reaches 40 km altitude.
BICEP and the Keck Array are a series of cosmic microwave background (CMB) experiments. They aim to measure the polarization of the CMB; in particular, measuring the B-mode of the CMB. The experiments have had five generations of instrumentation, consisting of BICEP1, BICEP2, the Keck Array, BICEP3, and the BICEP Array. The Keck Array started observations in 2012 and BICEP3 has been fully operational since May 2016, with the BICEP Array beginning installation in 2017/18.
POLARBEAR is a cosmic microwave background polarization experiment located in the Atacama Desert of northern Chile in the Antofagasta Region. The POLARBEAR experiment is mounted on the Huan Tran Telescope (HTT) at the James Ax Observatory in the Chajnantor Science Reserve. The HTT is located near the Atacama Cosmology Telescope on the slopes of Cerro Toco at an altitude of nearly 5,200 m (17,100 ft).
The Cosmology Large Angular Scale Surveyor (CLASS) is an array of microwave telescopes at a high-altitude site in the Atacama Desert of Chile as part of the Parque Astronómico de Atacama. The CLASS experiment aims to improve our understanding of cosmic dawn when the first stars turned on, test the theory of cosmic inflation, and distinguish between inflationary models of the very early universe by making precise measurements of the polarization of the Cosmic Microwave Background (CMB) over 65% of the sky at multiple frequencies in the microwave region of the electromagnetic spectrum.
The "axis of evil" is a name given to the apparent correlation between the plane of the Solar System and aspects of the cosmic microwave background (CMB). It gives the plane of the Solar System and hence the location of Earth a greater significance than might be expected by chance – a result which has been claimed to be evidence of a departure from the Copernican principle as assumed in the concordance model.
The QUIJOTE CMB Experiment is an ongoing experiment started in November 2012, and led by Rafael Rebolo López, with the goal of characterizing the polarization of the cosmic microwave background (CMB) and other galactic and extragalactic emission in the frequency range 10 to 40 GHz, at angular scales of 1°. These measurements will complement at low frequency and correct from galactic contamination those obtained by the Planck satellite from 2009 to 2013.
CMB spectral distortions are tiny departures of the average cosmic microwave background (CMB) frequency spectrum from the predictions given by a perfect black body. They can be produced by a number of standard and non-standard processes occurring at the early stages of cosmic history, and therefore allow us to probe the standard picture of cosmology. Importantly, the CMB frequency spectrum and its distortions should not be confused with the CMB anisotropy power spectrum, which relates to spatial fluctuations of the CMB temperature in different directions of the sky.
Marco Rinaldo Fedele Bersanelli is an Italian astrophysicist and academic, professor of astronomy at the University of Milan.
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