Planck reveals first stars were born

Polarisation of the Cosmic Microwave Background

Copyright: ESA and the Planck Collaboration

Hi-Res JPG - PNG   

New maps from ESA’s Planck satellite uncover the ‘polarised’ light from the early Universe across the entire sky, revealing that the first stars formed much later than previously thought.

The history of our Universe is a 13.8 billion-year tale that scientists endeavour to read by studying the planets, asteroids, comets and other objects in our Solar System, and gathering light emitted by distant stars, galaxies and the matter spread between them.

A major source of information used to piece together this story is the Cosmic Microwave Background, or CMB, the fossil light resulting from a time when the Universe was hot and dense, only 380 000 years after the Big Bang.

Thanks to the expansion of the Universe, we see this light today covering the whole sky at microwave wavelengths.

Between 2009 and 2013, Planck surveyed the sky to study this ancient light in unprecedented detail. Tiny differences in the background’s temperature trace regions of slightly different density in the early cosmos, representing the seeds of all future structure, the stars and galaxies of today.

Scientists from the Planck collaboration have published the results from the analysis of these data in a large number of scientific papers over the past two years, confirming the standard cosmological picture of our Universe with ever greater accuracy.

“But there is more: the CMB carries additional clues about our cosmic history that are encoded in its ‘polarisation’,” explains Jan Tauber, ESA’s Planck project scientist.

“Planck has measured this signal for the first time at high resolution over the entire sky, producing the unique maps released today.” 

The history of the Universe

Copyright: ESA

Hi-res JPG

Light is polarised when it vibrates in a preferred direction, something that may arise as a result of photons – the particles of light – bouncing off other particles. This is exactly what happened when the CMB originated in the early Universe.

Initially, photons were trapped in a hot, dense soup of particles that, by the time the Universe was a few seconds old, consisted mainly of electrons, protons and neutrinos. Owing to the high density, electrons and photons collided with one another so frequently that light could not travel any significant distant before bumping into another electron, making the early Universe extremely ‘foggy’. 

Slowly but surely, as the cosmos expanded and cooled, photons and the other particles grew farther apart, and collisions became less frequent. 

This had two consequences: electrons and protons could finally combine and form neutral atoms without them being torn apart again by an incoming photon, and photons had enough room to travel, being no longer trapped in the cosmic fog.

Polarisation of the Cosmic Microwave Background: full sky and details

Copyright: ESA and the Planck Collaboration

 Hi-Res - GIF

Once freed from the fog, the light was set on its cosmic journey that would take it all the way to the present day, where telescopes like Planck detect it as the CMB. But the light also retains a memory of its last encounter with the electrons, captured in its polarisation. 

“The polarisation of the CMB also shows minuscule fluctuations from one place to another across the sky: like the temperature fluctuations, these reflect the state of the cosmos at the time when light and matter parted company,” says François Bouchet of the Institut d’Astrophysique de Paris, France.

“This provides a powerful tool to estimate in a new and independent way parameters such as the age of the Universe, its rate of expansion and its essential composition of normal matter, dark matter and dark energy.”

Planck’s polarisation data confirm the details of the standard cosmological picture determined from its measurement of the CMB temperature fluctuations, but add an important new answer to a fundamental question: when were the first stars born? 

Polarisation of the Cosmic Microwave Background: zoom

Copyright: ESA and the Planck Collaboration

Hi-Res JPG - PNG

“After the CMB was released, the Universe was still very different from the one we live in today, and it took a long time until the first stars were able to form,” explains Marco Bersanelli of Università degli Studi di Milano, Italy. 

“Planck’s observations of the CMB polarisation now tell us that these ‘Dark Ages’ ended some 550 million years after the Big Bang – more than 100 million years later than previously thought.

“While these 100 million years may seem negligible compared to the Universe’s age of almost 14 billion years, they make a significant difference when it comes to the formation of the first stars.”

The Dark Ages ended as the first stars began to shine. And as their light interacted with gas in the Universe, more and more of the atoms were turned back into their constituent particles: electrons and protons.

This key phase in the history of the cosmos is known as the ‘epoch of reionisation’.  

Polarisation of the Cosmic Microwave Background: finer detail

Copyright: ESA and the Planck Collaboration

Hi-Res JPG - PNG

The newly liberated electrons were once again able to collide with the light from the CMB, albeit much less frequently now that the Universe had significantly expanded. Nevertheless, just as they had 380 000 years after the Big Bang, these encounters between electrons and photons left a tell-tale imprint on the polarisation of the CMB. 

“From our measurements of the most distant galaxies and quasars, we know that the process of reionisation was complete by the time that the Universe was about 900 million years old,” says George Efstathiou of the University of Cambridge, UK. 

“But, at the moment, it is only with the CMB data that we can learn when this process began.” 

Planck’s new results are critical, because previous studies of the CMB polarisation seemed to point towards an earlier dawn of the first stars, placing the beginning of reionisation about 450 million years after the Big Bang. 

This posed a problem. Very deep images of the sky from the NASA–ESA Hubble Space Telescope have provided a census of the earliest known galaxies in the Universe, which started forming perhaps 300–400 million years after the Big Bang. 

However, these would not have been powerful enough to succeed at ending the Dark Ages within 450 million years. 

“In that case, we would have needed additional, more exotic sources of energy to explain the history of reionisation,” says Professor Efstathiou.

The new evidence from Planck significantly reduces the problem, indicating that reionisation started later than previously believed, and that the earliest stars and galaxies alone might have been enough to drive it. 

This later end of the Dark Ages also implies that it might be easier to detect the very first generation of galaxies with the next generation of observatories, including the James Webb Space Telescope. 

Polarised emission from Milky Way dust

Copyright: ESA and the Planck Collaboration

Hi-Res JPG - PNG

But the first stars are definitely not the limit. With the new Planck data released today, scientists are also studying the polarisation of foreground emission from gas and dust in the Milky Way to analyse the structure of the Galactic magnetic field. 

The data have also enabled new important insights into the early cosmos and its components, including the intriguing dark matter and the elusive neutrinos, as described in papers also released today. 

The Planck data have delved into the even earlier history of the cosmos, all the way to inflation – the brief era of accelerated expansion that the Universe underwent when it was a tiny fraction of a second old. As the ultimate probe of this epoch, astronomers are looking for a signature of gravitational waves triggered by inflation and later imprinted on the polarisation of the CMB. 

No direct detection of this signal has yet been achieved, as reported last week. However, when combining the newest all-sky Planck data with those latest results, the limits on the amount of primordial gravitational waves are pushed even further down to achieve the best upper limits yet. 

“These are only a few highlights from the scrutiny of Planck's observations of the CMB polarisation, which is revealing the sky and the Universe in a brand new way,” says Jan Tauber. 

“This is an incredibly rich data set and the harvest of discoveries has just begun.” 

Notes for Editors

A series of scientific papers describing the new results was published on 5 February and it can be downloaded here.The new results from Planck are based on the complete surveys of the entire sky, performed between 2009 and 2013. New data, including temperature maps of the CMB at all nine frequencies observed by Planck and polarisation maps at four frequencies (30, 44, 70 and 353 GHz), are also released today. 

The three principal scientific leaders of the Planck mission, Nazzareno Mandolesi, Jean-Loup Puget and Jan Tauber, were recently awarded the 2015 EPS Edison Volta Prize for "directing the development of the Planck payload and the analysis of its data, resulting in the refinement of our knowledge of the temperature fluctuations in the Cosmic Microwave Background as a vastly improved tool for doing precision cosmology at unprecedented levels of accuracy, and consolidating our understanding of the very early universe." 

More about Planck

Launched in 2009, Planck was designed to map the sky in nine frequencies using two state-of-the-art instruments: the Low Frequency Instrument (LFI), which includes three frequency bands in the range 30–70 GHz, and the High Frequency Instrument (HFI), which includes six frequency bands in the range 100–857 GHz. 

HFI completed its survey in January 2012, while LFI continued to make science observations until 3 October 2013, before being switched off on 19 October 2013. Seven of Planck's nine frequency channels were equipped with polarisation-sensitive detectors. 

The Planck Scientific Collaboration consists of all the scientists who have contributed to the development of the mission, and who participate in the scientific exploitation of the data during the proprietary period.

These scientists are members of one or more of four consortia: the LFI Consortium, the HFI Consortium, the DK-Planck Consortium, and ESA’s Planck Science Office. The two European-led Planck Data Processing Centres are located in Paris, France and Trieste, Italy. 

The LFI consortium is led by N. Mandolesi, Università degli Studi di Ferrara, Italy (deputy PI: M. Bersanelli, Università degli Studi di Milano, Italy), and was responsible for the development and operation of LFI. The HFI consortium is led by J.L. Puget, Institut d’Astrophysique Spatiale in Orsay (CNRS/Université Paris-Sud), France (deputy PI: F. Bouchet, Institut d’Astrophysique de Paris (CNRS/UPMC), France), and was responsible for the development and operation of HFI. 

For further information, please contact:

Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799; +34 91 8131 199
Mob: +31 61 594 3954
Email: Markus.Bauer@esa.int

Jan Tauber
ESA Planck Project Scientist
Tel: +31 71 565 5342
Email: Jan.Tauber@esa.int

François Bouchet
Institut d’Astrophysique de Paris (CNRS/UPMC), France
Tel: +33 1 4432 8095
Email: bouchet@iap.fr
 
Marco Bersanelli
Università degli Studi di Milano, Italy
Tel: +39 02 50317264
Email: marco.bersanelli@mi.infn.it
 
George Efstathiou
University of Cambridge, UK
Tel: +44 1223 337530
Email: gpe@ast.cam.ac.uk

Source: ESA/Planck

Cosmology and the Spatial Distribution of Galaxies

Sound waves that propagate in the early universe, like spreading ripples in a pond, imprint a characteristic scale on cosmic microwave background fluctuations. These fluctuations have evolved today into the clustering of galaxies. The concept is illustrated here. SDSS III, BOSS 

Perhaps the most astonishing and revolutionary discovery in cosmology was that galaxies are moving away from us. Hubble's 1929 paper provides the underpinning of the big bang picture of creation in which the universe is expanding, and has been for 13.8 billion years. Astronomers since then have been steadily working to refine this general picture, and in 1998, two teams (one led by CfA scientists) further astonished the world with their results showing that the universe would expand forever -- and not only that: it is accelerating outward. They used supernovae to probe the distant cosmos. These discoveries have led to more sophisticated questions, with a primary task today being to understand in detail the expansion history of the universe, that is, how the rate of expansion of the universe evolved from the time of the big bang to the way it is today. The answers to this question directly address the properties of the acceleration mechanism, the nature of dark matter, the evolution of galaxies in early times, and more.

Precision measurements of the cosmic distance scale are crucial for probing this behavior, and one particularly powerful method uses what are called baryon acoustic oscillations (BAO). Baryons refer to ordinary matter, and acoustic oscillations are sound waves. Sound waves caused by density fluctuations were bouncing through the cosmos during its first 400,000 years. Then, once ionized atoms became neutral, radiation no longer interacted strongly with matter and the cosmic microwave background was released. The intensity maps of the background radiation contain a record of these sound waves – the BAO. Astronomers calculate that at the time the cosmic background was produced, sound waves (traveling at the speed of sound) could have spread across a distance of about 500 million light-years, leaving in their wake a coherent record in the matter distribution that eventually condensed into galaxies and clusters of galaxies. Because the scale of this acoustic distortion is so large, many times the size of galaxy clusters, the BAO signature was only modestly altered subsequently as the universe evolved; simulations and theory suggest deviations are below 1%. The robustness of the scale of this distinctive clustering signature allows it to be used as a standard ruler to measure the cosmic distance scale, and indeed the imprint of the BAOs has been detected in a variety of observations of the structure of the nearby universe.

CfA astronomers Daniel Eisenstein and Cameron McBride were among a large team of scientists probing BAOs by using the clustering of galaxies as seen at a time when the universe was about 8.2 billion years old. They examined 264,283 galaxies of this general epoch observed by the Sloan Digital Sky Survey, and measured from their spatial distribution the signature of the acoustic waves left behind to a precision of better than 10%. Their conclusions about the big bang are consistent overall with the picture of cosmic evolution that has emerged from many other lines of evidence (but add some tantalizing hints of mystery: their measurement of the current rate of expansion as 67.5 +- 1.7 km/second/megaparsec is actually a tad smaller than the currently favored value). The amazing power of the technique is that it gives a snapshot of the universe at this era, and that it relies on completely different data from those used by other studies that rely on supernova or cosmic background radiation.

Reference(s): 

"The Clustering of Galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Measuring DA and H at z = 0.57 from the Baryon Acoustic Peak in the Data Release 9 Spectroscopic Galaxy Sample," Lauren Anderson et al., MNRAS 439, 83, 2014.

Source: Smithsonian Astrophysical Observatory

BOSS Measures the Universe to One-Percent Accuracy

An artist's conception of the measurement scale of the universe. Baryon acoustic oscillations are the tendency of galaxies and other matter to cluster in spheres, which originated as density waves traveling through the plasma of the early universe. The clustering is greatly exaggerated in this illustration. The radius of the spheres (white line) is the scale of a “standard ruler” allowing astronomers to determine, within one percent accuracy, the large-scale structure of the universe and how it has evolved. (Image by Zosia Rostomian, Lawrence Berkeley National Laboratory)

The Baryon Oscillation Spectroscopic Survey makes the most precise calibration yet of the universe’s “standard ruler” 

Today the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration announced that BOSS has measured the scale of the universe to an accuracy of one percent. This and future measures at this precision are the key to determining the nature of dark energy.

“One-percent accuracy in the scale of the universe is the most precise such measurement ever made,” says BOSS’s principal investigator, David Schlegel, a member of the Physics Division of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). “Twenty years ago astronomers were arguing about estimates that differed by up to fifty percent. Five years ago, we’d refined that uncertainty to five percent; a year ago it was two percent. One-percent accuracy will be the standard for a long time to come.”

BOSS is the largest program in the third Sloan Digital Sky Survey (SDSS-III). Since 2009, BOSS has used the Sloan Foundation Telescope at the Apache Point Observatory in New Mexico to record high-precision spectra of well over a million galaxies with redshifts from 0.2 to 0.7, looking back over six billion years into the universe’s past. Schlegel says, “We believe the BOSS database includes more redshifts of galaxies than collected by all the other telescopes in the world.”

BOSS will continue gathering data until June, 2014. However, says Martin White, a member of Berkeley Lab, a professor of physics and astronomy at the University of California at Berkeley, and chair of the BOSS science survey team, “We’ve done the analysis now because we have 90 percent of BOSS’s final data and we’re tremendously excited by the results.”

Baryon acoustic oscillations (BAO) are the regular clustering of galaxies, whose scale provides a “standard ruler” to measure the evolution of the universe’s structure. Accurate measurement dramatically sharpens our knowledge of fundamental cosmological properties, including how dark energy accelerates the expansion of the universe.

Combined with recent measures of the cosmic microwave background radiation (CMB) and supernova measures of accelerating expansion, the BOSS results suggest that dark energy is a cosmological constant whose strength does not vary in space or time. Although unlikely to be a flaw in Einstein’s General Theory of Relativity, the authors of the BOSS analysis note that “understanding the physical cause of the accelerated expansion remains one of the most interesting problems in modern physics.”

Among other cosmic parameters, says White, the BOSS analysis “also provides one of the best-ever determinations of the curvature of space. The answer is, it’s not curved much.”

Calling a three-dimensional universe “flat” means its shape is well described by the Euclidean geometry familiar from high school: straight lines are parallel and triangles add up to 180 degrees. Extraordinary flatness means the universe experienced relatively prolonged inflation, up to a decillionth of a second or more, immediately after the big bang.

“One of the reasons we care is that a flat universe has implications for whether the universe is infinite,” says Schlegel. “That means – while we can’t say with certainty that it will never come to an end – it’s likely the universe extends forever in space and will go on forever in time. Our results are consistent with an infinite universe.”

The BOSS analysis is based on SDSS-III’s Data Releases 10 and 11 (DR 10 and DR 11) and has been submitted for publication in the Monthly Notices of the Royal Astronomical Society; the analysis is available online at http://arxiv.org/abs/1312.4877.

Ripples in a sea of galaxies 

The BOSS analysis incorporates spectra of 1,277,503 galaxies and covers 8,509 square degrees of the sky visible from the northern hemisphere. This is the largest sample of the universe ever surveyed at this density. When complete, BOSS will have collected high-quality spectra of 1.3 million galaxies, plus 160,000 quasars and thousands of other astronomical objects, covering 10,000 square degrees.

Periodic ripples of density in visible matter (“baryons,” for short) pervade the universe like raindrops on the surface of a pond. Regular galaxy clustering is the direct descendant of pressure waves that moved through the hot plasma of the early universe, which was so hot and dense that particles of light (photons) and particles of matter, including protons and electrons, were tightly coupled together. Invisible dark matter was also part of the mix.

By 380,000 years after the big bang, however, the temperature of the expanding mixture had cooled enough for light to escape, suffusing the newly transparent universe with intense radiation, which in the 13.4 billion years since has continued to cool to today’s faint but pervasive cosmic microwave background.

Minute variations in the temperature of the CMB record periodicity in the original density ripples, of which the European Space Agency’s Planck satellite has made the most recent and most accurate measures. The same periodicity is preserved in the clustering of the BOSS galaxies, a BAO signal which also mirrors the distribution of underlying dark matter.

Regular clustering at different eras, starting with the CMB, establishes the expansion history of the universe. BOSS collaborator Beth Reid of Berkeley Lab translates the two-dimensional sky coordinates of galaxies, plus their redshifts, into 3-D maps of the density of galaxies in space.

“It’s from fluctuations in the density of galaxies in the volume we’re looking at that we extract the BAO standard ruler,” she says. “To compare different regions of the sky on an equal footing, first we have to undo variations from atmospheric effects or other patterns caused by how we observe the sky with our telescope.” The results depend crucially on accurate measures of redshifts, which disclose the galaxies’ positions in space and time. But galaxies don’t move in lock step.

“When galaxies are close together their mutual gravitational attraction pushes them around and interferes with attempts to measure large-scale structure,” Schlegel says. “Their peculiar motion makes it hard to write a formula for overall gravitational growth.”

However, says Reid, “We have a very good model for what these distortions look like. The galaxy density field shows you where there are concentrations of matter, and the peculiar velocity field points in the direction of the net effect of all the local over- and under-densities.”

“The BOSS data are awe-inspiring,” says Martin White, “but many other pieces had to be put into place before we could get what we’re after out of the data.” Complex computer algorithms were essential for reconciling the inherent uncertainties. “We made thousands of model universes in a computer, and then observed them as BOSS would do and ran our analysis on them to answer the questions of ‘What if?’”

By gauging how well their algorithms could analyze these model universes, known as “mocks” and based on catalogues of realistic but artificial galaxies, the experienced BOSS team was able to assess and fine-tune the algorithms when they were applied to the real BOSS data.

The National Energy Research Scientific Computing Center (NERSC), based at Berkeley Lab, was critical to the analysis and the creation of the mocks. Says White, “NERSC set aside resources for us to push analyses through quickly when we were up against deadlines. They provide a virtual meeting place where members of the collaboration from all around the world can come together on a shared platform, with both the data and the computational resources they need to perform their research.”

BOSS has now provided the most accurate calibration ever of BAO’s standard ruler. The universe’s expansion history has been measured with unprecedented accuracy during the very stretch of ancient time, over six billion years in the past, when expansion had stopped slowing and acceleration began. But accurate as they are, the new BOSS results are just the beginning. Greater coverage and better resolution in scale are essential to understanding dark energy itself.

The proposed Dark Energy Spectroscopic Instrument (DESI), based on an international partnership of nearly 50 institutions led by Berkeley Lab, would enable the Mayall Telescope on Kitt Peak in Arizona to map over 20 million galaxies, plus over three million quasars, in 14,000 square degrees of the northern sky. By filling in the missing eons that BOSS can’t reach, DESI could sharpen and extend coverage of the expansion history of the universe from the first appearance of the cosmic background radiation to the present day.

In the meantime, BOSS, ahead of schedule for completion in June, 2014, continues to be the premier instrument for mapping the universe.

***

“The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 10 and 11 galaxy samples,” by Lauren Anderson, Eric Aubourg, Stephen Bailey, Florian Beutler, Vaishali Bhardwaj, Michael Blanton, Adam S. Bolton, J. Brinkmann, Joel R. Brownstein, Angela Burden, Chia-Hsun Chuang, Antonio J. Cuesta, Kyle S. Dawson, Daniel J. Eisenstein, Stephanie Escoffier, James E. Gunn,Hong Guo, Shirley Ho, Klaus Honscheid, Cullan Howlett, David Kirkby, Robert H. Lupton, Marc Manera, Claudia Maraston, Cameron K. McBride, Olga Mena, Francesco Montesano, Robert C. Nichol, Sebastian E. Nuza, Matthew D. Olmstead, Nikhil Padmanabhan, Nathalie Palanque-Delabrouille, John Parejko, Will J. Percival, Patrick Petitjean, Francisco Prada, Adrian M. Price-Whelan, Beth Reid, Natalie A. Roe,Ashley J. Ross, Nicholas P. Ross, Cristiano G. Sabiu, Shun Saito, Lado Samushia, Ariel G. Sanchez, David J. Schlegel, Donald P. Schneider, Claudia G. Scoccola, Hee-Jong Seo, Ramin A. Skibba, Michael A. Strauss, Molly E. C. Swanson, Daniel Thomas, Jeremy L. Tinker, Rita Tojeiro, Mariana Vargas Magana, Licia Verde, David A. Wake, Benjamin A. Weaver, David H. Weinberg, Martin White, Xiaoying Xu, Christophe Yeche, Idit Zehavi, and Gong-Bo Zhao, has been submitted to the Monthly Notices of the Royal Astronomical Society and is available online at http://arxiv.org/abs/1312.4877.

The SDSS-III Collaboration’s press release on this analysis may be found at http://www.sdss3.org/press/onepercent.php . 

Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/.

SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS‑III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

The National Energy Research Scientific Computing Center (NERSC) provides high-end scientific production computing resources for DOE’s Office of Science researchers, supporting work in a wide range of disciplines that span the DOE missions. For more information visit www.nersc.gov/.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov/.

Contact:

Paul Preuss 

Email: paul_preuss@lbl.gov

Source: Lawrence Berkeley National Laboratory (News Center)

Planck maps of the cosmic microwave background test the fundamental symmetry of space-time during cosmic inflation

Fig. 1: These images show the most probable locations of a preferred direction in the sky in the Galactic coordinates, estimated without beam asymmetry correction (top) and with correction (bottom). The top panel shows significant detection of a preferred direction toward the Ecliptic poles (marked in red), whereas the bottom panel shows no evidence for a preferred direction.

Fig. 2: The likelihood of the fractional strength g* of the quadrupole modulation from the Planck CMB temperature data: without the asymmetric beam correction (black) and with correction (red).

Temperature anisotropies seen in maps of the cosmic microwave background (CMB) offer a test of the fundamental symmetry of space-time during a period in the very early universe called cosmic inflation. If rotational symmetry (statistical isotropy) is violated during this time, a distinct signature is imprinted on the temperature correlations of two points in the sky. Using temperature data from the Planck mission published in 2013, we impose the most stringent constraints so far on a violation of rotational symmetry in the early Universe, once the known effects of the Planck beams and Galactic foreground emission that also cause asymmetry are removed. 

At the beginning of the universe, just after its birth but before the Big Bang when the universe became hot, our cosmos expanded exponentially during a very short period called cosmic inflation. This process is an indispensable building-block of the standard model of the universe; however, we do not yet know which physical mechanism caused this inflation. 

The standard inflation scenario is described by a nearly de Sitter space-time. In this framework, there are ten isometric transformations, i.e. mappings that preserve distances: three spatial translations; three spatial rotations; one time translation accompanied by spatial dilation; and three additional isometries, which reduce to special conformal transformations as time approaches infinity. 

As the expansion rate is necessarily time-dependent (because inflation must end) this breaks the time translation symmetry and hence the spatial dilation symmetry, limiting how much the universe deviates from dilation invariance. In terms of observations, such dilation invariance would give precisely scale-invariant initial fluctuations for the early universe, whereas a small deviation has been detected from CMB data by Planck with more than 5 sigma significance. 

In the usual model of inflation, six of the ten isometries remain unbroken: translations and rotations. But why must they remain unbroken while the others are broken? In fact, slight deviations from rotation symmetry naturally arise in "anisotropic inflation" models, in which a scalar field is coupled to a vector field. A violation of rotational symmetry also occurs when very long-wavelength perturbations on super-horizon scales are coupled with short-wavelength perturbation. Finally, a pre-inflationary universe was probably very chaotic and highly anisotropic, and thus a remnant of the pre-inflationary anisotropy may still be detectable. These models lead to a quadrupolar modulation of the primordial two-point correlation function, whose fractional strength is parametrized by g_*. When g_* is different from zero, the strength of the two-point correlation function depends on the angle between the line connecting the two points and some preferred direction in space. 

We tested the rotational symmetry by searching for such a preferred direction using the two-point correlation function of primordial perturbations. More precisely, we studied the CMB anisotropy, which is linearly related to the primordial perturbations. For our analysis, we used the CMB temperature data from the Planck mission released in 2013, which is publicly available at the Planck Legacy Archive. As the main "CMB channel" we use the map at 143 GHz, because at this frequency the contamination from synchrotron, free-free and dust emission of our own galaxy is weaker than in other, higher frequency channels. To further reduce the diffuse Galactic emission we fitted templates to the 143 GHz map and subsequently removed them from the observed maps. These foreground templates are created by subtracting one frequency map from the map at an adjacent frequency - similar to the "SEVEM"-method of the Planck collaboration.

From this preliminary analysis, we detect a significant quadrupolar modulation of the CMB power spectrum (g_* = -0.116 +/- 0.014 at 68% confidence level) with a direction close to the Ecliptic pole. This is shown in Figure 1a. 

However, there is another effect which causes asymmetry. The Planck beams at 143 GHz are not circular; the orientation of their semi-major axes is parallel to Planck's scan direction, which lies approximately along the Ecliptic longitudes. This means that the beams are "fatter" along the Ecliptic longitudes, and thus the Planck satellite measures less power along the Ecliptic north-south direction than in the east-west direction. In the data, this yields a quadrupolar power modulation (with g_* < 0). 

After quantifying and removing the effect of this beam asymmetry, the rotation asymmetry in the CMB basically vanishes (g_* = 0.002 +/- 0.016 at 68% confidence level). In Figure 1b, we show the probable locations of a preferred direction estimated with a correction for the beam asymmetry and Figure 2 shows the likelihood of the fractional strength of the quadrupole modulation, which peaks at zero, when the correction is added. 

In a final step we tested the effect of the Galactic foreground emission on our estimate. When we use the raw 143 GHz map without foreground cleaning, we find significant anisotropy both before and after the beam asymmetry correction (g_* = 0.305 and 0.295 +/- 0.015, respectively). The direction in this case lies close to the Galactic pole; the foreground reduction thus plays an important role in nulling artificial anisotropy in the data. 

In a nutshell: After removing the effects of Planck's asymmetric beams and of the Galactic foreground emission, we find no evidence for any rotational asymmetry in our early Universe, which would be predicted by anisotropic inflation models. Our limit (less than 2%) provides the most stringent test of rotational symmetry during inflation so far.

Jaiseung Kim and Eiichiro Komatsu

Source: Max Planck Institute for Astrophysics

Herschel throws new light on oldest cosmic light

Cosmologists have achieved a first detection of a long-sought component in the Cosmic Microwave Background (CMB). This component, known as B-mode polarisation, is caused by gravitational lensing, the bending of light by massive structures as it travels across the Universe. The result is based on the combination of data from the South Pole Telescope and ESA's Herschel Space Observatory. This detection is a milestone along the way to the possible discovery of another kind of B-mode signal in the polarised CMB - a signal produced by gravitational waves less than a second after the Universe began.

E-modes and B-modes in the CMB polarisation (left and right panels, respectively) and the gravitational potential of the large-scale distribution of matter that is lensing the CMB (central panel) from SPT and Herschel data. Credit: Image from D. Hanson, et al., 2013, Physical Review Letters, 111, 141301

The Cosmic Microwave Background is the most ancient light that has travelled almost unimpeded across the Universe, and it contains a wealth of information about the origin and nature of the cosmos. During their journey, photons from the CMB have encountered a multitude of galaxies and galaxy clusters and have been deflected by these large concentrations of matter.

This phenomenon, known as gravitational lensing, imprints a subtle distortion on the pattern of the CMB that encodes details about the large-scale distribution of structure in the Universe. In recent years, cosmologists have detected the signature of gravitational lensing on the CMB temperature using data from ground-based and space-borne experiments, including the first all-sky image of this effect achieved using ESA's Planck satellite.

Gravitational lensing of the Cosmic Microwave Background

Credit: ESA and the Planck Collaboration

A small portion of the CMB is polarised, and gravitational lensing also affects this part of the signal. In fact, the polarised CMB is an additional and even richer treasure trove than the unpolarised signal to use to explore the Universe's past. Now a team of cosmologists studying the polarised CMB has detected in it the signature of gravitational lensing, opening new and exciting possibilities to study the distribution of matter across the cosmos. This result is also the first detection of the elusive second component of the CMB polarisation – the long-sought B-modes.

The study is based on the combination of data from SPTpol, the polarisation-sensitive receiver on the National Science Foundation's South Pole Telescope (SPT), and the SPIRE instrument on board ESA's Herschel Space Observatory. The SPT is a ground-based telescope, located in Antarctica, to observe the CMB to very high angular resolution in a small patch of the southern sky.

"The CMB is partially polarised: this means that it carries additional directional information, like the light that can be observed using polarised glasses," explains Joaquin Vieira from the California Institute of Technology in Pasadena and University of Illinois at Urbana-Champaign, USA. Vieira led the Herschel survey that enabled this result.

"The pattern we observe in polarised light can be split in two distinctive components: we call these E-modes and B-modes. In the case of CMB polarisation, these two components carry very different and complementary information about both the early and the late Universe."

The CMB is the glow from the early Universe, when it first became transparent to radiation, about 380 000 years after the Big Bang. There are fluctuations in both the temperature of the CMB and its polarisation, which represent tiny differences in density and pressure at that epoch. The polarisation of the CMB has a distinctive pattern of E- and B-modes that dates back to the early Universe. But this pattern, and in particular the intensity of the B-mode component, underwent substantial changes as the polarised CMB propagated across the Universe.

"When gravitational lensing distorts the polarised CMB photons, it transforms part of the E-modes into B-modes," explains Vieira.

Only a small fraction of the CMB is polarised, so it is a very weak signal and extremely difficult to detect. The E-mode component of CMB polarisation, which has a stronger intensity than the B-mode one, was first observed in 2002 with the ground-based Degree Angular Scale Interferometer (DASI), and with a variety of other experiments in the following years. The B-modes are an extremely weak signal and, until now, had remained undetected.

"In our study, we combined the polarised CMB observed by SPT with independent data from Herschel. This technique allowed us to finally spot the B-modes induced by gravitational lensing," comments Vieira.

The cosmologists detected the B-mode signal due to gravitational lensing in the data from SPT. To make their detection more robust, they added complementary observations from Herschel to trace the large-scale distribution of galaxies that cause the lensing.

Joint observation from the South Pole Telescope (left panel) and Herschel (right panel)

Credit: Image from G. Holder et al., 2013,

The Astrophysical Journal Letters, 771, L16

"Herschel offers us a good data set to reconstruct the gravitational potential of the galaxies that are distorting the CMB," says Vieira.

"Including the Herschel data in our analysis made the SPTpol data less sensitive to instrumental effects and was key to isolating the lensing-induced B-mode signal."

With its wide spectral coverage ranging from far-infrared to sub-millimetre wavelengths, Herschel is sensitive to the Cosmic Infrared Background (CIB). In contrast to the CMB, which is the diffuse light from the early Universe, the CIB is a cumulative background, and arose with the formation of stars and galaxies, which started  several hundreds of millions of years after the Big Bang.

Whilst stars shine primarily at ultraviolet wavelengths, over the entire age of the Universe roughly half of this energy has been absorbed by cosmic dust within galaxies; this cold dust reradiates starlight at longer, far-infrared wavelengths. For this reason, the CIB encapsulates the cosmic history of star formation.

Galaxies tend to group in galaxy clusters, which are embedded in dark matter halos, and these large concentrations of dark and normal matter are what causes the gravitational lensing of the CMB. For this reason, there is a very strong correlation between the gravitationally-lensed CMB and the CIB detected by Herschel, as the latter traces the lenses responsible for the deflection. By locating points in the sky where more (or fewer) galaxies are present, the extra information contained in the Herschel data allowed the team to see the gravitational lensing effect more clearly.

The effect of gravitational lensing on the Cosmic Microwave Background.

Credit: Image from G. Holder et al., 2013, 
The Astrophysical Journal Letters, 771, L16 

This first result opens a new era in the study of the gravitationally-lensed CMB. So far, cosmologists have successfully studied gravitational lensing on the CMB temperature, but this signal is subject to a large degree of intrinsic noise, and it will be extremely difficult to improve significantly on the best current results. Studying the effect of gravitational lensing in the polarised CMB, instead, is expected to provide a much cleaner probe of the underlying distribution of matter causing the lensing.

"Polarisation holds the key to the future of gravitational lensing studies of the CMB," comments Duncan Hanson from McGill University in Montréal, Canada, who is first author of the paper reporting the discovery.

"This field is in its early stages right now, but as we collect more and more data, we will be able to study the large-scale distribution of matter with ever greater precision."

The study was based on observations with SPTpol together with Herschel data of a large patch of the sky, measuring 100 square degrees, that overlaps with the survey performed with SPTpol.

"It is great to see this ingenious use of Herschel data in achieving the first detection of B-modes in the CMB polarisation, which are fluctuations at a level of one in about ten million," comments Göran Pilbratt, Herschel Project Scientist at ESA.

"This work displays yet another use of the treasure trove of the available Herschel data," he adds.

Apart from its application to gravitational lensing, the discovery of B-modes is a milestone because it proves that it is possible to detect such a signal. Worldwide, cosmologists are still searching for a different type of B-modes, those created by primordial gravitational waves, using experiments including SPT and Planck.

Cosmologists believe that the Universe began with a very early phase of accelerated expansion known as inflation. During this very rapid phase, which boosted the size of the Universe exponentially, it is thought that gravitational waves were also generated.

"Gravitational waves are ripples in the fabric of space-time, and we think that those produced during inflation left an imprint in the B-mode component of the CMB polarisation," explains co-author Stephen Hoover from the Kavli Institute for Cosmological Physics at the University of Chicago, USA.

Finding such a signal would provide crucial information to study the very early Universe and inflation. Detection of B-modes induced by primordial gravitational waves, however, may prove even more complex as they are expected to have very different properties to those caused by gravitational lensing. Since primordial B-modes become apparent on much larger angular scales than those probed in this study, cosmologists will need to scan and analyse the signal on larger portions of the sky. Besides, cosmologists are still in the dark as to the amplitude and shape of the signal they are looking for, due to the many theoretical uncertainties that are still plaguing inflation.

"The fact that we were able to detect B-modes in the CMB polarisation at all is a great experimental success. We're all eager to find out whether this will be followed by the even more exciting discovery of primordial gravitational waves," concludes  Vieira.

Background information

The results described in this article are reported by D. Hanson and colleagues in the paper "Detection of B-mode Polarization in the Cosmic Microwave Background with Data from the South Pole Telescope", published in Physical Review Letters, 111, 141301 (2013).

The study is based on data from SPTpol, the polarisation-sensitive instrument of the National Science Foundation's South Pole Telescope (SPT), and from the SPIRE instrument on board ESA's Herschel Space Observatory.

The Cosmic Microwave Background (CMB) originated when photons last scattered off electrons at the epoch of recombination, when the Universe was about 380 000 years old. Since the scattering process polarises light, a small fraction of the CMB (less than ten per cent) is polarised.

Polarised light carries additional, directional information, and its pattern has two geometrical components. One way to split the polarised fraction of the CMB in its two components is into E-modes and B-modes, which are defined in a way that resembles the patterns of electric (E) and magnetic (B) fields in electromagnetism.

The pattern of E-modes is aligned either tangentially or radially; it would look the same when reflected in a mirror – something that scientists call 'even parity'. In contrast, the pattern of B-modes is aligned at an angle of 45 degrees with respect to that of E-modes: this creates a 'handedness', meaning that the pattern changes orientation when reflected in a mirror.

These two components of the CMB polarisation carry different, complementary information. Of the two components, E-modes have a higher intensity than B-modes.

Gravitational lensing, the bending of light caused by massive objects, also affects the CMB as it propagates across the large-scale distribution of structure that started populating the Universe a few hundred million years after the Big Bang. Massive bodies such as galaxies and galaxy clusters act as lenses and deflect the path of photons, causing distortions to the image of distant sources. The effect of the distortion on the CMB polarisation is a mixing of E- and B-modes: part of the signal contained in E-modes is transferred to the B-modes.

Like ordinary glass lenses, a gravitational lens is most effective when located half way between the source of light and the observer. In a cosmological context, the galaxies that most contribute to lens the CMB are those located at a redshift z~2. These galaxies are best probed through the longest-wavelength band on the SPIRE instrument on Herschel, which is centred on 500 microns.

The data from Herschel contained information about the distribution of the galaxies that are distorting the CMB (and its polarised component) via gravitational lensing. As such, they provided extra leverage to make the detection of the B-modes induced by gravitational lensing on the CMB polarisation more robust.

Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The SPIRE instrument contains an imaging photometer (camera) and an imaging spectrometer. The camera operates in three wavelength bands centred on 250, 350 and 500 µm, and so can make images of the sky simultaneously in three sub-millimetre colours; the spectrometer covers the wavelength range between 194 and 671 μm. SPIRE has been developed by a consortium of institutes led by Cardiff Univ. (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NAOC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC, UKSA  (UK); and NASA (USA).

Herschel was launched on 14 May 2009 and completed science observations on 29 April 2013.

The SPT is a 10-metre diameter telescope located at the Amundsen-Scott South Pole Station, Antarctica. It is supported by the National Science Foundation, the Kavli Foundation and the Betty Moore Foundation.

Contacts

Joaquin Vieira
California Institute of Technology
Pasadena, CA, USA
and University of Illinois at Urbana-Champaign
Urbana, IL, USA
Email: vieira@caltech.edu

Phone: +1-949-887-5795

Duncan Hanson
McGill University
Montréal, QC, Canada
Email: dhanson@physics.mcgill.ca

Phone: +1-514-398-6517

Stephen Hoover
Kavli Institute for Cosmological Physics
University of Chicago
Chicago, IL, USA
Email: hoover@kicp.uchicago.edu

Phone: +1-773-834-2103

Göran Pilbratt
Herschel Project Scientist
Research and Scientific Support Department
Science and Robotic Exploration Directorate
ESA, The Netherlands
Email: gpilbratt@rssd.esa.int

Phone: +31-71-565-3621

First Hundred Thousand Years of Our Universe

The microwave sky as seen by Planck

Mottled structure of the CMB, the oldest light in the universe, is displayed in the high-latitude regions of the map. The central band is the plane of our galaxy, the Milky Way. (Courtesy of European Space Agency)

Eric Linder is a theoretical physicist with Berkeley Lab’s Physics Division and member of the Supernova Cosmology Project. (Photo by Roy Kaltschmidt)

Mystery fans know that the best way to solve a mystery is to revisit the scene where it began and look for clues. To understand the mysteries of our universe, scientists are trying to go back as far they can to the Big Bang. A new analysis of cosmic microwave background (CMB) radiation data by researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) has taken the furthest look back through time yet – 100 years to 300,000 years after the Big Bang – and provided tantalizing new hints of clues as to what might have happened.

“We found that the standard picture of an early universe, in which radiation domination was followed by matter domination, holds to the level we can test it with the new data, but there are hints that radiation didn’t give way to matter exactly as expected,” says Eric Linder, a theoretical physicist with Berkeley Lab’s Physics Division and member of the Supernova Cosmology Project. “There appears to be an excess dash of radiation that is not due to CMB photons.”

Our knowledge of the Big Bang and the early formation of the universe stems almost entirely from measurements of the CMB, primordial photons set free when the universe cooled enough for particles of radiation and particles of matter to separate. These measurements reveal the CMB’s influence on the growth and development of the large-scale structure we see in the universe today.

Linder, working with Alireza Hojjati and Johan Samsing, who were then visiting scientists at Berkeley Lab, analyzed the latest satellite data from the European Space Agency’s Planck mission and NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), which pushed CMB measurements to higher resolution, lower noise, and more sky coverage than ever before.

“With the Planck and WMAP data we’re really pushing back the frontier and looking further back in the history of the universe, to regions of high energy physics we previously could not access,” Linder says. “While our analysis shows the CMB photon relic afterglow of the Big Bang being followed mainly by dark matter as expected, there was also a deviation from the standard that hints at relativistic particles beyond CMB light.”

Linder says the prime suspects behind these relativistic particles are “wild” versions of neutrinos, the phantomlike subatomic particles that are the second most populous residents (after photons) of today’s universe. The term “wild” is used to distinguish these primordial neutrinos from those expected within particle physics and being observed today. Another suspect is dark energy, the anti-gravitational force that accelerates our universe’s expansion. Again, however, this would be from the dark energy we observe today.

“Early dark energy is a class of explanations for the origin of cosmic acceleration that arises in some high energy physics models,” Linder says. “While conventional dark energy, such as the cosmological constant, are diluted to one part in a billion of total energy density around the time of the CMB’s last scattering, early dark energy theories can have 1-to-10 million times more energy density.”

Linder says early dark energy could have been the driver that seven billion years later caused the present cosmic acceleration. Its actual discovery would not only provide new insight into the origin of cosmic acceleration, but perhaps also provide new evidence for string theory and other concepts in high energy physics.

“New experiments for measuring CMB polarization that are already underway, such as the POLARBEAR and SPTpol telescopes, will enable us to further explore primeval physics, Linder says.

Linder, Hojjati and Samsing are the authors of a paper describing these results in the journal Physical Review Letters titled “New Constraints on the Early Expansion History of the Universe.” Hojjati is now with the Institute for the Early Universe in South Korea, and Samsing is with the DARK Cosmology Centre in Denmark.

This research was primarily supported by the DOE Office of Science.

For more about the Supernova Cosmology Project go here

Source: Lawrence Berkeley National Laboratory 

 

Planck reveals an almost perfect Universe

Planck CMB
Copyright: ESA and the Planck Collaboration

Acquired by ESA’s Planck space telescope, the most detailed map ever created of the cosmic microwave background – the relic radiation from the Big Bang – was released today revealing the existence of features that challenge the foundations of our current understanding of the Universe. 

The image is based on the initial 15.5 months of data from Planck and is the mission’s first all-sky picture of the oldest light in our Universe, imprinted on the sky when it was just 380 000 years old. 

At that time, the young Universe was filled with a hot dense soup of interacting protons, electrons and photons at about 2700ºC. When the protons and electrons joined to form hydrogen atoms, the light was set free. As the Universe has expanded, this light today has been stretched out to microwave wavelengths, equivalent to a temperature of just 2.7 degrees above absolute zero. 

This ‘cosmic microwave background’ – CMB – shows tiny temperature fluctuations that correspond to regions of slightly different densities at very early times, representing the seeds of all future structure: the stars and galaxies of today. 

According to the standard model of cosmology, the fluctuations arose immediately after the Big Bang and were stretched to cosmologically large scales during a brief period of accelerated expansion known as inflation. 

Planck was designed to map these fluctuations across the whole sky with greater resolution and sensitivity than ever before. By analysing the nature and distribution of the seeds in Planck’s CMB image, we can determine the composition and evolution of the Universe from its birth to the present day. 

 Planck anomalies

Copyright: ESA and the Planck Collaboration

 Overall, the information extracted from Planck’s new map provides an excellent confirmation of the standard model of cosmology at an unprecedented accuracy, setting a new benchmark in our manifest of the contents of the Universe.

But because precision of Planck’s map is so high, it also made it possible to reveal some peculiar unexplained features that may well require new physics to be understood.

“The extraordinary quality of Planck’s portrait of the infant Universe allows us to peel back its layers to the very foundations, revealing that our blueprint of the cosmos is far from complete. Such discoveries were made possible by the unique technologies developed for that purpose by European industry,” says Jean-Jacques Dordain, ESA’s Director General.

“Since the release of Planck’s first all-sky image in 2010, we have been carefully extracting and analysing all of the foreground emissions that lie between us and the Universe’s first light, revealing the cosmic microwave background in the greatest detail yet,” adds George Efstathiou of the University of Cambridge, UK. 

One of the most surprising findings is that the fluctuations in the CMB temperatures at large angular scales do not match those predicted by the standard model – their signals are not as strong as expected from the smaller scale structure revealed by Planck.

Planck enhanced anomalies
Copyright: ESA and the Planck Collaboration

Another is an asymmetry in the average temperatures on opposite hemispheres of the sky. This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look. 

Furthermore, a cold spot extends over a patch of sky that is much larger than expected. 

The asymmetry and the cold spot had already been hinted at with Planck’s predecessor, NASA’s WMAP mission, but were largely ignored because of lingering doubts about their cosmic origin. 

“The fact that Planck has made such a significant detection of these anomalies erases any doubts about their reality; it can no longer be said that they are artefacts of the measurements. They are real and we have to look for a credible explanation,” says Paolo Natoli of the University of Ferrara, Italy. 

“Imagine investigating the foundations of a house and finding that parts of them are weak. You might not know whether the weaknesses will eventually topple the house, but you’d probably start looking for ways to reinforce it pretty quickly all the same,” adds François Bouchet of the Institut d’Astrophysique de Paris. 

One way to explain the anomalies is to propose that the Universe is in fact not the same in all directions on a larger scale than we can observe. In this scenario, the light rays from the CMB may have taken a more complicated route through the Universe than previously understood, resulting in some of the unusual patterns observed today. 

“Our ultimate goal would be to construct a new model that predicts the anomalies and links them together. But these are early days; so far, we don’t know whether this is possible and what type of new physics might be needed. And that’s exciting,” says Professor Efstathiou.

 Planck cosmic recipe

Copyright: ESA and the Planck Collaboration

New Cosmic Recipe

Beyond the anomalies, however, the Planck data conform spectacularly well to the expectations of a rather simple model of the Universe, allowing scientists to extract the most refined values yet for its ingredients. 

Normal matter that makes up stars and galaxies contributes just 4.9% of the mass/energy density of the Universe. Dark matter, which has thus far only been detected indirectly by its gravitational influence, makes up 26.8%, nearly a fifth more than the previous estimate. 

Conversely, dark energy, a mysterious force thought to be responsible for accelerating the expansion of the Universe, accounts for less than previously thought. 

Finally, the Planck data also set a new value for the rate at which the Universe is expanding today, known as the Hubble constant. At 67.15 kilometres per second per megaparsec, this is significantly less than the current standard value in astronomy. The data imply that the age of the Universe is 13.82 billion years.

“With the most accurate and detailed maps of the microwave sky ever made, Planck is painting a new picture of the Universe that is pushing us to the limits of understanding current cosmological theories,” says Jan Tauber, ESA’s Planck Project Scientist. 

“We see an almost perfect fit to the standard model of cosmology, but with intriguing features that force us to rethink some of our basic assumptions. 

“This is the beginning of a new journey and we expect that our continued analysis of Planck data will help shed light on this conundrum.”

Note for Editors

For further information, please contact:
 
Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int

George Efstathiou
University of Cambridge, UK
Tel: +44 1223 337530
Email: gpe@ast.cam.ac.uk

François Bouchet
Institut d’Astrophysique de Paris, France
Tel: +33 1 44 32 80 95
Email: bouchet@iap.fr

Paolo Natoli
University of Ferrara, Italy
Tel: +39 0532 97 42 44
Email: Paolo.Natoli@unife.it

Jan Tauber

ESA Planck Project Scientist

Tel: +31 71 565 5342

Email: Jan.Tauber@esa.int