ESA Planck and NASA WMAP: Dark energy a mirage concealed behind phantom fields

Observations of ESA's Planck and NASA's WMAP satellites help to solve the equation of the state of dark energy. 

Credit: ESA et al.

Quintessence and phantom fields, two hypotheses formulated using data from satellites, such as ESA's Planck and NASA's Wilkinson Microwave Anisotropy Probe (WMAP), are among the many theories that try to explain the nature of dark energy.

Now researchers from Barcelona and Athens suggest that both possibilities are only a mirage in the observations and it is the quantum vacuum which could be behind this energy that moves our universe.

Cosmologists believe that some three quarters of the universe are made up of a mysterious dark energy which would explain its accelerated expansion.

The truth is that they do not know what it could be, therefore they put forward possible solutions.

One is the existence of quintessence, an invisible gravitating agent that instead of attracting, repels and accelerates the expansion of the cosmos.

WMAP Satellite Diagram

From the Classical World until the Middle Ages, this term has referred to the ether or fifth element of nature, together with earth, fire, water and air.

Another possibility is the presence of an energy or phantom field whose density increases with time, causing an exponential cosmic acceleration.

This would reach such speed that it could break the nuclear forces in the atoms and end the universe in some 20,000 million years, in what is called the Big Rip.

The experimental data that underlie these two hypotheses comes from satellites such as ESA's Planck and NASA's Wilkinson Microwave Anisotropy Probe (WMAP).

Observations from the two probes are essential for solving the so-called equation of the state of dark energy, a characterising mathematical formula, the same as that possessed by solid, liquid and gaseous states.

Now researchers from the University of Barcelona (Spain) and the Academy of Athens (Greece) have used the same satellite data to demonstrate that the behaviour of dark energy does not need to resort to either quintessence or phantom energy in order to be explained.

The details have been published in the Monthly Notices of the Royal Astronomical Society journal.

Joan Solà

"Our theoretical study demonstrates that the equation of the state of dark energy can simulate a quintessence field, or even a phantom field, without being one in reality, thus when we see these effects in the observations from WMAP, Planck and other instruments, what we are seeing is an mirage," told SINC Joan Solà, one of the authors from University of Barcelona.

Nothing fuller than the quantum vacuum
"What we think is happening is a dynamic effect of the quantum vacuum, a parameter that we can calculate," explained the researcher.

The concept of the quantum vacuum has nothing to do with the classic notion of absolute nothingness.

"Nothing is more 'full' than the quantum vacuum since it is full of fluctuations that contribute fundamentally to the values that we observe and measure," Solà pointed out.

The detailed, all-sky picture of the infant universe created from nine years of WMAP data. 

The image reveals 13.77 billion year old temperature fluctuations (shown as colour differences) that correspond to the seeds that grew to become the galaxies. 

The signal from our galaxy was subtracted using the multi-frequency data. This image shows a temperature range of ± 200 microKelvin.

Credit: NASA / WMAP Science Team

These scientists propose that dark energy is a type of dynamical quantum vacuum energy that acts in the accelerated expansion of our universe.

This is in contrast to the traditional static vacuum energy or cosmological constant.

The drawback with this strange vacuum is that it is the source of problems such as the cosmological constant, a discrepancy between the theoretical data and the predictions of the quantum theory that drives physicists mad.

"However, quintessence and phantom fields are still more problematic, therefore the explanation based on the dynamic quantum vacuum could be the more simple and natural one," concluded Solà.

More information: Spyros Basilakos, Joan Sola. "Effective equation of state for running vacuum: "mirage" quintessence and phantom dark energy". Monthly Notices of the Royal Astronomical Society 437(4), February 2014. DOI: 10.1093/mnras/stt2135

Planck: First hundred thousand years of our universe

This is 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. 

Credit: European Space Agency

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 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.

Planck Microwave Background Radiation: Seeing the Big Bang

Two Cosmic Microwave Background anomalies hinted at by the Planck observatory's predecessor, NASA's WMAP, are confirmed in new high-precision data revealed on March 21, 2013. 

In this image, the two anomalous regions have been enhanced with red and blue shading to make them more clearly visible.

Credit: ESA and the Planck Collaboration

The universe burst into existence 13.8 billion years ago in a "Big Bang" that blew space up like a giant balloon. For nearly 400,000 years after that, the universe remained a seething-hot, opaque fog of plasma and energy.

But then, in an epoch known as recombination, the temperature dropped enough to allow the formation of electrically neutral atoms, turning the universe transparent.

Photons began to travel freely, and the light we know as the cosmic microwave background (CMB) pervaded the heavens, filled with clues about the first few moments after creation.

John Mather

"As far as we know, that's as far [back] as we can see — we get an image of the universe as it was when it was about 389,000 years old," said John Mather of NASA's Goddard Space Flight Center in Greenbelt, Md., senior project scientist for the space agency's James Webb Space Telescope, the successor to the Hubble Space Telescope.

Mather and George Smoot won the 2006 Nobel Prize in Physics for their work on NASA's Cosmic Background Explorer satellite mission.

"We believe — although it's not 100 percent proven — that spots that we see in the microwave map from when the universe was 389,000 years old were actually imposed on it when [the universe] was sub-microseconds old," Mather told reporters.

"There's an interpretive step there, but it's probably right."

The CMB, which was first detected in 1964, is strikingly uniform. But COBE discovered in 1992 that it's studded with tiny temperature fluctuations. These variations have since been mapped out more precisely by two other space missions, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the ESA European Planck spacecraft.

The hot and cold areas — which differ from their homogeneous surroundings at a level of just 1 part per 100,000 — signify areas featuring different densities.

"You can imagine a cold spot being a gravitational overdensity; it's sitting at the bottom of a shallow gravity well," said Al Kogut of NASA Goddard, who has worked on COBE, WMAP and other efforts to map the CMB.

ESA PLANCK FSM Image

PLANCK_FSM_03 Image



The microwave sky as seen by ESA's Plancksatellite

This multi-frequency all-sky image of the microwave sky has been composed using data from Planck covering the electromagnetic spectrum from 30 GHz to 857 GHz.

The mottled structure of the CMBR, with its tiny temperature fluctuations reflecting the primordial density variations from which today’s cosmic structure originated, is clearly visible in the high-latitude regions of the map.

The central band is the plane of our Galaxy. A large portion of the image is dominated by the diffuse emission from its gas and dust. The image was derived from data collected by Planck during its first all-sky survey and comes from observations taken between August 2009 and June 2010. This image is a low- resolution version of the full data set.

To the right of the main image, below the plane of the Galaxy, is a large cloud of gas in our Galaxy. The obvious arc of light surrounding it is Barnard’s Loop – the expanding bubble of an exploded star. Planck has seen whole other galaxies.

The great spiral galaxy in Andromeda, 2.2 million light-years from Earth, appears as a sliver of microwave light, released by the coldest dust in its giant body. Other, more distant, galaxies with supermassive black holes appear as single points of microwaves dotting the image.

Planck was built for ESA by the Prime Contractor Thales Alenia Space (Cannes, France) with contributions from space industry drawn from ESA’s 18 Member States. Because of differing accounting procedures in the many bodies contributing, precise costings are impossible to give.

However, the overall cost to ESA and its Member State institutions as well as cooperating agencies world- wide (including NASA and Canadian Space Agency) in round figures is 600M€

Credits: ESA/ LFI & HFI Consortia

ESA's Planck Space Observatory images: Perseus

In contrast to Orion, the Perseus region is a less vigorous star-forming area but, as Planck shows in the other image, there is still plenty going on.

The images both show three physical processes taking place in the dust and gas of the interstellar medium. Planck can show us each process separately.

At the lowest frequencies, Planck maps emission caused by high-speed electrons interacting with the Galaxy’s magnetic fields. An additional diffuse component comes from spinning dust particles emitting at these frequencies.

At intermediate wavelengths of a few millimetres, the emission is from gas heated by newly formed hot stars.

At still higher frequencies, Planck maps the meagre heat given out by extremely cold dust. This can reveal the coldest cores in the clouds, which are approaching the final stages of collapse, before they are reborn as fully-fledged stars. The stars then disperse the surrounding clouds.

The delicate balance between cloud collapse and dispersion regulates the number of stars that the Galaxy makes. Planck will advance our understanding of this interplay hugely, because, for the first time, it provides data on several major emission mechanisms in one go.

Planck's mission
Planck’s primary mission is to observe the entire sky at microwave wavelengths in order to map the variations in the ancient radiation given out by the Big Bang. Thus, it cannot help but observe the Milky Way as it rotates and sweeps its electronic detectors across the night sky.

ESA's Planck Space Observatory: Orion Nebula

New images from ESA’s Planck space observatory reveal the forces driving star formation and give astronomers a way to understand the complex physics that shape the dust and gas in our Galaxy.

Star formation takes place hidden behind veils of dust but that doesn’t mean we can’t see through them.

Where optical telescopes see only black space, Planck’s microwave eyes reveal myriad glowing structures of dust and gas. Now, Planck has used this ability to probe two relatively nearby star-forming regions in our Galaxy.

The Orion region is a cradle of star formation, some 1500 light-years away. It is famous for the Orion Nebula, which can be seen by the naked eye as a faint smudge of pink.

Planck’s primary mission is to observe the entire sky at microwave wavelengths in order to map the variations in the ancient radiation given out by the Big Bang. Thus, it cannot help but observe the Milky Way as it rotates and sweeps its electronic detectors across the night sky.

ESA Planck scanning - Galactic, mollweide

The ring of sky which the Planck satellite scans at any one time is shown as a white ring. As it orbits the Sun, it maps out the sky, shown here as the sky as measured by the WMAP satellite (credit NASA/WMAP Science Team).

The map is shown in Galactic coordinates, aligned with the plane of our Galaxy, and projected in a "Mollweide" projection, meaning that entire sky is shown in one oval, just like in some maps of the world in an Atlas.

The solar system is tilted relative to the plane of the Galaxy, so the ring which Planck scans moves oddly around the sky in this view.

http://planck.cf.ac.uk/scanning

Herschel & Planck: High Risk and High Stakes

Herschel & Planck sits ready in the cargo bay of the Ariane 5 launcher.

Separately, each is a major mission. Together, they constitute a landmark in astrophysics. The probes could revolutionise our understanding of the cosmos. If everything goes to plan, Herschel and Plank will dominate space science for at least five years. But if the launch goes wrong...

With science budgets shrinking, launching two such important missions on the same rocket smacks of madness, especially given that the launcher, an Ariane 5 rocket, has suffered a couple of high-profile and expensive failures. In 1996, a computer bug caused the loss of ESA's Cluster mission, which was rebuilt at a cost of €315 million. In 2002, a commercial launch exploded, forcing ESA to delay its Rosetta mission and costing it a further €100 million.

With the combined bill for Herschel and Planck coming in at more than €2 billion, it is near-inconceivable that they will be rebuilt if something goes wrong. Their loss would leave ESA reeling. The agency has other missions in the pipeline, including a mission to Mercury and a star-mapping project called Gaia. These have excellent scientific potential but they somehow seem small in comparison.

In short, if we lose Herschel and Planck, the heart of ESA's - and arguably the world's - space science programme would be ripped out. Let us all wish ESA the very best of luck.

Herscel Planck: Ready for countdown

Herschel (left) and Planck (right) could revolutionise our understanding of the universe (Image: ESA)