The underlying matter of the universe is mapped by cosmologists using secondary fingerprints from the cosmic microwave background.
The primordial plasma of the young cosmos cooled enough for the first atoms to form about 400.000 years after the Big Bang, creating space for buried radiation to fly freely. The cosmic microwave background (CMB) light continues to flow in all directions across the sky, broadcasting an image of the early universe captured by special telescopes and even seen statically on old cathode ray televisions.
Cosmic microwave background glow
After the discovery of CMB radiation in 1965, researchers carefully watched for small temperature changes that revealed the exact state of the universe when it was just a foamy plasma. Researchers are now reusing CMB data to record the massive structures that have evolved over billions of years as the universe matures.
Kimmy Wu, cosmologist at the SLAC National Accelerator Laboratory, said: "This light has experienced a significant part of the history of the universe, and by seeing how it has changed, we can learn about different epochs.
Light from the CMB has been stretched, compressed, and bent by all the matter in its path during its nearly 14 billion-year journey.
In addition to primary changes in CMB light, cosmologists are beginning to study secondary traces created by interactions with galaxies and other cosmic structures. Thanks to these signals, they get a clearer picture of the distribution of both ordinary matter, which is everything made of atoms, and the mysterious dark matter. Such discoveries also help to both solve and raise new cosmic questions.
“We are beginning to realize that the CMB provides information about more than the initial conditions of the universe. According to SLAC cosmologist Emmanuel Schaan, it also provides information about the galaxies themselves. And this is proving to be really effective.
Unknown World of Shadows
Much of the underlying mass of galaxies is overlooked by standard optical surveys that track the light emitted by stars. This is because the vast majority of the universe's total matter is hidden from observatories in the form of dark matter clumps or scattered ionized gas that connects galaxies. However, the amplification and hue of incoming CMB light exhibit noticeable effects from both dark matter and diffuse gas.
According to Schaan, while galaxies are the main actors in the cosmos, the CMB serves as the backlight.
Higher energy is achieved as light particles or photons from the CMB scatter from electrons in the gas between galaxies. In addition, if these galaxies are moving relative to the expanding universe, the CMB photons undergo a second energy shift, which can be up or down depending on how the cluster moves.
Sunyaev-Zeldovich (SZ) effects, also known as thermal and kinematic effects, were first predicted in the late 1960s and have been seen more precisely in the last decade. Thanks to the combined signal of SZ effects that can be extracted from CMB photographs, scientists can map the position and temperature of all ordinary things in the universe.
The path of the CMB light is distorted as it passes through large objects due to a third phenomenon known as weak gravitational lensing, causing the CMB to appear as though it is seen through the bottom of a wine glass. Lensing, unlike SZ effects, is sensitive to all matter, dark or not.
When these effects are combined, cosmologists can distinguish between light and dark matter. Then, to calculate cosmic distances and even track star formation, researchers can overlay these maps with images from galaxy surveys.
A team led by Schaan and Stefania Amodeo used this strategy in supplemental publications released in 2021. They compared CMB images produced by the ground-based Atacama Cosmology Telescope and the European Space Agency's Planck spacecraft with additional optical surveys of about 500.000 galaxies. Thanks to this approach, they were able to measure the alignment of light and dark matter.
The research revealed that, contrary to what many models suggest, the gas in the region is not so tightly wound into the supporting dark matter web. Instead, the research suggests the gas was swept away from dark matter nodes by supernova explosions and supermassive black holes, and dispersed until it was too thin and cold for conventional observatories to detect.
Scientists have made progress in resolving the missing baryons dilemma, thanks to their discovery of diffuse gas in the shadows of the CMB. As a result, scientists can now refine the large-scale structure of the cosmos using models of galaxy evolution and estimates for the strength and temperature of dispersion bursts.
The observed distribution of matter in the current universe is more uniform than theory predicts, which has confused cosmologists in recent years. According to Colin Hill, if explosions that recycle intergalactic gas are more energetic than scientists think, as recent research by Schaan, Amodeo and others implied, this may be part of the reason why matter is more evenly distributed throughout the universe.
Hill and his colleagues at the Atacama Cosmology Telescope plan to provide an updated map of the CMB shadows in the coming months, with a noticeable improvement in both sky coverage and sensitivity.
According to Hill, we've only begun to touch the surface of what this map can do. “This is a tremendous advance over previous technologies. It's hard to believe this is real.
The standard model of cosmology, which serves as the main framework for understanding the origin, structure, and shape of the universe, has been established in large part thanks to the CMB. However, CMB backlight research now poses a threat to undermine that claim.
Eiichiro Komatsu, a cosmologist at the Max Planck Institute for Astrophysics, worked to develop the theory as a member of the Wilkinson Microwave Anisotropy Probe, which mapped the CMB from 2001-2010. “This paradigm has really survived the test of precision measurements until recently,” Komatsu said. “A new model of the universe may be at a crossroads,” the author says.
Komatsu and his colleagues have been searching for clues to a new character on the shadow theater scene for the past two years. The polarization or orientation of the CMB light waves exhibits the signal, which the conventional cosmology model predicts should remain constant throughout the waves' passage through the universe.
But the polarization could be driven by dark matter, dark energy, or an entirely new field of particles, as Sean Carroll and colleagues predicted three decades ago. Such a field would rotate the net polarization of the light and allow photons of various polarizations to travel at different speeds – a property known as "bird double refraction" shared by various crystals, including those that power LCD panels. A rotation of about 2020 degrees in the polarity of the CMB was discovered by Komatsu's team in 0,35. A follow-up study published the previous year enhanced this initial finding.
If the study of polarization or any other result regarding the distribution of galaxies is confirmed, it will turn out that the universe does not look the same from all directions to all observers. Both results are of interest to Hill and many others, but are not yet conclusive. Follow-up research is being done to examine these clues and rule out possible confounding factors. Some have even suggested building a special "backlight astronomy" spacecraft to study different shadows in greater detail.
According to Komatsu, people believed that cosmology was finished five to ten years ago. “Right now, this situation is changing. A new era is beginning for us.
Source: quantamagazine.org / Zack Savitsky
Günceleme: 23/03/2023 13:09