Recent imagery generated by the Atacama Cosmology Telescope (ACT) offers a glimpse into the cosmos at approximately 380,000 years post-Big Bang.
An image of the CMB radiation from the Atacama Cosmology Telescope; orange and blue represent more or less intense radiation. Image credit: ACT Collaboration.
These novel ACT observations of the renowned Cosmic Microwave Background (CMB) enhance the definition of previously captured data from ESA’s Planck space-based observatory, which operated over a decade ago.
“We are witnessing the foundational stages that led to the formation of the very first stars and galaxies,” stated Suzanne Staggs, a Professor at Princeton University and the Director of ACT.
“Beyond mere distinctions of brightness and darkness, these images resolve the polarization of light with exceptional clarity. This capability is what fundamentally differentiates ACT from Planck and earlier telescopic instruments.”
“ACT boasts five times the resolution of Planck, coupled with superior sensitivity,” commented Dr. Sigurd Naess, a researcher affiliated with the University of Oslo.
“Consequently, the subtle signals of polarization are now directly discernible.”
The resultant polarization map elucidates the intricate dynamics of hydrogen and helium gas during the universe’s nascent period.
“Previously, we could ascertain locations; now, we can also perceive motion,” Professor Staggs elaborated.
“Much like inferring the Moon’s presence by observing tidal forces, the movements detected through light’s polarization provide insights into the gravitational forces exerted across various cosmic regions.”
“The latest findings lend strong support to a simplified cosmological model, effectively invalidating a significant proportion of alternative theories.”
During its initial few hundred thousand years following the Big Bang, the universe was enveloped in a primordial plasma so intensely hot that light could not traverse it freely, rendering the cosmos practically opaque.
The CMB is understood as the earliest epoch of cosmic history accessible to observation—essentially, a baby photograph of the universe.
The current ACT imagery presents an astonishingly precise depiction of exceedingly subtle fluctuations in the density and velocity of the gases pervading the primordial universe.
“While other contemporary observatories are engaged in low-noise polarization measurements, none possess the extensive sky coverage that ACT offers,” noted Dr. Naess.
“What appear as diffuse formations in light intensity represent regions of varying density within a vast expanse of hydrogen and helium—analogous to hills and valleys stretching for millions of light-years.”
“Over the subsequent eons, gravitational forces progressively drew these denser gas concentrations inward, facilitating the genesis of stars and galaxies.”
These detailed depictions of the early cosmos are instrumental in assisting scientists to resolve enduring enigmas concerning the universe’s origins.
“By examining that era of relative simplicity, we can reconstruct the narrative of how our universe evolved into the rich and intricate realm we inhabit today,” remarked Professor Jo Dunkley of Princeton University, who leads ACT’s analysis efforts.
“We have achieved a more precise quantification that the observable universe extends approximately 50 billion light-years in all directions from our vantage point, and its total mass approximates 1,900 ‘zetta-suns,’ or nearly two trillion trillion Suns,” added Professor Erminia Calabrese from the University of Cardiff.
“Within that 1,900 zetta-sun total, the mass attributed to ordinary matter—the kind we can directly perceive and quantify—constitutes a mere 100.”
“An additional 500 zetta-suns of mass are accounted for by enigmatic dark matter, and the equivalent of 1,300 zetta-suns is attributed to the dominant vacuum energy (also termed dark energy) inherent in empty space.”
Subatomic neutrino particles contribute at most four zetta-suns to the overall mass. Of the normal matter component, three-quarters is hydrogen, and one-quarter is helium.
“Virtually all the helium present in the universe was synthesized within the initial three minutes of cosmic history,” stated Dr. Thibaut Louis, a researcher at the University Paris-Saclay and CNRS.
“Our contemporary measurements of its cosmic abundance align exceptionally well with theoretical predictions and with observational data from galaxies.”
“The elemental constituents from which we humans are formed—predominantly carbon, alongside oxygen, nitrogen, iron, and even trace amounts of gold—originated later within stellar furnaces and constitute a mere garnish atop this cosmic amalgam.”
ACT’s recent measurements have likewise refined estimations regarding the universe’s age and its current rate of expansion.
The inward flow of matter in the early universe generated acoustic waves that propagated through space, akin to concentric ripples expanding on a tranquil body of water.
“A less mature universe would have necessitated a more accelerated expansion to attain its present dimensions, and the observed images would appear to be originating from a closer proximity,” explained Professor Mark Devlin of the University of Pennsylvania, who serves as ACT’s deputy director.
“In such a scenario, the apparent scale of the ripples depicted in the images would be magnified, analogous to how a ruler held near one’s face appears larger than the same ruler extended at arm’s length.”
“The latest dataset corroborates the estimate of the universe’s age at 13.8 billion years, with a margin of error not exceeding 0.1%.”
Recent years have seen a divergence of opinion among cosmologists concerning the Hubble constant, which quantifies the current rate of cosmic expansion.
Measurements derived from the CMB consistently indicate an expansion rate between 67 and 68 km per second per megaparsec. Conversely, estimations based on the motion of nearby galaxies suggest a Hubble constant as high as 73 to 74 km per second per megaparsec.
Leveraging their recently published data, the ACT consortium has determined the Hubble constant with enhanced precision.
Their findings are in close agreement with prior CMB-derived estimations.
“We undertook this entirely novel observational approach to the sky, providing an independent validation of the prevailing cosmological model, and our outcomes demonstrate its continued robustness,” stated Dr. Adriaan Duivenvoorden, a researcher at the Max Planck Institute for Astrophysics.
A primary objective of this research endeavor was to scrutinize alternative cosmological frameworks that might account for the observed discrepancy.
“Our intention was to ascertain whether a cosmological model could be identified that not only aligned with our collected data but also posited a more rapid expansion rate,” explained Dr. Colin Hill, a researcher at Columbia University.
“Hypothetical alternatives include modifications to the behavior of neutrinos and elusive dark matter, the introduction of a phase of accelerated expansion in the early universe, or alterations to fundamental physical constants.”
“We have effectively employed the CMB as a sensitive probe for novel particles or fields present in the early universe, thereby venturing into previously unexplored cosmic territory,” Dr. Hill added.
“The data obtained from ACT do not exhibit any indication of such novel signals. Consequently, our recent findings signify that the standard cosmological model has successfully undergone an exceptionally stringent validation.”
“It was somewhat unexpected for us not to encounter even partial evidence supporting the higher observed value,” Professor Staggs commented.
“There were certain avenues where we anticipated discovering indications for potential explanations of this discrepancy, but they were simply not present within the data.”
