Cosmic Dawn Beckons: Scientists Nearing Detection of Clues from Universe's Infancy

An image of part of the sky seen in radio wavelengths. New research removed many sources of nearby radio “noise” to focus on some of the earliest light in the universe.(Image credit: ICRAR)

According to a fresh investigation, the nascent universe may have been simmering well before the light from stars initially inundated the cosmos.

The discoveries imply that roughly 800 million years following the Big Bang, energy originating from newly formed black holes and the diminishing remnants of the earliest stars had already begun to warm expansive formations of intergalactic hydrogen gas, presenting a unique insight into a largely unexplored phase of the universe’s genesis.

You may like

Scientists may finally know why the first stars in the universe left no trace
James Webb telescope pinpoints brightest FRB ever detected
James Webb Space Telescope uncovers 300 mysteriously luminous objects. Are they galaxies or something else?

Astronomers are aware that the universe started in an extremely scorching, concentrated state, the Big Bang, around 13.8 billion years prior, and subsequently cooled swiftly as it broadened. Approximately 400,000 years later, temperatures receded sufficiently for protons and electrons to coalesce into neutral hydrogen atoms, and the cosmos descended into the “cosmic dark ages” — a protracted, lightless span when space was concealed by a thick haze of hydrogen gas.

Hundreds of millions of years thereafter, the initial generations of colossal stars and faint nascent galaxies sparked into existence, discharging intense ultraviolet light that gradually incinerated this haze in a transformative phase referred to as the Epoch of Reionization. That mechanism, which concluded approximately 1 billion years following the Big Bang, rendered the universe transparent and permitted starlight to journey unhindered through space for the first time, signifying the inception of the cosmos as we perceive it.

The fresh conclusions, thoroughly described in an article issued on Sept. 30 in The Astrophysical Journal, propose that prior to the universe “illuminating,” it might not have been as cold as numerous models anticipate. By restricting the prospects for the conditions of the ancient cosmos, the outcomes furnish a noteworthy novel clue to comprehending how the initial stars and galaxies initiated the reshaping of their surroundings, researchers indicate.

The radio sky image (background) represents the cleanest signal ever produced from data collected by the Murchison Widefield Array (foreground) in Western Australia. The universe’s echoes

Given that direct observation of the universe’s inaugural stars remains unattainable — they were excessively dim, excessively fleeting, and excessively distant for even the most potent telescopes to identify — astronomers instead scrutinize the understated imprints those stars deposited in the hydrogen gas encompassing them.

Within the recent investigation, Nunhokee and her collaborators scrutinized almost a decade’s worth of information from the Murchison Widefield Array, a formidable radio telescope positioned in the secluded Western Australian desert, to seek a subtle radio “murmur” originating from that ancient hydrogen.

You may like

Scientists may finally know why the first stars in the universe left no trace
James Webb telescope pinpoints brightest FRB ever detected
James Webb Space Telescope uncovers 300 mysteriously luminous objects. Are they galaxies or something else?

The transmission emerges when a hydrogen atom’s singular proton and electron invert their spins relative to one another — a subtle modification that alters the atom’s energy and induces it to emit or absorb a photon at a specific wavelength. Astronomers pursue the delicate radio echo of this transition, which manifests at a wavelength of 21 centimeters — or, to our instruments, a frequency of approximately 1.42 gigahertz. As the signal’s magnitude is influenced by the temperature and milieu of the encompassing hydrogen gas, it functions akin to a cosmic thermometer, unveiling how the initial stars and black holes commenced influencing the ancient universe.

Nonetheless, pinpointing this primeval transmission is exceptionally arduous. It is obscured beneath strata of substantially more potent radio interference emanating from the Milky Way, other neighboring galaxies, Earth’s atmosphere, and even the telescope itself. To unveil it, the team cultivated a novel statistical filtering methodology to eradicate these foreground signals and segregate the most plausible emission originating from hydrogen gas dating back to roughly 800 million years following the Big Bang.

This innovative strategy yielded the most immaculate radio depiction thus far of the early universe and imposed the most rigorous constraints to date on the strength of the 21-centimeter transmission, the team indicated in the study.

Despite concentrating on what Nunhokee characterized as “sort of a tranquil region where we only have a scattering of sources,” and utilizing “the finest data accessible to us,” the team unearthed no substantiation of the telltale transmission. “Given its exceptional subtlety, it proves exceedingly challenging,” she remarked.

Following the refinement of the data, the researchers failed to discern the distinctive signature that would denote a “cold inception” to reionization. This attribute would have been perceptible within their data had the universe, approximately 800 million years following the Big Bang, remained frigid until the initial stars ignited, thus the outcome implied that the universe was warmer than anticipated, according to the investigation.

“As the universe advanced, the gas amidst galaxies expands and cools, thus we would anticipate it to be exceptionally, exceptionally cold,” expressed study lead author Cathryn Trott, a professor at the Curtin Institute of Radio Astronomy, in a declaration. “Our measurements reveal that it is at least heated by a definite quantity. Not substantially, yet it informs us that exceedingly cold reionisation is negated — that’s genuinely intriguing.”