A vast cosmic bubble filled with galaxies that is about 1 billion light-years big and appear to be an ancient remnant from the early universe was recently uncovered by astronomers.
The enormous bubble is known as Hooleilana, a tribute to a Hawaiian creation chant that recounts the beginning of structure and is believed to be a BAO, or baryon acoustic oscillation. More than 13 billion years ago, about 380,000 years after the Big Bang, the universe entered a new translucent phase, leaving behind fossilized imprints of matter.
In accordance with theory, Ho’oleilana, which is only 820 million light-years from the Milky Way, is made up of a whole spherical shell of galaxies with a supercluster center. The gigantic bubble is made up of previously discovered formations, some of which are among the largest known objects in the cosmos, and it also has an enhanced density of galaxies extending from its center.
 |
|
|
The new discovery, which was reported on September 5 in The Astrophysical Journal, will not only aid scientists in unraveling the mysteries of early galaxy evolution, but it may also provide a subtle clue as to the nature of the universe’s expansion rate.
How BAOs are born
On the basis of our present knowledge of the Big Bang and the evolution of the early cosmos, massive BAOs like Ho’oleilana are predicted.
Following the Big Bang, matter in the universe existed as a thick, uniform sea of extremely hot plasma for around 400,000 years, during which time electrons were too energetic to bind to atomic nuclei. Gravity tried to bring together larger pockets of matter due to minor density variations (of around one part in 100,000) inside this sea.
The cosmos was still too hot for particles to stick together when they collided, which caused a conflict between gravity’s pull and radiation’s outward pressure. In the plasma sea, this led to pressure oscillations that resembled sound waves. These pressure oscillations rippled outward, causing small overdensities of matter, which resulted in BAOs.
The universe then cooled to the point that the sea of electrons and nuclei merged into neutral atoms, making the cosmos transparent to radiation, about 380,000 years after the Big Bang. Any matter density peaks finally appeared as enormous bubbles that are heavily populated with galaxies as the bubbles became stuck in situ at that moment.
Astronomers can discover a lot about what created the biggest cosmic structures in the universe by studying and examining trends in galaxy distribution within BAOs.
Piecing together a cosmic jigsaw
The Sloan Digital Sky Survey, which photographed a portion of Ho’oleilana’s shell structure, discovered the first indications of the planet in 2016. However, because the full size of the billion-light-year-wide bubble remained unknown, that shell was never connected to a BAO.
According to the primary author of the new study and astronomer from the University of Hawaii, Brent Tully, “We were not looking for it.” It is so enormous that it extends beyond the boundaries of the area of the sky that we were examining.
The researchers created a three-dimensional picture of the enormous bubble using data from Cosmicflows-4, the largest-ever collection of exact galaxy distance measurements. This allowed them to see Ho’oleilana’s whole spherical shell and to understand how its numerous galaxies are organized.
Co-author and self-described mapper Daniel Pomarede of CEA Paris-Saclay University in France remarked, “Building this map and viewing the huge shell structure was an awe-inspiring task.
Hooleilana’s content and relationship to its surroundings can be better understood by “mapping it in three dimensions,” the author continued. The process of creating this map and observing how the massive shell structure of Hooleilana is made up of components that have previously been recognized as some of the largest structures in the cosmos was astounding.
The Sloan Great Wall, the Hercules complex, the Coma Great Wall, the Boötes Supercluster (near the core of the bubble), and the vast Boötes Void, which is a roughly 400-million-light-year-wide spherical underdensity of galaxies, are some of the previously identified enormous structures that are now linked to Ho’oleilana.
In conflict with the Hubble constant?
Ho’oleilana’s discovery may have far-reaching effects beyond only improving our knowledge of the hierarchy of adjacent galactic superstructures. Tully claims that the size and vicinity of Hooleilana call into question the universe’s alleged expanding rate.
“The very large diameter of one billion light years is beyond theoretical expectations,” Tully declared. “This BAO is closer than expected, implying a high value for the universe’s expansion rate, if its formation and evolution are consistent with theory.”
The Hubble constant, often known as the universe’s expansion rate, is now estimated to be between 67 and 74 km/s per megaparsec. However, the researchers determined a slightly quicker expansion rate of between 74.7 and 76.9 kilometers per second per megaparsec based on their examination of Hooleilana as a BAO in the latest study. If this conclusion is validated, it might further muddy the debate over how quickly the universe is actually expanding.
The finding of Hooleilana highlights the numerous mysteries that the cosmos still bears, especially in light of its enormous size and close proximity to the Milky Way. The researchers note that additional observations and research are required, as with all findings, in order to properly understand the true nature of this preserved bubble from the early cosmos.