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The red region (left) shows the shell closed by the Baryon Acoustic Oscillation, with individual galaxies shown as small bright dots. The blue filaments represent the great Cosmic Web, with features formerly known as Laniākea highlighted. Credit: Frédéric Durillon, Animea Studio; Daniel Pomarède, IRFU, CEA University of Paris-Saclay
The University of Hawai’i led discovery of a giant 820-million-light bubble from Earth is believed to be a fossil-like remnant of the birth of the universe. Astronomer Brent Tully from the UH Institute for Astronomy and his team discovered a bubble in the galaxy network. The entity was named Hoʻoleilana, a name derived from the Kumulipo, a Hawaiian creation song that evokes the origins of the structure.
New findings, published in The Astrophysical Journalmention that these large structures are predicted by the Big Bang theory, as a result of 3D ripples found in the first natural objects, known as Baryon Acoustic Oscillations (BAO).
“We weren’t looking at it. It’s so big that it’s at the edge of the part of the sky we’ve been analyzing,” Tully explained. “As the expansion of the intergalactic pressure is a stronger signal than expected. The very large size of a billion light years is beyond the theoretical expectations. If its composition and evolution are consistent with the theory, this BAO is closer than expected, which means a high value of the expansion rate of the universe.
Astronomers discovered the bubble using data from Cosmicflows-4, currently the largest collection of accurate distances to galaxies. Tully has published a special catalog for autumn 2022. His research team believes this may be the first time astronomers have identified a structure associated with the BAO. This discovery could help strengthen scientists’ knowledge of the effects of evolution on the galaxy.
Big bubbles of stuff
In the well-established Big Bang theory, for the first 400,000 years, the universe was a hot plasma ball like the inside of the sun. Within the plasma, electrons are separated from the nuclei of atoms. During this time, the slightly higher density regions began to collapse under gravity, as the deep shower of radiation tried to push matter inward. This battle between gravity and radiation causes the plasma to spin or rotate and spread outwards.
The largest waves in the universe depended on the distance a sound wave could travel. It is determined by the speed of sound inplasma, this distance was almost 500 million light-years, and it was fixed after the universe cooled and ceased to beplasma, leaving large three-dimensional waves. Over the course of eons, galaxies form at peak densities, in giant bubble-like structures. The distribution patterns of galaxies, properly understood, can reveal the characteristics of these ancient messengers.
“I am the artist of the group, and mapping Hoʻoleilana in three dimensions helps us understand its context and relationships with its surroundings,” said researcher Daniel Pomarede of the CEA of Paris-Saclay University in France. “It was an amazing process to build this map and see how the massive shell of Hoʻoleilana is made of materials that have been identified in the past as some of the largest structures in the universe.”
The same group of researchers identified the Laniākea Supercluster in 2014. That structure, which includes the Milky Way, is small in comparison. Stretching to a diameter of about 500 million light-years, Laniākea extends to the nearest edge of this very large bubble.
To reveal one BAO
Tully’s team found that Hoʻoleilana was recognized in a 2016 research paper as the most prominent of many shell-like structures seen in the Sloan Digital Sky Survey. However, previous work did not reveal the full extent of the structure, and the group did not conclude that it had discovered BAO.
Using the Cosmicflows-4 catalog, the researchers were able to see the entire spherical shell of galaxies, identify their centers, and show that there is a statistical increase in the mass of galaxies in all directions from that center. Hoʻoleilana includes many previously known structures discovered by astronomers, such as the Harvard/Smithsonian Great Wall containing the Coma Cluster, the Hercules Cluster and the Sloan Great Wall. The Boötes Supercluster resides at its center. The history of the Boötes Void, a large circular void, lies within Hoʻoleilana.
Ho’oleilana’s Influences
A simulation test showed that the shell structure identified as Hoʻoleilana had less than a 1% chance of being statistically dangerous. Hoʻoleilana has the theoretically expected characteristics of a baryon acoustic oscillation, including the prominence at its center of a rich massive cluster; however, it appears stronger than expected.
In detail, Hoʻoleilana is slightly larger than expected from the standard model theory of cosmology, and what has been found in previous mathematical studies of the separation of galaxies. Quantification is related to observations of the expansion rate of the universe and the movement of galaxies on large scales that also present subtle problems with the standard model.
More information:
R. Brent Tully et al, Ho’oleilana: An Individual Baryon Acoustic Oscillation?, The Astrophysical Journal (2023). DOI: 10.3847/1538-4357/aceaf3
R. Brent Tully et al, Cosmicflows-4, The Astrophysical Journal (2023). DOI: 10.3847/1538-4357/ac94d8
Journal information:
The Astrophysical Journal
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