Newly found bubble of galaxies, a billion light-years wide
Where are our Earth and Milky Way galaxy in this illustration of the billion-light-year-wide bubble of galaxies, just discovered by astronomers in Hawaii? Notice the Milky Way at the bottom of the green area called Laniakea, which is a supercluster of galaxies, home to our Milky Way and approximately 100,000 other nearby galaxies. And the new bubble? The even-bigger enclosed bubble is on the left in this illustration. Individual galaxies are depicted as tiny, luminous specks. Image via Frédéric Durillon, Animea Studio/ Daniel Pomarède, IRFU, CEA University Paris-Saclay/ UH.
A vast bubble of galaxies
Astronomers in Hawaii said this week (September 5, 2023) that they’ve discovered an immense bubble 820 million light-years from Earth. They called it:
… a fossil-like remnant of the birth of the universe.
And they said its size – a billion-light-years in diameter – is:
… beyond theoretical expectations.
Astronomer Brent Tully of the Institute for Astronomy at the University of Hawai’i – and his team – unexpectedly found the bubble within a known web of galaxies, a piece of the great cosmic web of galaxies thought to make up our universe as a whole.
They’ve given the name Ho’oleilana to the new super bubble. It’s a name drawn from the Kumulipo, a Hawaiian creation chant evoking the origin of structure.
The Astrophysical Journal published the new findings on September 5.
3D ripples in the early universe
This same team of researchers also identified the Laniakea Supercluster in 2014. That structure, which includes our Milky Way, is small in comparison. Stretching to a diameter of about 500 million light years, Laniakea extends to the near edge of this much larger bubble.
Astronomers located the bubble using data from Cosmicflows-4 – a catalog of distances to 55,877 galaxies – which Tully and his team published in the fall of 2022.
Their statement explained that – according to the standard model of cosmology – massive structures such as this giant bubble are the result of 3D ripples found in the material of the early universe. Scientists call them BAQ, which stands for Baryon Acoustic Oscillations. Tully explained:
We were not looking for it. It is so huge that it spills to the edges of the sector of the sky that we were analyzing.
As an enhancement in the density of galaxies it is a much stronger feature than expected. The very large diameter of one billion light years is beyond theoretical expectations.
If its formation and evolution are in accordance with theory, this BAO is closer than anticipated, implying a high value for the expansion rate of the universe.
The astronomers’ statement added that they believe:
… this may be the first time astronomers identified an individual structure associated with a BAO. The discovery could help bolster scientists’ knowledge of the effects of galaxy evolution.
What’s a BAQ?
In Big Bang theory, during the first 400,000 years of our universe, a cauldron of hot plasma – similar to the interior of the sun – pervaded all of space. Electrons within the plasma were separated from their atomic nuclei.
And, during this period, the astronomers said:
… regions with slightly higher density began to collapse under gravity, even as the intense bath of radiation attempted to push matter apart. This struggle between gravity and radiation made the plasma oscillate or ripple and spread outward.
The largest ripples in the early universe depended on the distance a sound wave could travel. Set by the speed of sound in the plasma, this distance was almost 500 million light years, and was fixed once the universe cooled and stopped being a plasma, leaving vast three-dimensional ripples.
Throughout the eons, galaxies formed at the density peaks, in enormous bubble-like structures.
And the astronomers said that:
… the distribution of galaxies, properly discerned, could reveal the properties of these ancient messengers.
Mapping the bubble of galaxies
Daniel Pomarède of CEA Paris-Saclay University in France said:
I am the cartographer of the group, and mapping Ho’oleilana in three dimensions helps us understand its content and relationship with its surroundings.
It was an amazing process to construct this map and see how the giant shell structure of Ho’oleilana is composed of elements that were identified in the past as being themselves some of the largest structures of the universe.
Uncovering a single BAO
Tully’s team discovered that Ho’oleilana had been noted in a 2016 research paper as the most prominent of several shell-like structures seen in the Sloan Digital Sky Survey. But, they said:
The earlier work did not reveal the full extent of the structure, and that team did not conclude they had found a BAO.
Using the Cosmicflows-4 catalog, [these] researchers were able to see a full spherical shell of galaxies, identify its center, and show that there is a statistical enhancement in the density of galaxies in all directions from that center.
They said Ho’oleilana encompasses many structures that had been previously found and are well known to astronomers who study galaxies, such as the Harvard/Smithsonian Great Wall containing the Coma Cluster, the Hercules Cluster of galaxies and the Sloan Great Wall.
The Boötes Supercluster resides at its center.
And the historic Boötes Void, a massive empty spherical region, lies inside Ho’oleilana.
Bottom line: Astronomers have discovered an immense bubble of galaxies, 820 million light-years from Earth and a billion light-years wide. They named it Ho’oleilana, from a Hawai’ian creation chant.