An illustration of the bubble of galaxies called Hoʻoleilana
Frédéric Durillon, Animea Studio; Daniel Pomarède, IRFU, CEA University Paris-Saclay
A huge bubble of galaxies that is one billion lightyears across could be a remnant of the ripples caused by the Big Bang, according to astronomers who have mapped the structure.
The structure, named Hoʻoleilana by University of Hawaii scientists, is thought to have been caused by so-called Baryon Acoustic Oscillations (BAOs).
These were ripples in the particles of the early Universe in the period following the Big Bang, when planets, solar systems and galaxies were not yet fully formed.
As the ripples went outward, they created areas of density in the particles, causing bubble-like structures in which galaxies eventually coalesced.
Until now, the BAOs were just a prediction – part of the wider Big Bang theory. No specific structures in the Universe had been found which mimicked their patterns.
But Hoʻoleilana fits the description of these huge cosmic bubbles perfectly, according to Brent Tully, who led the study at the University of Hawaii’s Institute for Astronomy.
“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,” he said.
“As an enhancement in the density of galaxies it is a much stronger feature than expected. The very large diameter of 1bn 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 bubble is absolutely huge. It is made up of several superclusters, structures which themselves are thought to be among the Universe’s largest arrangements of matter.
This includes the Hercules Supercluster, the Corona Borealis Supercluster and the Sloan Great Wall. All of these structures contain thousands of galaxies.
In the middle of Hoʻoleilana sits the Bootes Supercluster and the Bootes Void, an immense space of nothingness which is an incredible 330m lightyears across.
Daniel Pomarede, from the CEA Paris-Saclay University, who contributed to the research, said: “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.”
The research was published on 5 September in The Astrophysical Journal.