In our galactic neighborhood, astronomers have made a groundbreaking discovery—the first-ever “bubble of galaxies” known as Ho’oleilana, a colossal cosmic structure that’s believed to be a preserved relic from shortly after the Big Bang. This immense bubble extends across a staggering billion light years, dwarfing the size of our Milky Way galaxy by a factor of 10,000. Remarkably, Ho’oleilana is not hidden in the distant reaches of the cosmos; instead, it resides relatively nearby at a distance of 820 million light years from our home galaxy, within what astronomers refer to as the nearby universe.
Describing this celestial phenomenon, astrophysicist Daniel Pomarede of France’s Atomic Energy Commission characterizes Ho’oleilana as a “spherical shell with a heart.” Within this heart lies the Bootes supercluster of galaxies, encircled by a vast cosmic void often referred to as “the Great Nothing.” This shell also encompasses several other galaxy superclusters already familiar to the scientific community, including the immense Sloan Great Wall.
The revelation of this cosmic bubble, detailed in a research paper co-authored by Pomarede and published in The Astrophysical Journal, represents a significant milestone in a long scientific journey. It validates a concept first proposed in 1970 by American cosmologist Jim Peebles, who would later receive a Nobel Prize in Physics. Peebles theorized that in the early universe, when it was a seething sea of hot plasma, the interplay of gravity and radiation generated sound waves known as baryon acoustic oscillations (BAOs). These sound waves, as they rippled through the plasma, gave rise to these cosmic bubbles. Around 380,000 years after the Big Bang, as the universe cooled, this process halted, preserving the bubble structures. As the universe expanded, these bubbles grew, leaving them as fossilized remnants from the aftermath of the Big Bang.
While astronomers had previously detected signals of BAOs in 2005 by studying nearby galaxies, the recently discovered bubble stands out as the first known individual baryon acoustic oscillation, marking a groundbreaking achievement for the research team.
Interestingly, the astronomers have given this remarkable cosmic structure the name “Ho’oleilana,” derived from a Hawaiian creation chant, which translates to “sent murmurs of awakening.” This name originates from the lead author of the study, Brent Tully, an astronomer affiliated with the University of Hawaii.
The serendipitous discovery of Ho’oleilana was part of Tully’s work, involving an extensive search through new catalogs of galaxies. As Pomarede noted, the find was entirely unexpected, and Tully described the bubble as being so vast that it extends to the limits of the portion of the sky they were investigating.
To visualize the three-dimensional shape of Ho’oleilana and the arrangement of the galaxy archipelagos within it, the researchers collaborated with Australian cosmologist and BAO expert Cullan Howlett, who used mathematical techniques to accurately determine the spherical structure that matched the data.
This groundbreaking discovery may be the first of its kind, but astronomers anticipate the possibility of identifying more such cosmic bubbles throughout the universe. The Euclid space telescope, launched by Europe in July, offers a broad perspective of the cosmos, which could facilitate the detection of additional bubbles. Furthermore, the Square Kilometre Array, massive radio telescopes under construction in South Africa and Australia, may provide a new perspective on galaxies from the vantage point of the Southern Hemisphere, potentially leading to further discoveries in the realm of cosmic structures.
– 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