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Using a tactile 3D model of Ho’oleilana, a real BAO (Baryonic Acoustic Oscillations) structure discovered in the cosmic web, students explore how these ancient ripples shaped the Universe and how astronomers use them as a cosmic ruler to measure distances and study the expansion of the universe. Through hands-on exploration, students identify galaxy clusters and superclusters on the model, recognizing large-scale patterns in the distribution of matter. Using the 3D models developed in the A Touch of the Universe project, students analyze how matter is distributed across space and how immense gravitational structures shape cosmic dynamics through tactile exploration, guided discussion, and mathematical reasoning. The activity is designed to be inclusive and hands-on, ensuring that complex cosmological phenomena are accessible to all learners, including those who are visually impaired.
After the Big Bang, the matter in the universe was almost evenly distributed, like a vast sea of particles. Gravity tried to put this matter together to form structures and galaxies. But when matter came together, it got very hot, and that heat caused matter to push outward. Thus a kind of chain of "bounces" was created: gravity attracted matter, heat pushed it away, and it started again.
This tug-of-war game created something similar to sound waves traveling through the universe, like the ripples spreading in water when you throw a stone. These waves expanded as spherical bubbles, dragging some of the matter with them.
About 380,000 years after the Big Bang, the Universe had cooled enough for the first atoms to form. At that point, gravity won the game, beginning to form galaxies and other large-scale structures. The bubbles of matter that had formed earlier left a kind of "imprint" on the distribution of galaxies: these are the acoustic oscillations of baryons, or baryonic acoustic oscillations (BAOs).
A BAO is essentially a large sphere , a “bubble”, of millions of galaxies. The galaxies are not evenly distributed throughout the sphere but are clustered together on its outer shell, like a massive cosmic bubble.
Although these structures are subtle, they are very important. By studying them, astronomers can better understand how the Universe is expanding and how that expansion has changed over time. By comparing the BAOs size at different epochs with their original size when they froze in the early Universe, astronomers can measure how much the Universe has expanded and how much this expansion has been accelerated due to the presence of a mysterious dark energy.
Image: Illustration of Hoʻoleilana. Red region (left) shows the enclosed shell with individual galaxies depicted as luminous tiny specks. Photo credit: Frédéric Durillon, Animea Studio; Daniel Pomarède, IRFU, CEA University Paris-Saclay. This work benefited from a government funding by France 2030 (P2I-Graduate School of Physics) under reference ANR-11-IDEX-0003. See https://www.hawaii.edu/news/2023/09/05/bubble-of-galaxies-hooleilana/
Ho’oleilana is a Hawaiian word meaning "murmurs of awakening" and appears in a Hawaiian song of creation that evokes the origin of things.
Ho'oleilana is considered to be a BAO since it is a bubble-like structure with a shell formed by a multitude of galaxies whose radius coincides with what is predicted by the Big Bang theory: about 500 million light years.
The Boötes supercluster is located at the center of Ho'oleilana. On the surface of this cosmic bubble, millions of galaxies are grouped together in larger structures such as the galaxy clusters and superclusters of Coma, Hercules, Leo or the Sloan Great Wall.
It is important to note that this structure is actually very subtle and that it is totally submerged in the general distribution of galaxies that forms the large-scale superstructure of the Universe. Advanced statistical methods are needed to detect this object as an excess over the general distribution of galaxies in the Universe. If we were to consider all galaxies that we can see in this region, the spherical structure would hardly be noticeable.
Image: the printed 3D model
To better illustrate the complexity of Ho'oleilana and to make it accessible to visually impaired publics, we will use a 3D model developed by our group as part of the "A Touch of the Universe" 3D astronomy model collection.
The first thing you notice about the model is its spherical shape: we have in our hands the representation of a bubble of galaxies that originated only 380,000 years after the Big Bang.
The spherical surface is covered with small spheres that represent groups of galaxies, which in turn belong to larger groupings: galaxy clusters and superclusters.
The gaps in the surface of the sphere are real, although some have been exaggerated to allow access to its interior.
Inside, at the very center, we find a group of spheres representing the Boötes supercluster. Thin pillars connect it to the surface of the bubble. These pillars don't exist in reality but are necessary to hold the supercluster in its central position within the model.
On the surface of the bubble, we locate some of the most relevant galaxy clusters and superclusters:
The model has been created by Emilio Terol, from a 3D rendering of the real data made by Daniel Pomarède and published in "Ho’oleilana: An Individual Baryon Acoustic Oscillation?" by R. Brent Tully, Cullan Howlett, and Daniel Pomarède, The Astrophysical Journal (2023).
Getting ready:
Activity (ages 10-16):
Activity (ages 16-19+):
Physics & Astronomy:
Mathematics:
Social Sciences:
Accessibility and Inclusion:
