Massive ancient cosmological structure given Hawaiian name — Ho‘oleilana

LIHU‘E — As humans first inhabited Hawai‘i largely through celestial navigation, it’s only fitting that Hawai‘i name celestial bodies, too.

A University of Hawai‘i-led astronomy team has discovered an immense bubble 820 million light-years from Earth, believed to be a fossil-like remnant of the universe’s very beginnings. Following their findings, the team chose to give the newly-discovered structure an apt Hawaiian name — Ho‘oleilana.

“It’s drawn from the Hawaiiian chant of the origin of our universe (the Kumulipo), evoking this idea of the birth of the universe,” said Brent Tully, emeritus astronomer at the UH Institute for Astronomy and the project’s lead researcher. “So it was a fitting name.”

In the well-established Big Bang theory, the universe’s first 400,000 years consisted of a hot plasma, similar to the Sun’s interior today.

Higher-density regions of the plasma faced a push-and-pull effect during this period — the dense region’s own gravitational pull forced the matter to collapse in on itself, while radiation fought to push the matter apart. This effect created an oscillating ripple within the plasma, known as Baryon Acoustic Oscillations (BAOs), that spread the plasma outward in these large bubbles.

As the universe cooled and the universe’s first atoms began to form, these cosmological bubbles became effectively frozen in space, and continue to exist today.

“When you have a little bit higher density, there’s more gravity — and that’s where structures like galaxies are more likely to form,” said Roy Gal, associate astronomer at the UH Institute for Astronomy. “So when we look at the universe today, and we make a map of the galaxies, what we can see is that there is evidence for these ripples.”

With these structures having formed during the early universe, and with their structure largely unchanged since then, BAOs provide astronomers a unique glimpse at what the young universe was like, and how it’s developed into what it is today.

“In a lot of ways, we can compare it to geology,” said Roy Gal, associate astronomer at the UH Institute for Astronomy. “We can see ancient tsunamis, for instance, because you can see where the tsunami deposited ocean material on land that isn’t normally there … And from that, you can deduce something about how big the ocean was, how big the earthquake was, stuff like that, even though you didn’t see it.”

Prior to the discover of Ho‘oleilana though, no BAO had actually been directly identified, only statistically estimated.

“They’re too weak to see individually, so people thought,” Tully explained. “Anyways, we think we’ve actually seen one — an individual one. There had been strong evidence for them to have been seen statistically, but never had it been identified that, ‘Oh, this is an individual Baryon Acoustic Oscillation.’ So, that’s a big first.”

Ho‘oleilana is unfathomably large — at 1 billion light-years across, the BAO is equal to more than 1 percent of the entire observable universe.

While the team anticipated Ho‘oleilana would be immense, its size exceeded even their estimation by about 10 percent. As such, their findings now raise questions over fundamental properties of the universe.

“That implication, direct implication, is that the universe hasn’t been expanding in quite the way that our theory anticipated,” Tully said.

Known among astronomers as “Hubble tension,” stark differences in how quickly the universe should theoretically be expanding, and how fast it actually appears to be expanding, have befuddled scientists for decades.

As is typical of scientific discoveries, the team’s critical findings now leave their field with more questions than answers.

“Here is another little bit of evidence — not compelling in itself, but a suggestion that, again, is consistent with this idea that there’s something wrong at some subtle level in our ideas of how the universe has unfolded,” Tully said.

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Jackson Healy, reporter, can be reached at 808-647-4966 or jhealy@thegardenisland.com.