Research presented at the Royal Astronomical Society National Astronomy Meeting on Wednesday showed that data found by analyzing the sounds from the Big Bang, known as "baryon acoustic oscillations," suggest that the Milky Way Galaxy is floating in a region that is less dense than average.
The 2 billion light-year region that scientists have dubbed the "Hubble Bubble" is 20% less dense than the average matter density throughout the universe.
If proven correct, the findings can help settle an issue known as the "Hubble Tension" created by conflicting measurements of the expansion of the universe and could help reveal its true age.
The first measurement is based on small changes in the cosmic microwave background, which is "cosmic fossils" of the first light produced by the universe 380,000 years after the Big Bang, while the second measures distances between type la supernovas or variable stars and their host galaxies.
The first method found the universe expanded at a rate of 67 kilometers per second per megaparsec, while the second found a higher rate of 73.2 kilometers per second per megaparsec.
The study posits, however, that if the Milky Way is sitting in a "Hubble Bubble", it would be expanding faster than a higher-density cosmos.
"A potential solution to this inconsistency is that our Galaxy is close to the center of a large, local void," the study's lead author, Indranil Banik, said in a statement. "It would cause matter to be pulled by gravity towards the higher density exterior of the void, leading to the void becoming emptier with time."
That would make local expansion inside the void faster than it is in denser, more distant regions of the cosmos, he added.
The local void theory would mean the Earth would have to sit about in the center of the low-density "Hubble Bubble."
Banik and his team used the sounds of the Big Bang to bolster previous research from the 1990s, which found fewer galaxies in the local universe than previously believed.
"These sound waves traveled for only a short while before becoming frozen in place once the universe cooled enough for neutral atoms to form," Banik explained. "They act as a standard ruler, whose angular size we can use to chart the cosmic expansion history."
The researchers found that it is 100 times more likely that we live in a cosmic void than a region of average density.
Banik and his team's next step will be to compare their void model to other models to reconstruct the universe's expansion history. They will also explore tweaks to the standard model of cosmology.
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