Dec 19, 2024 11:30 PM
Astronomers need to escape the 'supervoid' to solve cosmology crisis
https://www.space.com/the-universe/hubbl...ogy-crisis
EXCERPTS: New research suggests that a troubling disparity in the rate of expansion of the universe, known as the Hubble constant, may arise from the fact Earth sits in a vast underdense region of the cosmos.
The issue has come to be known as the "Hubble tension." It arises from the fact that there are two ways to calculate the Hubble constant at the universe's current age, but these methods do not agree.
The team behind this research suggests that this issue arises from the fact that our galaxy, the Milky Way, sits in an underdense region or "supervoid." That would mean that space would appear to expand faster in this "Hubble bubble," officially known as the Keenan-Barger-Cowie (KBC) supervoid (also slightly unflatteringly referred to as "the local hole") thus skewing our observations.
"Voids are regions of the universe where the density is below average," team member and University of Saint Andrews cosmologist Indranil Banik told Space.com. "Supervoids are voids larger than about 300 million light-years."
The universe is expanding at an incredibly rapid rate, but though your commute to work may seem to get longer each day, this is only a noticeable factor at vast cosmic scales. That means that the Hubble constant measures the speed at which distant galaxies recede away from each other.
This may initially seem to make a discrepancy in rates of the Hubble constant a less pressing issue. After all, it doesn't affect how far you have to reach for your morning coffee.
The problem is without understanding how fast the universe is expanding, cosmologists can't understand how the cosmos evolved, and our best model of this evolution, the Lambda Cold Dark Matter (Lambda CDM) or "the standard model of cosmology," is missing something.
So, the Hubble tension is undoubtedly not something scientists can work around or ignore. The largest known supervoid in the universe is the Eridanus supervoid, which is 1.8 billion light-years wide, but the KBC supervoid is no slouch in the size department either.
"The KBC supervoid is a region that is about 20% less dense than the cosmic average, centered roughly where we are and extending out to about a billion light years," Banik said. "Typically, when people measure the Hubble constant using distances and redshifts, they don't go out too far because the universe's expansion rate has changed over time.
"This means that people typically don't look beyond about 2 billion light years. But that would mean observations are within the KBC void."
[...] the theory method averages the Hubble constant over the entire universe, while the observation method only calculates it within the KBC supervoid. Thus, within this "Hubble Bubble," we have a skewed and biased perspective. "This would make the universe locally look like it is expanding faster than it actually is, which in turn could solve the Hubble tension." (MORE - missing details)
https://www.space.com/the-universe/hubbl...ogy-crisis
EXCERPTS: New research suggests that a troubling disparity in the rate of expansion of the universe, known as the Hubble constant, may arise from the fact Earth sits in a vast underdense region of the cosmos.
The issue has come to be known as the "Hubble tension." It arises from the fact that there are two ways to calculate the Hubble constant at the universe's current age, but these methods do not agree.
The team behind this research suggests that this issue arises from the fact that our galaxy, the Milky Way, sits in an underdense region or "supervoid." That would mean that space would appear to expand faster in this "Hubble bubble," officially known as the Keenan-Barger-Cowie (KBC) supervoid (also slightly unflatteringly referred to as "the local hole") thus skewing our observations.
"Voids are regions of the universe where the density is below average," team member and University of Saint Andrews cosmologist Indranil Banik told Space.com. "Supervoids are voids larger than about 300 million light-years."
The universe is expanding at an incredibly rapid rate, but though your commute to work may seem to get longer each day, this is only a noticeable factor at vast cosmic scales. That means that the Hubble constant measures the speed at which distant galaxies recede away from each other.
This may initially seem to make a discrepancy in rates of the Hubble constant a less pressing issue. After all, it doesn't affect how far you have to reach for your morning coffee.
The problem is without understanding how fast the universe is expanding, cosmologists can't understand how the cosmos evolved, and our best model of this evolution, the Lambda Cold Dark Matter (Lambda CDM) or "the standard model of cosmology," is missing something.
So, the Hubble tension is undoubtedly not something scientists can work around or ignore. The largest known supervoid in the universe is the Eridanus supervoid, which is 1.8 billion light-years wide, but the KBC supervoid is no slouch in the size department either.
"The KBC supervoid is a region that is about 20% less dense than the cosmic average, centered roughly where we are and extending out to about a billion light years," Banik said. "Typically, when people measure the Hubble constant using distances and redshifts, they don't go out too far because the universe's expansion rate has changed over time.
"This means that people typically don't look beyond about 2 billion light years. But that would mean observations are within the KBC void."
[...] the theory method averages the Hubble constant over the entire universe, while the observation method only calculates it within the KBC supervoid. Thus, within this "Hubble Bubble," we have a skewed and biased perspective. "This would make the universe locally look like it is expanding faster than it actually is, which in turn could solve the Hubble tension." (MORE - missing details)
