How dark energy could ease ‘Hubble tension’ and galaxy headaches

A new model that proposes that dark energy, the mysterious force driving the universe’s accelerating expansion, emerged in the early cosmos could address two of the most pressing headaches in astrophysics.

One of these headaches is “Hubble tensionrefers to the long-standing apparent discrepancy with the measured rate at which the universe is expanding. The other is that bright galaxies in the early universeat a time when scientists thought the universe should be sparsely populated. The second problem is, James Webb Space Telescope (JWST) began making observations of the early and distant universe.

The new model is the work of a group of scientists from the Massachusetts Institute of Technology (MIT) and the University of Texas at Austin. They think the key to these two puzzles lies in an extra ingredient in the cosmic pudding: early dark energy.

In principle, early dark energy should have been something like this dark energy It drives the expansion of the universe today. But the difference would be that modern dark energy began acting about 4 billion years ago, while early dark energy would have appeared briefly in the early cosmos only thousands of years later. The Big Bang. Then it would be completely destroyed.

Relating to: ‘Hubble problem’ may deepen with new measurement of universe’s expansion

“There are these two vague open-ended puzzles,” says team member Rohan Naidu, a postdoctoral researcher at MIT’s Kavli Institute for Astrophysics and Space Research. made a statement. “We actually see that early dark energy is a very elegant and sparse solution to two of the most pressing problems in cosmology.”

We start working on Hubble tension

The so-called Hubble tension arises from the fact that there are two fundamental ways of measuring the “Hubble constant,” which measures the rate of expansion of the universe, and they don’t agree with each other.

One method looks at objects in the local universe, such as Type Ia Supernovas” astronomers”Standard candles“Because the light output is so uniform, it can be used to measure cosmic distances. The other technique involves making observations of the distant (and therefore early) universe and then calculating by inference how fast the universe is expanding.

But there’s a catch (isn’t there always?): These methods offer different values.

The team behind the new research believe that early dark energy could solve this. As an accelerating force that kicked in just a few thousand years after the Big Bang, this matter would have acted against the force of gravity. This means that there could be a discrepancy in the values caused by a failure to account for early dark energy in the calculation of the Hubble constant. observations of the early universe.

“Early dark energy is a possible addition to the standard cosmological model that would preserve many of its successes and resolve the Hubble tension,” team member Michael Boylan-Kolchin, professor of astronomy at the University of Texas at Austin, said in a statement.

A diagram of the history of the universe suggests that ‘early dark energy’ may have played a role in its beginnings (Image credit: NASA/WMAP Science Team/Artist: Dana Berry)

So what about the second problem, which really starts to emerge when JWST finds early galaxies all nearly the same size? Milky Way in the early universe?

Bright galaxies giving you headaches? Try early dark energy!

This problem arises from the fact that it takes billions of years for hydrogen and helium gas to condense into stars large enough to form large, bright galaxies like the Milky Way.

Still in 2023, JWST detects surprising number of large and bright galaxies Just 500 million years after the Big Bang, the universe was only 3% of its current age of 13.8 billion years.

“The bright galaxies that JWST sees would be like seeing a cluster of lights around major cities, whereas theory predicts something like the light in more rural areas like Yellowstone National Park,” said team leader Xuejian (Jacob) Shen, a Kavli postdoctoral researcher at MIT. “And we don’t expect this cluster of light this early.”

Six bright and massive galaxies in the early universe seen by JWST (Image credit: NASA, ESA, CSA, I. LABBE)

But instead of throwing away all our models of galactic evolution, the team proposes adding early dark energy to the models.

By creating their own model of galaxy formation that takes this into account, the team found that the same early dark energy component that reduces the Hubble stress also suggests the formation of the large, bright galaxies that JWST is now observing.

But this required researchers to change some cosmological parameters of the universe and other celestial components, such as the volume of celestial bodies. dark matter The change in density and mass in the universe immediately after the Big Bang.

It is unclear how early dark energy could have led to the early formation of massive galaxies. Baby Universe — but the fact that this model could kill two cosmic birds with one stone means the team found it worth investigating.

“The fact that a single model can explain these two unrelated issues makes it intriguing and worth investigating in more detail,” Boylan-Kolchin concluded. “As we get more data with JWST and study the oldest light in the universe in more detail, we should really know in the next year or so whether early dark energy is the right answer, which is really exciting.”

The team’s research was published in the journal Monthly Notices of the Royal Astronomical Society.