{"id":25224,"date":"2024-09-17T09:31:07","date_gmt":"2024-09-17T03:46:07","guid":{"rendered":"https:\/\/www.revoscience.com\/en\/?p=25224"},"modified":"2024-09-17T09:31:10","modified_gmt":"2024-09-17T03:46:10","slug":"study-early-dark-energy-could-resolve-cosmologys-two-biggest-puzzles","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/study-early-dark-energy-could-resolve-cosmologys-two-biggest-puzzles\/","title":{"rendered":"Study:\u00a0Early dark energy could resolve cosmology\u2019s two biggest puzzles"},"content":{"rendered":"\n

In the universe\u2019s first billion years, this brief and mysterious force could have produced more bright galaxies than theory predicts.<\/strong><\/em><\/p>\n\n\n

By Jennifer Chu<\/a><\/div>\n\n\n
\"\"
Early dark energy could have triggered the formation of numerous bright galaxies, very early in the universe, a new study finds. The mysterious unknown force could have caused early seeds of galaxies (depicted at left) to sprout many more bright galaxies (at right) than theory predicts. <\/em>IMAGE:<\/strong> Josh Borrow\/Thesan Team<\/figcaption><\/figure>\n\n\n\n

CAMBRIDGE, Mass. — A new study by MIT physicists proposes that a mysterious force known as early dark energy could solve two of the biggest puzzles in cosmology and fill in some major gaps in our understanding of how the early universe evolved. <\/p>\n\n\n\n

One puzzle in question is the \u201cHubble tension,\u201d which refers to a mismatch in measurements of how fast the universe is expanding. The other involves observations of numerous early, bright galaxies that existed at a time when the early universe should have been much less populated.<\/p>\n\n\n\n

Now, the MIT team has found that both puzzles could be resolved if the early universe had one extra, fleeting ingredient: early dark energy. Dark energy is an unknown form of energy that physicists suspect is driving the expansion of the universe today. Early dark energy is a similar, hypothetical phenomenon that may have made only a brief appearance, influencing the expansion of the universe in its first moments before disappearing entirely. <\/p>\n\n\n\n

Some physicists have suspected that early dark energy could be the key to solving the Hubble tension, as the mysterious force could accelerate the early expansion of the universe by an amount that would resolve the measurement mismatch. <\/p>\n\n\n\n

The MIT researchers have now found that early dark energy could also explain the baffling number of bright galaxies that astronomers have observed in the early universe. In their new study, reported in the Monthly Notices of the Royal Astronomical Society<\/a>,<\/em> the team modeled the formation of galaxies in the universe\u2019s first few hundred million years. When they incorporated a dark energy component only in that earliest sliver of time, they found the number of galaxies that arose from the primordial environment bloomed to fit astronomers\u2019 observations. <\/p>\n\n\n\n

\u201c<\/strong>You have these two looming open-ended puzzles,\u201d says study co-author Rohan Naidu, a postdoc in MIT\u2019s Kavli Institute for Astrophysics and Space Research. \u201cWe find that in fact, early dark energy is a very elegant and sparse solution to two of the most pressing problems in cosmology.\u201d<\/p>\n\n\n\n

The study\u2019s co-authors include lead author and Kavli postdoc Xuejian (Jacob) Shen, and MIT professor of physics Mark Vogelsberger, along with Michael Boylan-Kolchin at the University of Texas at Austin, and Sandro Tacchella at the University of Cambridge.<\/p>\n\n\n\n

Big city lights<\/strong><\/p>\n\n\n\n

Based on standard cosmological and galaxy formation models, the universe should have taken its time spinning up the first galaxies. It would have taken billions of years for primordial gas to coalesce into galaxies as large and bright as the Milky Way.<\/p>\n\n\n\n

But in 2023, NASA\u2019s James Webb Space Telescope (JWST) made a startling observation. With an ability to peer farther back in time than any observatory to date, the telescope uncovered a surprising number of bright galaxies as large as the modern Milky Way within the first 500 million years, when the universe was just 3 percent of its current age. <\/p>\n\n\n\n

\u201cThe bright galaxies that JWST saw would be like seeing a clustering of lights around big cities, whereas theory predicts something like the light around more rural settings like Yellowstone National Park,\u201d Shen says. \u201cAnd we don\u2019t expect that clustering of light so early on.\u201d<\/p>\n\n\n\n

For physicists, the observations imply that there is either something fundamentally wrong with the physics underlying the models or a missing ingredient in the early universe that scientists have not accounted for. The MIT team explored the possibility of the latter, and whether the missing ingredient might be early dark energy. <\/p>\n\n\n\n

Physicists have proposed that early dark energy is a sort of antigravitational force that is turned on only at very early times. This force would counteract gravity\u2019s inward pull and accelerate the early expansion of the universe, in a way that would resolve the mismatch in measurements. Early dark energy, therefore, is considered the most likely solution to the Hubble tension.<\/p>\n\n\n\n

Galaxy skeleton<\/strong><\/p>\n\n\n\n

The MIT team explored whether early dark energy could also be the key to explaining the unexpected population of large, bright galaxies detected by JWST. In their new study, the physicists considered how early dark energy might affect the early structure of the universe that gave rise to the first galaxies. They focused on the formation of dark matter halos \u2014 regions of space where gravity happens to be stronger, and where matter begins to accumulate. <\/p>\n\n\n\n

\u201cWe believe that dark matter halos are the invisible skeleton of the universe,\u201d Shen explains. \u201cDark matter structures form first, and then galaxies form within these structures. So, we expect the number of bright galaxies should be proportional to the number of big dark matter halos.\u201d<\/p>\n\n\n\n

The team developed an empirical framework for early galaxy formation, which predicts the number, luminosity, and size of galaxies that should form in the early universe, given some measures of \u201ccosmological parameters.\u201d Cosmological parameters are the basic ingredients, or mathematical terms, that describe the evolution of the universe. <\/p>\n\n\n\n

Physicists have determined that there are at least six main cosmological parameters, one of which is the Hubble constant \u2014 a term that describes the universe\u2019s rate of expansion. Other parameters describe density fluctuations in the primordial soup, immediately after the Big Bang, from which dark matter halos eventually form. <\/p>\n\n\n\n

The MIT team reasoned that if early dark energy affects the universe\u2019s early expansion rate, in a way that resolves the Hubble tension, then it could affect the balance of the other cosmological parameters, in a way that might increase the number of bright galaxies that appear at early times. To test their theory, they incorporated a model of early dark energy (the same one that happens to resolve the Hubble tension) into an empirical galaxy formation framework to see how the earliest dark matter structures evolve and give rise to the first galaxies. <\/p>\n\n\n\n

\u201cWhat we show is, the skeletal structure of the early universe is altered in a subtle way where the amplitude of fluctuations goes up, and you get bigger halos, and brighter galaxies that are in place at earlier times, more so than in our more vanilla models,\u201d Naidu says. \u201cIt means things were more abundant, and more clustered in the early universe.\u201d<\/p>\n\n\n\n

\u201cA priori, I would not have expected the abundance of JWST\u2019s early bright galaxies to have anything to do with early dark energy, but their observation that EDE pushes cosmological parameters in a direction that boosts the early-galaxy abundance is interesting,\u201d says Marc Kamionkowski, professor of theoretical physics at Johns Hopkins University, who was not involved with the study. \u201cI think more work will need to be done to establish a link between early galaxies and EDE, but regardless of how things turn out, it\u2019s a clever \u2014 and hopefully ultimately fruitful \u2014 thing to try.\u201d<\/p>\n\n\n\n

\u201c<\/strong>We demonstrated the potential of early dark energy as a unified solution to the two major issues faced by cosmology. This might be an evidence for its existence if the observational findings of JWST get further consolidated,\u201d Vogelsberger concludes. \u201cIn the future, we can incorporate this into large cosmological simulations to see what detailed predictions we get.\u201d <\/p>\n\n\n\n

This research was supported, in part, by NASA and the National Science Foundation.<\/p>\n

TAGS: <\/strong>physics<\/a> <\/div>","protected":false},"excerpt":{"rendered":"

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