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Transmasc flag colorpicked from artist’s impression of galaxy formation in the early universe

Study: Early dark energy could resolve cosmology’s two biggest puzzles

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Study: Early dark energy could resolve cosmology’s two biggest puzzles

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.

One puzzle in question is the “Hubble tension,” 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.

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.

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.

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 today in the Monthly Notices of the Royal Astronomical Society, the team modeled the formation of galaxies in the universe’s 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’ observations.

“You have these two looming open-ended puzzles,” says study co-author Rohan Naidu, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research. “We find that in fact, early dark energy is a very elegant and sparse solution to two of the most pressing problems in cosmology.”

The study’s 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.

Big city lights

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.

But in 2023, NASA’s 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.

“The 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,” Shen says. “And we don’t expect that clustering of light so early on.”

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.

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’s 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.

Galaxy skeleton

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 — regions of space where gravity happens to be stronger, and where matter begins to accumulate.

“We believe that dark matter halos are the invisible skeleton of the universe,” Shen explains. “Dark 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.”

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 “cosmological parameters.” Cosmological parameters are the basic ingredients, or mathematical terms, that describe the evolution of the universe.

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

The MIT team reasoned that if early dark energy affects the universe’s 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.

“What 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,” Naidu says. “It means things were more abundant, and more clustered in the early universe.”

“A priori, I would not have expected the abundance of JWST’s 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,” says Marc Kamionkowski, professor of theoretical physics at Johns Hopkins University, who was not involved with the study. “I 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’s a clever — and hopefully ultimately fruitful — thing to try.”

“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,” Vogelsberger concludes. “In the future, we can incorporate this into large cosmological simulations to see what detailed predictions we get.”

This research was supported, in part, by NASA and the National Science Foundation.

JWST and the First Galaxies

The standard model (pre-JWST) predicted that the first galaxies would be made of population III stars, almost pure hydrogen and helium with little or no metallicity (atoms beyond Helium), simply because they were made from the material newly created after the big bang, and stars hadn't yet started to fuse these atoms together to make heavier elements.

With Hubble observations, galaxies no matter how far back we looked, seem to obey this simple rule, that the larger the amount of stars, the more metallicity the galaxy had (taking account of starburst galaxies).

Then JWST came along, and found MUCH larger galaxies than was expected in the early universe, and seemed to throw this rule book out completely, finding the very first galaxies were not only much larger than expected, but without the metallicity relationship we see in all Hubble observable galaxies.

That at first sight may appear to challenge the model, however astronomers from the Danish Cosmic Dawn Centre believe some models did actually predict this, and that after the first stars were created, galaxies begin to form but there's still a large amount of neutral hydrogen being pulled in and forming low metallic (population III) stars. This can account for the observations without redrawing the rules.

If this is indeed true, then what we're looking at in these first galaxies, are population III stars but not necessarily the first generation of them.

As the mass increases around clusters of stars, it pulls in more gas, creates more stars, which increase the mass, pulling in even more gas. The entire process not too dissimilar to how stars are born in the first place, would allow for exponential growth assuming enough neutral hydrogen was available, finally being re-seeded by supernova and the more metal rich elements formed in the first wave of stars, but that process would have taken some time to switch.

The conclusion being, galaxies grew large very quickly, then as they pushed away from each other, became isolated and fed more on the elements within, occasionally pulling in more materials as they came across them or combined via mergers.

#big bang #jwst #galaxies #galaxy formation #stars #astronomy #cosmology

A Theory On Black Holes

Today i just want to talk about black holes.

So we all know that black holes can be very dangerous, but aren't close enough to earth to pose a danger to us.

If you were to get too close to a black hole you would go through a process called "spaghettification" which is when the gravitational force of the BH causes you to stretch in the direction of the BH (and compressed perpendicular to it as you fall). It is a very painful process.

Spaghettification can happen to anything, there just needs to be a strong enough gravitational field.

Now, that i have explained spaghettification i can move on to the theory part.

(I actually have 2 theories on black holes.)

So black holes basically suck in everything around them, and i was wondering what would happen to all that matter if a BH was to explode. I came to a conclusion that maybe, just maybe a new galaxy could form. I know it's far fetched but that's why it is called a theory.

To go into more detail, all the matter that the BH swallowed, has to go somewhere right? So where would it go if the BH exploded? It could form new planets and stars, create entirely new solar systems.

The only thing is scientists created computer models to understand the formation of galaxies and it indicated that they are formed when dark matter joins and groups together.

It could be possible though, maybe.

Let me know if you want to know my other theory. :)

#black holes #astronomy #outer space #theory #theories #galaxy formation

A spinning disk galaxy has been found in the early universe. Its existence is a surprise.

Astronomers have spotted the oldest disk galaxy they’ve ever seen. Shaped like a pancake, it’s been around for billions of years. In fact, this galaxy got its flat shape a mere 1.5 billion years after the universe was born.

That’s far earlier than astronomers had expected.

The universe was born as a single point in what is known as the Big Bang. It then stretched like an inflated balloon. Scientists think the Big Bang happened about 13.8 billion years ago. A little more than a billion years later, there’s this pancake galaxy.

Scientists had thought the type of pancake galaxy just seen would not develop for at least 3 billion to 4 billion years after the Big Bang.

This galaxy is disk-shaped, just like the Milky Way galaxy in which we live. Our galaxy has spiral arms. The old galaxy may have those too. That’s important to note. It means that the old disk galaxy formed its pancake shape and spiral structure pretty quickly after the Big Bang. It suggests galaxies like the Milky Way can grow up relatively quickly, astronomers now say.

The oldest disk galaxy ever spotted is shown in radio waves. Astronomers observed it with the ALMA radio telescope in Chile. CREDIT: M. NEELEMAN, ESO, NAOJ, ALMA, S. DAGNELLO/NRAO, AUI, NSF

Marcel Neeleman works at the Max Planck Institute for Astronomy in Heidelberg, Germany. He headed a team of astronomers that reported the new find May 21 in Nature.

Such an old disk galaxy “challenges the accepted paradigm [PAIR-uh-dyme] for how disk galaxies form and evolve in the universe,” says Rachel Somerville. She is an astrophysicist and works at the Flatiron Institute in New York City. She was not involved with the new study.

The accepted idea had been that the earliest galaxies probably where not flat but shaped like a ball. The galaxies were made with the help of dark matter. That’s invisible stuff in the universe. We don’t know what it is yet. Still, dark matter has mass. So it could pull in surrounding gas and dust to make stars.

Explainer: What is a computer model?

As more material got pulled in, galaxies that were round and blobby emerged. At least, that’s what astronomers had observed before. It’s also what computer models suggest. Theory had suggested that creating those early galaxies was a violent process. Gas got scrambled and heated. Hot gas expands. That should make the early galaxies spherical blobs. They were too hot for the gas to settle into a disk. Only when that gas had lots and lots of time to cool off should it collapse into bright, starry disk galaxies.

Or so researchers thought.

#science #scied #sciblr #oldest disk galaxy #galaxy formation #space

This One Distant, Red, Gas-Free Galaxy Defies Astronomers' Expectations

“When two similarly-sized galaxies merge, it triggers a starburst: a massive formation of new stars. Under the right circumstances, some gas will form stars while the remainder is expelled, lost forever to the intergalactic medium. Once the gas for forming new stars is used up, the galaxy simply ages as the bluest, most massive stars die off. Over billions of years, only the redder, dimmer, lower mass stars remain.”

In astronomy, young galaxies actively form stars, and glow bright blue through the process. Only after many billions of years and at least one cataclysmic event do galaxies settle down into a gas-free, red state, once all the bluer stars have died out. “Red and dead” galaxies appear in the late Universe, normally as giant elliptical galaxies that lost their gas aeons ago.

Which is why this one galaxy is so puzzling: it’s red, dead, massive and compact, but it’s also sending us its light from 10.8 billion years ago!

How did this galaxy get so old-looking when it’s actually so young? The mystery continues, but here’s what we know so far.

#galaxy formation #star formation #red and dead #astronomy #space #universe

From Astronomy Picture of the Day; February 19, 2018:

Galaxy Formation in a Magnetic Universe Video Credit: IllustrisTNG Project; Visualization: Mark Vogelsberger (MIT) et al.; Music: Gymnopedie 3 (Composer: Erik Satie, Musician: Wahneta Meixsell)

How did we get here? We know that we live on a planet orbiting a star orbiting a galaxy, but how did all of this form? To understand details better, astrophysicists upgraded the famous Illustris Simulation into IllustrisTNG -- now the most sophisticated computer model of how galaxies evolved in our universe. Specifically, this featured video tracks magnetic fields from the early universe (redshift 5) until today (redshift 0). Here blue represents relatively weak magnetic fields, while white depicts strong. These B fields are closely matched with galaxies and galaxy clusters. As the simulation begins, a virtual camera circles the virtual IllustrisTNG universe showing a young region -- 30-million light years across -- to be quite filamentary. Gravity causes galaxies to form and merge as the universe expands and evolves. At the end, the simulated IllustrisTNG universe is a good statistical match to our present real universe, although some interesting differences arise -- for example a discrepancy involving the power in radio waves emitted by rapidly moving charged particles.