What does a newborn galaxy look like?
For a long time, many astrophysicists and cosmologists have assumed that newborn galaxies would resemble the familiar spheres or spider-like disks of the modern universe.
But an analysis of new images from the James Webb Space Telescope shows that the baby galaxy was neither an egg nor a disk. They were bananas. Choose your own metaphor, such as a pickle, a cigar, or a surfboard. That’s the tentative conclusion of a team of astronomers who reviewed images of about 4,000 newborn galaxies observed by Webb in the early days.
“This is a surprising and unexpected result, even though there were already signs of this happening with the Hubble Space Telescope,” Viraj Pandya, a postdoctoral fellow at Columbia University, said of the Hubble Space Telescope. He is the lead author of a paper soon to be published in the Astrophysical Journal with the provocative title “Galaxy Going Banana.” Dr. Pandya is scheduled to speak about his research Wednesday at the American Astronomical Society meeting in New Orleans.
If true, the results could revolutionize our understanding of how galaxies emerge and grow, astronomers say. It could also provide insight into the mysterious nature of dark matter, an unknown and invisible substance that astronomers say makes up most of the universe and outnumbers atomic matter by 5 to 1. . Dark matter engulfs galaxies and provides gravitational seedbeds. A new galaxy is born.
The results build on hints from early Hubble observations that early galaxies were shaped like pickles, said UC Santa Cruz astronomer and author of the new paper. said Joel Primack.
In an email, Alan Dressler of the Carnegie Observatory, who was not involved in Dr. Pandya’s study, called the results “important — I think it’s important — if it’s true. It’s very important.”
“I’m somewhat skeptical about this result, given how difficult it is to make such measurements,” he added. “This is especially true for galaxies (I’m talking about galaxies) that are far away, small, and not very bright.”
Dr. Pandya’s team analyzed images of galaxies in a region of the sky smaller than the full moon known as the extended growth strip, studied by many other telescopes, including Hubble. These images were obtained through an international collaboration called the Cosmic Evolution and Early Emission Science (CEERS) Survey.
The research team plans to expand observations to other well-studied regions of the universe. “This will allow us to identify galaxies with different 3D shapes across the sky,” facilitating much-needed spectroscopic follow-up observations, Dr. Pandya wrote in an email.
Galaxies are city-states in space. There are an estimated 2 trillion stars in the visible universe, and each star contains as many as 1 trillion stars. However, the visible universe is only a small part of what is out there. Most of the matter in the universe appears to be in the form of dark matter. Whatever dark matter is, it makes up the invisible bones of the universe we see.
Astronomers now believe that galaxies were formed by random fluctuations in the density of matter and energy during the Big Bang. As the universe expanded, denser regions lagged behind, allowing dark matter to pool and draw in normal matter. This material eventually returned to its original state, glowing as stars and galaxies, or disappearing into black holes. The Webb Telescope was designed to investigate this formative and mysterious era. Equipped with giant mirrors and infrared sensors, it can see the most distant, and therefore oldest, galaxies.
Dr. Pandya and his collaborators investigated the three-dimensional shapes of galaxies by statistically analyzing their two-dimensional projections onto the sky. If these early galaxies were spheres or disks oriented randomly in space, their complete faces would sometimes appear round and circular to a telescope.
But astronomers don’t see much of it. Instead, there are lots of cigars and bananas.
“They appear very linear throughout,” Dr. Pandya said, “and some galaxies show multiple bright clumps arranged like pearls on a necklace.”
Although these rectangular galaxies are rare today, they make up 80% of the galaxies in the CEERS sample, which dates back about 500 million years after the Big Bang.
“Their mass is such that they appear to be the ancestors of galaxies like the Milky Way. This suggests that our own galaxy may have gone through a similar cigar/surfboard morphological stage in the past. ,” Dr. Pandya said.
In the modern universe, galaxies appear to have two basic shapes. One is a featureless round cloud called an ellipse, and the other is a flat, spider-like disk like our home Milky Way.
Obviously, the first newborn didn’t start out that way. Astronomers think the reason may have something to do with the properties of dark matter, but it’s unclear exactly what properties they have or how this happens. .
A leading theory holds that dark matter consists of a cloud of exotic particles left behind by the Big Bang. Computer simulations show that ordinary matter drawn into these clouds by gravity condenses and glows into stars and galaxies.
In a common variant called cold dark matter, these leftover particles would be heavy and slow compared to protons, neutrons, and other more familiar inhabitants of the quantum atomic world. Computer simulations show that cold dark matter would easily clump together to form the large-scale patterns that astronomers see in the sky.
Identifying these slow, heavy particles would shake up the world of particle physics and cosmology. But so far, experiments in laboratories such as CERN’s Large Hadron Collider have been unable to detect or produce cold dark matter particles. More recently, interest has shifted to other proposed forms of dark matter, including whole galleries of “dark” particles that interact invisibly through “dark” forces, or “dark sectors.” .
This mixture contains axions. Axions are theoretically very light and behave more like waves than particles. Generally speaking, it is “fuzzy dark matter” or “wavy dark matter.” Computer simulations of galaxy formation show that such waves can interfere with each other, producing knobby, filament-like structures rather than the round shape predicted by cold dark matter.
“Yes, the relationship with dark matter is interesting,” Dr. Pandya says, explaining the trickery of “gas physics” that explains how turbulence, hot gas and magnetic fields interact to light up stars and galaxies. He added that the devil is in the details.
Jeremiah Ostriker, professor emeritus of astrophysics at Princeton University and now at Columbia University, has been focusing on fuzzy dark matter in recent years. In 1973, Dr. Ostriker and his Princeton colleague James Peebles came up with the idea of dark matter.
He and others point out that fuzzy dark matter will leave its own imprint on the size and shape of baby galaxies. Because of their inherent undulations, axions do not aggregate as effectively as cold dark matter, making it difficult to generate baby galaxies with solar masses less than 1 billion. Cold dark matter has no such limit. However, today’s telescopes are not sensitive enough to observe such infants. Larger, newer generation equipment may be required to complete this job.
Dr. Ostriker learned about Dr. Pandya’s work and said that the prospects for fuzzy dark matter are getting better and better. “Keep up the good work,” he said.