Our home galaxy, the Milky Way, is known for its famous glittering spiral.
But we’re not the only ones with a sparkly arm. This class of galaxies, known as spiral galaxies, is estimated to make up 60 percent of all galaxies in the universe. Spiral galaxies occur in low-density regions of the universe and are not common in every corner of the universe. In fact, they are rare among galaxy clusters.
And it turns out that there is a part of the universe called the Supergalactic Plane. It is an enormous flattened structure nearly a billion light-years across that is teeming with bright elliptical galaxies and bright disk galaxies – but strangely no spiral galaxies. An international team of researchers wanted to know: Why are spiral galaxies like our own Milky Way missing from the supergalactic plane? And what can this tell us about the evolution of our galaxy?
Maybe they would have found an answer. New research in the journal Natural astronomy Spiral galaxies are reportedly rare in the Supergalactic Plane because galaxies in this region often merge with other galaxies.
Think of it like a very populated city or a busy highway. These mergers transform spiral galaxies into elliptical galaxies, i.e. egg-shaped galaxies without spiral arms, which leads to the growth of supermassive black holes. (These black holes live up to their name, sometimes being billions of times more massive than our Sun.) In contrast, spiral galaxies that do not populate the supergalactic plane evolve in isolation, allowing them to maintain their beautiful spirals.
“Our simulation reveals the intimate details of galaxy formation, such as the transformation of spirals into ellipses through galaxy mergers.”
The research team reached their conclusion using the supercomputer simulation SIBELIUS (Simulations Beyond the Local Universe). Through this simulation, they tracked the evolution of the universe over 13.8 billion years, from the early universe to the present day. The researchers said the final simulation is consistent with observations of our universe through telescopes.
“It is rare, but not a complete anomaly: our simulation reveals the intimate details of galaxy formation, such as the transformation of spirals into ellipses through galaxy mergers,” said co-author Professor Carlos Frenk in a media statement. “In addition, the simulation shows that our Standard Model of the Universe, based on the idea that most of its mass is cold dark matter, can reproduce the most remarkable structures in the Universe, including the spectacular structure that includes the Milky Way. “”
Distribution of the brightest galaxies in the local Universe observed in the 2MASS survey (left panel) and reproduced in the SIBELIUS simulation (right panel). (Dr Till Sawala)Astronomers believe the Milky Way is an estimated 13.51 billion years old. However, it remains unclear what happened during each phase of its development and how long these phases lasted until it reached its current form. A leading theory is that the Milky Way’s collision with a dwarf galaxy nearly 10 billion years ago was a turning point, setting in motion the changes that paralleled our modern galaxy. Others believe our galaxy may have matured sooner than previously thought. However, galaxies, like humans, go through different stages of maturity.
A separate study published in The astrophysical diary letters highlights unexpected observations in “teenage galaxies,” i.e. galaxies that formed two to three billion years after the Big Bang.
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In the study, a group of scientists from Northwestern University analyzed the results of the Chemical Evolution Constrained using Ionized Lines in Interstellar Aurorae (CECILIA) survey, which used NASA’s James Webb Space Telescope (JWST) to study the chemistry of distant galaxies . The results showed that these so-called teenage galaxies go through an unpleasant growth spurt during their teenage years, similar to humans.
“Using JWST, our program targets juvenile galaxies as they experienced a chaotic period of growth spurts and changes,” Northwestern says Allison Strom, who led the study, said in a media statement. “Adolescents often have experiences that determine their path into adulthood. It’s the same with galaxies.”
To make these discoveries, Strom and her collaborators used JWST to observe 33 distant teenage galaxies for 30 hours. They then combined the spectra of 23 of these galaxies. Strom emphasized that the biggest surprises were the observations of nickel and the finding that the juvenile galaxies were extremely hot.
“This is just additional evidence of how different galaxies likely were when they were younger,” Strom said. “Never in my wildest dreams did I think we would see nickel.”
Light from 23 distant galaxies, marked by red rectangles in the Hubble Space Telescope image above, was combined to capture incredibly faint emissions from eight different elements, marked below in the JWST spectrum. (Aaron M. Geller, Northwestern, CIERA + IT-RCDS)
Dr. Gwen Rudie, an astronomer at the Carnegie Observatories, told Salon via email that the existence of the elements in these galaxies is no surprise, but the ability to measure their light is “unprecedented” and underscores the power of the JWST.
“The pattern we see in the light of these different elements (how bright each element’s signatures shine) is very different from what we see in local galaxies – and our own galaxy,” Rudie said. “So the next big puzzle is to explain why the pattern in their spectra is different and what it means for these early galaxies.”
Rudie added that astronomers have a pretty good idea of how galaxies like the Milky Way formed, but are missing “very important clues.” The most important thing, she said, is the chemical composition of the galaxy.
Strom further stated that the strongest growth of a galaxy occurs during this period, proving why this period is important to study. It could also provide clues as to why the Milky Way has its spiral arm.
“By studying this, we can begin to explore the physics that made the Milky Way look like the Milky Way,” she said. “And why it might look different than its neighboring galaxies.”