galaxies Archives

October 14, 2024October 14, 2024 by Carolyn Collins Petersen

It’s Like Looking into a Mirror, 13 Billion Years Ago

This image shows the galaxy REBELS-25 as seen by the Atacama Large Millimeter/submillimeter Array (ALMA), overlaid on an infrared image of other stars and galaxies. Courtesy ESO.

The early Universe continues to offer surprises and the latest observations of infant galaxies are no exception. Astronomers found a surprisingly Milky Way-like galaxy that existed more than 13 billion years ago. That was a time when the Universe was really just an infant and galaxies should still be early in their formation. A well-formed one in such early history is a bit of a surprise.

The newly discovered galaxy is called REBELS-25. It was found as part of the “Reionization Era Bright Emission Line Survey (REBELS) survey using the Atacama Large Millimeter Array (ALMA) in Chile. The idea of the survey is to search out and measure early galaxies.

REBELS-24 is a massive disc-like galaxy with structures that look like spiral arms. That’s pretty similar to our Milky Way Galaxy. It’s more than 13 billion years old and took billions of years to evolve into its present shape. Like REBELS-25, the Milky Way began as a clumpy, disorganized proto-galaxy not long after the Universe began. It merged with other protogalaxies and evolved into a beautiful spiral shape. It appears to be actively forming stars and is incredibly massive for such a young galaxy.

Early Spirals Aren’t New

So, REBELS-25 raises a big question: why is it so massive and well-evolved at a time when the infant Milky Way was still a clump? That’s what astronomers are working to figure out. “According to our understanding of galaxy formation, we expect most early galaxies to be small and messy looking,” said Jacqueline Hodge, an astronomer at Leiden University, the Netherlands. The fact that REBELS-25 looks so “modern” after less than a billion years does—in a sense—rebel against the generally accepted theories about galaxy formation and evolution.

This isn’t the first time that astronomical observations uncovered early spirals. JWST observations suggest that perhaps a third of early galaxies are already spirals in the infant Universe. Its Cosmic Evolution Early Release Science Survey (CEERS) found many of these in the first 700 million years of cosmic history. So, finding this one looking almost “modern” some 13 billion years ago just adds to the mystery of their formation.

REBELS-25 showed up in ALMA observations, which also gave hints that it had a rotating disk. A set of follow-up observations confirmed the rotation of this galaxy and its spiral arm structures. In addition, the ALMA data found hints of a central bar (just like our Milky Way galaxy has). “ALMA is the only telescope in existence with the sensitivity and resolution to achieve this,” said Renske Smit, a researcher at Liverpool John Moores University in the UK and part of the team that worked on this discovery.

The ALMA data produced an image of REBELS-25 (left) and a map of gas motions in this galaxy. Blue colouring indicates movement towards Earth and red indicates movement away from Earth, with a darker shade representing faster movement. In this case, the red-blue divide of the image shows clearly that the object is rotating, making REBELS-25 the most distant rotating disc galaxy ever discovered. Courtesy ESO. — The ALMA data produced an image of REBELS-25 (left) and a map of gas motions in this galaxy which lies more than 13 billion light-years away. Blue coloring indicates movement towards Earth. Red indicates movement away from Earth, with a darker shade representing faster movement. In this case, the red-blue divide of the image shows clearly that the object is rotating, making REBELS-25 the most distant and early (13 billion years old) rotating disc galaxy ever discovered. Courtesy ESO.

Surprisingly, the ALMA data also hinted at more developed features similar to those of the Milky Way. It looks like there’s a central elongated bar, and even spiral arms in REBELS0-25. “Seeing a galaxy with such similarities to our own Milky Way, that is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early Universe evolve into the orderly galaxies of today’s cosmos,” said Lucie Rowland, a doctoral student at Leiden University who led the research into REBELS-25. “Finding further evidence of more evolved structures would be an exciting discovery, as it would be the most distant galaxy with such structures observed to date.”

What Does This Mean for Galaxy Evolution?

As astronomers discover more of these well-evolved galaxies in the early Universe, they’ll have to adjust the working model of galactic birth and evolution. In that model, the baby galaxies are clumps of stars and gas that come together in collisions and cannibalism to form larger galaxies. It’s typically considered a messy and turbulent time in cosmic history. Infant galaxies collided and grew. They combined their stars and gases to make larger structures. Over time they begin to rotate, which also influences the formation of structures inside the galaxy. Further collisions add more mass to the galaxy, and they also spur bursts of star formation. All of this takes billions of years to accomplish. Or so astronomers always thought.

REBELS-25 and other early spirals challenge that general model. For one thing, REBELS-25 looks like a galaxy that’s evolving at an accelerated pace. Compared to the Milky Way’s ponderous billions of years of evolution, REBELS-25 is going at warp speed. That implies something is pushing that acceleration. T he big thing now will be to explain its advanced evolution at a very young age.

The REBELS program should help astronomers understand more about the processes at work only a few hundred million years after the Big Bang. That survey will supply large enough amounts of data about high-mass galaxies in the early Universe. Those samples should allow astronomers to do targeted studies of more galaxies using both ALMA and JWST. Both observatories are powerful enough to give detailed looks at individual galaxies in those very early epochs of cosmic history.

For More Information

Space Oddity: Most Distant Rotating Disc Galaxy Found (PR)
Space oddity: Most Distant Rotating Disc Galaxy Found (the paper)
About REBELS

October 5, 2024October 5, 2024 by Carolyn Collins Petersen

The Milky Way Might be Part of an Even Larger Structure than Laniakea

A data visualization of the motions of galaxies in structures called basins of attraction. The Milky Way is the red dot. Courtesy of the University of Hawai'i.

If you want to pinpoint your place in the Universe, start with your cosmic address. You live on Earth->Solar System->Milky Way Galaxy->Local Cluster->Virgo Cluster->Virgo Supercluster->Laniakea. Thanks to new deep sky surveys, astronomers now think all those places are part of an even bigger cosmic structure in the “neighborhood” called The Shapley Concentration.

September 28, 2024September 28, 2024 by Brian Koberlein

How Does the Milky Way Compare to Other Galaxies?

A mosaic of the images of 378 satellites across 101 Milky Way-like systems. Credit: Yao-Yuan Mao (Utah), with images from the DESI Legacy Surveys Sky Viewer

The Milky Way is special because it is our home. No matter where we are on Earth we can see its arc of light overhead if the night is dark enough. But how similar is our galaxy to others? Is it an unusual spiral galaxy, or is it rather typical in the cosmos?

September 16, 2024September 16, 2024 by Evan Gough

A Black Hole has Almost Halted Star Formation in its Galaxy

This is a quiescent galaxy in the early Universe named GS-10578 but nicknamed ‘Pablo’s Galaxy’. It has an SMBH in its center, and astronomers have used the NASA/ESA James Webb Space Telescope to confirm that supermassive black holes can starve their host galaxies of the fuel they need to form new stars. Image Credit: JADES Collaboration

When the James Webb Space Telescope was launched on Christmas Day in 2021, it faced a whole host of intriguing questions. By the time it finally launched, astronomers had a big list of targets begging for the type of detailed observations that only the powerful infrared space telescope could perform. One of the targets was an ancient, massive galaxy that’s basically dead and forms no new stars.

The results are in, and an international team of astronomers know what happened to the quiescent galaxy.

September 10, 2024September 10, 2024 by Carolyn Collins Petersen

Two Supermassive Black Holes on a Collision Course With Each Other

An artist's concept of what two merging supermassive black holes might look like. Each one is surrounded by an accretion disk of hot gas and material streaming away via jets. CourtesyNASA, ESA, Joseph Olmsted (STScI)

Galaxy collisions are foundational events in the Universe. They happen when two systems mingle stars in a cosmic dance. They also cause spectacular mergers of supermassive black holes. The result is one very changed galaxy and a singular, ultra-massive black hole.

September 9, 2024September 9, 2024 by Evan Gough

The True Size of Galaxies is Much Larger Than We Thought

Visualisation of the gas shroud of starburst galaxy IRAS 08339+6517. Astronomers struggle to observe this gas clearly, but new research found a way. Image Credit: Cristy Roberts ANU/ASTRO 3D

Ask most people what a galaxy is made up of, and they’ll say it’s made of stars. Our own galaxy, the Milky Way, hosts between about 100 to 300 billion stars, and we can see thousands of them with our unaided eyes. But most of a galaxy’s mass is actually gas, and the extent of the gas has been difficult to measure.

Researchers have found a way to see how far that gas extends into the cosmos.

September 6, 2024September 6, 2024 by Evan Gough

JWST Reveals Star Formation at Cosmic Noon

A massive galaxy cluster named MACS-J0417.5-1154 is warping and distorting the appearance of galaxies behind it, an effect known as gravitational lensing. This natural phenomenon magnifies distant galaxies and can also make them appear in an image multiple times, as NASA’s James Webb Space Telescope saw here. Two distant, interacting galaxies — a face-on spiral and a dusty red galaxy seen from the side — appear multiple times, tracing a familiar shape across the sky. NASA, ESA, CSA, STScI, V. Estrada-Carpenter (Saint Mary's University).

Understanding the star formation rate (SFR) in a galaxy is critical to understanding the galaxy itself. Some galaxies are starburst galaxies with extremely high SFRs, some are quenched or quiescent galaxies with very low SFRs, and some are in the middle. Researchers used the JWST to observe a pair of galaxies at Cosmic Noon that are just beginning to merge to see how SFRs vary in different regions of both galaxies.

September 3, 2024September 3, 2024 by Evan Gough

This Ancient Galaxy Merger Will Produce a very Luminous Quasar

This illustration depicts two quasars in the process of merging. There are many unanswered questions around galaxy mergers and the quasars that can result. Image Credit: NOIRLab/NSF/AURA/M. Garlick)

In the contemporary Universe, massive galaxies are plentiful. But the Universe wasn’t always like this. Astronomers think that galaxies grew large through mergers, so what we see in space is the result of billions of years of galaxies merging. When galaxies merge, the merger can feed large quantities of gas into their centers, sometimes creating a quasar.

Much of this is theoretical and shrouded in mystery, but astronomers might have found evidence of a galaxy merger creating a quasar.

August 12, 2024August 12, 2024 by Andy Tomaswick

Are Andromeda and the Milky Way Doomed to Collide? Maybe Not

Scientists discovered the Andromeda galaxy, known as M31, hundreds of years ago, and around a century ago, we realized that it had negative radial velocity toward the Milky Way. In other words, eventually, the two galaxies would merge spectacularly. That has been common knowledge for astronomers since then, but is it really true? A new paper from researchers at the University of Helsinki looks at several confounding factors, including the gravitational influence of other galaxies in our local group, and finds only a 50% chance that the Milky Way will merge with the Andromeda galaxy in the next 10 billion years.

August 9, 2024August 9, 2024 by Evan Gough

The JWST Reveals the Nature of Dust Around an Active Galactic Nuclei

The James Webb Space Telescope captured this three colour image of the galaxy ESO 428-G14. New research shows how the dust near the galaxy's supermassive black hole is heated up. Image Credit: NASA, ESA, CSA, and STScI

Supermassive Black Holes (SMBHs) are located in the centers of large galaxies like ours. When they’re actively feeding, they produce more light and are called active galactic nuclei (AGN). But their details are difficult to observe clearly because large clouds of gas block our view.

The JWST was built just for circumstances like these.