Researchers analyzing images from NASA’s James Webb Space Telescope have found that galaxies in the early universe are often flat and elongated, like surfboards and pool noodles – and are rarely round, like volleyballs or frisbees. “Roughly 50 to 80% of the galaxies we studied appear to be flattened in two dimensions,” explained lead author Viraj Pandya, a NASA Hubble Fellow at Columbia University in New York. “Galaxies that look like pool noodles or surfboards seem to be very common in the early universe, which is surprising, since they are uncommon nearby.”
The team focused on a vast field of near-infrared images delivered by Webb, known as the Cosmic Evolution Early Release Science (CEERS) Survey, plucking out galaxies that are estimated to exist when the universe was 600 million to 6 billion years old.
While most distant galaxies look like surfboards and pool noodles, others are shaped like frisbees and volleyballs. The “volleyballs,” or sphere-shaped galaxies, appear the most compact type on the cosmic “ocean” and were also the least frequently identified. The frisbees were found to be as large as the surfboard- and pool noodle-shaped galaxies along the “horizon,” but become more common closer to “shore” in the nearby universe. (Compare them in this illustration.)
Which category would our Milky Way galaxy fall into if we were able to wind the clock back by billions of years? “Our best guess is that it might have appeared more like a surfboard,” said co-author Haowen Zhang, a PhD candidate at the University of Arizona in Tucson. This hypothesis is based partly on new evidence from Webb – theorists have “wound back the clock” to estimate the Milky Way’s mass billions of years ago, which correlates with shape at that time.
These distant galaxies are also far less massive than nearby spirals and ellipticals – they are precursors to more massive galaxies like our own. “In the early universe, galaxies had had far less time to grow,” said Kartheik Iyer, a co-author and NASA Hubble Fellow also at Columbia University. “Identifying additional categories for early galaxies is exciting – there’s a lot more to analyze now. We can now study how galaxies’ shapes relate to how they look and better project how they formed in much more detail.”
Webb’s sensitivity, high-resolution images, and specialization in infrared light allowed the team to make quick work of characterizing many CEERS galaxies, and model their 3D geometries. Pandya also says their work wouldn’t be possible without the extensive research astronomers have done using NASA’s Hubble Space Telescope.
For decades, Hubble has wowed us with images of some of the earliest galaxies, beginning with its first “deep field” in 1995 and continuing with a seminal survey known as Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. Deep sky surveys like these led to far greater statistics, leading astronomers to create robust 3D models of distant galaxies over all of cosmic time. Today, Webb is helping to enhance these efforts, adding a bounty of distant galaxies beyond Hubble’s reach and revealing the early universe in far greater detail than previously possible.
Webb’s images of the early universe have acted like an ocean swell – delivering new waves of evidence. “Hubble has long showed an excess of elongated galaxies,” explained co-author Marc Huertas-Company, a faculty research scientist at the Institute of Astrophysics on the Canary Islands. But researchers still wondered: Would additional detail show up better with sensitivity to infrared light? “Webb confirmed that Hubble didn’t miss any additional features in the galaxies they both observed. Plus, Webb showed us many more distant galaxies with similar shapes, all in great detail.”
There are still gaps in our knowledge – researchers not only need an even larger sample size from Webb to further refine the properties and precise locations of distant galaxies, they will also need to spend ample time tweaking and updating their models to better reflect the precise geometries of distant galaxies. “These are early results,” said co-author Elizabeth McGrath, an associate professor at Colby College in Waterville, Maine. “We need to delve more deeply into the data to figure out what’s going on, but we’re very excited about these early trends.”
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.