Free Astronomy Magazine March-April 2024

43 MARCH-APRIL 2024 ASTRO PUBLISHING 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. 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 Uni- versity of Arizona in Tucson. This hy- pothesis is based partly on new evidence from Webb – theorists have “wound back the clock” to es- timate 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 Uni- versity. “Identifying additional cate- gories 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 in- frared 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 as- tronomers 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 Cos- mic Assembly Near-infrared Deep Extragalactic Legacy Survey. Deep sky surveys like these led to T hese are examples of distant galaxies captured by NASA’s James Webb Space Telescope in its Cosmic Evolution Early Release Science (CEERS) Survey. Recent research of the CEERS field led by Viraj Pandya showed that galaxies frequently appear flat and elongated, like pool noodles or surfboards (along the top row). Thin, circular disk-like galaxies, which resemble frisbees, are the next major grouping (bottom left and center). Finally, galaxies that are shaped like spheres, or volleyballs, made up the smallest fraction of their detections (bottom right). All of these galaxies are estimated to have existed when the universe was 600 mil- lion to 6 billion years old. [NASA, ESA, CSA, STScI, Steve Finkelstein (UT Austin), Micaela Bagley (UT Austin), Rebecca Larson (UT Austin)] far greater statistics, leading as- tronomers to create robust 3D mod- els 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 – de- livering 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 Insti- tute of Astrophysics on the Canary Islands. But researchers still won- dered: Would additional detail show up better with sensitivity to infrared light? “Webb confirmed that Hub- ble didn’t miss any additional fea- tures in the galaxies they both ob- served. Plus, Webb showed us many more distant galaxies with similar shapes, all in great detail.” There are still gaps in our knowl- edge – 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-au- thor Elizabeth McGrath, an associate professor at Colby College in Water- ville, Maine. “We need to delve more deeply into the data to figure out what’s going on, but we’re very ex- cited about these early trends.” !