“Surboard” galaxies are numerous in the early universe

Images from the Webb Space Telescope reveal that galaxies in the early universe are typically flat and elongated, like surfboards, and rarely round, like volleyballs. “About 50 to 80% of the galaxies we study appear to be flattened in two dimensions,” lead author of the new study on the topic, Viraj Pandya, a NASA fellow at Columbia University in New York, explained in a statement. “Galaxies that look like pool noodles or surfboards seem to be very common in the early universe, which is surprising because they are rare in the neighborhood.” The team focused on a large field of near-infrared images provided by Webb, known as the Cosmic Evolution Early Release Science Survey (CEERS), extracting galaxies estimated to have existed when the universe was 600 to 6 billion years old. While the most distant galaxies look like surfboards and pool noodles, others are shaped like frisbees and volleyballs. “Volleyball” or ball-shaped galaxies appear to be the most compact type of cosmic “ocean” and have also been the least identified. Frisbees were found to be as large as surfboard- and pool-shaped noodle-shaped galaxies along the “horizon,” but become more common closer to the “shore” in the near universe. If we could turn back the clock billions of years, what category would our Milky Way galaxy fall into? “The best guess is that it may have looked more like a surfboard,” said co-author Haowen Zhang, a doctoral student at the University of Arizona in Tucson. This hypothesis is partly based on new evidence from Webb: theorists have “turned back time” to estimate the mass of the Milky Way billions of years ago, which correlates with its shape at the time. These distant galaxies are also much less massive than nearby spiral and elliptical galaxies: they are the progenitors of more massive galaxies like our own. “In the early universe, galaxies had much less time to grow,” said co-author Kartheik Iyer, also of Columbia University.