Written by: Paola Pinto July 14, 2023 A group of galaxies plunging into the Coma galaxy cluster. Credit: NASA's Chandra X-ray Observatory. Dr. Stephen Walker, an Assistant Professor from the Department of Physics and Astronomy in the College of Science at The University of Alabama in Huntsville (UAH), a part of the University of Alabama System, has made significant strides in astrophysics. Recently, his groundbreaking research, conducted in collaboration with fellow astronomers, was featured in a NASA article, unveiling the longest-known tail ever observed trailing behind a group of galaxies within the Coma galaxy cluster. As an astrophysicist, Dr. Stephen Walker focuses on exploring the gravitational clustering of galaxies and their impact on the universe's structure. Reflecting on the importance of his work, Dr. Walker states, "Galaxies like our Milky Way don't live in isolation. Gravity tends to cluster them together. They are the largest gravitationally bound structures in the universe." Dr. Walker defines his work in simple words: "Basically, I look at big things crashing into each other." Utilizing NASA's Chandra X-ray Observatory, Dr. Walker and his team delved into the galaxy group NGC 4839, located near the Coma galaxy cluster approximately 340 million light-years away. By examining the emissions of superheated gas from NGC 4839, the researchers sought to unravel the intricate processes that drive the growth of galaxy clusters, which are among the largest structures in the universe. The team's groundbreaking research revealed a remarkable phenomenon: as NGC 4839 moves towards the center of the Coma cluster, "the hot gas in the galaxy group is stripped away by its collision with gas in the cluster," NASA says. Shockingly, this tail spans a staggering 1.5 million light-years, surpassing all previously recorded lengths and solidifying its place in scientific history. The Chandra data analysis conducted by Dr. Walker and his colleagues also led to valuable insights into the underlying physics at play. They identified a shock wave comparable to the sonic boom produced by a supersonic jet, indicating that NGC 4839 is speeding through the galaxy cluster at approximately 3 million miles per hour. Dr. Walker presented his findings at the 242nd meeting of the American Astronomical Society in Albuquerque, New Mexico, and published a paper co-authored by Mohammad Mirakhor and James Runge in the June issue of the Monthly Notices of the Royal Astronomical Society. Reflecting on the opportunities available to aspiring astronomers, Dr. Walker encourages students to take advantage of NASA's open-access data, emphasizing that real scientific work can be conducted with a regular computer without requiring extensive equipment or supercomputers. At UAH, students can engage in astronomy from their earliest years, benefiting from introductory courses and the guidance of passionate professors eager to share their research and provide valuable learning opportunities. The extraordinary discovery made by Dr. Stephen Walker and his team highlights their significant contributions to advancing our understanding of the vast structures within our universe. As the College of Science continues to push the boundaries of knowledge, Dr. Walker's work is a testament to dedicated researchers' impact in furthering scientific progress.
