Free Astronomy Magazine July-August 2025

detected water ice with Webb, they have opened the door for all re- searchers to study how these processes play out in new ways in many other planetary systems. The star, cataloged HD 181327, is significantly younger than our Sun. It’s estimated to be 23 million years old, compared to the Sun’s more mature 4.6 billion years. The star is slightly more massive than the Sun, and it’s hotter, which led to the for- mation of a slightly larger system around it. Webb’s observations confirm a sig- nificant gap between the star and its debris disk — a wide area that is free of dust. Farther out, its debris disk is similar to our solar system’s Kuiper Belt, where dwarf planets, comets, and other bits of ice and rock are found (and sometimes col- lide with one another). Billions of years ago, our Kuiper Belt was likely similar to this star’s debris disk. “HD 181327 is a very active system,” Chen said. “There are regular, ongo- ing collisions in its debris disk. When those icy bodies collide, they release tiny particles of dusty water ice that are perfectly sized for Webb to de- tect.” Water ice isn’t spread evenly throughout this system. The major- ity is found where it’s coldest and farthest from the star. “The outer area of the debris disk consists of over 20% water ice,” Xie said. The closer in the researchers looked, the less water ice they found. To- ward the middle of the debris disk, Webb detected about 8% water ice. Here, it’s likely that frozen water particles are produced slightly faster than they are destroyed. In the area of the debris disk closest to the star, Webb detected almost none. It’s likely that the star’s ultra- violet light vaporizes the closest specks of water ice. It’s also possible that rocks known as planetesimals have “locked up” frozen water in their interiors, which Webb can’t detect. This team and many more re- searchers will continue to search for — and study — water ice in debris disks and actively forming planetary systems throughout our Milky Way galaxy. “The presence of water ice helps facilitate planet formation,” Xie said. “Icy materials may also ul- timately be ‘delivered’ to terrestrial planets that may form over a couple hundred million years in systems like this.” The researchers observed HD 181327 with Webb’s NIRSpec (Near-Infrared Spectrograph), which is super-sensitive to extremely faint dust particles that can only be de- tected from space. JULY-AUGUST 2025 F or the first time, researchers con- firmed the presence of crystalline water ice in a dusty debris disk that orbits a Sun-like star, using NASA’s James Webb Space Telescope. All the frozen water detected by Webb is paired with fine dust particles throughout the disk. The majority of the water ice observed is found where it’s coldest and farthest from the star. The closer to the star the researchers looked, the less water ice they found. [NASA, ESA, CSA, STScI, Ralf Crawford (STScI)] !