James Webb finds frozen water in a young star system for the first time

It had been previously found in Saturn's rings and icy bodies in our Solar System's Kuiper Belt, but never in a place like this. An international team of researchers, including astrophysicist Noemí Pinilla of the University of Oviedo and the Institute of Space Sciences and Technologies of Asturias (ICTEA), has discovered, for the first time, crystalline water ice in a disk of dusty debris around a young Sun-like star. The future star system, located 155 light-years away, was observed with NASA's James Webb Space Telescope. The discovery "reinforces the idea that there may be life not only on our planet, or in our neighborhood, but anywhere in the universe that has similar conditions," Pinilla tells this newspaper.

Astronomers have been waiting for this "irrefutable" data for decades. In 2008, observations by NASA's Spitzer Space Telescope already hinted at the possibility of frozen water in this system, but it wasn't until now that the James Webb Space Telescope detected it "unambiguously," according to Chen Xie, a scientist at Johns Hopkins University in Baltimore, Maryland (USA) and lead author of the article published this Wednesday in the journal 'Nature'. All the frozen water detected is paired with fine dust particles throughout the disk, like "dirty snowballs."

The star, cataloged as HD 181327, is significantly younger than our Sun. It's estimated to be 23 million years old, compared to our star's 4.6 billion years. It's also slightly more massive and hotter, which led to the formation of a slightly larger system around it.

Webb's observations confirm a significant gap between the star and its debris disk, a wide area that is free of dust. That disk is similar to our own Kuiper Belt, where dwarf planets, comets, and other chunks of ice and rock sometimes collide. Billions of years ago, our Kuiper Belt was likely similar to this star's debris disk. "It's like seeing our solar system billions of years ago, in its cosmic infancy," Pinilla notes.

"HD 181327 is a very active system," Chen said. "There are regular, ongoing collisions in its debris disk. When these icy bodies collide, they release tiny particles of dusty water ice that are the perfect size for Webb to detect."

Water ice is not evenly distributed throughout this system. The majority, 20%, is found where it is coldest and farthest from the star. However, the closer the researchers looked, the less water ice they found. Toward the center of the debris disk, Webb detected about 8% water ice. Here, frozen water particles are likely produced slightly faster than they are destroyed. In the area of ​​the debris disk closest to the star, almost none was detected. The star's ultraviolet light likely vaporizes the nearest specks, or rocks known as planetesimals have "trapped" them within.

Water ice is a vital ingredient in the disks surrounding young stars. It greatly influences the formation of giant planets and can also be transported by small bodies like comets and asteroids to fully formed rocky planets. And with water, hope for life in other corners of the universe grows.

"From what we know, if there is liquid water and carbon molecules, the development of life is more likely," says Pinilla. "In our Solar System, we look for signs of life on icy satellites, like Europa (Jupiter's moon), where there are oceans of liquid water beneath the layer of structural ice. Now that we have confirmed the presence of water ice and probably carbon-molecular ice, we know that icy planetesimals similar to the ocean worlds of our Solar System may exist, and the collisions that give rise to this icy dust could send the seeds of life to warmer, rocky planets," he explains.

As he explains, "If giant planets have already formed in a debris disk, icy planets or their moons can still form. This discovery tells us that the planet formation we theorize in our solar system could be a universal process, common to exoplanets."

Now that Webb has detected water ice, it has opened the door for all researchers to study how these processes unfold in new ways in many other planetary systems. Noemí Pinilla arrived at ICTEA in October with an ATRAE grant to attract Spanish researchers abroad. She hopes to add students to her group.

Although she was not originally part of this research team, her experience studying the solar system—particularly icy objects—proved relevant and necessary for the interpretation of their data. When the principal investigator examined the obtained spectra, he identified features that pointed to the presence of a disk of icy planetesimals, very similar to the one that, in early times, gave rise to the trans-Neptunian belt and to such iconic objects as Pluto. It was then that he turned to the Asturian researcher to collaborate on the spectral interpretation, given her experience with small bodies in the solar system.

According to the astrophysicist, the James Webb Space Telescope has become a "wish machine" for science, transforming many of the hypotheses that guided the exploration of the cosmos for decades into real data and detections. "Webb is building bridges between key scales and stages of planetary formation, from the interstellar medium and molecular clouds to protoplanetary disks, exoplanets, and, ultimately, our own solar system," she emphasized.