Astronomy

Clouds of water ice thread stellar nurseries in the Milky Way

The findings support the idea that water pervades the galaxy’s planet-building material

Vast clouds of interstellar water ice (blue in this false color mosaic) reach hundreds of light-years across Cygnus X, a large star-forming region in the Milky Way. This mosaic of images, captured by NASA’s SPHEREx, spans the width of roughly 11 full moons.

JPL-Caltech/NASA, IPAC, J.L. Hora et al/Astrophysical Journal 2026

By Nikk Ogasa

60 minutes ago

A vast, frozen fog of interstellar ice has been charted across expanses of the Milky Way, poised to supply water to newborn worlds.

Reaching hundreds of light-years in length, the icy clouds drape two of the galaxy’s active star-forming regions, astronomer Gary Melnick and colleagues report in the April 20 Astrophysical Journal. The findings paint the broadest picture thus far of interstellar ice’s distribution, and seem to confirm predictions that water, a key ingredient for life on Earth, occurs across huge areas of interstellar space, says Melnick, of the Harvard-Smithsonian Center for Astrophysics.

That’s significant because, as stars form, some of that ice may get swept into the gravitational collapse of giant clouds of dust and gas, where it could coalesce with other material to form new planets. If there’s a lot of this ice nearby, Melnick says, “that provides a likely answer to how these newly forming worlds could acquire their own oceans.”

In fact, he says, much of Earth’s water — if not all of it — probably originated as interstellar ice.

Clouds of icy dust

SPHEREx observations show that large amounts of water ice occur in dust-rich regions of Cygnus X, a stellar nursery. Use the slider to compare how the ice, shown in blue in the false color infrared image on the left, coincides with dark filaments of interstellar dust, shown in different wavelengths of light on the right.

The observations were made by — take a deep breath — NASA’s Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, or SPHEREx. Since launching to low Earth orbit in March 2025, SPHEREx has been using its infrared eyes to survey the entire sky, a process it will complete four times during its two-year mission. The observatory can discern the ice within clouds of gas and dust because ice absorbs certain wavelengths of infrared light and thus appears dark in starlight.

Within a couple of stellar nurseries known as Cygnus X and the North American Nebula, the densest, dustiest areas were threaded with wispy clouds of ice, the researchers found. That supports the hypothesis that the ice is dispersed upon the surfaces of countless dust motes in these stellar nurseries, Melnick says.

While the James Webb Space Telescope has previously generated maps of interstellar ice, the new SPHEREx maps are dozens of times wider. SPHEREx is providing a more zoomed-out view of the environments in which these ices occur, Melnick says. “We’re seeing the bigger picture.”

The researchers hope to soon use SPHEREx data to determine the abundance of interstellar ice, which could help reveal regions where newborn worlds are likely to possess oceans of water.