SPHEREx maps vast interstellar ices and carbon-rich dust across Cygnus X and North American Nebula

NASA’s SPHEREx space observatory has produced some of the largest near-infrared spectral maps yet of interstellar ice and carbon-rich dust in major Milky Way star-forming regions, giving astronomers a new way to trace the raw materials of stars and planets across vast stretches of space rather than along just a few isolated lines of sight.

The new results, released by NASA this week, focus on Cygnus X and the North American Nebula, two active stellar nurseries in the Milky Way. NASA’s Jet Propulsion Laboratory said the mapped ice-rich regions span more than 600 light-years across, underscoring the scale of what the mission can survey in a single, uniform data set.

According to a paper by Joseph L. Hora and colleagues, accepted to The Astrophysical Journal and posted on arXiv, SPHEREx detected signatures of water ice, carbon dioxide ice and carbon monoxide ice, along with emission from polycyclic aromatic hydrocarbons, or PAHs, a class of carbon-based molecules or very small grains commonly used to trace dust chemistry and ultraviolet-lit environments. The features highlighted in the study include water ice at 3.0 microns, carbon dioxide ice at 4.27 microns, carbon monoxide ice at 4.67 microns and PAH emission at 3.28 microns.

That is the scientific draw of the result: not simply detecting these materials, but mapping how they are distributed over enormous contiguous regions. Earlier observatories such as Spitzer, the Infrared Space Observatory, AKARI and JWST detected the same kinds of ices and dust signatures, but largely through pointed observations or smaller maps. SPHEREx, which launched March 11, 2025, was built to do something different: a two-year all-sky infrared survey in 102 spectral bands spanning about 0.75 to 5.0 microns.

Those broad maps can help astronomers sort out how conditions vary inside molecular clouds, the cold, dense birthplaces of stars. In the new data, water and carbon dioxide ice broadly trace the cold, shielded parts of those clouds, where molecules can freeze onto dust grains. PAH emission, by contrast, traces dustier environments exposed to radiation. The paper says differences in the relative strengths of these features from one sightline to another point to real environmental and chemical variation within the same star-forming complex.

That matters because interstellar ices are thought to be important reservoirs of water and other molecules that can later be incorporated into comets, planet-building debris and planets. Cygnus X, one of the galaxy’s most active and turbulent star-forming regions, is a particularly useful test for a mission designed to study chemistry on large scales.

“We expected to detect these ices in front of individual bright stars: The light from a star acts like a spotlight, revealing any ice in the space between us and that star. But this is something different,” Hora, the lead author, said in NASA’s release. “SPHEREx can see the spatial distribution of the ices they contain in incredible detail.”

NASA and JPL published the new result April 15, followed by a NASA image release April 17. The paper is available now on arXiv and has been accepted for publication in The Astrophysical Journal. NASA says SPHEREx data products are being handled through IPAC’s Infrared Science Archive, where public archive tools and higher-level maps will be made available.