Science

Astronomers Uncover Ancient Ice-Covered Dust in Distant Galaxy—What It Means for Planet Formation!

2025-06-09

Author: Jia

Astronomers have long faced a daunting challenge when examining galaxies from billions of years ago: dust. This cosmic debris often obscures their view, making it difficult to decipher the details of star and black hole formation in these ancient celestial bodies.

Thanks to the groundbreaking capabilities of the James Webb Space Telescope (JWST), a team led by Tufts University astronomer Anna Sajina has made a fascinating discovery. They found that the ice-covered dust in a galaxy located 5 billion light-years away closely resembles dust found closer to home, providing insights into the universe's early history.

This revelation could revolutionize our understanding of star and black hole formation, allowing astronomers to refine their measurements and theories about events occurring shortly after the universe came into existence—a mere 14 billion years ago.

Sajina focuses her research on the significant challenges dust presents in studying galaxies. Dust absorbs starlight, then re-emits it in infrared wavelengths—light invisible to the naked eye. To accurately assess star formation, astronomers must correct for the effects of this obscuration, which has often relied on assumptions about dust properties.

Previously, the tools available to study the characteristics of dust in far-off galaxies were minimal, leading researchers to default to the idea that distant dust was similar to that of our Milky Way—an assumption that lacked solid confirmation.

The makeup of interstellar dust consists of tiny grains rich in elements like carbon, silicon, and iron, situated in regions dense with cold gas. These areas are crucial for star formation but can be heavily concealed by dust.

"If the dust properties in far-off galaxies mirror those in our galaxy, then it's reasonable to surmise that their planets will share similar characteristics as well," Sajina explains.

Utilizing the JWST's advanced mid-infrared viewing technology, the research team analyzed the galaxy SSTXFLS J172458.3+591545, located 5 billion light-years away. The light that reached JWST originated from this galaxy five billion years ago, revealing startling features.

This galaxy is home to a rapidly growing black hole, known as an active galactic nucleus, consuming interstellar gas. The JWST's high sensitivity surpassed even that of the Hubble Space Telescope, allowing the detection of solid-phase molecules such as carbon dioxide, carbon monoxide, and water, marking the first time all these ices have been identified together this far back in time.

"While we’ve identified gaseous molecules in space for years, Seeing solid ice mantles on dust grains is a groundbreaking achievement," states Sajina. These observations push the boundaries of our knowledge beyond the local universe, delving several billion years into the past.

The team discovered that the composition of ice-covered dust grains in this ancient galaxy mirrors that of similar materials found in our vicinity. "This similarity suggests that if planets were indeed forming in these galaxies, they would have access to the same building blocks as ours," Sajina concluded.

This remarkable find also sheds light on how dust was distributed in these distant, obscured systems, revealing compact dense cores—a significant clue in the galaxy formation puzzle.